#!/usr/bin/env lua
--
-- xB seen plugin
--
-- Copyright 2016 Přemysl Eric Janouch <p@janouch.name>
-- See the file LICENSE for licensing information.
--

function parse (line)
	local msg = { params = {} }
	line = line:match ("[^\r]*")
	for start, word in line:gmatch ("()([^ ]+)") do
		local colon = word:match ("^:(.*)")
		if start == 1 and colon then
			msg.prefix = colon
		elseif not msg.command then
			msg.command = word
		elseif colon then
			table.insert (msg.params, line:sub (start + 1))
			break
		elseif start ~= #line then
			table.insert (msg.params, word)
		end
	end
	return msg
end

function get_config (name)
	io.write ("XB get_config :", name, "\r\n")
	return parse (io.read ()).params[1]
end

-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

io.output ():setvbuf ('line')
local prefix = get_config ('prefix')
io.write ("XB register\r\n")

local db = {}
local db_filename = "seen.db"
local db_garbage = 0

function remember (who, where, when, what)
	if not db[who] then db[who] = {} end
	if db[who][where] then db_garbage = db_garbage + 1 end
	db[who][where] = { tonumber (when), what }
end

-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

local db_file, e = io.open (db_filename, "a+")
if not db_file then error ("cannot open database: " .. e, 0) end

function db_store (who, where, when, what)
	db_file:write (string.format
		(":%s %s %s %s :%s\n", who, "PRIVMSG", where, when, what))
end

function db_compact ()
	db_file:close ()

	-- Unfortunately, default Lua doesn't have anything like mkstemp()
	local db_tmpname = db_filename .. "." .. os.time ()
	db_file, e = io.open (db_tmpname, "a+")
	if not db_file then error ("cannot save database: " .. e, 0) end

	for who, places in pairs (db) do
		for where, data in pairs (places) do
			db_store (who, where, data[1], data[2])
		end
	end
	db_file:flush ()

	local ok, e = os.rename (db_tmpname, db_filename)
	if not ok then error ("cannot save database: " .. e, 0) end
	db_garbage = 0
end

for line in db_file:lines () do
	local msg = parse (line)
	remember (msg.prefix, table.unpack (msg.params))
end

-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

function seen (who, where, args)
	local respond = function (...)
		local privmsg = function (target, ...)
			io.write ("PRIVMSG ", target, " :", table.concat { ... }, "\r\n")
		end
		if where:match ("^[#&!+]") then
			privmsg (where, who, ": ", ...)
		else
			privmsg (who, ...)
		end
	end

	local whom, e, garbage = args:match ("^(%S+)()%s*(.*)")
	if not whom or #garbage ~= 0 then
		return respond ("usage: <name>")
	elseif who:lower () == whom:lower () then
		return respond ("I can see you right now.")
	end

	local top = {}
	-- That is, * acts like a wildcard, otherwise everything is escaped
	local pattern = "^" .. whom:gsub ("[%^%$%(%)%%%.%[%]%+%-%?]", "%%%0")
		:gsub ("%*", ".*"):lower () .. "$"
	for name, places in pairs (db) do
		if places[where] and name:lower ():match (pattern) then
			local when, what = table.unpack (places[where])
			table.insert (top, { name = name, when = when, what = what })
		end
	end
	if #top == 0 then
		return respond ("I have not seen \x02" .. whom .. "\x02 here.")
	end

	-- Get all matching nicknames ordered from the most recently active
	-- and make the list case insensitive (remove older duplicates)
	table.sort (top, function (a, b) return a.when > b.when end)
	for i = #top, 2, -1 do
		if top[i - 1].name:lower () == top[i].name:lower () then
			table.remove (top, i)
		end
	end

	-- Hopefully the formatting mess will disrupt highlights in clients
	for i = 1, math.min (#top, 3) do
		local name = top[i].name:gsub ("^.", "%0\x02\x02")
		respond (string.format ("\x02%s\x02 -> %s -> %s",
			name, os.date ("%c", top[i].when), top[i].what))
	end
end

function handle (msg)
	local who = msg.prefix:match ("^[^!@]*")
	local where, what = table.unpack (msg.params)
	local when = os.time ()

	local what_log = what:gsub ("^\x01ACTION", "*"):gsub ("\x01$", "")
	remember (who, where, when, what_log)
	db_store (who, where, when, what_log)

	-- Comment out to reduce both disk load and reliability
	db_file:flush ()

	if db_garbage > 5000 then db_compact () end

	if what:sub (1, #prefix) == prefix then
		local command = what:sub (#prefix + 1)
		local name, e = command:match ("^(%S+)%s*()")
		if name == 'seen' then seen (who, where, command:sub (e)) end
	end
end

for line in io.lines () do
	local msg = parse (line)
	if msg.command == "PRIVMSG" then handle (msg) end
end