Initial commit

6 files changed, 3766 insertions, 0 deletions

diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..f47959a
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,17 @@
+SHELL = /bin/sh
+CC = clang
+CFLAGS = -ggdb -Wall -Wextra -std=c99
+LDFLAGS = `pkg-config --libs libssl`
+
+.PHONY: all clean
+
+targets = zyklonb
+
+all: $(targets)
+
+clean:
+	rm -f $(targets)
+
+zyklonb: src/zyklonb.c src/siphash.c
+	$(CC) $^ -o $@ $(CFLAGS) $(LDFLAGS)
+
diff --git a/README b/README
new file mode 100644
index 0000000..d00bd27
--- /dev/null
+++ b/README
@@ -0,0 +1,21 @@
+ZyklonB
+=======
+
+`ZyklonB' is an experimental IRC bot, building upon the concept of my other
+VitaminA IRC bot.  The main characteristic of these two bots is that they run
+plugins as coprocesses, which allows for enhanced reliability and programming
+language freedom.
+
+While originally intended to be a simple C99 rewrite of the original bot, which
+was written in the GNU dialect of AWK, it fairly quickly became a playground
+where I added everything that seemed nice.
+
+License
+-------
+`ZyklonB' is written by Přemysl Janouch <p.janouch@gmail.com>.
+
+You may use the software under the terms of the ISC license, the text of which
+is included within the package, or, at your option, you may relicense the work
+under the MIT or the Modified BSD License, as listed at the following site:
+
+http://www.gnu.org/licenses/license-list.html
diff --git a/plugins/eval b/plugins/eval
new file mode 100755
index 0000000..97c3349
--- /dev/null
+++ b/plugins/eval
@@ -0,0 +1,312 @@
+#!/usr/bin/awk -f
+#
+# ZyklonB eval plugin, LISP-like expression evaluator
+#
+# Copyright 2013, 2014 Přemysl Janouch.  All rights reserved.
+# See the file LICENSE for licensing information.
+#
+
+BEGIN \
+{
+	RS = "\r"
+	ORS = "\r\n"
+	IGNORECASE = 1
+	srand()
+
+	prefix = get_config("prefix")
+
+	print "ZYKLONB register"
+	fflush("")
+
+	# All functions have to be in this particular array
+	min_args["int"]    = 1
+	min_args["+"]      = 1
+	min_args["-"]      = 1
+	min_args["*"]      = 1
+	min_args["/"]      = 1
+	min_args["%"]      = 1
+	min_args["^"]      = 1
+	min_args["**"]     = 1
+	min_args["exp"]    = 1
+	min_args["sin"]    = 1
+	min_args["cos"]    = 1
+	min_args["atan2"]  = 2
+	min_args["log"]    = 1
+	min_args["rand"]   = 0
+	min_args["sqrt"]   = 1
+
+	min_args["pi"]     = 0
+	min_args["e"]      = 0
+
+	min_args["min"]    = 1
+	min_args["max"]    = 1
+
+	# Whereas here their presence is only optional
+	max_args["int"]    = 1
+	max_args["sin"]    = 1
+	max_args["cos"]    = 1
+	max_args["atan2"]  = 2
+	max_args["log"]    = 1
+	max_args["rand"]   = 0
+	max_args["sqrt"]   = 1
+
+	max_args["pi"]     = 0
+	max_args["e"]      = 0
+}
+
+{
+	parse($0)
+}
+
+msg_command == "PRIVMSG" \
+{
+	# Context = either channel or user nickname
+	match(msg_prefix, /^[^!]+/)
+	ctx = substr(msg_prefix, RSTART, RLENGTH)
+	if (msg_param[0] ~ /^[#&!+]/)
+	{
+		ctxquote = ctx ": "
+		ctx = msg_param[0]
+	}
+	else
+		ctxquote = ""
+
+
+	if (substr(msg_param[1], 1, length(prefix)) == prefix)
+	{
+		keyword = "eval"
+		text = substr(msg_param[1], 1 + length(prefix))
+	 	if (match(text, "^" keyword "([^A-Za-z0-9].*|$)"))
+			process_request(substr(text, 1 + length(keyword)))
+	}
+}
+
+{
+	fflush("")
+}
+
+function pmrespond (text)
+{
+	print "PRIVMSG " ctx " :" ctxquote text
+}
+
+function process_request (input,    res, x)
+{
+	delete funs
+	delete accumulator
+	delete n_args
+
+	res = ""
+	fun_top = 0
+	funs[0] = ""
+	accumulator[0] = 0
+	n_args[0] = 0
+
+	if (match(input, "^[ \t]*"))
+		input = substr(input, RLENGTH + 1)
+	if (input == "")
+		res = "expression missing"
+
+	while (res == "" && input != "") {
+		if (match(input, "^-?[0-9]+\\.?[0-9]*")) {
+			x = substr(input, RSTART, RLENGTH)
+			input = substr(input, RLENGTH + 1)
+
+			match(input, "^ *")
+			input = substr(input, RLENGTH + 1)
+
+			res = process_argument(x)
+		} else if (match(input, "^[(]([^ ()]+)")) {
+			x = substr(input, RSTART + 1, RLENGTH - 1)
+			input = substr(input, RLENGTH + 1)
+
+			match(input, "^ *")
+			input = substr(input, RLENGTH + 1)
+
+			if (!(x in min_args)) {
+				res = "undefined function '" x "'"
+			} else {
+				fun_top++
+				funs[fun_top] = x
+				accumulator[fun_top] = 636363
+				n_args[fun_top] = 0
+			}
+		} else if (match(input, "^[)] *")) {
+			input = substr(input, RLENGTH + 1)
+			res = process_end()
+		} else
+			res = "invalid input at '" substr(input, 1, 10) "...'"
+	}
+
+	if (res == "") {
+		if (fun_top != 0)
+			res = "unclosed '" funs[fun_top] "'"
+		else if (n_args[0] != 1)
+			res = "internal error, expected one result" \
+				", got " n_args[0] " instead"
+	}
+
+	if (res == "")
+		pmrespond(accumulator[0])
+	else
+		pmrespond(res)
+}
+
+function process_argument (arg)
+{
+	if (fun_top == 0) {
+		if (n_args[0]++ != 0)
+			return "too many results, I only expect one"
+
+		accumulator[0] = arg
+		return ""
+	}
+
+	fun = funs[fun_top]
+	if (fun in max_args && max_args[fun] <= n_args[fun_top])
+		return "too many operands for " fun
+
+	if (fun == "int") {
+		accumulator[fun_top] = int(arg)
+	} else if (fun == "+") {
+		if (n_args[fun_top] == 0)
+			accumulator[fun_top] = arg
+		else
+			accumulator[fun_top] += arg
+	} else if (fun == "-") {
+		if (n_args[fun_top] == 0)
+			accumulator[fun_top] = arg
+		else
+			accumulator[fun_top] -= arg
+	} else if (fun == "*") {
+		if (n_args[fun_top] == 0)
+			accumulator[fun_top] = arg
+		else
+			accumulator[fun_top] *= arg
+	} else if (fun == "/") {
+		if (n_args[fun_top] == 0)
+			accumulator[fun_top] = arg
+		else if (arg == 0)
+			return "division by zero"
+		else
+			accumulator[fun_top] /= arg
+	} else if (fun == "%") {
+		if (n_args[fun_top] == 0)
+			accumulator[fun_top] = arg
+		else if (arg == 0)
+			return "division by zero"
+		else
+			accumulator[fun_top] %= arg
+	} else if (fun == "^" || fun == "**" || fun == "exp") {
+		if (n_args[fun_top] == 0)
+			accumulator[fun_top] = arg
+		else
+			accumulator[fun_top] ^= arg
+	} else if (fun == "sin") {
+		accumulator[fun_top] = sin(arg)
+	} else if (fun == "cos") {
+		accumulator[fun_top] = cos(arg)
+	} else if (fun == "atan2") {
+		if (n_args[fun_top] == 0)
+			accumulator[fun_top] = arg
+		else
+			accumulator[fun_top] = atan2(accumulator[fun_top], arg)
+	} else if (fun == "log") {
+		accumulator[fun_top] = log(arg)
+	} else if (fun == "rand") {
+		# Just for completeness, execution never gets here
+	} else if (fun == "sqrt") {
+		accumulator[fun_top] = sqrt(arg)
+	} else if (fun == "min") {
+		if (n_args[fun_top] == 0)
+			accumulator[fun_top] = arg
+		else if (accumulator[fun_top] > arg)
+			accumulator[fun_top] = arg
+	} else if (fun == "max") {
+		if (n_args[fun_top] == 0)
+			accumulator[fun_top] = arg
+		else if (accumulator[fun_top] < arg)
+			accumulator[fun_top] = arg
+	} else
+		return "internal error, unhandled operands for " fun
+
+	n_args[fun_top]++
+	return ""
+}
+
+function process_end ()
+{
+	if (fun_top <= 0)
+		return "extraneous ')'"
+
+	fun = funs[fun_top]
+	if (!(fun in min_args))
+		return "internal error, unhandled ')' for '" fun "'"
+	if (min_args[fun] > n_args[fun_top])
+		return "not enough operands for '" fun "'"
+
+	# There's no 'init' function to do it in
+	if (fun == "rand")
+		accumulator[fun_top] = rand()
+	else if (fun == "pi")
+		accumulator[fun_top] = 3.141592653589793
+	else if (fun == "e")
+		accumulator[fun_top] = 2.718281828459045
+
+	return process_argument(accumulator[fun_top--])
+}
+
+function get_config (key)
+{
+	print "ZYKLONB get_config :" key
+	fflush("")
+
+	getline
+	parse($0)
+	return msg_param[0]
+}
+
+function parse (line,     s, n, id, token)
+{
+	s = 1
+	id = 0
+
+	# NAWK only uses the first character of RS
+	if (line ~ /^\n/)
+		line = substr(line, 2)
+
+	msg_prefix = ""
+	msg_command = ""
+	delete msg_param
+
+	n = match(substr(line, s), / |$/)
+	while (n)
+	{
+		token = substr(line, s, n - 1)
+		if (token ~ /^:/)
+		{
+			if (s == 1)
+				msg_prefix = substr(token, 2)
+			else
+			{
+				msg_param[id] = substr(line, s + 1)
+				break
+			}
+		}
+		else if (!msg_command)
+			msg_command = toupper(token)
+		else
+			msg_param[id++] = token
+
+		s = s + n
+		n = index(substr(line, s), " ")
+
+		if (!n)
+		{
+		       n = length(substr(line, s)) + 1
+		       if (n == 1)
+			       break;
+		}
+	}
+}
+
diff --git a/src/siphash.c b/src/siphash.c
new file mode 100644
index 0000000..fa102cc
--- /dev/null
+++ b/src/siphash.c
@@ -0,0 +1,86 @@
+// Code taken from https://github.com/floodyberry/siphash with some edits.
+//
+// To the extent possible under law, the author(s) have dedicated all copyright
+// and related and neighboring rights to this software to the public domain
+// worldwide. This software is distributed without any warranty.
+//
+// You should have received a copy of the CC0 Public Domain Dedication along
+// with this software. If not, see <http://creativecommons.org/publicdomain/zero/1.0/>.
+
+#include "siphash.h"
+
+static uint64_t inline
+u8to64_le (const unsigned char *p)
+{
+	return
+		(uint64_t) p[0]       |
+		(uint64_t) p[1] <<  8 |
+		(uint64_t) p[2] << 16 |
+		(uint64_t) p[3] << 24 |
+		(uint64_t) p[4] << 32 |
+		(uint64_t) p[5] << 40 |
+		(uint64_t) p[6] << 48 |
+		(uint64_t) p[7] << 56 ;
+}
+
+uint64_t
+siphash (const unsigned char key[16], const unsigned char *m, size_t len)
+{
+	uint64_t v0, v1, v2, v3;
+	uint64_t mi, k0, k1;
+	uint64_t last7;
+	size_t i, blocks;
+
+	k0 = u8to64_le (key + 0);
+	k1 = u8to64_le (key + 8);
+	v0 = k0 ^ 0x736f6d6570736575ull;
+	v1 = k1 ^ 0x646f72616e646f6dull;
+	v2 = k0 ^ 0x6c7967656e657261ull;
+	v3 = k1 ^ 0x7465646279746573ull;
+
+	last7 = (uint64_t) (len & 0xff) << 56;
+
+#define ROTL64(a,b) (((a)<<(b))|((a)>>(64-b)))
+
+#define COMPRESS                              \
+	v0 += v1; v2 += v3;                       \
+	v1 = ROTL64 (v1,13); v3 = ROTL64 (v3,16); \
+	v1 ^= v0; v3 ^= v2;                       \
+	v0 = ROTL64 (v0,32);                      \
+	v2 += v1; v0 += v3;                       \
+	v1 = ROTL64 (v1,17); v3 = ROTL64 (v3,21); \
+	v1 ^= v2; v3 ^= v0;                       \
+	v2 = ROTL64(v2,32);
+
+	for (i = 0, blocks = (len & ~7); i < blocks; i += 8) {
+		mi = u8to64_le (m + i);
+		v3 ^= mi;
+		COMPRESS
+		COMPRESS
+		v0 ^= mi;
+	}
+
+	switch (len - blocks)
+	{
+	case 7: last7 |= (uint64_t) m[i + 6] << 48;
+	case 6: last7 |= (uint64_t) m[i + 5] << 40;
+	case 5: last7 |= (uint64_t) m[i + 4] << 32;
+	case 4: last7 |= (uint64_t) m[i + 3] << 24;
+	case 3: last7 |= (uint64_t) m[i + 2] << 16;
+	case 2: last7 |= (uint64_t) m[i + 1] <<  8;
+	case 1: last7 |= (uint64_t) m[i + 0]      ;
+	default:;
+	};
+	v3 ^= last7;
+	COMPRESS
+	COMPRESS
+	v0 ^= last7;
+	v2 ^= 0xff;
+	COMPRESS
+	COMPRESS
+	COMPRESS
+	COMPRESS
+
+	return v0 ^ v1 ^ v2 ^ v3;
+}
+
diff --git a/src/siphash.h b/src/siphash.h
new file mode 100644
index 0000000..dca7c42
--- /dev/null
+++ b/src/siphash.h
@@ -0,0 +1,10 @@
+#ifndef SIPHASH_H
+#define SIPHASH_H
+
+#include <stdint.h>
+#include <stdlib.h>
+
+uint64_t siphash (const unsigned char key[16],
+	const unsigned char *m, size_t len);
+
+#endif // SIPHASH_H
diff --git a/src/zyklonb.c b/src/zyklonb.c
new file mode 100644
index 0000000..a182d17
--- /dev/null
+++ b/src/zyklonb.c
@@ -0,0 +1,3320 @@
+/*
+ * zyklonb.c: the experimental IRC bot
+ *
+ * Copyright (c) 2014, Přemysl Janouch <p.janouch@gmail.com>
+ * All rights reserved.
