-----------------------------------------------------------------------------
-- SMTP client support for the Lua language.
-- LuaSocket toolkit.
-- Author: Diego Nehab
-----------------------------------------------------------------------------
-----------------------------------------------------------------------------
-- Declare module and import dependencies
-----------------------------------------------------------------------------
local base = _G
local coroutine = require("coroutine")
local string = require("string")
local math = require("math")
local os = require("os")
local socket = require("socket")
local tp = require("socket.tp")
local ltn12 = require("ltn12")
local headers = require("socket.headers")
local mime = require("mime")
socket.smtp = {}
local _M = socket.smtp
-----------------------------------------------------------------------------
-- Program constants
-----------------------------------------------------------------------------
-- timeout for connection
_M.TIMEOUT = 60
-- default server used to send e-mails
_M.SERVER = "localhost"
-- default port
_M.PORT = 25
-- domain used in HELO command and default sendmail
-- If we are under a CGI, try to get from environment
_M.DOMAIN = os.getenv("SERVER_NAME") or "localhost"
-- default time zone (means we don't know)
_M.ZONE = "-0000"
---------------------------------------------------------------------------
-- Low level SMTP API
-----------------------------------------------------------------------------
local metat = {__index = {}}

function metat.__index:greet(domain)
	self.try(self.tp:check("2.."))
	self.try(self.tp:command("EHLO", domain or _M.DOMAIN))
	return socket.skip(1, self.try(self.tp:check("2..")))
end

function metat.__index:mail(from)
	self.try(self.tp:command("MAIL", "FROM:" .. from))
	return self.try(self.tp:check("2.."))
end

function metat.__index:rcpt(to)
	self.try(self.tp:command("RCPT", "TO:" .. to))
	return self.try(self.tp:check("2.."))
end

function metat.__index:data(src, step)
	self.try(self.tp:command("DATA"))
	self.try(self.tp:check("3.."))
	self.try(self.tp:source(src, step))
	self.try(self.tp:send("\r\n.\r\n"))
	return self.try(self.tp:check("2.."))
end

function metat.__index:quit()
	self.try(self.tp:command("QUIT"))
	return self.try(self.tp:check("2.."))
end

function metat.__index:close()
	return self.tp:close()
end

function metat.__index:login(user, password)
	self.try(self.tp:command("AUTH", "LOGIN"))
	self.try(self.tp:check("3.."))
	self.try(self.tp:send(mime.b64(user) .. "\r\n"))
	self.try(self.tp:check("3.."))
	self.try(self.tp:send(mime.b64(password) .. "\r\n"))
	return self.try(self.tp:check("2.."))
end

function metat.__index:plain(user, password)
	local auth = "PLAIN " .. mime.b64("\0" .. user .. "\0" .. password)
	self.try(self.tp:command("AUTH", auth))
	return self.try(self.tp:check("2.."))
end

function metat.__index:auth(user, password, ext)
	if not user or not password then return 1 end

	if string.find(ext, "AUTH[^\n]+LOGIN") then
		return self:login(user, password)
	elseif string.find(ext, "AUTH[^\n]+PLAIN") then
		return self:plain(user, password)
	else
		self.try(nil, "authentication not supported")
	end
end

-- send message or throw an exception
function metat.__index:send(mailt)
	self:mail(mailt.from)

	if base.type(mailt.rcpt) == "table" then
		for i, v in base.ipairs(mailt.rcpt) do
			self:rcpt(v)
		end
	else
		self:rcpt(mailt.rcpt)
	end

	self:data(ltn12.source.chain(mailt.source, mime.stuff()), mailt.step)
end

function _M.open(server, port, create)
	local tp = socket.try(tp.connect(server or _M.SERVER, port or _M.PORT, _M.TIMEOUT, create))
	local s = base.setmetatable({tp = tp}, metat)
	-- make sure tp is closed if we get an exception
	s.try = socket.newtry(function()
		s:close()
	end)
	return s
end

