#!/usr/bin/env lua
--[[
	The GPLv2 License (GPLv2)
	Copyright (c) 2022 Jeremy Baxter
	
	This program is free software: you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation; either version 2 of the License, or
	(at your option) any later version.
	
	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	See the
	GNU General Public License for more details.
	
	You should have received a copy of the GNU General Public License
	along with this program.	If not, see <http://www.gnu.org/licenses/>.
]]--

require "luarocks.loader"
getopt = require "posix.unistd".getopt
 mkdir = require "posix.sys.stat".mkdir
 bname = require "posix.libgen".basename
  http = require "socket.http"
 cjson = require "cjson"
 ltn12 = require "ltn12"

 version = "2.0"
 confdir = string.gsub("~/.config/matrix-send", '~', os.getenv("HOME"), 1)
confpath = confdir .. "/config.lua"
confvarv = os.getenv("MATRIXSEND_CONFIG")
hostname = io.input("/etc/hostname"):read("l")

matrix = {}
  json = {}
   uri = {}
    sh = os.execute

-----------------
--- Functions ---
-----------------

-- Returns true if the given file name file exists, otherwise returns false.
function fileexists(file)
	local f, err = io.open(file, 'r')
	if f then
		f:close()
		return true
	else
		return false, err
	end
end

-- Prints a message to stdout in the following format:
-- matrix-send: s
function msg(s)
	io.stdout:write(string.format("%s: %s\n", bname(arg[0]), s))
end

-- Prints an error message to stderr in the following format:
-- matrix-send: s
-- After that, exits and returns 1 to the OS.
function panic(s)
	io.stderr:write(string.format("%s: %s\n", bname(arg[0]), s))
	os.exit(1)
end

-- Prints an error message to stderr in the following format:
-- matrix-send: confpath: s
-- After that, exits and returns 1 to the OS.
function confpanic(s)
	panic(string.format("%s: %s", bname(confpath), s))
	os.exit(1)
end

------------------------
--- Matrix functions ---
------------------------

function matrix.login(uri, json)
	local respbody = {}
	local result, respcode, respheaders, respstatus = http.request {
			method = "POST",
			url = uri,
			source = ltn12.source.string(json),
			headers = {
					["content-type"] = "application/json",
					["content-length"] = tostring(#json)
			},
			sink = ltn12.sink.table(respbody)
	}
	local body = table.concat(respbody)
	local t = cjson.decode(body)
	if t.error then
		panic("server: " .. t.error)
	else
		return t.access_token
	end
end

function matrix.send(uri, json, login_uri, login_json)
	local respbody = {}
	local result, respcode, respheaders, respstatus = http.request {
			method = "PUT",
			url = uri,
			source = ltn12.source.string(json),
			headers = {
					["content-type"] = "application/json",
					["content-length"] = tostring(#json)
			},
			sink = ltn12.sink.table(respbody)
	}
	local body = table.concat(respbody)
	local t = cjson.decode(body)
	if t.error then
		if t.errcode == "M_UNKNOWN_TOKEN" then
			msg("token expired/invalidated; re-authenticating")
			-- I mean, it works
			t = setmetatable({}, {
				__concat = function(left, right)
					if type(left) == "string" then
						return left .. tostring(right)
					end
					return tostring(left) .. tostring(right)
				end
			})
			t.token = matrix.login(login_uri, login_json)
			if not cache.disable then
				mkdir(cache.location)
				cf = io.open(cache.location .. "/token", 'w+')
				cf:write(t.token)
				cf:close()
			end
			matrix.send(string.gsub(uri, "access_token=.+", "access_token=" .. t.token), json, login_uri, login_json)
		else
			panic("server: " .. t.error)
		end
	else
		return t
	end
end

-- Default configuration file
default_config = [[
-- Default configuration file for matrix-send
-- In comments, here is a simple example configuration.

--login = {
--	server = "envs.net",
--	username = "john",
--	password = "examplepassword
--}

-- You could also do it this way:

--login.server = "envs.net"
--login.username = "john"
--login.password = "examplepassword"

-- Both configurations do the same thing.