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+ * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+ * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+ * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ */
+
+#define _POSIX_C_SOURCE 199309L
+#define _XOPEN_SOURCE 500
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
+#include <stdarg.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <ctype.h>
+
+#include <unistd.h>
+#include <sys/wait.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <poll.h>
+#include <signal.h>
+#include <strings.h>
+#include <regex.h>
+#include <libgen.h>
+
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <netdb.h>
+
+#ifndef NI_MAXHOST
+#define NI_MAXHOST 1025
+#endif // ! NI_MAXHOST
+
+#include <getopt.h>
+#include <openssl/ssl.h>
+#include <openssl/err.h>
+#include "siphash.h"
+
+#define PROGRAM_NAME "ZyklonB"
+#define PROGRAM_VERSION "alpha"
+
+extern char **environ;
+
+#if defined __GNUC__
+#define ATTRIBUTE_PRINTF(x, y) __attribute__ ((format (printf, x, y)))
+#else // ! __GNUC__
+#define ATTRIBUTE_PRINTF(x, y)
+#endif // ! __GNUC__
+
+#if defined __GNUC__ && __GNUC__ >= 4
+#define ATTRIBUTE_SENTINEL __attribute__ ((sentinel))
+#else // ! __GNUC__ || __GNUC__ < 4
+#define ATTRIBUTE_SENTINEL
+#endif // ! __GNUC__ || __GNUC__ < 4
+
+#define N_ELEMENTS(a) (sizeof (a) / sizeof ((a)[0]))
+
+#define BLOCK_START  do {
+#define BLOCK_END    } while (0)
+
+// --- Utilities ---------------------------------------------------------------
+
+static void
+print_message (FILE *stream, const char *type, const char *fmt, ...)
+	ATTRIBUTE_PRINTF (3, 4);
+
+static void
+print_message (FILE *stream, const char *type, const char *fmt, ...)
+{
+	va_list ap;
+
+	va_start (ap, fmt);
+	fprintf (stream, "%s ", type);
+	vfprintf (stream, fmt, ap);
+	fputs ("\n", stream);
+	va_end (ap);
+}
+
+#define print_fatal(...)    print_message (stderr, "fatal:",   __VA_ARGS__)
+#define print_error(...)    print_message (stderr, "error:",   __VA_ARGS__)
+#define print_warning(...)  print_message (stderr, "warning:", __VA_ARGS__)
+#define print_status(...)   print_message (stdout, "--",       __VA_ARGS__)
+
+// --- Debugging and assertions ------------------------------------------------
+
+// We should check everything that may possibly fail with at least a soft
+// assertion, so that any causes for problems don't slip us by silently.
+//
+// `g_soft_asserts_are_deadly' may be useful while running inside a debugger.
+
+static bool g_debug_mode;               ///< Debug messages are printed
+static bool g_soft_asserts_are_deadly;  ///< soft_assert() aborts as well
+
+#define print_debug(...)                                                       \
+	BLOCK_START                                                                \
+		if (g_debug_mode)                                                      \
+			print_message (stderr, "debug:", __VA_ARGS__);                     \
+	BLOCK_END
+
+static void
+assertion_failure_handler (bool is_fatal, const char *file, int line,
+	const char *function, const char *condition)
+{
+	if (is_fatal)
+	{
+		print_fatal ("assertion failed [%s:%d in function %s]: %s",
+			file, line, function, condition);
+		abort ();
+	}
+	else
+		print_debug ("assertion failed [%s:%d in function %s]: %s",
+			file, line, function, condition);
+}
+
+#define soft_assert(condition)                                                 \
+	((condition) ? true :                                                      \
+		(assertion_failure_handler (g_soft_asserts_are_deadly,                 \
+		__FILE__, __LINE__, __func__, #condition), false))
+
+#define hard_assert(condition)                                                 \
+	((condition) ? (void) 0 :                                                  \
+		assertion_failure_handler (true,                                       \
+		__FILE__, __LINE__, __func__, #condition))
+
+// --- Safe memory management --------------------------------------------------
+
+// When a memory allocation fails and we need the memory, we're usually pretty
+// much fucked.  Use the non-prefixed versions when there's a legitimate
+// worry that an unrealistic amount of memory may be requested for allocation.
+
+// XXX: it's not a good idea to use print_message() as it may want to allocate
+//   further memory for printf() and the output streams.  That may fail.
+
+static void *
+xmalloc (size_t n)
+{
+	void *p = malloc (n);
+	if (!p)
+	{
+		print_fatal ("malloc: %s", strerror (errno));
+		exit (EXIT_FAILURE);
+	}
+	return p;
+}
+
+static void *
+xcalloc (size_t n, size_t m)
+{
+	void *p = calloc (n, m);
+	if (!p && n && m)
+	{
+		print_fatal ("calloc: %s", strerror (errno));
+		exit (EXIT_FAILURE);
+	}
+	return p;
+}
+
+static void *
+xrealloc (void *o, size_t n)
+{
+	void *p = realloc (o, n);
+	if (!p && n)
+	{
+		print_fatal ("realloc: %s", strerror (errno));
+		exit (EXIT_FAILURE);
+	}
+	return p;
+}
+
+static void *
+xreallocarray (void *o, size_t n, size_t m)
+{
+	if (m && n > SIZE_MAX / m)
+	{
+		errno = ENOMEM;
+		print_fatal ("reallocarray: %s", strerror (errno));
+		exit (EXIT_FAILURE);
+	}
+	return xrealloc (o, n * m);
+}
+
+static char *
+xstrdup (const char *s)
+{
+	return strcpy (xmalloc (strlen (s) + 1), s);
+}
+
+static char *
+xstrndup (const char *s, size_t n)
+{
+	size_t size = strlen (s);
+	if (n > size)
+		n = size;
+
+	char *copy = xmalloc (n + 1);
+	memcpy (copy, s, n);
+	copy[n] = '\0';
+	return copy;
+}
+
+// --- Double-linked list helpers ----------------------------------------------
+
+// The links of the list need to have the members `prev' and `next'.
+
+#define LIST_PREPEND(head, link)                                               \
+	BLOCK_START                                                                \
+		(link)->prev = NULL;                                                   \
+		(link)->next = (head);                                                 \
+		if ((link)->next)                                                      \
+			(link)->next->prev = (link);                                       \
+		(head) = (link);                                                       \
+	BLOCK_END
+
+#define LIST_UNLINK(head, link)                                                \
+	BLOCK_START                                                                \
+		if ((link)->prev)                                                      \
+			(link)->prev->next = (link)->next;                                 \
+		else                                                                   \
+			(head) = (link)->next;                                             \
+		if ((link)->next)                                                      \
+			(link)->next->prev = (link)->prev;                                 \
+	BLOCK_END
+
+// --- Dynamically allocated string array --------------------------------------
+
+struct str_vector
+{
+	char **vector;
+	size_t len;
+	size_t alloc;
+};
+
+static void
+str_vector_init (struct str_vector *self)
+{
+	self->alloc = 4;
+	self->len = 0;
+	self->vector = xcalloc (sizeof *self->vector, self->alloc);
+}
+
+static void
+str_vector_free (struct str_vector *self)
+{
+	unsigned i;
+	for (i = 0; i < self->len; i++)
+		free (self->vector[i]);
+
+	free (self->vector);
+	self->vector = NULL;
+}
+
+static void
+str_vector_add_owned (struct str_vector *self, char *s)
+{
+	self->vector[self->len] = s;
+	if (++self->len >= self->alloc)
+		self->vector = xreallocarray (self->vector,
+			sizeof *self->vector, (self->alloc <<= 1));
+	self->vector[self->len] = NULL;
+}
+
+static void
+str_vector_add (struct str_vector *self, const char *s)
+{
+	str_vector_add_owned (self, xstrdup (s));
+}
+
+static void
+str_vector_add_args (struct str_vector *self, const char *s, ...)
+	ATTRIBUTE_SENTINEL;
+
+static void
+str_vector_add_args (struct str_vector *self, const char *s, ...)
+{
+	va_list ap;
+
+	va_start (ap, s);
+	while (s)
+	{
+		str_vector_add (self, s);
+		s = va_arg (ap, const char *);
+	}
+	va_end (ap);
+}
+
+static void
+str_vector_add_vector (struct str_vector *self, char **vector)
+{
+	while (*vector)
+		str_vector_add (self, *vector++);
+}
+
+static void
+str_vector_remove (struct str_vector *self, size_t i)
+{
+	hard_assert (i < self->len);
+	free (self->vector[i]);
+	memmove (self->vector + i, self->vector + i + 1,
+		(self->len-- - i) * sizeof *self->vector);
+}
+
+// --- Dynamically allocated strings -------------------------------------------
+
+// Basically a string builder to abstract away manual memory management.
+
+struct str
+{
+	char *str;                          ///< String data, null terminated
+	size_t alloc;                       ///< How many bytes are allocated
+	size_t len;                         ///< How long the string actually is
+};
+
+/// We don't care about allocations that are way too large for the content, as
+/// long as the allocation is below the given threshold.  (Trivial heuristics.)
+#define STR_SHRINK_THRESHOLD (1 << 20)
+
+static void
+str_init (struct str *self)
+{
+	self->alloc = 16;
+	self->len = 0;
+	self->str = strcpy (xmalloc (self->alloc), "");
+}
+
+static void
+str_free (struct str *self)
+{
+	free (self->str);
+	self->str = NULL;
+	self->alloc = 0;
+	self->len = 0;
+}
+
+static void
+str_reset (struct str *self)
+{
+	str_free (self);
+	str_init (self);
+}
+
+static char *
+str_steal (struct str *self)
+{
+	char *str = self->str;
+	self->str = NULL;
+	str_free (self);
+	return str;
+}
+
+static void
+str_ensure_space (struct str *self, size_t n)
+{
+	// We allocate at least one more byte for the terminating null character
+	size_t new_alloc = self->alloc;
+	while (new_alloc <= self->len + n)
+		new_alloc <<= 1;
+	if (new_alloc != self->alloc)
+		self->str = xrealloc (self->str, (self->alloc = new_alloc));
+}
+
+static void
+str_append_data (struct str *self, const char *data, size_t n)
+{
+	str_ensure_space (self, n);
+	memcpy (self->str + self->len, data, n);
+	self->len += n;
+	self->str[self->len] = '\0';
+}
+
+static void
+str_append_c (struct str *self, char c)
+{
+	str_append_data (self, &c, 1);
+}
+
+static void
+str_append (struct str *self, const char *s)
+{
+	str_append_data (self, s, strlen (s));
+}
+
+static void
+str_append_str (struct str *self, const struct str *another)
+{
+	str_append_data (self, another->str, another->len);
+}
+
+static int
+str_append_vprintf (struct str *self, const char *fmt, va_list va)
+{
+	va_list ap;
+	int size;
+
+	va_copy (ap, va);
+	size = vsnprintf (NULL, 0, fmt, ap);
+	va_end (ap);
+
+	if (size < 0)
+		return -1;
+
+	va_copy (ap, va);
+	str_ensure_space (self, size);
+	size = vsnprintf (self->str + self->len, self->alloc - self->len, fmt, ap);
+	va_end (ap);
+
+	if (size > 0)
+		self->len += size;
+
+	return size;
+}
+
+static int
+str_append_printf (struct str *self, const char *fmt, ...)
+	ATTRIBUTE_PRINTF (2, 3);
+
+static int
+str_append_printf (struct str *self, const char *fmt, ...)
+{
+	va_list ap;
+
+	va_start (ap, fmt);
+	int size = str_append_vprintf (self, fmt, ap);
+	va_end (ap);
+	return size;
+}
+
+static void
+str_remove_slice (struct str *self, size_t start, size_t length)
+{
+	size_t end = start + length;
+	hard_assert (end <= self->len);
+	memmove (self->str + start, self->str + end, self->len - end);
+	self->str[self->len -= length] = '\0';
+
+	// Shrink the string if the allocation becomes way too large
+	if (self->alloc >= STR_SHRINK_THRESHOLD && self->len < (self->alloc >> 2))
+		self->str = xrealloc (self->str, self->alloc >>= 2);
+}
+
+// --- Errors ------------------------------------------------------------------
+
+// Error reporting utilities.  Inspired by GError, only much simpler.
+
+struct error
+{
+	size_t domain;                      ///< The domain of the error
+	int id;                             ///< The concrete error ID
+	char *message;                      ///< Textual description of the event
+};
+
+static size_t
+error_resolve_domain (size_t *tag)
+{
+	// This method is fairly sensitive to the order in which resolution
+	// requests come in, does not provide a good way of decoding the number
+	// back to a meaningful identifier, and may not play all too well with
+	// dynamic libraries when a module is e.g. statically linked into multiple
+	// libraries, but it's fast, simple, and more than enough for our purposes.
+	static size_t domain_counter;
+
+	if (!*tag)
+		*tag = ++domain_counter;
+	return *tag;
+}
+
+static void
+error_set (struct error **e, size_t domain, int id,
+	const char *message, ...) ATTRIBUTE_PRINTF (4, 5);
+
+static void
+error_set (struct error **e, size_t domain, int id,
+	const char *message, ...)
+{
+	if (!e)
+		return;
+
+	va_list ap;
+	va_start (ap, message);
+	int size = snprintf (NULL, 0, message, ap);
+	va_end (ap);
+
+	hard_assert (size >= 0);
+
+	struct error *tmp = xmalloc (sizeof *tmp);
+	tmp->domain = domain;
+	tmp->id = id;
+	tmp->message = xmalloc (size + 1);
+
+	va_start (ap, message);
+	size = snprintf (tmp->message, size + 1, message, ap);
+	va_end (ap);
+
+	hard_assert (size >= 0);
+
+	soft_assert (*e == NULL);
+	*e = tmp;
+}
+
+static void
+error_free (struct error *e)
+{
+	free (e->message);
+	free (e);
+}
+
+static void
+error_propagate (struct error **destination, struct error *source)
+{
+	if (!destination)
+	{
+		error_free (source);
+		return;
+	}
+
+	soft_assert (*destination == NULL);
+	*destination = source;
+}
+
+// --- String hash map ---------------------------------------------------------
+
+// The most basic <string, managed pointer> map (or associative array).
