1 files changed, 68 insertions, 0 deletions
diff --git a/plugins/xC/prime.lua b/plugins/xC/prime.lua
new file mode 100644
index 0000000..23740ee
--- /dev/null
+++ b/plugins/xC/prime.lua
@@ -0,0 +1,68 @@
+--
+-- prime.lua: highlight prime numbers in messages
+--
+-- Copyright (c) 2020, Přemysl Eric Janouch <p@janouch.name>
+--
+-- Permission to use, copy, modify, and/or distribute this software for any
+-- purpose with or without fee is hereby granted.
+--
+-- 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.
+--
+
+local smallest, highlight = 0, "\x1f"
+xC.setup_config {
+	smallest = {
+		type = "integer",
+		default = "0",
+		comment = "smallest number to scan for primality",
+		on_change = function (v) smallest = math.max (v, 2) end
+	},
+	highlight = {
+		type = "string",
+		default = "\"\\x1f\"",
+		comment = "the attribute to use for highlights",
+		on_change = function (v) highlight = v end
+	},
+}
+
+-- The prime test is actually very fast, so there is no DoS concern
+local do_intercolour = function (text)
+	return tostring (text:gsub ("%f[%w_]%d+", function (n)
+		if tonumber (n) < smallest then return nil end
+		for i = 2, n ^ (1 / 2) do if (n % i) == 0 then return nil end end
+		return highlight .. n .. highlight
+	end))
+end
+
+local do_interlink = function (text)
+	local rebuilt, last = {""}, 1
+	for start in text:gmatch ('()\x03') do
+		table.insert (rebuilt, do_intercolour (text:sub (last, start - 1)))
+		local sub = text:sub (start + 1)
+		last = start + (sub:match ('^%d%d?,%d%d?()') or sub:match ('^%d?%d?()'))
+		table.insert (rebuilt, text:sub (start, last - 1))
+	end
+	return table.concat (rebuilt) .. do_intercolour (text:sub (last))
+end
+
+local do_message = function (text)
+	local rebuilt, last = {""}, 1
+	for run, link, endpos in text:gmatch ('(.-)(%f[%g]https?://%g+)()') do
+		last = endpos
+		table.insert (rebuilt, do_interlink (run) .. link)
+	end
+	return table.concat (rebuilt) .. do_interlink (text:sub (last))
+end
+
+-- XXX: sadly it won't typically highlight primes in our own messages,
+-- unless IRCv3 echo-message is on
+xC.hook_irc (function (hook, server, line)
+	local start, message = line:match ("^(.- PRIVMSG .- :)(.*)$")
+	return message and start .. do_message (message) or line
+end)