Start X11 and web frontends for xC

For this, we needed a wire protocol.  After surveying available options,
it was decided to implement an XDR-like protocol code generator
in portable AWK.  It now has two backends, per each of:

 - xF, the X11 frontend, is in C, and is meant to be the primary
   user interface in the future.

 - xP, the web frontend, relies on a protocol proxy written in Go,
   and is meant for use on-the-go (no pun intended).

They are very much work-in-progress proofs of concept right now,
and the relay protocol is certain to change.

1 files changed, 742 insertions, 43 deletions

diff --git a/xC.c b/xC.c
index c80499c..e0c9e01 100644
--- a/xC.c
+++ b/xC.c
@@ -50,6 +50,7 @@ enum
 
 #include "common.c"
 #include "xD-replies.c"
+#include "xC-proto.c"
 
 #include <math.h>
 #include <langinfo.h>
@@ -1526,6 +1527,7 @@ enum buffer_line_flags
 	BUFFER_LINE_HIGHLIGHT   = 1 << 2,   ///< The user was highlighted by this
 };
 
+// NOTE: This sequence must match up with xC-proto, only one lower.
 enum buffer_line_rendition
 {
 	BUFFER_LINE_BARE,                   ///< Unadorned
@@ -1666,6 +1668,50 @@ buffer_destroy (struct buffer *self)
 REF_COUNTABLE_METHODS (buffer)
 #define buffer_ref do_not_use_dangerous
 
+// ~~~ Relay ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+struct client
+{
+	LIST_HEADER (struct client)
+	struct app_context *ctx;            ///< Application context
+
+	// TODO: Convert this all to TLS, and only TLS, with required client cert.
+	//   That means replacing plumbing functions with the /other/ set from xD.
+
+	int socket_fd;                      ///< The TCP socket
+	struct str read_buffer;             ///< Unprocessed input
+	struct str write_buffer;            ///< Output yet to be sent out
+
+	uint32_t event_seq;                 ///< Outgoing message counter
+	bool initialized;                   ///< Initial sync took place
+
+	struct poller_fd socket_event;      ///< The socket can be read/written to
+};
+
+static struct client *
+client_new (void)
+{
+	struct client *self = xcalloc (1, sizeof *self);
+	self->socket_fd = -1;
+	self->read_buffer = str_make ();
+	self->write_buffer = str_make ();
+	return self;
+}
+
+static void
+client_destroy (struct client *self)
+{
+	if (!soft_assert (self->socket_fd == -1))
+		xclose (self->socket_fd);
+
+	str_free (&self->read_buffer);
+	str_free (&self->write_buffer);
+	free (self);
+}
+
+static void client_kill (struct client *c);
+static bool client_process_buffer (struct client *c);
+
 // ~~~ Server ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 // The only real purpose of this is to abstract away TLS
@@ -2079,10 +2125,19 @@ struct app_context
 
 	struct str_map servers;             ///< Our servers
 
+	// Relay:
+
+	int relay_fd;                       ///< Listening socket FD
+	struct client *clients;             ///< Our relay clients
+
+	/// A single message buffer to prepare all outcoming messages within
+	struct relay_event_message relay_message;
+
 	// Events:
 
 	struct poller_fd tty_event;         ///< Terminal input event
 	struct poller_fd signal_event;      ///< Signal FD event
+	struct poller_fd relay_event;       ///< New relay connection available
 
 	struct poller_timer flush_timer;    ///< Flush all open files (e.g. logs)
 	struct poller_timer date_chg_tmr;   ///< Print a date change
@@ -2129,6 +2184,8 @@ struct app_context
 	char *editor_filename;              ///< The file being edited by user
 	int terminal_suspended;             ///< Terminal suspension level
 
+	// Plugins:
+
 	struct plugin *plugins;             ///< Loaded plugins
 	struct hook *input_hooks;           ///< Input hooks
 	struct hook *irc_hooks;             ///< IRC hooks
@@ -2197,6 +2254,8 @@ app_context_init (struct app_context *self)
 	self->config = config_make ();
 	poller_init (&self->poller);
 
+	self->relay_fd = -1;
+
 	self->servers = str_map_make ((str_map_free_fn) server_unref);
 	self->servers.key_xfrm = tolower_ascii_strxfrm;
 
@@ -2223,6 +2282,17 @@ app_context_init (struct app_context *self)
 }
 
 static void
+app_context_relay_stop (struct app_context *self)
+{
+	if (self->relay_fd != -1)
+	{
+		poller_fd_reset (&self->relay_event);
+		xclose (self->relay_fd);
+		self->relay_fd = -1;
+	}
+}
+
+static void
 app_context_free (struct app_context *self)
 {
 	// Plugins can try to use of the other fields when destroyed
@@ -2247,6 +2317,11 @@ app_context_free (struct app_context *self)
 	}
 	str_map_free (&self->buffers_by_name);
 