+
+struct str_map_link
+{
+	struct str_map_link *next;          ///< The next link in a chain
+	struct str_map_link *prev;          ///< The previous link in a chain
+
+	void *data;                         ///< Payload
+	size_t key_length;                  ///< Length of the key without '\0'
+	char key[];                         ///< The key for this link
+};
+
+struct str_map
+{
+	struct str_map_link **map;          ///< The hash table data itself
+	size_t alloc;                       ///< Number of allocated entries
+	size_t len;                         ///< Number of entries in the table
+	void (*free) (void *);              ///< Callback to destruct the payload
+};
+
+#define STR_MAP_MIN_ALLOC 16
+
+typedef void (*str_map_free_func) (void *);
+
+static void
+str_map_init (struct str_map *self)
+{
+	self->alloc = STR_MAP_MIN_ALLOC;
+	self->len = 0;
+	self->free = NULL;
+	self->map = xcalloc (self->alloc, sizeof *self->map);
+}
+
+static void
+str_map_free (struct str_map *self)
+{
+	struct str_map_link **iter, **end = self->map + self->alloc;
+	struct str_map_link *link, *tmp;
+
+	for (iter = self->map; iter < end; iter++)
+		for (link = *iter; link; link = tmp)
+		{
+			tmp = link->next;
+			if (self->free)
+				self->free (link->data);
+			free (link);
+		}
+
+	free (self->map);
+	self->map = NULL;
+}
+
+static uint64_t
+str_map_hash (const char *s, size_t len)
+{
+	static unsigned char key[16] = "SipHash 2-4 key!";
+	return siphash (key, (const void *) s, len);
+}
+
+static uint64_t
+str_map_pos (struct str_map *self, const char *s)
+{
+	size_t mask = self->alloc - 1;
+	return str_map_hash (s, strlen (s)) & mask;
+}
+
+static uint64_t
+str_map_link_hash (struct str_map_link *self)
+{
+	return str_map_hash (self->key, self->key_length);
+}
+
+static void
+str_map_resize (struct str_map *self, size_t new_size)
+{
+	struct str_map_link **old_map = self->map;
+	size_t i, old_size = self->alloc;
+
+	// Only powers of two, so that we don't need to compute the modulo
+	hard_assert ((new_size & (new_size - 1)) == 0);
+	size_t mask = new_size - 1;
+
+	self->alloc = new_size;
+	self->map = xcalloc (self->alloc, sizeof *self->map);
+	for (i = 0; i < old_size; i++)
+	{
+		struct str_map_link *iter = old_map[i], *next_iter;
+		while (iter)
+		{
+			next_iter = iter->next;
+			uint64_t pos = str_map_link_hash (iter) & mask;
+			LIST_PREPEND (self->map[pos], iter);
+			iter = next_iter;
+		}
+	}
+
+	free (old_map);
+}
+
+static void
+str_map_set (struct str_map *self, const char *key, void *value)
+{
+	uint64_t pos = str_map_pos (self, key);
+	struct str_map_link *iter = self->map[pos];
+	for (; iter; iter = iter->next)
+	{
+		if (strcmp (key, iter->key))
+			continue;
+
+		// Storing the same data doesn't destroy it
+		if (self->free && value != iter->data)
+			self->free (iter->data);
+
+		if (value)
+		{
+			iter->data = value;
+			return;
+		}
+
+		LIST_UNLINK (self->map[pos], iter);
+		free (iter);
+		self->len--;
+
+		// The array should be at least 1/4 full
+		if (self->alloc >= (STR_MAP_MIN_ALLOC << 2)
+		 && self->len < (self->alloc >> 2))
+			str_map_resize (self, self->alloc >> 2);
+		return;
+	}
+
+	if (!value)
+		return;
+
+	if (self->len >= self->alloc)
+	{
+		str_map_resize (self, self->alloc << 1);
+		pos = str_map_pos (self, key);
+	}
+
+	// Link in a new element for the given <key, value> pair
+	size_t key_length = strlen (key);
+	struct str_map_link *link = xmalloc (sizeof *link + key_length + 1);
+	link->data = value;
+	link->key_length = key_length;
+	memcpy (link->key, key, key_length + 1);
+
+	LIST_PREPEND (self->map[pos], link);
+	self->len++;
+}
+
+static void *
+str_map_find (struct str_map *self, const char *key)
+{
+	struct str_map_link *iter = self->map[str_map_pos (self, key)];
+	for (; iter; iter = iter->next)
+		if (!strcmp (key, (char *) iter + sizeof *iter))
+			return iter->data;
+	return NULL;
+}
+
+// --- File descriptor utilities -----------------------------------------------
+
+static void
+set_cloexec (int fd)
+{
+	soft_assert (fcntl (fd, F_SETFD, fcntl (fd, F_GETFD) | FD_CLOEXEC) != -1);
+}
+
+static bool
+set_blocking (int fd, bool blocking)
+{
+	int flags = fcntl (fd, F_GETFL);
+	hard_assert (flags != -1);
+
+	bool prev = !(flags & O_NONBLOCK);
+	if (blocking)
+		flags &= ~O_NONBLOCK;
+	else
+		flags |=  O_NONBLOCK;
+
+	hard_assert (fcntl (fd, F_SETFL, flags) != -1);
+	return prev;
+}
+
+static void
+xclose (int fd)
+{
+	while (close (fd) == -1)
+		if (!soft_assert (errno == EINTR))
+			break;
+}
+
+// --- Polling -----------------------------------------------------------------
+
+// Basically the poor man's GMainLoop/libev/libuv.  It might make some sense
+// to instead use those tested and proven libraries but we don't need much
+// and it's interesting to implement.
+
+// At the moment the FD's are stored in an unsorted array.  This is not ideal
+// complexity-wise but I don't think I have much of a choice with poll(),
+// and neither with epoll for that matter.
+//
+//                         unsorted array       sorted array
+//           search             O(n)       O(log n) [O(log log n)]
+//           insert by fd       O(n)                O(n)
+//           delete by fd       O(n)                O(n)
+//
+// Insertion in the unsorted array can be reduced to O(1) if I maintain a
+// bitmap of present FD's but that's still not a huge win.
+//
+// I don't expect this to be much of an issue, as there are typically not going
+// to be that many FD's to watch, and the linear approach is cache-friendly.
+
+typedef void (*poller_dispatcher_func) (const struct pollfd *, void *);
+
+#define POLLER_MIN_ALLOC 16
+
+#ifdef __linux__
+
+// I don't really need this, I've basically implemented this just because I can.
+
+#include <sys/epoll.h>
+
+struct poller_info
+{
+	int fd;                             ///< Our file descriptor
+	uint32_t events;                    ///< The events we registered
+	poller_dispatcher_func dispatcher;  ///< Event dispatcher
+	void *user_data;                    ///< User data
+};
+
+struct poller
+{
+	int epoll_fd;                       ///< The epoll FD
+	struct poller_info **info;          ///< Information associated with each FD
+	struct epoll_event *revents;        ///< Output array for epoll_wait()
+	size_t len;                         ///< Number of polled descriptors
+	size_t alloc;                       ///< Number of entries allocated
+
+	/// Index of the element in `revents' that's currently being dispatched,
+	/// or -1 if we're not dispatching at the moment.
+	int dispatch_iterator;
+
+	/// The total number of entries stored in `revents' by epoll_wait().
+	int dispatch_total;
+};
+
+static void
+poller_init (struct poller *self)
+{
+	self->epoll_fd = epoll_create (POLLER_MIN_ALLOC);
+	hard_assert (self->epoll_fd != -1);
+	set_cloexec (self->epoll_fd);
+
+	self->len = 0;
+	self->alloc = POLLER_MIN_ALLOC;
+	self->info = xcalloc (self->alloc, sizeof *self->info);
+	self->revents = xcalloc (self->alloc, sizeof *self->revents);
+
+	self->dispatch_iterator = -1;
+	self->dispatch_total = 0;
+}
+
+static void
+poller_free (struct poller *self)
+{
+	for (size_t i = 0; i < self->len; i++)
+	{
+		struct poller_info *info = self->info[i];
+		hard_assert (epoll_ctl (self->epoll_fd,
+			EPOLL_CTL_DEL, info->fd, (void *) "") != -1);
+		free (info);
+	}
+
+	xclose (self->epoll_fd);
+	free (self->info);
+	free (self->revents);
+}
+
+static ssize_t
+poller_find_by_fd (struct poller *self, int fd)
+{
+	for (size_t i = 0; i < self->len; i++)
+		if (self->info[i]->fd == fd)
+			return i;
+	return -1;
+}
+
+static void
+poller_ensure_space (struct poller *self)
+{
+	if (self->len < self->alloc)
+		return;
+
+	self->alloc <<= 1;
+	self->revents = xreallocarray
+		(self->revents, sizeof *self->revents, self->alloc);
+	self->info = xreallocarray
+		(self->info, sizeof *self->info, self->alloc);
+}
+
+static int
+poller_epoll_to_poll_events (int events)
+{
+	int result = 0;
+	if (events & EPOLLIN)   result |= POLLIN;
+	if (events & EPOLLOUT)  result |= POLLOUT;
+	if (events & EPOLLERR)  result |= POLLERR;
+	if (events & EPOLLHUP)  result |= POLLHUP;
+	if (events & EPOLLPRI)  result |= POLLPRI;
+	return result;
+}
+
+static uint32_t
+poller_poll_to_epoll_events (uint32_t events)
+{
+	uint32_t result = 0;
+	if (events & POLLIN)   result |= EPOLLIN;
+	if (events & POLLOUT)  result |= EPOLLOUT;
+	if (events & POLLERR)  result |= EPOLLERR;
+	if (events & POLLHUP)  result |= EPOLLHUP;
+	if (events & POLLPRI)  result |= EPOLLPRI;
+	return result;
+}
+
+static void
+poller_set (struct poller *self, int fd, short int events,
+	poller_dispatcher_func dispatcher, void *data)
+{
+	ssize_t index = poller_find_by_fd (self, fd);
+	bool modifying = true;
+	if (index == -1)
+	{
+		poller_ensure_space (self);
+		self->info[index = self->len++] = xcalloc (1, sizeof **self->info);
+		modifying = false;
+	}
+
+	struct poller_info *info = self->info[index];
+	info->fd = fd;
+	info->dispatcher = dispatcher;
+	info->user_data = data;
+
+	struct epoll_event event;
+	event.events = poller_poll_to_epoll_events (events);
+	event.data.ptr = info;
+	hard_assert (epoll_ctl (self->epoll_fd,
+		modifying ? EPOLL_CTL_MOD : EPOLL_CTL_ADD, fd, &event) != -1);
+}
+
+static void
+poller_remove_from_dispatch (struct poller *self,
+	const struct poller_info *info)
+{
+	if (self->dispatch_iterator == -1)
+		return;
+
+	int i;
+	for (i = self->dispatch_iterator; i < self->dispatch_total; i++)
+		if (self->revents[i].data.ptr == info)
+			break;
+	if (i == self->dispatch_total)
+		return;
+
+	if (i != --self->dispatch_total)
+		self->revents[i] = self->revents[self->dispatch_total];
+
+	// We've removed the element we're currently processing; go back one entry
+	// so that we don't skip the one we might have replaced it with.
