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