+	app_context_relay_stop (self);
+	LIST_FOR_EACH (struct client, c, self->clients)
+		client_kill (c);
+	relay_event_message_free (&self->relay_message);
+
 	str_map_free (&self->servers);
 	poller_free (&self->poller);
 
@@ -2285,6 +2360,7 @@ on_config_show_all_prefixes_change (struct config_item *item)
 	refresh_prompt (ctx);
 }
 
+static void on_config_relay_bind_change (struct config_item *item);
 static void on_config_backlog_limit_change (struct config_item *item);
 static void on_config_attribute_change (struct config_item *item);
 static void on_config_logging_change (struct config_item *item);
@@ -2479,6 +2555,11 @@ static struct config_schema g_config_general[] =
 	  .comment   = "Plugins to automatically load on start",
 	  .type      = CONFIG_ITEM_STRING_ARRAY,
 	  .validate  = config_validate_nonjunk_string },
+	{ .name      = "relay_bind",
+	  .comment   = "Address to bind to for a user interface relay point",
+	  .type      = CONFIG_ITEM_STRING,
+	  .validate  = config_validate_nonjunk_string,
+	  .on_change = on_config_relay_bind_change },
 
 	// Buffer history:
 	{ .name      = "backlog_limit",
@@ -2681,6 +2762,418 @@ serialize_configuration (struct config_item *root, struct str *output)
 	config_item_write (root, true, output);
 }
 