+	if (i == self->dispatch_iterator)
+		self->dispatch_iterator--;
+}
+
+static void
+poller_remove_at_index (struct poller *self, size_t index)
+{
+	hard_assert (index < self->len);
+	struct poller_info *info = self->info[index];
+
+	poller_remove_from_dispatch (self, info);
+	hard_assert (epoll_ctl (self->epoll_fd,
+		EPOLL_CTL_DEL, info->fd, (void *) "") != -1);
+
+	free (info);
+	if (index != --self->len)
+		self->info[index] = self->info[self->len];
+}
+
+static void
+poller_run (struct poller *self)
+{
+	// Not reentrant
+	hard_assert (self->dispatch_iterator == -1);
+
+	int n_fds;
+	do
+		n_fds = epoll_wait (self->epoll_fd, self->revents, self->len, -1);
+	while (n_fds == -1 && errno == EINTR);
+
+	if (n_fds == -1)
+	{
+		print_fatal ("%s: %s", "epoll", strerror (errno));
+		exit (EXIT_FAILURE);
+	}
+
+	for (int i = 0; i < n_fds; i++)
+	{
+		struct epoll_event *revents = self->revents + i;
+		struct poller_info *info = revents->data.ptr;
+
+		struct pollfd pfd;
+		pfd.fd = info->fd;
+		pfd.revents = poller_epoll_to_poll_events (revents->events);
+		pfd.events = poller_epoll_to_poll_events (info->events);
+
+		self->dispatch_iterator = i;
+		self->dispatch_total = n_fds;
+
+		info->dispatcher (&pfd, info->user_data);
+
+		i = self->dispatch_iterator;
+		n_fds = self->dispatch_total;
+	}
+
+	self->dispatch_iterator = -1;
+	self->dispatch_total = 0;
+}
+
+#else  // !__linux__
+
+struct poller_info
+{
+	poller_dispatcher_func dispatcher;  ///< Event dispatcher
+	void *user_data;                    ///< User data
+};
+
+struct poller
+{
+	struct pollfd *fds;                 ///< Polled descriptors
+	struct poller_info *fds_info;       ///< Additional information for each FD
+	size_t len;                         ///< Number of polled descriptors
+	size_t alloc;                       ///< Number of entries allocated
+
+	int dispatch_index;                 ///< The currently dispatched FD or -1
+};
+
+static void
+poller_init (struct poller *self)
+{
+	self->alloc = POLLER_MIN_ALLOC;
+	self->len = 0;
+	self->fds = xcalloc (self->alloc, sizeof *self->fds);
+	self->fds_info = xcalloc (self->alloc, sizeof *self->fds_info);
+	self->dispatch_index = -1;
+}
+
+static void
+poller_free (struct poller *self)
+{
+	free (self->fds);
+	free (self->fds_info);
+}
+
+static ssize_t
+poller_find_by_fd (struct poller *self, int fd)
+{
+	for (size_t i = 0; i < self->len; i++)
+		if (self->fds[i].fd == fd)
+			return i;
+	return -1;
+}
+
+static void
+poller_ensure_space (struct poller *self)
+{
+	if (self->len < self->alloc)
+		return;
+
+	self->alloc <<= 1;
+	self->fds = xreallocarray (self->fds, sizeof *self->fds, self->alloc);
+	self->fds_info = xreallocarray
+		(self->fds_info, sizeof *self->fds_info, self->alloc);
+}
+
+static void
+poller_set (struct poller *self, int fd, short int events,
+	poller_dispatcher_func dispatcher, void *data)
+{
+	ssize_t index = poller_find_by_fd (self, fd);
+	if (index == -1)
+	{
+		poller_ensure_space (self);
+		index = self->len++;
+	}
+
+	struct pollfd *new_entry = self->fds + index;
+	memset (new_entry, 0, sizeof *new_entry);
+	new_entry->fd = fd;
+	new_entry->events = events;
+
+	self->fds_info[self->len] = (struct poller_info) { dispatcher, data };
+}
+
+static void
+poller_remove_at_index (struct poller *self, size_t index)
+{
+	hard_assert (index < self->len);
+	if (index == --self->len)
+		return;
+
+	// Make sure that we don't disrupt the dispatch loop; kind of crude
+	if ((int) index < self->dispatch_index)
+	{
+		memmove (self->fds + index, self->fds + index + 1,
+			(self->len - index) * sizeof *self->fds);
+		memmove (self->fds_info + index, self->fds_info + index + 1,
+			(self->len - index) * sizeof *self->fds_info);
+	}
+	else
+	{
+		self->fds[index]      = self->fds[self->len];
+		self->fds_info[index] = self->fds_info[self->len];
+	}
+
+	if ((int) index <= self->dispatch_index)
+		self->dispatch_index--;
+}
+
+static void
+poller_run (struct poller *self)
+{
+	// Not reentrant
+	hard_assert (self->dispatch_index == -1);
+
+	int result;
+	do
+		result = poll (self->fds, self->len, -1);
+	while (result == -1 && errno == EINTR);
+
+	if (result == -1)
+	{
+		print_fatal ("%s: %s", "poll", strerror (errno));
+		exit (EXIT_FAILURE);
+	}
+
+	for (int i = 0; i < (int) self->len; i++)
+	{
+		struct pollfd pfd = self->fds[i];
+		if (!pfd.revents)
+			continue;
+
+		struct poller_info *info = self->fds_info + i;
+		self->dispatch_index = i;
+		info->dispatcher (&pfd, info->user_data);
+		i = self->dispatch_index;
+	}
+
+	self->dispatch_index = -1;
+}
+
+#endif  // !__linux__
+
+// --- Utilities ---------------------------------------------------------------
+
+static void
+split_str_ignore_empty (const char *s, char delimiter, struct str_vector *out)
+{
+	const char *begin = s, *end;
+
+	while ((end = strchr (begin, delimiter)))
+	{
+		if (begin != end)
+			str_vector_add_owned (out, xstrndup (begin, end - begin));
+		begin = ++end;
+	}
+
+	if (*begin)
+		str_vector_add (out, begin);
+}
+
+static char *
+strip_str_in_place (char *s, const char *stripped_chars)
+{
+	char *end = s + strlen (s);
+	while (end > s && strchr (stripped_chars, end[-1]))
+		*--end = '\0';
+
+	char *start = s + strspn (s, stripped_chars);
+	if (start > s)
+		memmove (s, start, end - start + 1);
+	return s;
+}
+
+static bool
+str_append_env_path (struct str *output, const char *var, bool only_absolute)
+{
+	const char *value = getenv (var);
+
+	if (!value || (only_absolute && *value != '/'))
+		return false;
+
+	str_append (output, value);
+	return true;
+}
+
+static void
+get_xdg_home_dir (struct str *output, const char *var, const char *def)
+{
+	str_reset (output);
+	if (!str_append_env_path (output, var, true))
+	{
+		str_append_env_path (output, "HOME", false);
+		str_append_c (output, '/');
+		str_append (output, def);
+	}
+}
+
+static size_t io_error_domain_tag;
+#define IO_ERROR (error_resolve_domain (&io_error_domain_tag))
+
+enum
+{
+	IO_ERROR_FAILED
+};
+
+static bool
+ensure_directory_existence (const char *path, struct error **e)
+{
+	struct stat st;
+
+	if (stat (path, &st))
+	{
+		if (mkdir (path, S_IRWXU | S_IRWXG | S_IRWXO))
+		{
+			error_set (e, IO_ERROR, IO_ERROR_FAILED,
+				"cannot create directory `%s': %s",
+				path, strerror (errno));
+			return false;
+		}
+	}
+	else if (!S_ISDIR (st.st_mode))
+	{
+		error_set (e, IO_ERROR, IO_ERROR_FAILED,
+			"cannot create directory `%s': %s",
+			path, "file exists but is not a directory");
+		return false;
+	}
+	return true;
+}
+
+static bool
+mkdir_with_parents (char *path, struct error **e)
+{
+	char *p = path;
+
+	// XXX: This is prone to the TOCTTOU problem.  The solution would be to
+	//   rewrite the function using the {mkdir,fstat}at() functions from
+	//   POSIX.1-2008, ideally returning a file descriptor to the open
+	//   directory, with the current code as a fallback.  Or to use chdir().
+	while ((p = strchr (p + 1, '/')))
+	{
+		*p = '\0';
+		bool success = ensure_directory_existence (path, e);
+		*p = '/';
+
+		if (!success)
+			return false;
+	}
+
+	return ensure_directory_existence (path, e);
+}
+
+static bool
+set_boolean_if_valid (bool *out, const char *s)
+{
+	if      (!strcasecmp (s, "yes"))    *out = true;
+	else if (!strcasecmp (s, "no"))     *out = false;
+	else if (!strcasecmp (s, "on"))     *out = true;
+	else if (!strcasecmp (s, "off"))    *out = false;
+	else if (!strcasecmp (s, "true"))   *out = true;
+	else if (!strcasecmp (s, "false"))  *out = false;
+	else return false;
+
+	return true;
+}
+
+static void
+regerror_to_str (int code, const regex_t *preg, struct str *out)
+{
+	size_t required = regerror (code, preg, NULL, 0);
+	str_ensure_space (out, required);
+	out->len += regerror (code, preg,
+		out->str + out->len, out->alloc - out->len) - 1;
+}
+
+static size_t regex_error_domain_tag;
+#define REGEX_ERROR (error_resolve_domain (&regex_error_domain_tag))
+
+enum
+{
+	REGEX_ERROR_COMPILATION_FAILED
+};
+
+static bool
+regex_match (const char *regex, const char *s, struct error **e)
+{
+	regex_t re;
+	int err = regcomp (&re, regex, REG_EXTENDED | REG_NOSUB);
+	if (err)
+	{
+		struct str desc;
+
+		str_init (&desc);
+		regerror_to_str (err, &re, &desc);
+		error_set (e, REGEX_ERROR, REGEX_ERROR_COMPILATION_FAILED,
+			"failed to compile regular expression: %s", desc.str);
+		str_free (&desc);
+		return false;
+	}
+
+	bool result = regexec (&re, s, 0, NULL, 0) != REG_NOMATCH;
+	regfree (&re);
+	return result;
+}
+
+static bool
+read_line (FILE *fp, struct str *s)
+{
+	int c;
+	bool at_end = true;
+
+	str_reset (s);
+	while ((c = fgetc (fp)) != EOF)
+	{
+		at_end = false;
+		if (c == '\r')
+			continue;
+		if (c == '\n')
+			break;
+		str_append_c (s, c);
+	}
+
+	return !at_end;
+}
+
+// --- IRC utilities -----------------------------------------------------------
+
+struct irc_message
+{
+	char *prefix;
+	char *command;
+	struct str_vector params;
+};
+
+static void
+irc_parse_message (struct irc_message *msg, const char *line)
+{
+	msg->prefix = NULL;
+	msg->command = NULL;
+	str_vector_init (&msg->params);
+
+	// Prefix
+	if (*line == ':')
+	{
+		size_t prefix_len = strcspn (++line, " ");
+		msg->prefix = xstrndup (line, prefix_len);
+		line += prefix_len;
+	}
+
+	// Command name
+	{
+		while (*line == ' ')
+			line++;
+
+		size_t cmd_len = strcspn (line, " ");
+		msg->command = xstrndup (line, cmd_len);
+		line += cmd_len;
+	}
+
+	// Arguments
+	while (true)
+	{
+		while (*line == ' ')
+			line++;
+
+		if (*line == ':')
+		{
+			str_vector_add (&msg->params, ++line);
+			break;
+		}
+
+		size_t param_len = strcspn (line, " ");
+		if (!param_len)
+			break;
+
+		str_vector_add_owned (&msg->params, xstrndup (line, param_len));
+		line += param_len;
+	}
+}
+
+static void
+irc_free_message (struct irc_message *msg)
+{
+	free (msg->prefix);
+	free (msg->command);
+	str_vector_free (&msg->params);
+}
+
+static void
+irc_process_buffer (struct str *buf,
+	void (*callback)(const struct irc_message *, const char *, void *),
+	void *user_data)
+{
+	char *start = buf->str;
+	char *end = start + buf->len;
+
+	for (char *p = start; p + 1 < end; p++)
+	{
+		// Split the input on newlines
+		if (p[0] != '\r' || p[1] != '\n')
+			continue;
+
+		*p = 0;
+
+		struct irc_message msg;
+		irc_parse_message (&msg, start);
+		callback (&msg, start, user_data);
+		irc_free_message (&msg);
+
+		start = p + 2;
+	}
+
+	str_remove_slice (buf, 0, start - buf->str);
+}
+
+// --- Configuration -----------------------------------------------------------
+
+// The keys are stripped of surrounding whitespace, the values are not.
+
+static size_t config_error_domain_tag;
+#define CONFIG_ERROR (error_resolve_domain (&config_error_domain_tag))
+
+enum
+{
+	CONFIG_ERROR_MALFORMED
+};
+
+struct config_item
+{
+	const char *key;
+	const char *default_value;
+	const char *description;
+};
+
+static FILE *
+get_config_file (void)
+{
+	struct str_vector paths;
+	struct str config_home, file;
+	const char *xdg_config_dirs;
+	unsigned i;
+	FILE *fp = NULL;
+
+	str_vector_init (&paths);
+
+	str_init (&config_home);
+	get_xdg_home_dir (&config_home, "XDG_CONFIG_HOME", ".config");
+	str_vector_add (&paths, config_home.str);
+	str_free (&config_home);
+
+	if ((xdg_config_dirs = getenv ("XDG_CONFIG_DIRS")))
+		split_str_ignore_empty (xdg_config_dirs, ':', &paths);
+
+	str_init (&file);
+	for (i = 0; i < paths.len; i++)
+	{
+		// As per spec, relative paths are ignored
+		if (*paths.vector[i] != '/')
+			continue;
+
+		str_reset (&file);
+		str_append (&file, paths.vector[i]);
+		str_append (&file, "/" PROGRAM_NAME "/" PROGRAM_NAME ".conf");
+
+		if ((fp = fopen (file.str, "r")))
+			break;
+	}
+
+	str_free (&file);
+	str_vector_free (&paths);
+	return fp;
+}
+
+static bool
+read_config_file (struct str_map *config, struct error **e)
+{
+	struct str line;
+	FILE *fp = get_config_file ();
+	unsigned line_no = 0;
+	bool errors = false;
+
+	if (!fp)
+		return true;
+
+	str_init (&line);
+	for (line_no = 1; read_line (fp, &line); line_no++)
+	{
+		char *start = line.str;
+		if (*start == '#')
+			continue;
+
+		while (isspace (*start))
+			start++;
+
+		char *end = strchr (start, '=');
+		if (!end)
+		{
+			if (*start)
+			{
+				error_set (e, CONFIG_ERROR, CONFIG_ERROR_MALFORMED,
+					"line %u in config: %s", line_no, "malformed input");
+				errors = true;
+				break;
+			}
+		}
+		else
+		{
+			char *value = end + 1;
+			do
+				*end = '\0';
+			while (isspace (*--end));
+
+			str_map_set (config, start, xstrdup (value));
+		}
+	}
+
+	str_free (&line);
+	fclose (fp);
+
+	return !errors;
+}
+
+// --- Configuration (application-specific) ------------------------------------
+
+static struct config_item g_config_table[] =
+{
+	{ "nickname",        "ZyklonB",         "IRC nickname"                   },
+	{ "username",        "bot",             "IRC user name"                  },
+	{ "fullname",        "ZyklonB IRC bot", "IRC full name/e-mail"           },
+
+	{ "irc_host",        NULL,              "Address of the IRC server"      },
+	{ "irc_port",        "6667",            "Port of the IRC server"         },
+	{ "ssl_use",         "off",             "Whether to use SSL"             },
+	{ "ssl_cert",        NULL,              "Client SSL certificate (PEM)"   },
+	{ "autojoin",        NULL,              "Channels to join on start"      },
+	{ "reconnect",       "on",              "Whether to reconnect on error"  },
+	{ "reconnect_delay", "5",               "Time between reconnecting"      },
+
+	{ "prefix",          ":",               "The prefix for bot commands"    },
+	{ "admin",           NULL,              "Host mask for administrators"   },
+	{ "plugins",         NULL,              "The plugins to load on startup" },
+	{ "plugin_dir",      NULL,              "Where to search for plugins"    },
+	{ "recover",         "on",              "Whether to re-launch on crash"  },
+};
+
+static void
+load_config_defaults (struct str_map *config)
+{
+	for (size_t i = 0; i < N_ELEMENTS (g_config_table); i++)
+	{
+		const struct config_item *item = g_config_table + i;
+		if (item->default_value)
+			str_map_set (config, item->key, xstrdup (item->default_value));
+	}
+}
+
+// --- Application data --------------------------------------------------------
+
+struct plugin_data
+{
+	struct plugin_data *next;           ///< The next link in a chain
+	struct plugin_data *prev;           ///< The previous link in a chain
+
+	struct bot_context *ctx;            ///< Parent context
+
+	pid_t pid;                          ///< PID of the plugin process
+	char *name;                         ///< Plugin identifier
+
+	bool is_zombie;                     ///< Whether the child is a zombie
+	bool initialized;                   ///< Ready to exchange IRC messages
+	struct str queued_output;           ///< Output queued up until initialized
+
+	// Since we're doing non-blocking I/O, we need to queue up data so that
+	// we don't stall on plugins unnecessarily.
