require 'socket'
require 'logger'
require 'thread'
require 'numeric'

module Flux
	#
	# Flux::Client is the client interface which connects to the IRC server through
	# a socket and sends/receives messages. It can be used to send users or channels
	# messages, notices or any other information. Flux::Client.connect is an alias
	# and may also be used... it also has a better name.
	#
	class Client
		@@messages = {}

		#
		# Associate certain messages with classes. This method calls `merge!' on the
		# @@messages class variable, so it's not complex. Special messages are
		# :notice_auth, :numeric, and :unknown. So that means if the server sends a
		# NOTICE_AUTH or a NUMERIC or UNKNOWN literal, they won't get handled.
		# Everything else is handled, so PRIVMSG is associated with :privmsg, and so
		# on. Pass a hash of key/value pairs to this method (:privmsg => Privmsg).
		#
		def self.register_messages(messages = {})
			@@messages.merge!(messages)
		end

		require 'messages'

		attr_reader   :address, :port, :debug, :mutex, :logger, :buffer, :threads
		attr_accessor :handlers
		alias_method  :debug? , :debug

		#
		# Initialize a new client object. `address' is the server address, for example
		# a string like 'irc.freenode.net', and `attr' is a hash of pre-defined
		# attributes. The predefined attributes are:
		#
		# 	:port   => A fixnum port number
		# 	:debug  => A boolean whether to enable debug output
		# 	:logdev => Log device, such as STDOUT for the Logger instance
		# 	:nick   => Nickname to register as
		# 	:user   => Username
		# 	:real   => Supposedly your real name
		# 	:pass   => The server password (PASS command)
		#
		# This method also has an alias, Flux::Client.connect. Alternatively, when
		# initializing a client object, you can pass a block which passes the client
		# object as the block parameter and assumes Flux::Client#process! and
		# Flux::Client#disconnect! at the end of the block.
		#
		#
		# <b>Flux::Client#threads</b>
		#
		#
		# Flux::Client#threads is an array of threads that the client spawns.
		# Flux::Client.new does some tricky stuff to this array; It adds a method
		# to the metaclass called `purge!' which removes all dead threads.
		#
		# This note is kept here to avoid any confusion or debugging hassles to
		# people extending or modifying the client library.
		#
		def initialize(address, attr = {})
			@mutex    = Mutex.new
			@address  = address
			@port     = (attr[:port] || 6667).to_i
			@debug    = attr[:debug] ? true : false
 			@logger   = Logger.new(attr[:logdev] || STDOUT)
			@buffer   = []
			@handlers = []
			@threads  = []
			@threads.instance_variable_set('@logger', @logger)

			# Let's abort when a thread fails.
			Thread.abort_on_exception = true

			class << @threads
				def purge!
					dead = find_all { |thread| !thread.alive? }
					@logger.debug("Purging threads array: #{dead.size} thread(s) removed, #{size - dead.size} still alive")

					unless dead.empty?
						for thread in dead
							delete(thread)
						end

						return self
					end
				end

				alias_method :purge, :purge!
			end

			@logger.debug("Attempting to connect to #@address:#@port") if @debug
			@socket = TCPSocket.new(@address, @port)
			@logger.debug("You are now connected to #@address:#@port") if @debug

			# Automatic login?
			login(attr[:nick], attr[:user] || attr[:nick], attr[:real] || attr[:nick]) if attr[:nick]

			if block_given?
				@logger.debug('Initializing client object via block form') if @debug
				yield self
				process!
				disconnect!
			end
		end

		#
		# Disconnect from the server. It does nothing if you're not connected in the
		# first place. Flux::Client#disconnect! is an alias.
		#
		def disconnect
			if connected?
				@socket.close unless @socket.closed?
				@logger.debug('Disconnected') if @debug
			else
				@logger.debug('Disconnect attempted, but not connected') if @debug
			end
		end

		#
		# This is a convenience method for checking the connection status between the
		# client and the server. It'll return true if the client is still connected
		# and false if it isn't.
		#
		def connected?
			@socket ? true : false
		end