+// --- Relay plumbing ----------------------------------------------------------
+
+static void
+client_kill (struct client *c)
+{
+	struct app_context *ctx = c->ctx;
+	poller_fd_reset (&c->socket_event);
+	xclose (c->socket_fd);
+	c->socket_fd = -1;
+
+	LIST_UNLINK (ctx->clients, c);
+	client_destroy (c);
+}
+
+static bool
+client_try_read (struct client *c)
+{
+	struct str *buf = &c->read_buffer;
+	ssize_t n_read;
+
+	while ((n_read = read (c->socket_fd, buf->str + buf->len,
+		buf->alloc - buf->len - 1 /* null byte */)) > 0)
+	{
+		buf->len += n_read;
+		if (!client_process_buffer (c))
+			break;
+		str_reserve (buf, 512);
+	}
+
+	if (n_read < 0)
+	{
+		if (errno == EAGAIN || errno == EINTR)
+			return true;
+
+		print_debug ("%s: %s: %s", __func__, "read", strerror (errno));
+	}
+
+	client_kill (c);
+	return false;
+}
+
+static bool
+client_try_write (struct client *c)
+{
+	struct str *buf = &c->write_buffer;
+	ssize_t n_written;
+
+	while (buf->len)
+	{
+		n_written = write (c->socket_fd, buf->str, buf->len);
+		if (n_written >= 0)
+		{
+			str_remove_slice (buf, 0, n_written);
+			continue;
+		}
+		if (errno == EAGAIN || errno == EINTR)
+			return true;
+
+		print_debug ("%s: %s: %s", __func__, "write", strerror (errno));
+		client_kill (c);
+		return false;
+	}
+	return true;
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+
+static void
+client_update_poller (struct client *c, const struct pollfd *pfd)
+{
+	int new_events = POLLIN;
+	if (c->write_buffer.len)
+		new_events |= POLLOUT;
+
+	hard_assert (new_events != 0);
+	if (!pfd || pfd->events != new_events)
+		poller_fd_set (&c->socket_event, new_events);
+}
+
+static void
+on_client_ready (const struct pollfd *pfd, void *user_data)
+{
+	struct client *c = user_data;
+	if (client_try_read (c) && client_try_write (c))
+		client_update_poller (c, pfd);
+}
+
+static bool
+relay_try_fetch_client (struct app_context *ctx, int listen_fd)
+{
+	// XXX: `struct sockaddr_storage' is not the most portable thing
+	struct sockaddr_storage peer;
+	socklen_t peer_len = sizeof peer;
+
+	int fd = accept (listen_fd, (struct sockaddr *) &peer, &peer_len);
+	if (fd == -1)
+	{
+		if (errno == EAGAIN || errno == EWOULDBLOCK)
+			return false;
+		if (errno == EINTR)
+			return true;
+
+		if (accept_error_is_transient (errno))
+			print_warning ("%s: %s", "accept", strerror (errno));
+		else
+			print_fatal ("%s: %s", "accept", strerror (errno));
+		return true;
+	}
+
+	hard_assert (peer_len <= sizeof peer);
+	set_blocking (fd, false);
+	set_cloexec (fd);
+
+	// We already buffer our output, so reduce latencies.
+	int yes = 1;
+	soft_assert (setsockopt (fd, IPPROTO_TCP, TCP_NODELAY,
+		&yes, sizeof yes) != -1);
+
+	struct client *c = client_new ();
+	c->ctx = ctx;
+	c->socket_fd = fd;
+	LIST_PREPEND (ctx->clients, c);
+
+	c->socket_event = poller_fd_make (&c->ctx->poller, c->socket_fd);
+	c->socket_event.dispatcher = (poller_fd_fn) on_client_ready;
+	c->socket_event.user_data = c;
+
+	client_update_poller (c, NULL);
+	return true;
+}
+
+static void
+on_relay_client_available (const struct pollfd *pfd, void *user_data)
+{
+	struct app_context *ctx = user_data;
+	while (relay_try_fetch_client (ctx, pfd->fd))
+		;
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+
+static int
+relay_listen (struct addrinfo *ai, struct error **e)
+{
+	int fd = socket (ai->ai_family, ai->ai_socktype, ai->ai_protocol);
+	if (fd == -1)
+	{
+		error_set (e, "socket: %s", strerror (errno));
+		return -1;
+	}
+
+	set_cloexec (fd);
+
+	int yes = 1;
+	soft_assert (setsockopt (fd, SOL_SOCKET, SO_KEEPALIVE,
+		&yes, sizeof yes) != -1);
+	soft_assert (setsockopt (fd, SOL_SOCKET, SO_REUSEADDR,
+		&yes, sizeof yes) != -1);
+
+	if (bind (fd, ai->ai_addr, ai->ai_addrlen))
+		error_set (e, "bind: %s", strerror (errno));
+	else if (listen (fd, 16 /* arbitrary number */))
+		error_set (e, "listen: %s", strerror (errno));
+	else
+		return fd;
+
+	xclose (fd);
+	return -1;
+}
+
+static int
+relay_listen_with_context (struct addrinfo *ai, struct error **e)
+{
+	char *address = gai_reconstruct_address (ai);
+	print_debug ("binding to `%s'", address);
+
+	struct error *error = NULL;
+	int fd = relay_listen (ai, &error);
+	if (fd == -1)
+	{
+		error_set (e, "binding to `%s' failed: %s", address, error->message);
+		error_free (error);
+	}
+	free (address);
+	return fd;
+}
+
+static bool
+relay_start (struct app_context *ctx, char *address, struct error **e)
+{
+	const char *port = NULL, *host = tokenize_host_port (address, &port);
+	if (!port || !*port)
+		return error_set (e, "missing port");
+
+	struct addrinfo hints = {}, *result = NULL;
+	hints.ai_socktype = SOCK_STREAM;
+	hints.ai_flags = AI_PASSIVE;
+
+	int err = getaddrinfo (*host ? host : NULL, port, &hints, &result);
+	if (err)
+	{
+		return error_set (e, "failed to resolve `%s', port `%s': %s: %s",
+			host, port, "getaddrinfo", gai_strerror (err));
+	}
+
+	// Just try the first one, disregarding IPv4/IPv6 ordering.
+	int fd = relay_listen_with_context (result, e);
+	freeaddrinfo (result);
+	if (fd == -1)
+		return false;
+
+	set_blocking (fd, false);
+
+	struct poller_fd *event = &ctx->relay_event;
+	*event = poller_fd_make (&ctx->poller, fd);
+	event->dispatcher = (poller_fd_fn) on_relay_client_available;
+	event->user_data = ctx;
+
+	ctx->relay_fd = fd;
+	poller_fd_set (event, POLLIN);
+	return true;
+}
+
+static void
+on_config_relay_bind_change (struct config_item *item)
+{
+	struct app_context *ctx = item->user_data;
+	char *value = item->value.string.str;
+	app_context_relay_stop (ctx);