+
+	int read_fd;                        ///< The read end of the comm. pipe
+	struct str read_buffer;             ///< Unprocessed input
+
+	int write_fd;                       ///< The write end of the comm. pipe
+	struct str write_buffer;            ///< Output yet to be sent out
+};
+
+static void
+plugin_data_init (struct plugin_data *self)
+{
+	memset (self, 0, sizeof *self);
+
+	self->pid = -1;
+	str_init (&self->queued_output);
+
+	self->read_fd = -1;
+	str_init (&self->read_buffer);
+	self->write_fd = -1;
+	str_init (&self->write_buffer);
+}
+
+static void
+plugin_data_free (struct plugin_data *self)
+{
+	soft_assert (self->pid == -1);
+	free (self->name);
+
+	str_free (&self->read_buffer);
+	if (!soft_assert (self->read_fd == -1))
+		xclose (self->read_fd);
+
+	str_free (&self->write_buffer);
+	if (!soft_assert (self->write_fd == -1))
+		xclose (self->write_fd);
+
+	if (!self->initialized)
+		str_free (&self->queued_output);
+}
+
+static size_t connect_error_domain_tag;
+#define CONNECT_ERROR (error_resolve_domain (&connect_error_domain_tag))
+
+enum
+{
+	CONNECT_ERROR_INVALID_CONFIGURATION,
+	CONNECT_ERROR_FAILED
+};
+
+struct bot_context
+{
+	struct str_map config;              ///< User configuration
+
+	int irc_fd;                         ///< Socket FD of the server
+	struct str read_buffer;             ///< Input yet to be processed
+	bool irc_ready;                     ///< Whether we may send messages now
+
+	SSL_CTX *ssl_ctx;                   ///< SSL context
+	SSL *ssl;                           ///< SSL connection
+
+	struct plugin_data *plugins;        ///< Linked list of plugins
+	struct str_map plugins_by_name;     ///< Indexes @em plugins by their name
+
+	struct poller poller;               ///< Manages polled descriptors
+	bool quitting;                      ///< User requested quitting
+	bool polling;                       ///< The event loop is running
+};
+
+static void
+bot_context_init (struct bot_context *ctx)
+{
+	str_map_init (&ctx->config);
+	ctx->config.free = free;
+	load_config_defaults (&ctx->config);
+
+	ctx->irc_fd = -1;
+	str_init (&ctx->read_buffer);
+	ctx->irc_ready = false;
+
+	ctx->ssl = NULL;
+	ctx->ssl_ctx = NULL;
+
+	ctx->plugins = NULL;
+	str_map_init (&ctx->plugins_by_name);
+
+	poller_init (&ctx->poller);
+	ctx->quitting = false;
+	ctx->polling = false;
+}
+
+static void
+bot_context_free (struct bot_context *ctx)
+{
+	str_map_free (&ctx->config);
+	str_free (&ctx->read_buffer);
+
+	// TODO: terminate the plugins properly before this is called
+	struct plugin_data *link, *tmp;
+	for (link = ctx->plugins; link; link = tmp)
+	{
+		tmp = link->next;
+		plugin_data_free (link);
+		free (link);
+	}
+
+	if (ctx->irc_fd != -1)
+		xclose (ctx->irc_fd);
+	if (ctx->ssl)
+		SSL_free (ctx->ssl);
+	if (ctx->ssl_ctx)
+		SSL_CTX_free (ctx->ssl_ctx);
+
+	str_map_free (&ctx->plugins_by_name);
+	poller_free (&ctx->poller);
+}
+
+static void
+irc_shutdown (struct bot_context *ctx)
+{
+	// Generally non-critical
+	if (ctx->ssl)
+		soft_assert (SSL_shutdown (ctx->ssl) != -1);
+	else
+		soft_assert (shutdown (ctx->irc_fd, SHUT_WR) == 0);
+}
+
+static void
+initiate_quit (struct bot_context *ctx)
+{
+	irc_shutdown (ctx);
+	ctx->quitting = true;
+}
+
+static void
+try_finish_quit (struct bot_context *ctx)
+{
+	if (!ctx->quitting)
+		return;
+	if (ctx->irc_fd == -1 && !ctx->plugins)
+		ctx->polling = false;
+}
+
+static bool irc_send (struct bot_context *ctx,
+	const char *format, ...) ATTRIBUTE_PRINTF (2, 3);
+
+// XXX: is it okay to just ignore the return value and wait until we receive
+//   it in on_irc_readable()?
+static bool
+irc_send (struct bot_context *ctx, const char *format, ...)
+{
+	va_list ap;
+
+	if (g_debug_mode)
+	{
+		fputs ("[IRC] <== \"", stderr);
+		va_start (ap, format);
+		vfprintf (stderr, format, ap);
+		va_end (ap);
+		fputs ("\"\n", stderr);
+	}
+
+	soft_assert (ctx->irc_fd != -1);
+
+	va_start (ap, format);
+	struct str str;
+	str_init (&str);
+	str_append_vprintf (&str, format, ap);
+	str_append (&str, "\r\n");
+	va_end (ap);
+
+	bool result = true;
+	if (ctx->ssl)
+	{
+		// TODO: call SSL_get_error() to detect if a clean shutdown has occured
+		if (SSL_write (ctx->ssl, str.str, str.len) != (int) str.len)
+		{
+			print_debug ("%s: %s: %s", __func__, "SSL_write",
+				ERR_error_string (ERR_get_error (), NULL));
+			result = false;
+		}
+	}
+	else if (write (ctx->irc_fd, str.str, str.len) != (ssize_t) str.len)
+	{
+		print_debug ("%s: %s: %s", __func__, "write", strerror (errno));
+		result = false;
+	}
+
+	str_free (&str);
+	return result;
+}
+
+static bool
+irc_initialize_ssl (struct bot_context *ctx, struct error **e)
+{
+	ctx->ssl_ctx = SSL_CTX_new (SSLv23_client_method ());
+	if (!ctx->ssl_ctx)
+		goto error_ssl_1;
+	// We don't care; some encryption is always better than no encryption
+	SSL_CTX_set_verify (ctx->ssl_ctx, SSL_VERIFY_NONE, NULL);
+	// XXX: maybe we should call SSL_CTX_set_options() for some workarounds
+
+	ctx->ssl = SSL_new (ctx->ssl_ctx);
+	if (!ctx->ssl)
+		goto error_ssl_2;
+
+	const char *ssl_cert = str_map_find (&ctx->config, "ssl_cert");
+	if (ssl_cert
+	 && !SSL_use_certificate_file (ctx->ssl, ssl_cert, SSL_FILETYPE_PEM))
+	{
+		// XXX: perhaps we should read the file ourselves for better messages
+		print_error ("%s: %s", "setting the SSL client certificate failed",
+			ERR_error_string (ERR_get_error (), NULL));
+	}
+
+	SSL_set_connect_state (ctx->ssl);
+	if (!SSL_set_fd (ctx->ssl, ctx->irc_fd))
+		goto error_ssl_3;
+	// Avoid SSL_write() returning SSL_ERROR_WANT_READ
+	SSL_set_mode (ctx->ssl, SSL_MODE_AUTO_RETRY);
+	if (SSL_connect (ctx->ssl) > 0)
+		return true;
+
+error_ssl_3:
+	SSL_free (ctx->ssl);
+	ctx->ssl = NULL;
+error_ssl_2:
+	SSL_CTX_free (ctx->ssl_ctx);
+	ctx->ssl_ctx = NULL;
+error_ssl_1:
+	// XXX: these error strings are really nasty; also there could be
+	//   multiple errors on the OpenSSL stack.
+	error_set (e, CONNECT_ERROR, CONNECT_ERROR_FAILED,
+		"%s: %s", "could not initialize SSL",
+		ERR_error_string (ERR_get_error (), NULL));
+	return false;
+}
+
+static bool
+irc_establish_connection (struct bot_context *ctx,
+	const char *host, const char *port, bool use_ssl, struct error **e)
+{
+	struct addrinfo gai_hints, *gai_result, *gai_iter;
+	memset (&gai_hints, 0, sizeof gai_hints);
+
+	// We definitely want TCP.
+	gai_hints.ai_socktype = SOCK_STREAM;
+
+	int err = getaddrinfo (host, port, &gai_hints, &gai_result);
+	if (err)
+	{
+		error_set (e, CONNECT_ERROR, CONNECT_ERROR_FAILED, "%s: %s: %s",
+			"connection failed", "getaddrinfo", gai_strerror (err));
+		return false;
+	}
+
+	int sockfd;
+	for (gai_iter = gai_result; gai_iter; gai_iter = gai_iter->ai_next)
+	{
+		sockfd = socket (gai_iter->ai_family,
+			gai_iter->ai_socktype, gai_iter->ai_protocol);
+		if (sockfd == -1)
+			continue;
+		set_cloexec (sockfd);
+
+		int yes = 1;
+		soft_assert (setsockopt (sockfd, SOL_SOCKET, SO_KEEPALIVE,
+			&yes, sizeof yes) != -1);
+
+		const char *real_host = host;
+
+		// Let's try to resolve the address back into a real hostname;
+		// we don't really need this, so we can let it quietly fail
+		char buf[NI_MAXHOST];
+		err = getnameinfo (gai_iter->ai_addr, gai_iter->ai_addrlen,
+			buf, sizeof buf, NULL, 0, 0);
+		if (err)
+			print_debug ("%s: %s", "getnameinfo", gai_strerror (err));
+		else
+			real_host = buf;
+
+		// XXX: we shouldn't mix these statuses with `struct error'; choose 1!
+		print_status ("connecting to `%s:%s'...", real_host, port);
+		if (!connect (sockfd, gai_iter->ai_addr, gai_iter->ai_addrlen))
+			break;
+
+		xclose (sockfd);
+	}
+
+	freeaddrinfo (gai_result);
+
+	if (!gai_iter)
+	{
+		error_set (e, CONNECT_ERROR, CONNECT_ERROR_FAILED, "connection failed");
+		return false;
+	}
+
+	ctx->irc_fd = sockfd;
+	if (use_ssl && !irc_initialize_ssl (ctx, e))
+	{
+		xclose (ctx->irc_fd);
+		ctx->irc_fd = -1;
+		return false;
+	}
+
+	print_status ("connection established");
+	return true;
+}
+
+// --- Signals -----------------------------------------------------------------
+
+static int g_signal_pipe[2];            ///< A pipe used to signal... signals
+
+static struct str_vector
+	g_original_argv,                    ///< Original program arguments
+	g_recovery_env;                     ///< Environment for re-exec recovery
+
+/// Program termination has been requested by a signal
+static volatile sig_atomic_t g_termination_requested;
+
+/// Points to startup reason location within `g_recovery_environment'
+static char **g_startup_reason_location;
+/// The environment variable used to pass the startup reason when re-executing
+static const char g_startup_reason_str[] = "STARTUP_REASON";
+
+static void
+sigchld_handler (int signum)
+{
+	(void) signum;
+
+	int original_errno = errno;
+	// Just so that the read end of the pipe wakes up the poller.
+	// NOTE: Linux has signalfd() and eventfd(), and the BSD's have kqueue.
+	//   All of them are better than this approach, although platform-specific.
+	if (write (g_signal_pipe[1], "c", 1) == -1)
+		soft_assert (errno == EAGAIN);
+	errno = original_errno;
+}
+
+static void
+sigterm_handler (int signum)
+{
+	(void) signum;
+
+	g_termination_requested = true;
+
+	int original_errno = errno;
+	if (write (g_signal_pipe[1], "t", 1) == -1)
+		soft_assert (errno == EAGAIN);
+	errno = original_errno;
+}
+
+static void
+setup_signal_handlers (void)
+{
+	if (pipe (g_signal_pipe) == -1)
+	{
+		print_fatal ("pipe: %s", strerror (errno));
+		exit (EXIT_FAILURE);
+	}
+
+	set_cloexec (g_signal_pipe[0]);
+	set_cloexec (g_signal_pipe[1]);
+
+	// So that the pipe cannot overflow; it would make write() block within
+	// the signal handler, which is something we really don't want to happen.
+	// The same holds true for read().
+	set_blocking (g_signal_pipe[0], false);
+	set_blocking (g_signal_pipe[1], false);
+
+	struct sigaction sa;
+	sa.sa_flags = SA_RESTART;
+	sa.sa_handler = sigchld_handler;
+	sigemptyset (&sa.sa_mask);
+
+	if (sigaction (SIGCHLD, &sa, NULL) == -1)
+	{
+		print_fatal ("sigaction: %s", strerror (errno));
+		exit (EXIT_FAILURE);
+	}
+
+	signal (SIGPIPE, SIG_IGN);
+
+	sa.sa_handler = sigterm_handler;
+	if (sigaction (SIGINT, &sa, NULL) == -1
+	 || sigaction (SIGTERM, &sa, NULL) == -1)
+		print_error ("sigaction: %s", strerror (errno));
+}
+
+static void
+translate_signal_info (int no, const char **name, int code, const char **reason)
+{
+	if (code == SI_USER)         *reason = "signal sent by kill()";
+	if (code == SI_QUEUE)        *reason = "signal sent by sigqueue()";
+
+	switch (no)
+	{
+	case SIGILL:
+		*name = "SIGILL";
+		if (code == ILL_ILLOPC)  *reason = "illegal opcode";
+		if (code == ILL_ILLOPN)  *reason = "illegal operand";
+		if (code == ILL_ILLADR)  *reason = "illegal addressing mode";
+		if (code == ILL_ILLTRP)  *reason = "illegal trap";
+		if (code == ILL_PRVOPC)  *reason = "privileged opcode";
+		if (code == ILL_PRVREG)  *reason = "privileged register";
+		if (code == ILL_COPROC)  *reason = "coprocessor error";
+		if (code == ILL_BADSTK)  *reason = "internal stack error";
+		break;
+	case SIGFPE:
+		*name = "SIGFPE";
+		if (code == FPE_INTDIV)  *reason = "integer divide by zero";
+		if (code == FPE_INTOVF)  *reason = "integer overflow";
+		if (code == FPE_FLTDIV)  *reason = "floating-point divide by zero";
+		if (code == FPE_FLTOVF)  *reason = "floating-point overflow";
+		if (code == FPE_FLTUND)  *reason = "floating-point underflow";
+		if (code == FPE_FLTRES)  *reason = "floating-point inexact result";
+		if (code == FPE_FLTINV)  *reason = "invalid floating-point operation";
+		if (code == FPE_FLTSUB)  *reason = "subscript out of range";
+		break;
+	case SIGSEGV:
+		*name = "SIGSEGV";
+		if (code == SEGV_MAPERR)
+			*reason = "address not mapped to object";
+		if (code == SEGV_ACCERR)
+			*reason = "invalid permissions for mapped object";
+		break;
+	case SIGBUS:
+		*name = "SIGBUS";
+		if (code == BUS_ADRALN)  *reason = "invalid address alignment";
+		if (code == BUS_ADRERR)  *reason = "nonexistent physical address";
+		if (code == BUS_OBJERR)  *reason = "object-specific hardware error";
+		break;
+	default:
+		*name = NULL;
+	}
+}
+
+static void
+recovery_handler (int signum, siginfo_t *info, void *context)
+{
+	(void) context;
+
+	// TODO: maybe try to force a core dump like this: if (fork() == 0) return;
+	// TODO: maybe we could even send "\r\nQUIT :reason\r\n" to the server. >_>
+	//   As long as we're not connected via TLS, that is.
