-----------------------------------------------------------------------------
-- POP3 support for the Lua language.
-- 
-- Author: Guilherme Martins
-- Bug Fixes: Brett England
-- Conforming to: RFC 1939
-----------------------------------------------------------------------------

module("pop3", package.seeall)

local messages = require("pop3.message")
require("socket")

local class = require("pl.class").class

class.Client()

local Private = {}

--- Timeout in seconds before the program gives up on a connection.
Private.TIMEOUT = 60
--- default port for pop3 service.
Private.PORT = 110
--Debug option
Private.DEBUG = false


local function debug(...)
   if Private.DEBUG then print(unpack(arg)) end
end
---------------------------
-- 
-- function : cmd(conn,command,params) 
--
-- Sends a command to the pop3 server
--
-- Return the response of this command
---------------------------------------------------
function Private.cmd(conn,command, params)
   
   local popMsg
   
   -- Checks for a previous connection
   if not conn then error("No POP3 Client Connection.") end
   
   --creates the message that will be sent to server
   if params then		
      if type(params)=='table' then
	 popMsg = command .. " " .. table.concat(params," ")
      elseif type(params)=='string' then
	 popMsg = command .. " " .. params
      else
	 error("Invalid Parameter Type to compile a POP3 Command")
      end
   else
      popMsg = command
   end
   
   popMsg = popMsg .. "\r\n"
   
   debug("POP3 REQUEST", popMsg )
   
   -- send the command
   local ok, errMsg = conn:send(popMsg)
   
   -- in case of erro close the connection and throw a error
   if not ok then conn:close() end
   if errMsg then error(errMsg) end
   
   -- returns the response
   return Private.getResponse(conn)
end


---------------------------------
-- function : geResponse(client)
--
-- Get the server Response for any command
--
-- Returns the response string
--------------------------------------------------
function Private.getResponse(client)
   local resp, errMsg = client:receive()
   if not resp then 
      client:close()
      error(errMsg)
   end

   debug("POP3 RESPONSE : ",resp)
   
   local __,__,code, info = string.find(resp,"(+OK)(.*)") 
   
   debug(code,info)
   if code == "+OK"  then
      return code, info
   elseif code == "-ERR" then
      return nil , info
   elseif not code then
      return nil , resp
   end
   debug("Return CODE : " , code)
   client:close()
   error(resp)

end

---------------------------
-- 
-- function : conn(_,conf)
-- 
-- Start a pop3 server connection and pass 
-- to the transaction state
--
-- Needs conf.user,conf.pass,conf.host
--
-- Returns a pop3client instance
-------------------------------
function Client:_init(conf)
   --connect to the pop3 server
   local errMsg
   self.client , errMsg = socket.connect(conf.host,Private.PORT)		
   if not self.client then error(errMsg) end
   --settimeout
   self.client:settimeout(Private.TIMEOUT)
   
   -- get the Server Welcome response
   -- donīt need this
   Private.getResponse(self.client)
   
   local code , resp
   -- Noop Server
   code , resp = Private.cmd(self.client,"NOOP")
   if code == "-ERR" then error(resp) end
   
   --AUTHORIZATION STATE
   if not conf.secure then 
      -- non secure authetication with plain password
      code , resp = Private.cmd(self.client,"USER",conf.user)
      if code == "-ERR" then error(resp) end
      code , resp = Private.cmd(self.client,"PASS",conf.pass)
      if code == "-ERR" then error(resp) end
   else
      -- secure password md5 hash
      code , resp = Private.cmd(self.client,"APOP",{conf.user,conf.pass})
      if code == "-ERR" then error(resp) end
   end
   
   --Logged , end of AUTHORIZATION STATE
   debug("Welcome to " .. conf.host .. " pop3 server")
   
   return self
end

---------
-- function : mailinfo()
--
-- Returns the count of msgs and the total size of the maildrop
--
-------------------

function Client:mailinfo()
   
   -- Send the STAT Command
   local code , resp = Private.cmd(self.client,"STAT")
   
   --Check for ERRORS
   if code == "-ERR" then error(resp) end
   
   -- Parse the response
   local _,_,numStr,sizeStr = string.find(resp,"(.*%s)(.*)")
   
   debug(numStr,sizeStr)
   
   --Conversion to number...
   return tonumber(numStr), tonumber(sizeStr)

end

-------------
-- function : messages()
--
-- Iterator to all server menssages, intent to be used like a iterator
-- 
-- Returns a function the iterate under the server messages
------------------------
function Client:messages()
   local c = 1
   local total, _ = self:mailinfo()
   
   return function ()
	     if(c > total) then  return nil end
	     msg = Private.getmessage(self.client,c)
	     c=c+1
	     return msg 
	  end

end

-------
-- function : getmessage(num)
--
-- Gets the mensage that has a index 'num' at the maildrop
--
-- Returns the message Object
-------------------
function Private.getmessage(client,num)
   
   -- get message information
   local code , resp = Private.cmd(client,"LIST",tostring(num))
   
   if code == "-ERR" then return nil end
   
   _,_,_,sizeStr = string.find(resp,"(.*%s)(.*)")
   
   -- Sends the RERT command to the server
   local code , resp = Private.retr(client,num)
   -- parse the message
   local msg = messages.getParsedMessage(resp);
   
   -- set some properties as index id , size and uid
   msg.id   = num
   msg.size = tonumber(sizeStr)
   msg.uid  = Private.uid(client,num) 
   
   return msg

end

-------------
-- function : message(num)
-- 
-- Returns the message with  the index 'num'
---------------------------------------------

function Client:message(num)

   return Private.getmessage(self.client,num)

end


-------------------
-- function : retr(client, num)
--
-- Gets the message with index equals to 'num'
--
-----------------------------------------
function Private.retr(client,num)

   
   local code, resp = Private.cmd(client,"RETR", tostring(num))
   if code == "-ERR" then error(resp) end
   if code == "+OK" then
      local all = {}
      --for each line , use a table like a buffer
      local line = client:receive()
      while line ~= "." do
	 table.insert(all, line)
	 line = client:receive()	
      end
      return nil, all
   end
   return code, resp

   
end

----------------------
-- function : uid(num)
-- 
-- Gets the unique identifier to the message with index 'num'
--
-- Returns the identifier as a string or throw a error
-------------------------------------------------------------
function Private.uid(client,num)
   local code, resp = Private.cmd(client,"UIDL", tostring(num))
   if code == "-ERR" then error(resp) end
   if code == "+OK" then return resp end
end


----------------------
-- function : delete(num)
-- 
-- Deletes the message from the maildrop
--
-- Returns true if deleted or nil,errMsg
------------------------------------
function Client:delete(num)
   local code, resp = Private.cmd(self.client,"DELE", tostring(num))
   if code == "-ERR" then return nil, resp end
   if code == "+OK" then return true end
end

----------------------
-- function : quit()
--
-- Closes the server connection
--
---------------------------------------
function Client:quit()
   Private.cmd(self.client,"QUIT")
   self.client:close()
end