+	if (!value)
+		return;
+
+	struct error *e = NULL;
+	char *address = xstrdup (value);
+	if (!relay_start (ctx, address, &e))
+	{
+		// TODO: Try to make sure this finds its way to the global buffer.
+		print_error ("%s: %s", item->schema->name, e->message);
+		error_free (e);
+	}
+	free (address);
+}
+
+// --- Relay output ------------------------------------------------------------
+
+static void
+relay_send (struct client *c)
+{
+	struct relay_event_message *m = &c->ctx->relay_message;
+	m->event_seq = c->event_seq++;
+
+	// TODO: Also don't try sending anything if half-closed.
+	if (!c->initialized || c->socket_fd == -1)
+		return;
+
+	// liberty has msg_{reader,writer} already, but they use 8-byte lengths.
+	size_t frame_len_pos = c->write_buffer.len, frame_len = 0;
+	str_pack_u32 (&c->write_buffer, 0);
+	if (!relay_event_message_serialize (m, &c->write_buffer)
+	 || (frame_len = c->write_buffer.len - frame_len_pos - 4) > UINT32_MAX)
+	{
+		print_error ("serialization failed, killing client");
+		client_kill (c);
+		return;
+	}
+
+	uint32_t len = htonl (frame_len);
+	memcpy (c->write_buffer.str + frame_len_pos, &len, sizeof len);
+	client_update_poller (c, NULL);
+}
+
+static void
+relay_broadcast (struct app_context *ctx)
+{
+	LIST_FOR_EACH (struct client, c, ctx->clients)
+		relay_send (c);
+}
+
+static struct relay_event_message *
+relay_prepare (struct app_context *ctx)
+{
+	struct relay_event_message *m = &ctx->relay_message;
+	relay_event_message_free (m);
+	memset (m, 0, sizeof *m);
+	return m;
+}
+
+static void
+relay_prepare_ping (struct app_context *ctx)
+{
+	relay_prepare (ctx)->data.event = RELAY_EVENT_PING;
+}
+
+static void
+relay_prepare_buffer_update (struct app_context *ctx, struct buffer *buffer)
+{
+	struct relay_event_message *m = relay_prepare (ctx);
+	struct relay_event_data_buffer_update *e = &m->data.buffer_update;
+	e->event = RELAY_EVENT_BUFFER_UPDATE;
+	e->buffer_name = str_from_cstr (buffer->name);
+}
+
+static void
+relay_prepare_buffer_rename (struct app_context *ctx, struct buffer *buffer,
+	const char *new_name)
+{
+	struct relay_event_message *m = relay_prepare (ctx);
+	struct relay_event_data_buffer_rename *e = &m->data.buffer_rename;
+	e->event = RELAY_EVENT_BUFFER_RENAME;
+	e->buffer_name = str_from_cstr (buffer->name);
+	e->new = str_from_cstr (new_name);
+}
+
+static void
+relay_prepare_buffer_remove (struct app_context *ctx, struct buffer *buffer)
+{
+	struct relay_event_message *m = relay_prepare (ctx);
+	struct relay_event_data_buffer_remove *e = &m->data.buffer_remove;
+	e->event = RELAY_EVENT_BUFFER_REMOVE;
+	e->buffer_name = str_from_cstr (buffer->name);
+}
+
+static void
+relay_prepare_buffer_activate (struct app_context *ctx, struct buffer *buffer)
+{
+	struct relay_event_message *m = relay_prepare (ctx);
+	struct relay_event_data_buffer_activate *e = &m->data.buffer_activate;
+	e->event = RELAY_EVENT_BUFFER_ACTIVATE;
+	e->buffer_name = str_from_cstr (buffer->name);
+}
+
+static void
+relay_prepare_buffer_line (struct app_context *ctx, struct buffer *buffer,
+	struct buffer_line *line)
+{
+	struct relay_event_message *m = relay_prepare (ctx);
+	struct relay_event_data_buffer_line *e = &m->data.buffer_line;
+	e->event = RELAY_EVENT_BUFFER_LINE;
+	e->buffer_name = str_from_cstr (buffer->name);
+	e->is_unimportant = !!(line->flags & BUFFER_LINE_UNIMPORTANT);
+	e->is_highlight = !!(line->flags & BUFFER_LINE_HIGHLIGHT);
+	e->rendition = 1 + line->r;
+	e->when = line->when;
+
+	size_t len = 0;
+	for (size_t i = 0; line->items[i].type; i++)
+		len++;
+
+	// XXX: This way helps xP's JSON conversion, but is super annoying for us.
+	union relay_item_data *p = e->items = xcalloc (len * 6, sizeof *e->items);
+	for (struct formatter_item *i = line->items; len--; i++)
+	{
+		switch (i->type)
+		{
+		case FORMATTER_ITEM_TEXT:
+			p->text.text = str_from_cstr (i->text);
+			(p++)->kind = RELAY_ITEM_TEXT;
+			break;
+		case FORMATTER_ITEM_ATTR:
+			// For future consideration.
+			(p++)->kind = RELAY_ITEM_RESET;
+			break;
+		case FORMATTER_ITEM_FG_COLOR:
+			p->fg_color.color = i->color;
+			(p++)->kind = RELAY_ITEM_FG_COLOR;
+			break;
+		case FORMATTER_ITEM_BG_COLOR:
+			p->bg_color.color = i->color;
+			(p++)->kind = RELAY_ITEM_BG_COLOR;
+			break;
+		case FORMATTER_ITEM_SIMPLE:
+			if (i->attribute & TEXT_BOLD)
+				(p++)->kind = RELAY_ITEM_FLIP_BOLD;
+			if (i->attribute & TEXT_ITALIC)
+				(p++)->kind = RELAY_ITEM_FLIP_ITALIC;
+			if (i->attribute & TEXT_UNDERLINE)
+				(p++)->kind = RELAY_ITEM_FLIP_UNDERLINE;
+			if (i->attribute & TEXT_INVERSE)
+				(p++)->kind = RELAY_ITEM_FLIP_INVERSE;
+			if (i->attribute & TEXT_CROSSED_OUT)
+				(p++)->kind = RELAY_ITEM_FLIP_CROSSED_OUT;
+			if (i->attribute & TEXT_MONOSPACE)
+				(p++)->kind = RELAY_ITEM_FLIP_MONOSPACE;
+			break;
+		default:
+			break;
+		}
+	}
+
+	e->items_len = p - e->items;
+}
+
+static void
+relay_prepare_buffer_clear (struct app_context *ctx,
+	struct buffer *buffer)
+{
+	struct relay_event_message *m = relay_prepare (ctx);
+	struct relay_event_data_buffer_clear *e = &m->data.buffer_clear;
+	e->event = RELAY_EVENT_BUFFER_CLEAR;
+	e->buffer_name = str_from_cstr (buffer->name);
+}
+
+static void
+relay_prepare_error (struct app_context *ctx, uint32_t seq, const char *message)
+{
+	struct relay_event_message *m = relay_prepare (ctx);
+	struct relay_event_data_error *e = &m->data.error;
+	e->event = RELAY_EVENT_ERROR;
+	e->command_seq = seq;
+	e->error = str_from_cstr (message);
+}
+
 // --- Terminal output ---------------------------------------------------------
 