+
+	const char *signal_name = NULL, *reason = NULL;
+	translate_signal_info (signum, &signal_name, info->si_code, &reason);
+
+	char buf[128], numbuf[8];
+	if (!signal_name)
+	{
+		snprintf (numbuf, sizeof numbuf, "%d", signum);
+		signal_name = numbuf;
+	}
+
+	if (reason)
+		snprintf (buf, sizeof buf, "%s=%s: %s: %s", g_startup_reason_str,
+			"signal received", signal_name, reason);
+	else
+		snprintf (buf, sizeof buf, "%s=%s: %s", g_startup_reason_str,
+			"signal received", signal_name);
+	*g_startup_reason_location = buf;
+
+	// TODO: maybe pregenerate the path, see the following for some other ways
+	//   that would be illegal to do from within a signal handler:
+	//     http://stackoverflow.com/a/1024937
+	//     http://stackoverflow.com/q/799679
+	//   Especially if we change the current working directory in the program.
+	//
+	//   Note that I can just overwrite g_orig_argv[0].
+
+	// NOTE: our children will read EOF on the read ends of their pipes as a
+	//   a result of O_CLOEXEC.  That should be enough to make them terminate.
+
+	char **argv = g_original_argv.vector, **argp = g_recovery_env.vector;
+	execve ("/proc/self/exe",        argv, argp);  // Linux
+	execve ("/proc/curproc/file",    argv, argp);  // BSD
+	execve ("/proc/curproc/exe",     argv, argp);  // BSD
+	execve ("/proc/self/path/a.out", argv, argp);  // Solaris
+	execve (argv[0],                 argv, argp);  // unreliable fallback
+
+	// Let's just crash
+	perror ("execve");
+	signal (signum, SIG_DFL);
+	raise (signum);
+}
+
+static void
+prepare_recovery_environment (void)
+{
+	str_vector_init (&g_recovery_env);
+	str_vector_add_vector (&g_recovery_env, environ);
+
+	// Prepare a location within the environment where we will put the startup
+	// (or maybe rather restart) reason in case of an irrecoverable error.
+	char **iter;
+	for (iter = g_recovery_env.vector; *iter; iter++)
+	{
+		const size_t len = sizeof g_startup_reason_str - 1;
+		if (!strncmp (*iter, g_startup_reason_str, len) && (*iter)[len] == '=')
+			break;
+	}
+
+	if (iter)
+		g_startup_reason_location = iter;
+	else
+	{
+		str_vector_add (&g_recovery_env, "");
+		g_startup_reason_location =
+			g_recovery_env.vector + g_recovery_env.len - 1;
+	}
+}
+
+static void
+setup_recovery_handler (struct bot_context *ctx)
+{
+	const char *recover_str = str_map_find (&ctx->config, "recover");
+	hard_assert (recover_str != NULL);  // We have a default value for this
+
+	bool recover;
+	if (!set_boolean_if_valid (&recover, recover_str))
+	{
+		print_fatal ("invalid configuration value for `%s'", "recover");
+		exit (EXIT_FAILURE);
+	}
+	if (!recover)
+		return;
+
+	// Make sure these signals aren't blocked, otherwise we would be unable
+	// to handle them, making the critical conditions fatal.
+	sigset_t mask;
+	sigemptyset (&mask);
+	sigaddset (&mask, SIGSEGV);
+	sigaddset (&mask, SIGBUS);
+	sigaddset (&mask, SIGFPE);
+	sigaddset (&mask, SIGILL);
+	sigprocmask (SIG_UNBLOCK, &mask, NULL);
+
+	struct sigaction sa;
+	sa.sa_flags = SA_SIGINFO;
+	sa.sa_sigaction = recovery_handler;
+	sigemptyset (&sa.sa_mask);
+
+	prepare_recovery_environment ();
+
+	// TODO: also handle SIGABRT... or avoid doing abort() in the first place?
+	if (sigaction (SIGSEGV, &sa, NULL) == -1
+	 || sigaction (SIGBUS,  &sa, NULL) == -1
+	 || sigaction (SIGFPE,  &sa, NULL) == -1
+	 || sigaction (SIGILL,  &sa, NULL) == -1)
+		print_error ("sigaction: %s", strerror (errno));
+}
+
+// --- Plugins -----------------------------------------------------------------
+
+/// The name of the special IRC command for interprocess communication
+static const char *plugin_ipc_command = "ZYKLONB";
+
+static size_t plugin_error_domain_tag;
+#define PLUGIN_ERROR (error_resolve_domain (&plugin_error_domain_tag))
+
+enum
+{
+	PLUGIN_ERROR_ALREADY_LOADED,
+	PLUGIN_ERROR_NOT_LOADED,
+	PLUGIN_ERROR_LOADING_FAILED
+};
+
+static struct plugin_data *
+plugin_find_by_pid (struct bot_context *ctx, pid_t pid)
+{
+	struct plugin_data *iter;
+	for (iter = ctx->plugins; iter; iter = iter->next)
+		if (iter->pid == pid)
+			return iter;
+	return NULL;
+}
+
+static bool
+plugin_zombify (struct plugin_data *plugin)
+{
+	if (plugin->is_zombie)
+		return false;
+
+	// FIXME: make sure that we don't remove entries from the poller while we
+	//   still may have stuff to read; maybe just check that the read pipe is
+	//   empty before closing it... and then on EOF check if `pid == -1' and
+	//   only then dispose of it (it'd be best to simulate that both of these
+	//   cases may happen).
+	ssize_t poller_idx =
+		poller_find_by_fd (&plugin->ctx->poller, plugin->write_fd);
+	if (poller_idx != -1)
+		poller_remove_at_index (&plugin->ctx->poller, poller_idx);
+
+	// TODO: try to flush the write buffer (non-blocking)?
+
+	// The plugin should terminate itself after it receives EOF.
+	xclose (plugin->write_fd);
+	plugin->write_fd = -1;
+
+	// Make it a pseudo-anonymous zombie.  In this state we process any
+	// remaining commands it attempts to send to us before it finally dies.
+	str_map_set (&plugin->ctx->plugins_by_name, plugin->name, NULL);
+	plugin->is_zombie = true;
+	return true;
+}
+
+static void
+on_plugin_writable (const struct pollfd *fd, struct plugin_data *plugin)
+{
+	struct bot_context *ctx = plugin->ctx;
+	struct str *buf = &plugin->write_buffer;
+	size_t written_total = 0;
+
+	// TODO: see "Advanced Programming in the UNIX Environment" Figure C.19;
+	//   check for any unexpected behaviour that might occur
+	if (fd->revents != POLLOUT)
+		print_debug ("poller fd %d: revents: %d", fd->fd, fd->revents);
+
+	while (written_total != buf->len)
+	{
+		ssize_t n_written = write (fd->fd, buf->str + written_total,
+			buf->len - written_total);
+
+		if (n_written < 0)
+		{
+			if (errno == EAGAIN)
+				break;
+
+			if (!soft_assert (errno == EINTR) && !plugin->is_zombie)
+			{
+				print_debug ("%s: %s", "recv", strerror (errno));
+				print_error ("failure on writing to plugin `%s',"
+					" therefore I'm unloading it", plugin->name);
+				plugin_zombify (plugin);
+				break;
+			}
+		}
+
+		// This may be equivalent to EAGAIN on some implementations
+		if (n_written == 0)
+			break;
+
+		written_total += n_written;
+	}
+
+	if (written_total != 0)
+		str_remove_slice (buf, 0, written_total);
+
+	if (buf->len == 0)
+	{
+		// Everything has been written, there's no need to end up in here again
+		ssize_t index = poller_find_by_fd (&ctx->poller, fd->fd);
+		if (index != -1)
+			poller_remove_at_index (&ctx->poller, index);
+	}
+}
+
+static void
+plugin_queue_write (struct plugin_data *plugin)
+{
+	if (plugin->is_zombie)
+		return;
+
+	// Don't let the write buffer grow infinitely.  If there's a ton of data
+	// waiting to be processed by the plugin, it usually means there's something
+	// wrong with it (such as someone stopping the process).
+	if (plugin->write_buffer.len >= (1 << 20))
+	{
+		print_warning ("plugin `%s' does not seem to process messages fast"
+			" enough, I'm unloading it", plugin->name);
+		plugin_zombify (plugin);
+		return;
+	}
+
+	poller_set (&plugin->ctx->poller, plugin->write_fd, POLLOUT,
+		(poller_dispatcher_func) on_plugin_writable, plugin);
+}
+
+static void
+plugin_send (struct plugin_data *plugin, const char *format, ...)
+	ATTRIBUTE_PRINTF (2, 3);
+
+static void
+plugin_send (struct plugin_data *plugin, const char *format, ...)
+{
+	va_list ap;
+
+	if (g_debug_mode)
+	{
+		fprintf (stderr, "[%s] <-- \"", plugin->name);
+		va_start (ap, format);
+		vfprintf (stderr, format, ap);
+		va_end (ap);
+		fputs ("\"\n", stderr);
+	}
+
+	va_start (ap, format);
+	str_append_vprintf (&plugin->write_buffer, format, ap);
+	va_end (ap);
+	str_append (&plugin->write_buffer, "\r\n");
+
+	plugin_queue_write (plugin);
+}
+
+static void
+plugin_process_message (const struct irc_message *msg,
+	const char *raw, void *user_data)
+{
+	struct plugin_data *plugin = user_data;
+	struct bot_context *ctx = plugin->ctx;
+
+	if (g_debug_mode)
+		fprintf (stderr, "[%s] --> \"%s\"\n", plugin->name, raw);
+
+	if (!strcasecmp (msg->command, plugin_ipc_command))
+	{
+		// Replies are sent in the order in which they came in, so there's
+		// no need to attach a special identifier to them.  It might be
+		// desirable in some cases, though.
+
+		if (msg->params.len < 1)
+			return;
+
+		const char *command = msg->params.vector[0];
+		if (!strcasecmp (command, "register"))
+		{
+			// Register for relaying of IRC traffic
+			plugin->initialized = true;
+
+			// Flush any queued up traffic here.  The point of queuing it in
+			// the first place is so that we don't have to wait for plugin
+			// initialization during startup.
+			//
+			// Note that if we start filtering data coming to the plugins e.g.
+			// based on what it tells us upon registration, we might need to
+			// filter `queued_output' as well.
+			str_append_str (&plugin->write_buffer, &plugin->queued_output);
+			str_free (&plugin->queued_output);
+
+			// NOTE: this may trigger the buffer length check
+			plugin_queue_write (plugin);
+		}
+		else if (!strcasecmp (command, "get_config"))
+		{
+			if (msg->params.len < 2)
+				return;
+
+			const char *value =
+				str_map_find (&ctx->config, msg->params.vector[1]);
+			// TODO: escape the value (although there's no need to ATM)
+			plugin_send (plugin, "%s :%s",
+				plugin_ipc_command, value ? value : "");
+		}
+		else if (!strcasecmp (command, "print"))
+		{
+			if (msg->params.len < 2)
+				return;
+
+			printf ("%s", msg->params.vector[1]);
+		}
+	}
+	else if (plugin->initialized)
+	{
+		// Pass everything else through to the IRC server
+		irc_send (ctx, "%s", raw);
+	}
+}
+
+static void
+on_plugin_readable (const struct pollfd *fd, struct plugin_data *plugin)
+{
+	// TODO: see "Advanced Programming in the UNIX Environment" Figure C.19;
+	//   check for any unexpected behaviour that might occur
+	if (fd->revents != POLLIN)
+		print_debug ("poller fd %d: revents: %d", fd->fd, fd->revents);
+
+	// TODO: see if I can reuse irc_fill_read_buffer()
+	struct str *buf = &plugin->read_buffer;
+	while (true)
+	{
+		str_ensure_space (buf, 512 + 1);
+		ssize_t n_read = read (fd->fd, buf->str + buf->len,
+			buf->alloc - buf->len - 1);
+
+		if (n_read < 0)
+		{
+			if (errno == EAGAIN)
+				break;
+			if (soft_assert (errno == EINTR))
+				continue;
+
+			if (!plugin->is_zombie)
+			{
+				print_error ("failure on reading from plugin `%s',"
+					" therefore I'm unloading it", plugin->name);
+				plugin_zombify (plugin);
+			}
+			return;
+		}
+
+		// EOF; hopefully it will die soon (maybe it already has)
+		if (n_read == 0)
+			break;
+
+		buf->str[buf->len += n_read] = '\0';
+		if (buf->len >= (1 << 20))
+		{
+			// XXX: this isn't really the best flood prevention mechanism,
+			//   but it wasn't even supposed to be one.