-- See matrix-send.conf(5) for more information
-- on configuration files.
]]

------------------------------------
--- Default configuration values ---
------------------------------------

-- Initialise tables
login = {}
cache = {}
rooms = {}
advanced = {}

-- Cache location
cache.location = "~/.cache/matrix-send"

-- Disable caching access tokens?
cache.disable = false

-- Message type
advanced.event = "m.text"

----------------------
--- Initial checks ---
----------------------

if arg[1] == nil then
	io.stderr:write("usage: " .. bname(arg[0]) .. " [-c config] [-t type] [-CV] message room\n")
	os.exit(1)
end

if confvarv then
	if fileexists(confvarv) then
		confpath = os.getenv("MATRIXSEND_CONFIG")
	else
		local _, err = fileexists(os.getenv("MATRIXSEND_CONFIG"))
		panic("error opening " .. err)
	end
end

if not fileexists(confpath) then
	mkdir(confdir)
	f = io.open(confpath, 'w')
	f:write(default_config)
	f:close()
end
dofile(confpath)

cache.location = string.gsub(cache.location, '~', os.getenv("HOME"), 1)

-- Make sure all required values are set
if not login.server then
	 confpanic("required value 'login.server' left unset")
end

-- login.token always supersedes login.username and password
if not login.token then
	if not login.username then
		 confpanic("required value 'login.username' left unset")
	elseif not login.password then
		 confpanic("required value 'login.password' left unset")
	end
end

-- Parse options
for opt, optarg, ind in getopt(arg, ':Cc:t:V') do
	optind = ind
	if opt == 'C' then
		msg("clearing cache")
		os.execute("rm -rf " .. cache.location) -- TODO: replace this os.execute line
		os.exit(0)
	elseif opt == 'c' then
		confpath = optarg
	elseif opt == 't' then
		if optarg:match("m%.text")
		or optarg:match("m%.notice") then
			advanced.event = optarg
		else panic("unknown message type '" .. optarg .. "'")
		end
	elseif opt == 'V' then
		io.stdout:write("matrix-send version " .. version .. '\n')
		io.stdout:write(_VERSION .. '\n')
		os.exit(0)
	elseif opt == '?' then
		panic("unknown option " .. arg[optind-1])
		os.exit(1)
	elseif opt == ':' then
		panic("missing argument for option " .. arg[optind-1])
		os.exit(1)
	end
end

if optind == nil then
	message = arg[1]
	room = arg[2]
else
	message = arg[optind+1]
	room = arg[optind+2]
end

if room:match("^!") then
	room_id = room
else
	if rooms[room] ~= nil then
		room_id = rooms[room]
	else
		panic("alias '" .. room .. "' invalid")
	end
end

if fileexists(cache.location .. "/txnid") then
	txnidf = io.open(cache.location .. "/txnid", 'r')
	txnid = txnidf:read('l')
	txnidf:close()
else
	txnid = 0
end

-- Get .well-known
uri.well_known = string.format("https://%s/.well-known/matrix/client", login.server)
wellknown_body, errno = http.request(uri.well_known)
if errno ~= 200 then
	panic("server: Error " .. errno .. " while getting /.well-known/matrix/client")
end
wellknown_t = cjson.decode(wellknown_body)
login.server = wellknown_t["m.homeserver"].base_url

-- Assign URIs and JSON bodies
uri.login = string.format("%s/_matrix/client/v3/login", login.server)
json.login = string.format([[
{
	"identifier": {
		"type": "m.id.user",
		"user": "%s"
	},
	"initial_device_display_name": "matrix-send@%s",
	"password": "%s",
	"type": "m.login.password"
}
]], login.username, hostname, login.password)

json.message = string.format([[
{
	"body": "%s",
	"msgtype": "%s"
}
]], message, advanced.event)

-- Get the access token if credentials are used
if not login.token then
	if fileexists(cache.location .. "/token") then
		cf = io.open(cache.location .. "/token", 'r')
		login.token = cf:read('l')
		cf:close()
	else
		-- Login
		login.token = matrix.login(uri.login, json.login)

		-- Cache the access token
		if not cache.disable then
			mkdir(cache.location)
			cf = io.open(cache.location .. "/token", 'w+')
			cf:write(login.token)
			cf:close()
		end
	end
end

uri.message = string.format("%s/_matrix/client/v3/rooms/%s/send/m.room.message/%d?access_token=%s",
	login.server, room_id, txnid, login.token)

-- Send the message!
matrix.send(uri.message, json.message, uri.login, json.login)

-- Increment txnid and cache
if not cache.disable then
	txnidf = io.open(cache.location .. "/txnid", 'w+')
	txnidf:write(txnid + 1)
	txnidf:close()
end