 /// Default colour pair
@@ -4089,6 +4582,9 @@ log_formatter (struct app_context *ctx, struct buffer *buffer,
 	if (buffer->log_file)
 		buffer_line_write_to_log (ctx, line, buffer->log_file);
 
+	relay_prepare_buffer_line (ctx, buffer, line);
+	relay_broadcast (ctx);
+
 	bool unseen_pm = buffer->type == BUFFER_PM
 		&& buffer != ctx->current_buffer
 		&& !(flags & BUFFER_LINE_UNIMPORTANT);
@@ -4302,6 +4798,9 @@ buffer_add (struct app_context *ctx, struct buffer *buffer)
 
 	buffer_open_log_file (ctx, buffer);
 
+	relay_prepare_buffer_update (ctx, buffer);
+	relay_broadcast (ctx);
+
 	// Normally this doesn't cause changes in the prompt but a prompt hook
 	// could decide to show some information for all buffers nonetheless
 	refresh_prompt (ctx);
@@ -4328,6 +4827,9 @@ buffer_remove (struct app_context *ctx, struct buffer *buffer)
 	if (buffer->type == BUFFER_SERVER)
 		buffer->server->buffer = NULL;
 
+	relay_prepare_buffer_remove (ctx, buffer);
+	relay_broadcast (ctx);
+
 	str_map_set (&ctx->buffers_by_name, buffer->name, NULL);
 	LIST_UNLINK_WITH_TAIL (ctx->buffers, ctx->buffers_tail, buffer);
 	buffer_unref (buffer);
@@ -4457,6 +4959,9 @@ buffer_activate (struct app_context *ctx, struct buffer *buffer)
 	ctx->last_buffer = ctx->current_buffer;
 	ctx->current_buffer = buffer;
 
+	relay_prepare_buffer_activate (ctx, buffer);
+	relay_broadcast (ctx);
+
 	refresh_prompt (ctx);
 }
 
@@ -4491,12 +4996,19 @@ buffer_merge (struct app_context *ctx,
 	merged->lines_tail = start->prev;
 	merged->lines_count -= n;
 
-	// And append them to current lines in the buffer
+	// Append them to current lines in the buffer
 	buffer->lines_tail->next = start;
 	start->prev = buffer->lines_tail;
 	buffer->lines_tail = tail;
 	buffer->lines_count += n;
 