+			if (plugin->is_zombie)
+			{
+				print_error ("a zombie of plugin `%s' is trying to flood us,"
+					" therefore I'm killing it", plugin->name);
+				kill (plugin->pid, SIGKILL);
+			}
+			else
+			{
+				print_error ("plugin `%s' seems to spew out data frantically,"
+					" therefore I'm unloading it", plugin->name);
+				plugin_zombify (plugin);
+			}
+			return;
+		}
+	}
+
+	// Hold it in the buffer while we're disconnected
+	struct bot_context *ctx = plugin->ctx;
+	if (ctx->irc_fd != -1 && ctx->irc_ready)
+		irc_process_buffer (buf, plugin_process_message, plugin);
+}
+
+static bool
+is_valid_plugin_name (const char *name)
+{
+	if (!*name)
+		return false;
+	for (const char *p = name; *p; p++)
+		if (!isgraph (*p) || *p == '/')
+			return false;
+	return true;
+}
+
+static bool
+plugin_load (struct bot_context *ctx, const char *name, struct error **e)
+{
+	const char *plugin_dir = str_map_find (&ctx->config, "plugin_dir");
+	if (!plugin_dir)
+	{
+		error_set (e, PLUGIN_ERROR, PLUGIN_ERROR_LOADING_FAILED,
+			"plugin directory not set");
+		return false;
+	}
+
+	if (!is_valid_plugin_name (name))
+	{
+		error_set (e, PLUGIN_ERROR, PLUGIN_ERROR_LOADING_FAILED,
+			"invalid plugin name");
+		return false;
+	}
+
+	if (str_map_find (&ctx->plugins_by_name, name))
+	{
+		error_set (e, PLUGIN_ERROR, PLUGIN_ERROR_ALREADY_LOADED,
+			"the plugin has already been loaded");
+		return false;
+	}
+
+	int stdin_pipe[2];
+	if (pipe (stdin_pipe) == -1)
+	{
+		error_set (e, PLUGIN_ERROR, PLUGIN_ERROR_LOADING_FAILED, "%s: %s: %s",
+			"failed to load the plugin", "pipe", strerror (errno));
+		goto fail_1;
+	}
+
+	int stdout_pipe[2];
+	if (pipe (stdout_pipe) == -1)
+	{
+		error_set (e, PLUGIN_ERROR, PLUGIN_ERROR_LOADING_FAILED, "%s: %s: %s",
+			"failed to load the plugin", "pipe", strerror (errno));
+		goto fail_2;
+	}
+
+	set_cloexec (stdin_pipe[1]);
+	set_cloexec (stdout_pipe[0]);
+
+	pid_t pid = fork ();
+	if (pid == -1)
+	{
+		error_set (e, PLUGIN_ERROR, PLUGIN_ERROR_LOADING_FAILED, "%s: %s: %s",
+			"failed to load the plugin", "fork", strerror (errno));
+		goto fail_3;
+	}
+
+	if (pid == 0)
+	{
+		// Redirect the child's stdin and stdout to the pipes
+		hard_assert (dup2 (stdin_pipe[0],  STDIN_FILENO)  != -1);
+		hard_assert (dup2 (stdout_pipe[1], STDOUT_FILENO) != -1);
+
+		xclose (stdin_pipe[0]);
+		xclose (stdout_pipe[1]);
+
+		struct str pathname;
+		str_init (&pathname);
+		str_append (&pathname, plugin_dir);
+		str_append_c (&pathname, '/');
+		str_append (&pathname, name);
+
+		// Restore some of the signal handling
+		signal (SIGPIPE, SIG_DFL);
+
+		char *const argv[] = { pathname.str, NULL };
+		execve (argv[0], argv, environ);
+
+		// We will collect the failure later via SIGCHLD
+		print_fatal ("%s: %s: %s",
+			"failed to load the plugin", "exec", strerror (errno));
+		_exit (EXIT_FAILURE);
+	}
+
+	xclose (stdin_pipe[0]);
+	xclose (stdout_pipe[1]);
+
+	set_blocking (stdout_pipe[0], false);
+	set_blocking (stdin_pipe[1], false);
+
+	struct plugin_data *plugin = xmalloc (sizeof *plugin);
+	plugin_data_init (plugin);
+	plugin->ctx = ctx;
+	plugin->pid = pid;
+	plugin->name = xstrdup (name);
+	plugin->read_fd = stdout_pipe[0];
+	plugin->write_fd = stdin_pipe[1];
+
+	LIST_PREPEND (ctx->plugins, plugin);
+	str_map_set (&ctx->plugins_by_name, name, plugin);
+
+	poller_set (&ctx->poller, stdout_pipe[0], POLLIN,
+		(poller_dispatcher_func) on_plugin_readable, plugin);
+	return true;
+
+fail_3:
+	xclose (stdout_pipe[0]);
+	xclose (stdout_pipe[1]);
+fail_2:
+	xclose (stdin_pipe[0]);
+	xclose (stdin_pipe[1]);
+fail_1:
+	return false;
+}
+
+static bool
+plugin_unload (struct bot_context *ctx, const char *name, struct error **e)
+{
+	struct plugin_data *plugin = str_map_find (&ctx->plugins_by_name, name);
+
+	if (!plugin)
+	{
+		error_set (e, PLUGIN_ERROR, PLUGIN_ERROR_NOT_LOADED,
+			"no such plugin is loaded");
+		return false;
+	}
+
+	plugin_zombify (plugin);
+
+	// TODO: add a `kill zombies' command to forcefully get rid of processes
+	//   that do not understand the request.
+	// TODO: set a timeout before we go for a kill automatically (and if this
+	//   was a reload request, try to bring the plugin back up)
+	return true;
+}
+
+static void
+plugin_load_all_from_config (struct bot_context *ctx)
+{
+	const char *plugin_list = str_map_find (&ctx->config, "plugins");
+	if (!plugin_list)
+		return;
+
+	struct str_vector plugins;
+	str_vector_init (&plugins);
+
+	split_str_ignore_empty (plugin_list, ',', &plugins);
+	for (size_t i = 0; i < plugins.len; i++)
+	{
+		char *name = strip_str_in_place (plugins.vector[i], " ");
+
+		struct error *e = NULL;
+		if (!plugin_load (ctx, name, &e))
+		{
+			print_error ("plugin `%s' failed to load: %s", name, e->message);
+			error_free (e);
+		}
+	}
+
+	str_vector_free (&plugins);
+}
+
+// --- Main program ------------------------------------------------------------
+
+static bool
+parse_bot_command (const char *s, const char *command, const char **following)
+{
+	size_t command_len = strlen (command);
+	if (strncasecmp (s, command, command_len))
+		return false;
+	s += command_len;
+
+	// Expect a word boundary, so that we don't respond to invalid things
+	if (isalnum (*s))
+		return false;
+
+	// Ignore any initial spaces; the rest is the command's argument
+	while (isblank (*s))
+		s++;
+	*following = s;
+	return true;
+}
+
+static void
+split_bot_command_argument_list (const char *arguments, struct str_vector *out)
+{
+	split_str_ignore_empty (arguments, ',', out);
+	for (size_t i = 0; i < out->len; )
+	{
+		if (!*strip_str_in_place (out->vector[i], " \t"))
+			str_vector_remove (out, i);
+		else
+			i++;
+	}
+}
+
+static bool
+is_private_message (const struct irc_message *msg)
+{
+	hard_assert (msg->params.len);
+	return !strchr ("#&+!", *msg->params.vector[0]);
+}
+
+static bool
+is_sent_by_admin (struct bot_context *ctx, const struct irc_message *msg)
+{
+	const char *admin = str_map_find (&ctx->config, "admin");
+
+	// No administrator set -> everyone is an administrator
+	if (!admin)
+		return true;
+
+	// TODO: precompile the regex
+	struct error *e = NULL;
+	if (regex_match (admin, msg->prefix, NULL))
+		return true;
+
+	if (e)
+	{
+		print_error ("%s: %s", "invalid admin mask", e->message);
+		error_free (e);
+		return true;
+	}
+
+	return false;
+}
+
+static void respond_to_user (struct bot_context *ctx, const struct
+	irc_message *msg, const char *format, ...) ATTRIBUTE_PRINTF (3, 4);
+
+static void
+respond_to_user (struct bot_context *ctx, const struct irc_message *msg,
+	const char *format, ...)
+{
+	if (!soft_assert (msg->prefix && msg->params.len))
+		return;
+
+	char nick[strcspn (msg->prefix, "!") + 1];
+	strncpy (nick, msg->prefix, sizeof nick - 1);
+	nick[sizeof nick - 1] = '\0';
+
+	struct str text;
+	va_list ap;
+
+	str_init (&text);
+	va_start (ap, format);
+	str_append_vprintf (&text, format, ap);
+	va_end (ap);
+
+	if (is_private_message (msg))
+		irc_send (ctx, "PRIVMSG %s :%s", nick, text.str);
+	else
+		irc_send (ctx, "PRIVMSG %s :%s: %s",
+			msg->params.vector[0], nick, text.str);
+
+	str_free (&text);
+}
+
+static void
+process_plugin_load (struct bot_context *ctx,
+	const struct irc_message *msg, const char *name)
+{
+	struct error *e = NULL;
+	if (plugin_load (ctx, name, &e))
+		respond_to_user (ctx, msg, "plugin `%s' queued for loading", name);
+	else
+	{
+		respond_to_user (ctx, msg, "plugin `%s' could not be loaded: %s",
+			name, e->message);
+		error_free (e);
+	}
+}
+
+static void
+process_plugin_unload (struct bot_context *ctx,
+	const struct irc_message *msg, const char *name)
+{
+	struct error *e = NULL;
+	if (plugin_unload (ctx, name, &e))
+		respond_to_user (ctx, msg, "plugin `%s' unloaded", name);
+	else
+	{
+		respond_to_user (ctx, msg, "plugin `%s' could not be unloaded: %s",
+			name, e->message);
+		error_free (e);
+	}
+}
+
+static void
+process_plugin_reload (struct bot_context *ctx,
+	const struct irc_message *msg, const char *name)
+{
+	// So far the only error that can occur is that the plugin hasn't been
+	// loaded, which in this case doesn't really matter.
+	plugin_unload (ctx, name, NULL);
+
+	process_plugin_load (ctx, msg, name);
+}
+
+static void
+process_privmsg (struct bot_context *ctx, const struct irc_message *msg)
+{
+	if (!is_sent_by_admin (ctx, msg))
+		return;
+	if (msg->params.len < 2)
+		return;
+
+	const char *prefix = str_map_find (&ctx->config, "prefix");
+	hard_assert (prefix != NULL);  // We have a default value for this
+
+	// For us to recognize the command, it has to start with the prefix,
+	// with the exception of PM's sent directly to us.
+	const char *text = msg->params.vector[1];
+	if (!strncmp (text, prefix, strlen (prefix)))
+		text += strlen (prefix);
+	else if (!is_private_message (msg))
+		return;
+
+	const char *following;
+	struct str_vector list;
+	str_vector_init (&list);
+
+	if (parse_bot_command (text, "quote", &following))
+		// This seems to replace tons of random stupid commands
+		irc_send (ctx, "%s", following);
+	else if (parse_bot_command (text, "quit", &following))
+	{
+		// We actually need this command (instead of just `quote') because we
+		// could try to reconnect to the server automatically otherwise.
+		if (*following)
+			irc_send (ctx, "QUIT :%s", following);
+		else
+			irc_send (ctx, "QUIT");
+		initiate_quit (ctx);
+	}
+	else if (parse_bot_command (text, "status", &following))
+	{
+		struct str report;
+		str_init (&report);
+
+		const char *reason = getenv (g_startup_reason_str);
+		if (!reason)
+			reason = "launched normally";
+		str_append_printf (&report, "\x02startup reason:\x0f %s, ", reason);
+
+		str_append (&report, "\x02plugins:\x0f ");
+		size_t zombies = 0;
+		for (struct plugin_data *plugin = ctx->plugins;
+			 plugin; plugin = plugin->next)
+		{
+			if (plugin->is_zombie)
+				zombies++;
+			else
+				str_append_printf (&report, "%s, ", plugin->name);
+		}
+		if (!ctx->plugins)
+			str_append (&report, "\x02none\x0f, ");
+		str_append_printf (&report, "\x02zombies:\x0f %zu", zombies);
+
+		respond_to_user (ctx, msg, "%s", report.str);
+		str_free (&report);
+	}
+	else if (parse_bot_command (text, "load", &following))
+	{
+		split_bot_command_argument_list (following, &list);
+		for (size_t i = 0; i < list.len; i++)
+			process_plugin_load (ctx, msg, list.vector[i]);
+	}
+	else if (parse_bot_command (text, "reload", &following))
+	{
+		split_bot_command_argument_list (following, &list);
+		for (size_t i = 0; i < list.len; i++)
+			process_plugin_reload (ctx, msg, list.vector[i]);
+	}
+	else if (parse_bot_command (text, "unload", &following))
+	{
+		split_bot_command_argument_list (following, &list);
+		for (size_t i = 0; i < list.len; i++)
+			process_plugin_unload (ctx, msg, list.vector[i]);
+	}
+
+	str_vector_free (&list);
+}
+
+static void
+irc_process_message (const struct irc_message *msg,
+	const char *raw, void *user_data)
+{
+	struct bot_context *ctx = user_data;
+	if (g_debug_mode)
+		fprintf (stderr, "[%s] ==> \"%s\"\n", "IRC", raw);
+
+	// This should be as minimal as possible, I don't want to have the whole bot
+	// written in C, especially when I have this overengineered plugin system.
+	// Therefore the very basic functionality only.
+	//
+	// I should probably even rip out the autojoin...
+
+	// First forward the message to all the plugins
+	for (struct plugin_data *plugin = ctx->plugins;
+		 plugin; plugin = plugin->next)
+	{
+		if (plugin->is_zombie)
+			continue;
+
+		if (plugin->initialized)
+			plugin_send (plugin, "%s", raw);
+		else
+			// TODO: make sure that this buffer doesn't get too large either
+			str_append_printf (&plugin->queued_output, "%s\r\n", raw);
+	}
+
+	if (!strcasecmp (msg->command, "PING"))
+	{
+		if (msg->params.len)
+			irc_send (ctx, "PONG :%s", msg->params.vector[0]);
+		else
+			irc_send (ctx, "PONG");
+	}
+	else if (!ctx->irc_ready && (!strcasecmp (msg->command, "MODE")
+		|| !strcasecmp (msg->command, "376")    // RPL_ENDOFMOTD
+		|| !strcasecmp (msg->command, "422")))  // ERR_NOMOTD
+	{
+		print_status ("successfully connected");
+		ctx->irc_ready = true;
+
+		const char *autojoin = str_map_find (&ctx->config, "autojoin");
+		if (autojoin)
+			irc_send (ctx, "JOIN :%s", autojoin);
+	}
+	else if (!strcasecmp (msg->command, "PRIVMSG"))
+		process_privmsg (ctx, msg);
+}
+
+enum irc_read_result
+{
+	IRC_READ_OK,                        ///< Some data were read successfully
+	IRC_READ_EOF,                       ///< The server has closed connection
+	IRC_READ_AGAIN,                     ///< No more data at the moment
+	IRC_READ_ERROR                      ///< General connection failure
+};
+
+static enum irc_read_result
+irc_fill_read_buffer_ssl (struct bot_context *ctx, struct str *buf)
+{
+	int n_read;
+start:
+	n_read = SSL_read (ctx->ssl, buf->str + buf->len,
+		buf->alloc - buf->len - 1 /* null byte */);
+
+	const char *error_info = NULL;
+	switch (SSL_get_error (ctx->ssl, n_read))
+	{
+	case SSL_ERROR_NONE:
+		buf->str[buf->len += n_read] = '\0';
+		return IRC_READ_AGAIN;
+	case SSL_ERROR_ZERO_RETURN:
+		return IRC_READ_EOF;
+	case SSL_ERROR_WANT_READ:
+		return IRC_READ_AGAIN;
+	case SSL_ERROR_WANT_WRITE:
+	{
+		// Let it finish the handshake as we don't poll for writability;
+		// any errors are to be collected by SSL_read() in the next iteration
+		struct pollfd pfd = { .fd = ctx->irc_fd, .events = POLLOUT };
+		soft_assert (poll (&pfd, 1, 0) > 0);
+		goto start;
+	}
+	case SSL_ERROR_SYSCALL:
+	{
+		int err;
+		if ((err = ERR_get_error ()))
+			error_info = ERR_error_string (err, NULL);
+		else if (n_read == 0)
+			return IRC_READ_EOF;
+		else
+		{
+			if (errno == EINTR)
+				goto start;
+			error_info = strerror (errno);
+		}
+		break;
+	}
+	case SSL_ERROR_SSL:
+	default:
+		error_info = ERR_error_string (ERR_get_error (), NULL);
+	}
+
+	print_debug ("%s: %s: %s", __func__, "SSL_read", error_info);
+	return IRC_READ_ERROR;
+}
+
+static enum irc_read_result
+irc_fill_read_buffer (struct bot_context *ctx, struct str *buf)
+{
+	ssize_t n_read;
+start:
+	n_read = recv (ctx->irc_fd, buf->str + buf->len,
+		buf->alloc - buf->len - 1 /* null byte */, 0);
+
+	if (n_read > 0)
+	{
+		buf->str[buf->len += n_read] = '\0';
+		return IRC_READ_OK;
+	}
+	if (n_read == 0)
+		return IRC_READ_EOF;
+
+	if (errno == EAGAIN)
+		return IRC_READ_AGAIN;
+	if (errno == EINTR)
+		goto start;
+
+	print_debug ("%s: %s: %s", __func__, "recv", strerror (errno));
+	return IRC_READ_ERROR;
+}
+
+static bool irc_connect (struct bot_context *ctx, struct error **e);
+
+static void
+irc_try_reconnect (struct bot_context *ctx)
+{
+	if (!soft_assert (ctx->irc_fd == -1))
+		return;
+
+	const char *reconnect_str = str_map_find (&ctx->config, "reconnect");
+	hard_assert (reconnect_str != NULL);  // We have a default value for this
+
+	bool reconnect;
+	if (!set_boolean_if_valid (&reconnect, reconnect_str))
+	{
+		print_fatal ("invalid configuration value for `%s'", "recover");
+		try_finish_quit (ctx);
+		return;
+	}
+	if (!reconnect)
+		return;
+
+	const char *delay_str = str_map_find (&ctx->config, "reconnect_delay");
+	hard_assert (delay_str != NULL);  // We have a default value for this
+
+	char *end_ptr;
+	errno = 0;
+	long delay = strtol (delay_str, &end_ptr, 10);
+	if (errno != 0 || end_ptr == delay_str || *end_ptr)
+	{
+		print_error ("invalid configuration value for `%s'",
+			"reconnect_delay");
+		delay = 0;
+	}
+
+	while (true)
+	{
+		// TODO: this would be better suited by a timeout event;
+		//   remember to update try_finish_quit() etc. to reflect this
+		print_status ("trying to reconnect in %ld seconds...", delay);
+		sleep (delay);
+
+		struct error *e = NULL;
+		if (irc_connect (ctx, &e))
+			break;
+
+		print_error ("%s", e->message);
+		error_free (e);
+	}
+
+	// TODO: inform plugins about the new connection
+}
+
+static void
+on_irc_disconnected (struct bot_context *ctx)
+{
+	// Get rid of the dead socket etc.