-- convert headers to lowercase
local function lower_headers(headers)
	local lower = {}

	for i, v in base.pairs(headers or lower) do
		lower[string.lower(i)] = v
	end

	return lower
end

---------------------------------------------------------------------------
-- Multipart message source
-----------------------------------------------------------------------------
-- returns a hopefully unique mime boundary
local seqno = 0

local function newboundary()
	seqno = seqno + 1
	return string.format("%s%05d==%05u", os.date("%d%m%Y%H%M%S"), math.random(0, 99999), seqno)
end

-- send_message forward declaration
local send_message

-- yield the headers all at once, it's faster
local function send_headers(tosend)
	local canonic = headers.canonic
	local h = "\r\n"

	for f, v in base.pairs(tosend) do
		h = (canonic[f] or f) .. ": " .. v .. "\r\n" .. h
	end

	coroutine.yield(h)
end

-- yield multipart message body from a multipart message table
local function send_multipart(mesgt)
	-- make sure we have our boundary and send headers
	local bd = newboundary()
	local headers = lower_headers(mesgt.headers or {})
	headers["content-type"] = headers["content-type"] or "multipart/mixed"
	headers["content-type"] = headers["content-type"] .. "; boundary=\"" .. bd .. "\""
	send_headers(headers)

	-- send preamble
	if mesgt.body.preamble then
		coroutine.yield(mesgt.body.preamble)
		coroutine.yield("\r\n")
	end

	-- send each part separated by a boundary
	for i, m in base.ipairs(mesgt.body) do
		coroutine.yield("\r\n--" .. bd .. "\r\n")
		send_message(m)
	end

	-- send last boundary
	coroutine.yield("\r\n--" .. bd .. "--\r\n\r\n")

	-- send epilogue
	if mesgt.body.epilogue then
		coroutine.yield(mesgt.body.epilogue)
		coroutine.yield("\r\n")
	end
end

-- yield message body from a source
local function send_source(mesgt)
	-- make sure we have a content-type
	local headers = lower_headers(mesgt.headers or {})
	headers["content-type"] = headers["content-type"] or "text/plain; charset=\"iso-8859-1\""
	send_headers(headers)

	-- send body from source
	while true do
		local chunk, err = mesgt.body()

		if err then
			coroutine.yield(nil, err)
		elseif chunk then
			coroutine.yield(chunk)
		else
			break
		end
	end
end

-- yield message body from a string
local function send_string(mesgt)
	-- make sure we have a content-type
	local headers = lower_headers(mesgt.headers or {})
	headers["content-type"] = headers["content-type"] or "text/plain; charset=\"iso-8859-1\""
	send_headers(headers)
	-- send body from string
	coroutine.yield(mesgt.body)
end

-- message source
function send_message(mesgt)
	if base.type(mesgt.body) == "table" then
		send_multipart(mesgt)
	elseif base.type(mesgt.body) == "function" then
		send_source(mesgt)
	else
		send_string(mesgt)
	end
end

-- set defaul headers
local function adjust_headers(mesgt)
	local lower = lower_headers(mesgt.headers)
	lower["date"] = lower["date"] or
		os.date("!%a, %d %b %Y %H:%M:%S ") .. (
			mesgt.zone or
			_M.ZONE
		)
	lower["x-mailer"] = lower["x-mailer"] or socket._VERSION
	-- this can't be overriden
	lower["mime-version"] = "1.0"
	return lower
end

function _M.message(mesgt)
	mesgt.headers = adjust_headers(mesgt)
	-- create and return message source
	local co = coroutine.create(function()
		send_message(mesgt)
	end)
	return function()
		local ret, a, b = coroutine.resume(co)

		if ret then return a, b else return nil, a end
	end
end

---------------------------------------------------------------------------
-- High level SMTP API
-----------------------------------------------------------------------------
_M.send = socket.protect(function(mailt)
	local s = _M.open(mailt.server, mailt.port, mailt.create)
	local ext = s:greet(mailt.domain)
	s:auth(mailt.user, mailt.password, ext)
	s:send(mailt)
	s:quit()
	return s:close()
end)
return _M