+	// And since there is no log_*() call, send them to relays manually
+	LIST_FOR_EACH (struct buffer_line, line, start)
+	{
+		relay_prepare_buffer_line (ctx, buffer, line);
+		relay_broadcast (ctx);
+	}
+
 	log_full (ctx, NULL, buffer, BUFFER_LINE_SKIP_FILE, BUFFER_LINE_STATUS,
 		"End of merged content");
 }
@@ -4511,6 +5023,9 @@ buffer_rename (struct app_context *ctx,
 
 	hard_assert (!collision);
 
+	relay_prepare_buffer_rename (ctx, buffer, new_name);
+	relay_broadcast (ctx);
+
 	str_map_set (&ctx->buffers_by_name, buffer->name, NULL);
 	str_map_set (&ctx->buffers_by_name, new_name, buffer);
 
@@ -4524,13 +5039,16 @@ buffer_rename (struct app_context *ctx,
 }
 
 static void
-buffer_clear (struct buffer *buffer)
+buffer_clear (struct app_context *ctx, struct buffer *buffer)
 {
 	LIST_FOR_EACH (struct buffer_line, iter, buffer->lines)
 		buffer_line_destroy (iter);
 
 	buffer->lines = buffer->lines_tail = NULL;
 	buffer->lines_count = 0;
+
+	relay_prepare_buffer_clear (ctx, buffer);
+	relay_broadcast (ctx);
 }
 
 static struct buffer *
@@ -5947,29 +6465,6 @@ irc_finish_connection (struct server *s, int socket, const char *hostname)
 	refresh_prompt (s->ctx);
 }
 
-/// Unwrap IPv6 addresses in format_host_port_pair() format
-static void
-irc_split_host_port (char *s, char **host, char **port)
-{
-	*host = s;
-	*port = "6667";
-
-	char *right_bracket = strchr (s, ']');
-	if (s[0] == '[' && right_bracket)
-	{
-		*right_bracket = '\0';
-		*host = s + 1;
-		s = right_bracket + 1;
-	}
-
-	char *colon = strchr (s, ':');
-	if (colon)
-	{
-		*colon = '\0';
-		*port = colon + 1;
-	}
-}
-
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 
 static void
@@ -6019,8 +6514,8 @@ irc_setup_connector (struct server *s, const struct strv *addresses)
 
 	for (size_t i = 0; i < addresses->len; i++)
 	{
-		char *host, *port;
-		irc_split_host_port (addresses->vector[i], &host, &port);
+		const char *port = "6667",
+			*host = tokenize_host_port (addresses->vector[i], &port);
 		connector_add_target (connector, host, port);
 	}
 }
@@ -6062,9 +6557,8 @@ irc_setup_connector_socks (struct server *s, const struct strv *addresses,
 
 	for (size_t i = 0; i < addresses->len; i++)
 	{
-		char *host, *port;
-		irc_split_host_port (addresses->vector[i], &host, &port);
-
+		const char *port = "6667",
+			*host = tokenize_host_port (addresses->vector[i], &port);
 		if (!socks_connector_add_target (connector, host, port, e))
 			return false;
 	}
@@ -7644,7 +8138,7 @@ irc_on_registered (struct server *s, const char *nickname)
 	if (command)
 	{
 		log_server_debug (s, "Executing \"#s\"", command);
-		process_input_utf8 (s->ctx, s->buffer, command, 0);
+		(void) process_input_utf8 (s->ctx, s->buffer, command, 0);
 	}
 
 	int64_t command_delay = get_config_integer (s->config, "command_delay");
@@ -8230,6 +8724,24 @@ irc_handle_rpl_isupport (struct server *s, const struct irc_message *msg)
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 
 static void
+irc_adjust_motd (char **motd)
+{
+	// Heuristic, force MOTD to be monospace in graphical frontends.
+	if (!strchr (*motd, '\x11'))
+	{
+		struct str s = str_make ();
+		str_append_c (&s, '\x11');
+		for (const char *p = *motd; *p; p++)
+		{
+			str_append_c (&s, *p);
+			if (*p == '\x0f')
+				str_append_c (&s, '\x11');
+		}
+		cstr_set (motd, str_steal (&s));
+	}
+}
+
+static void
 irc_process_numeric (struct server *s,
 	const struct irc_message *msg, unsigned long numeric)
 {
@@ -8251,6 +8763,10 @@ irc_process_numeric (struct server *s,
 		if (msg->params.len == 2)
 			irc_try_parse_welcome_for_userhost (s, msg->params.vector[1]);
 		break;
+	case IRC_RPL_MOTD:
+		if (copy.len)
+			irc_adjust_motd (&copy.vector[0]);
+		break;
 
 	case IRC_RPL_ISUPPORT:
 		irc_handle_rpl_isupport      (s, msg);                break;
@@ -9248,7 +9764,7 @@ lua_buffer_execute (lua_State *L)
 	struct lua_weak *wrapper = lua_weak_deref (L, &lua_buffer_info);
 	struct buffer *buffer = wrapper->object;
 	const char *line = lua_plugin_check_utf8 (L, 2);
-	process_input_utf8 (wrapper->plugin->ctx, buffer, line, 0);
+	(void) process_input_utf8 (wrapper->plugin->ctx, buffer, line, 0);
 	return 0;
 }
 