+	if (ctx->ssl)
+	{
+		SSL_free (ctx->ssl);
+		ctx->ssl = NULL;
+		SSL_CTX_free (ctx->ssl_ctx);
+		ctx->ssl_ctx = NULL;
+	}
+
+	ssize_t i = poller_find_by_fd (&ctx->poller, ctx->irc_fd);
+	if (i != -1)
+		poller_remove_at_index (&ctx->poller, i);
+
+	xclose (ctx->irc_fd);
+	ctx->irc_fd = -1;
+
+	// TODO: inform plugins about the disconnect event
+
+	if (ctx->quitting)
+	{
+		// Unload all plugins
+		// TODO: wait for a few seconds and then send SIGKILL to all plugins
+		for (struct plugin_data *plugin = ctx->plugins;
+			plugin; plugin = plugin->next)
+			plugin_zombify (plugin);
+
+		try_finish_quit (ctx);
+		return;
+	}
+
+	irc_try_reconnect (ctx);
+}
+
+static void
+on_irc_readable (const struct pollfd *fd, struct bot_context *ctx)
+{
+	if (fd->revents != POLLIN)
+		print_debug ("poller fd %d: revents: %d", fd->fd, fd->revents);
+
+	(void) set_blocking (ctx->irc_fd, false);
+
+	struct str *buf = &ctx->read_buffer;
+	enum irc_read_result (*fill_buffer)(struct bot_context *, struct str *)
+		= ctx->ssl
+		? irc_fill_read_buffer_ssl
+		: irc_fill_read_buffer;
+	bool disconnected = false;
+	while (true)
+	{
+		str_ensure_space (buf, 512);
+		switch (fill_buffer (ctx, buf))
+		{
+		case IRC_READ_AGAIN:
+			goto end;
+		case IRC_READ_ERROR:
+			print_error ("reading from the IRC server failed");
+			disconnected = true;
+			goto end;
+		case IRC_READ_EOF:
+			print_status ("the IRC server closed the connection");
+			disconnected = true;
+			goto end;
+		case IRC_READ_OK:
+			break;
+		}
+
+		if (buf->len >= (1 << 20))
+		{
+			print_fatal ("the IRC server seems to spew out data frantically");
+			irc_shutdown (ctx);
+			goto end;
+		}
+	}
+end:
+	(void) set_blocking (ctx->irc_fd, true);
+	irc_process_buffer (buf, irc_process_message, ctx);
+
+	if (disconnected)
+		on_irc_disconnected (ctx);
+}
+
+static bool
+irc_connect (struct bot_context *ctx, struct error **e)
+{
+	const char *irc_host = str_map_find (&ctx->config, "irc_host");
+	const char *irc_port = str_map_find (&ctx->config, "irc_port");
+	const char *ssl_use_str = str_map_find (&ctx->config, "ssl_use");
+
+	const char *nickname = str_map_find (&ctx->config, "nickname");
+	const char *username = str_map_find (&ctx->config, "username");
+	const char *fullname = str_map_find (&ctx->config, "fullname");
+
+	// We have a default value for these
+	hard_assert (irc_port && ssl_use_str);
+	hard_assert (nickname && username && fullname);
+
+	// TODO: again, get rid of `struct error' in here.  The question is: how
+	//   do we tell our caller that he should not try to reconnect?
+	if (!irc_host)
+	{
+		error_set (e, CONNECT_ERROR, CONNECT_ERROR_INVALID_CONFIGURATION,
+			"no hostname specified in configuration");
+		return false;
+	}
+
+	bool use_ssl;
+	if (!set_boolean_if_valid (&use_ssl, ssl_use_str))
+	{
+		error_set (e, CONNECT_ERROR, CONNECT_ERROR_INVALID_CONFIGURATION,
+			"invalid configuration value for `%s'", "use_ssl");
+		return false;
+	}
+
+	if (!irc_establish_connection (ctx, irc_host, irc_port, use_ssl, e))
+		return false;
+
+	// TODO: set a timeout on the socket, something like 30 minutes, then we
+	//   should ideally send a PING... or just forcefully reconnect.
+	//
+	// TODO: in exec try: 1/ set blocking, 2/ setsockopt() SO_LINGER,
+	//   (struct linger) { .l_onoff = true; .l_linger = 1 /* 1s should do */; }
+	//   3/ /* O_CLOEXEC */  But only if the QUIT message proves unreliable.
+	poller_set (&ctx->poller, ctx->irc_fd, POLLIN,
+		(poller_dispatcher_func) on_irc_readable, ctx);
+
+	// TODO: probably check for errors from these calls as well
+	irc_send (ctx, "NICK %s", nickname);
+	irc_send (ctx, "USER %s 8 * :%s", username, fullname);
+	return true;
+}
+
+static void
+on_signal_pipe_readable (const struct pollfd *fd, struct bot_context *ctx)
+{
+	char *dummy;
+	(void) read (fd->fd, &dummy, 1);
+
+	// XXX: do we need to check if we have a connection?
+	if (g_termination_requested && !ctx->quitting)
+	{
+		irc_send (ctx, "QUIT :Terminated by signal");
+		initiate_quit (ctx);
+	}
+
+	// Reap all dead children (since the pipe may overflow, we ask waitpid()
+	// to return all the zombies it knows about).
+	while (true)
+	{
+		int status;
+		pid_t zombie = waitpid (-1, &status, WNOHANG);
+
+		if (zombie == -1)
+		{
+			// No children to wait on
+			if (errno == ECHILD)
+				break;
+
+			hard_assert (errno == EINTR);
+			continue;
+		}
+
+		if (zombie == 0)
+			break;
+
+		struct plugin_data *plugin = plugin_find_by_pid (ctx, zombie);
+		// Something has died but we don't recognize it (re-exec?)
+		if (!soft_assert (plugin != NULL))
+			continue;
+
+		// TODO: callbacks on children death, so that we may tell the user
+		//       "plugin `name' died like a dirty jewish pig"; use `status'
+		if (!plugin->is_zombie && WIFSIGNALED (status))
+		{
+			char *notes = "";
+#ifdef WCOREDUMP
+			if (WCOREDUMP (status))
+				notes = " (core dumped)";
+#endif
+			print_warning ("Plugin `%s' died from signal %d%s",
+				plugin->name, WTERMSIG (status), notes);
+		}
+
+		// Let's go through the zombie state to simplify things a bit
+		// TODO: might not be a completely bad idea to restart the plugin
+		plugin_zombify (plugin);
+
+		plugin->pid = -1;
+
+		ssize_t poller_idx = poller_find_by_fd (&ctx->poller, plugin->read_fd);
+		if (poller_idx != -1)
+			poller_remove_at_index (&ctx->poller, poller_idx);
+
+		xclose (plugin->read_fd);
+		plugin->read_fd = -1;
+
+		LIST_UNLINK (ctx->plugins, plugin);
+		plugin_data_free (plugin);
+		free (plugin);
+
+		// Living child processes block us from quitting
+		try_finish_quit (ctx);
+	}
+}
+
+static void
+write_default_configuration (const char *filename)
+{
+	struct str path, base;
+	int status = EXIT_SUCCESS;
+
+	str_init (&path);
+	str_init (&base);
+
+	if (filename)
+	{
+		char *tmp = xstrdup (filename);
+		str_append (&path, dirname (tmp));
+		strcpy (tmp, filename);
+		str_append (&base, basename (tmp));
+		free (tmp);
+	}
+	else
+	{
+		get_xdg_home_dir (&path, "XDG_CONFIG_HOME", ".config");
+		str_append (&path, "/" PROGRAM_NAME);
+		str_append (&base, PROGRAM_NAME ".conf");
+	}
+
+	struct error *e = NULL;
+	if (!mkdir_with_parents (path.str, &e))
+	{
+		print_fatal ("%s", e->message);
+		status = EXIT_FAILURE;
+		goto out;
+	}
+
+	str_append_c (&path, '/');
+	str_append_str (&path, &base);
+
+	FILE *fp = fopen (path.str, "w");
+	if (!fp)
+	{
+		print_fatal ("could not open `%s' for writing: %s",
+			path.str, strerror (errno));
+		status = EXIT_FAILURE;
+		goto out;
+	}
+
+	errno = 0;
+	for (size_t i = 0; i < N_ELEMENTS (g_config_table); i++)
+	{
+		const struct config_item *item = g_config_table + i;
+		fprintf (fp, "# %s\n", item->description);
+		if (item->default_value)
+			fprintf (fp, "%s=%s\n", item->key, item->default_value);
+		else
+			fprintf (fp, "#%s=\n", item->key);
+	}
+	fclose (fp);
+	if (errno)
+	{
+		print_fatal ("writing to `%s' failed: %s", path.str, strerror (errno));
+		status = EXIT_FAILURE;
+		goto out;
+	}
+	print_status ("configuration written to `%s'", path.str);
+
+out:
+	str_free (&path);
+	str_free (&base);
+	exit (status);
+}
+
+static void
+print_usage (const char *program_name)
+{
+	fprintf (stderr,
+		"Usage: %s [OPTION]...\n"
+		"Experimental IRC bot.\n"
+		"\n"
+		"  -d, --debug     run in debug mode\n"
+		"  -h, --help      display this help and exit\n"
+		"  -V, --version   output version information and exit\n"
+		"  --write-default-cfg [filename]\n"
+		"                  write a default configuration file and exit\n",
+		program_name);
+}
+
+int
+main (int argc, char *argv[])
+{
+	const char *invocation_name = argv[0];
+	str_vector_init (&g_original_argv);
+	str_vector_add_vector (&g_original_argv, argv);
+
+	static struct option opts[] =
+	{
+		{ "debug",             no_argument,       NULL, 'd' },
+		{ "help",              no_argument,       NULL, 'h' },
+		{ "version",           no_argument,       NULL, 'V' },
+		{ "write-default-cfg", optional_argument, NULL, 'w' },
+		{ NULL,                0,                 NULL,  0  }
+	};
+
+	while (1)
+	{
+		int c, opt_index;
+
+		c = getopt_long (argc, argv, "dhV", opts, &opt_index);
+		if (c == -1)
+			break;
+
+		switch (c)
+		{
+		case 'd':
+			g_debug_mode = true;
+			break;
+		case 'h':
+			print_usage (invocation_name);
+			exit (EXIT_SUCCESS);
+		case 'V':
+			printf (PROGRAM_NAME " " PROGRAM_VERSION "\n");
+			exit (EXIT_SUCCESS);
+		case 'w':
+			write_default_configuration (optarg);
+			abort ();
+		default:
+			print_fatal ("error in options");
+			exit (EXIT_FAILURE);
+		}
+	}
+
+	print_status (PROGRAM_NAME " " PROGRAM_VERSION " starting");
+	setup_signal_handlers ();
+
+	SSL_library_init ();
+	atexit (EVP_cleanup);
+	SSL_load_error_strings ();
+	atexit (ERR_free_strings);
+
+	struct bot_context ctx;
+	bot_context_init (&ctx);
+
+	struct error *e = NULL;
+	if (!read_config_file (&ctx.config, &e))
+	{
+		print_fatal ("error loading configuration: %s", e->message);
+		error_free (e);
+		exit (EXIT_FAILURE);
+	}
+
+	setup_recovery_handler (&ctx);
+	poller_set (&ctx.poller, g_signal_pipe[0], POLLIN,
+		(poller_dispatcher_func) on_signal_pipe_readable, &ctx);
+
+	plugin_load_all_from_config (&ctx);
+	if (!irc_connect (&ctx, &e))
+	{
+		print_error ("%s", e->message);
+		error_free (e);
+		exit (EXIT_FAILURE);
+	}
+
+	// TODO: clean re-exec support; to save the state I can either use argv,
+	//   argp, or I can create a temporary file, unlink it and use the FD
+	//   (mkstemp() on a `struct str' constructed from XDG_RUNTIME_DIR, TMPDIR
+	//   or /tmp as a last resort + PROGRAM_NAME + ".XXXXXX" -> unlink();
+	//   remember to use O_CREAT | O_EXCL).  The state needs to be versioned.
+	//   Unfortunately I cannot de/serialize SSL state.
+
+	ctx.polling = true;
+	while (ctx.polling)
+		poller_run (&ctx.poller);
+
+	bot_context_free (&ctx);
+	str_vector_free (&g_original_argv);
+	return EXIT_SUCCESS;
+}
+