		#
		# Write data to the socket.
		#
		def write(msg)
			@logger.debug("OUTGOING: #{msg.strip}") if @debug
			@socket.write("#{msg}\r\n")
		end

		#
		# Login to the IRC server.
		#
		def login(nick, user = nick, real = nick, pass = nil)
			nick(nick)
			user(user, real)
			pass(pass) if pass
		end

		#
		# Send NICK command.
		#
		def nick(nickname = nil)
			nickname ? _write("NICK #{nickname}") : write('NICK')
		end

		#
		# Send USER command.
		#
		def user(username, realname)
			_write("USER #{username} #{username} #{username} :#{realname}")
		end

		#
		# Send PASS command.
		#
		def pass(password)
			_write("PASS #{password}")
		end

		#
		# Process incoming data infinitely and sort them into their corresponding message
		# objects such that a PRIVMSG is a PrivateMessage object, a NOTICE is a Notice
		# object, and so on. Flux::Client#main is an alias.
		#
		def process!
			@logger.debug('Entering main processing loop') if @debug

			loop do
				rw, wr, err = select([@socket], [@socket], [@socket])
				read  unless rw.empty?
				write unless wr.empty?
				@logger.error("Socket error") if @debug and !err.empty?
			end
		end

		class << self
			alias_method :connect, :new
		end

		alias_method :disconnect!, :disconnect
		alias_method :main, :process!

		#
		# This method is invoked when the socket is writable or can be
		# invoked when you want to write data to the socket.
		#
		def write(data = nil)
			@buffer << data if data

			if true # change to `if connection_registered?' later
				for line in @buffer
					_write(line)
				end

				@buffer.clear
			end
		end

	private

		#
		# This method is invoked when the socket is readable, and it grabs
		# a line of data from the server and processes it in its own thread.
		#
		def read
			@logger.debug("INCOMING << #{data = @socket.gets.strip}") if @debug
			@threads << Thread.new { invoke_handlers(parse_message(data)) }
		end

		#
		# This method is like Flux::Client#write, except it bypasses any
		# buffer queueing and writes straight to the socket.
		#
		def _write(data)
			@logger.debug("OUTGOING >> #{data}") if @debug
			@socket.write("#{data}\r\n")
		end

		#
		# Parse a line into its corresponding Flux::Message object.
		#
		def parse_message(data)
			server, line = data.match(/^(?::(\S ) )?(. )$/).to_a[1..-1]

			case line
			# parse NOTICE AUTH messages
			when /^NOTICE AUTH :(. )$/
				command         = :notice_auth
				message         = @@messages[:notice_auth].new(self, data, command, [], $1)
			when /^(\d ) (\S ) (?:([^:] ) )?(?::(. ))?$/
				command         = :numeric
				arguments       = $3 ? $3.split(' ') : []
				message         = @@messages[:numeric].new(self, data, command, arguments, $4)
				message.numeric = $1.to_i
				message.my_nick = $2
			when /^(\S ) (?:([^:] ) )?(?::(. ))?$/
				command         = $1.downcase.to_sym
				arguments       = $2 ? $2.split(' ') : []
				message         = @@messages[command].new(self, data, command, arguments, $3)
			else
				command         = :unknown
				message         = @@messages[:unknown].new(self, data, command, [], nil)
			end

			@logger.debug("Parsed (#{message.class.name.split('::')[-1]}): #{data.inspect}") if @debug
			message.server = server
			message.customize
			message
		end

		#
		# Invoke handlers which correspond to a given message's signal.
		#
		def invoke_handlers(message)
			if handlers = @handlers.find_all { |h| h.signals.include?(message.command) }
				command = case message.command
					when :notice_auth then 'NOTICE AUTH message'
					when :numeric     then "numeric message (#{Reply[message.numeric]}: #{message.numeric})"
					when :unknown     then 'unknown message'
					else                   message.command.to_s.upcase
				end

				@logger.debug("Invoking #{handlers.size} handlers for #{command}")

				for handler in handlers
					@threads << Thread.new do
						if handler.threaded?
							handler.call(self, message)
						else
							@mutex.synchronize { handler.call(self, message) }
						end
					end
				end
			end

			@threads.purge!
		end
	end
end