@@ -11304,7 +11820,7 @@ handle_command_buffer (struct handler_args *a)
 		show_buffers_list (ctx);
 	else if (!strcasecmp_ascii (action, "clear"))
 	{
-		buffer_clear (a->buffer);
+		buffer_clear (ctx, a->buffer);
 		if (a->buffer == ctx->current_buffer)
 			buffer_print_backlog (ctx, a->buffer);
 	}
@@ -12926,8 +13442,8 @@ complete_set_value_array (struct config_item *item, const char *word,
 	cstr_split (item->value.string.str, ",", false, &items);
 	for (size_t i = 0; i < items.len; i++)
 	{
-		struct str wrapped = str_make (), serialized = str_make ();
-		str_append (&wrapped, items.vector[i]);
+		struct str wrapped = str_from_cstr (items.vector[i]);
+		struct str serialized = str_make ();
 		config_item_write_string (&serialized, &wrapped);
 		str_free (&wrapped);
 
@@ -13546,6 +14062,25 @@ on_display_backlog_nowrap (int count, int key, void *user_data)
 	return display_backlog (user_data, FLUSH_OPT_NOWRAP);
 }
 
+static FILE *
+open_log_path (struct app_context *ctx, struct buffer *buffer, const char *path)
+{
+	FILE *fp = fopen (path, "rb");
+	if (!fp)
+	{
+		log_global_error (ctx,
+			"Failed to open `#l': #l", path, strerror (errno));
+		return NULL;
+	}
+
+	if (buffer->log_file)
+		// The regular flush will log any error eventually
+		(void) fflush (buffer->log_file);
+
+	set_cloexec (fileno (fp));
+	return fp;
+}
+
 static bool
 on_display_full_log (int count, int key, void *user_data)
 {
@@ -13555,20 +14090,13 @@ on_display_full_log (int count, int key, void *user_data)
 
 	struct buffer *buffer = ctx->current_buffer;
 	char *path = buffer_get_log_path (buffer);
-	FILE *full_log = fopen (path, "rb");
+	FILE *full_log = open_log_path (ctx, buffer, path);
 	if (!full_log)
 	{
-		log_global_error (ctx, "Failed to open log file for #s: #l",
-			ctx->current_buffer->name, strerror (errno));
 		free (path);
 		return false;
 	}
 
-	if (buffer->log_file)
-		// The regular flush will log any error eventually
-		(void) fflush (buffer->log_file);
-
-	set_cloexec (fileno (full_log));
 	launch_pager (ctx, fileno (full_log), buffer->name, path);
 	fclose (full_log);
 	free (path);
@@ -14601,6 +15129,177 @@ init_poller_events (struct app_context *ctx)
 	ctx->input_event.user_data = ctx;
 }
 
