--
-- censor.lua: black out certain users' messages
--
-- Copyright (c) 2016 - 2021, 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 to_pattern = function (mask)
	if not mask:match ("!") then mask = mask .. "!*" end
	if not mask:match ("@") then mask = mask .. "@*" end

	-- That is, * acts like a wildcard, otherwise everything is escaped
	return "^" .. mask:gsub ("[%^%$%(%)%%%.%[%]%+%-%?]", "%%%0")
		:gsub ("%*", ".*") .. "$"
end

local patterns = {}
local read_masks = function (v)
	patterns = {}
	local add = function (who, where)
		local channels = patterns[who] or {}
		table.insert (channels, where)
		patterns[who] = channels
	end
	for item in v:lower ():gmatch ("[^,]+") do
		local who, where = item:match ("^([^/]+)/*(.*)")
		if who then add (to_pattern (who), where == "" or where) end
	end
end

local quote
degesch.setup_config {
	masks = {
		type = "string_array",
		default = "\"\"",
		comment = "user masks (optionally \"/#channel\") to censor",
		on_change = read_masks
	},
	quote = {
		type = "string",
		default = "\"\\x0301,01\"",
		comment = "formatting prefix for censored messages",
		on_change = function (v) quote = v end
	},
}

local decolor = function (text)
	local rebuilt, last = {""}, 1
	for start in text:gmatch ('()\x03') do
		table.insert (rebuilt, text:sub (last, start - 1))
		local sub = text:sub (start + 1)
		last = start + (sub:match ('^%d%d?,%d%d?()') or sub:match ('^%d?%d?()'))
	end
	return table.concat (rebuilt) .. text:sub (last)
end

local censor = function (line)
	-- Taking a shortcut to avoid lengthy message reassembly
	local start, text = line:match ("^(.- PRIVMSG .- :)(.*)$")
	local ctcp, rest = text:match ("^(\x01%g+ )(.*)")
	text = ctcp and ctcp .. quote .. decolor (rest) or quote .. decolor (text)
	return start .. text
end

degesch.hook_irc (function (hook, server, line)
	local msg = degesch.parse (line)
	if msg.command ~= "PRIVMSG" then return line end

	local channel = msg.params[1]:lower ()
	for who, where in pairs (patterns) do
		if msg.prefix:lower ():match (who) then
			for _, x in pairs (where) do
				if x == true or x == channel then
					return censor (line)
				end
			end
		end
	end
	return line
end)