+// --- Relay processing --------------------------------------------------------
+
+// XXX: This could be below completion code if reset_autoaway() was higher up.
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+
+static void
+client_resync (struct client *c)
+{
+	LIST_FOR_EACH (struct buffer, buffer, c->ctx->buffers)
+	{
+		relay_prepare_buffer_update (c->ctx, buffer);
+		relay_send (c);
+
+		LIST_FOR_EACH (struct buffer_line, line, buffer->lines)
+		{
+			relay_prepare_buffer_line (c->ctx, buffer, line);
+			relay_send (c);
+		}
+	}
+
+	relay_prepare_buffer_activate (c->ctx, c->ctx->current_buffer);
+	relay_send (c);
+}
+
+static const char *
+client_message_buffer_name (const struct relay_command_message *m)
+{
+	switch (m->data.command)
+	{
+	case RELAY_COMMAND_BUFFER_COMPLETE:
+		return m->data.buffer_input.buffer_name.str;
+	case RELAY_COMMAND_BUFFER_INPUT:
+		return m->data.buffer_input.buffer_name.str;
+	case RELAY_COMMAND_BUFFER_ACTIVATE:
+		return m->data.buffer_activate.buffer_name.str;
+	case RELAY_COMMAND_BUFFER_LOG:
+		return m->data.buffer_log.buffer_name.str;
+	default:
+		return NULL;
+	}
+}
+
+static void
+client_process_buffer_log
+	(struct client *c, uint32_t seq, struct buffer *buffer)
+{
+	struct relay_event_message *m = relay_prepare (c->ctx);
+	struct relay_event_data_response *e = &m->data.response;
+	e->event = RELAY_EVENT_RESPONSE;
+	e->command_seq = seq;
+	e->data.command = RELAY_COMMAND_BUFFER_LOG;
+
+	char *path = buffer_get_log_path (buffer);
+	FILE *fp = open_log_path (c->ctx, buffer, path);
+	if (fp)
+	{
+		struct str log = str_make ();
+		char buf[BUFSIZ];
+		size_t len;
+		while ((len = fread (buf, 1, sizeof buf, fp)))
+			str_append_data (&log, buf, len);
+		if (ferror (fp))
+			log_global_error (c->ctx, "Failed to read `#l': #l",
+				path, strerror (errno));
+
+		// On overflow, it will later fail serialization.
+		e->data.buffer_log.log_len = MIN (UINT32_MAX, log.len);
+		e->data.buffer_log.log = (uint8_t *) str_steal (&log);
+		fclose (fp);
+	}
+
+	// XXX: We log failures to the global buffer,
+	//   so the client just receives nothing if there is no log file.
+
+	free (path);
+	relay_send (c);
+}
+
+static bool
+client_process_message (struct client *c,
+	struct msg_unpacker *r, struct relay_command_message *m)
+{
+	if (!relay_command_message_deserialize (m, r)
+	 || msg_unpacker_get_available (r))
+	{
+		print_error ("deserialization failed, killing client");
+		return false;
+	}
+
+	const char *buffer_name = client_message_buffer_name (m);
+	struct buffer *buffer = NULL;
+	if (buffer_name && !(buffer = buffer_by_name (c->ctx, buffer_name)))
+	{
+		relay_prepare_error (c->ctx, m->command_seq, "Unknown buffer");
+		relay_send (c);
+		return true;
+	}
+
+	switch (m->data.command)
+	{
+	case RELAY_COMMAND_HELLO:
+		if (m->data.hello.version != RELAY_VERSION)
+		{
+			// TODO: This should send back an error message and shut down.
+			print_error ("protocol version mismatch, killing client");
+			return false;
+		}
+		c->initialized = true;
+		client_resync (c);
+		break;
+	case RELAY_COMMAND_PING:
+		relay_prepare_ping (c->ctx);
+		relay_send (c);
+		break;
+	case RELAY_COMMAND_ACTIVE:
+		reset_autoaway (c->ctx);
+		break;
+	case RELAY_COMMAND_BUFFER_COMPLETE:
+		// TODO: Run the completion machinery.
+		relay_prepare_error (c->ctx, m->command_seq, "Not implemented");
+		relay_send (c);
+		break;
+	case RELAY_COMMAND_BUFFER_INPUT:
+		(void) process_input_utf8 (c->ctx,
+			buffer, m->data.buffer_input.text.str, 0);
+		break;
+	case RELAY_COMMAND_BUFFER_ACTIVATE:
+		buffer_activate (c->ctx, buffer);
+		break;
+	case RELAY_COMMAND_BUFFER_LOG:
+		client_process_buffer_log (c, m->command_seq, buffer);
+		break;
+	default:
+		print_warning ("unhandled client command");
+		relay_prepare_error (c->ctx, m->command_seq, "Unknown command");
+		relay_send (c);
+	}
+	return true;
+}
+
+static bool
+client_process_buffer (struct client *c)
+{
+	struct str *buf = &c->read_buffer;
+	size_t offset = 0;
+	while (true)
+	{
+		uint32_t frame_len = 0;
+		struct msg_unpacker r =
+			msg_unpacker_make (buf->str + offset, buf->len - offset);
+		if (!msg_unpacker_u32 (&r, &frame_len))
+			break;
+
+		r.len = MIN (r.len, sizeof frame_len + frame_len);
+		if (msg_unpacker_get_available (&r) < frame_len)
+			break;
+
+		struct relay_command_message m = {};
+		bool ok = client_process_message (c, &r, &m);
+		relay_command_message_free (&m);
+		if (!ok)
+			return false;
+
+		offset += r.offset;
+	}
+
+	str_remove_slice (buf, 0, offset);
+	return true;
+}
+
 // --- Tests -------------------------------------------------------------------
 
 // The application is quite monolithic and can only be partially unit-tested.