#!/usr/bin/env ruby

require 'socket'
require 'io/console'
require 'optparse'

PUBLIC_HOST = '0.0.0.0'
PRIVATE_HOST = '127.0.0.1'
DEFAULT_CLIENT_HOST = '127.0.0.1'
options = {
  :port => 7570,
  :server => false,
  :host => DEFAULT_CLIENT_HOST,
  :server_host => PRIVATE_HOST,
  :rows => 24,
  :cols => 40,
}
OptionParser.new do |opt|
  opt.on('-pPORT', '--port PORT', Integer,
         'Port to serve/listen on (defaults to 7570)') do |o|
    options[:port] = o
  end
  opt.on('-S', '--server',
         'Make this instance function as a server'
        ) do
    options[:server] = true
  end
  opt.on('-s', '--client',
         'Make this instance function as a client'
        ) do
    options[:server] = false
  end
  opt.on('-HHOST', '--host HOST', String,
        '(client only) Host to connect to (defaults to `localhost`)') do |o|
    options[:host] = o
  end
  opt.on('-rROWS', '--rows ROWS', Integer,
         '(server only) The number of rows to have in the shared buffer'
        ) do |o|
    options[:rows] = o
  end
  opt.on('-cCOLS', '--cols COLS', Integer,
         '(server only) The number of columns to have in the shared buffer'
        ) do |o|
    options[:cols] = o
  end
  opt.on('--expose-this-instance-for-the-world-to-see-because-I-know-what-I\'m-doing [please]',
         # X -- eXposed
         '(server only) Serve publicly, rather than privately. Please ONLY add this option if you entierly know what you\'re doing and have permission from/are the server owner. Say please to expose.'
        ) do |o|
          if o == "please"
            options[:server_host] = PUBLIC_HOST
          end
  end
  opt.on('-x', '--private',
         # x -- not visible
         '(server only) Serve privately, rather than publicly (default)'
        ) do
    options[:server_host] = PRIVATE_HOST
  end
  opt.on('-h', '--help', 'Get help with this command') do
    puts opt
    exit
  end
end.parse!(into: options)

HOST = options[:host]
SRV_HOST = options[:server_host]
PORT = options[:port]

ROWS = options[:rows]
COLS = options[:cols]
VERSION = {
  :SRV_TXT => '0.01',
  :CLN_TXT => '0.01',
  :CLN_ARO => '0.02',
}

def do_server
  server = TCPServer.new(SRV_HOST, PORT)
  sockets = [server]

  puts "PORT: #{PORT}"
  puts "GRID SIZE: #{ROWS}r#{COLS}c"
  if SRV_HOST == PUBLIC_HOST then puts "EXPOSED" end
  puts 'Listening...'

  pre = "#{ROWS}r#{COLS}c >>> "
  buffer = pre.ljust(ROWS*COLS)[0...ROWS*COLS]
  windex = pre.length # Wipe your buffer clean with your write index
  windex %= buffer.length
  motions = []

  def new_buf_wi_out(buf, wi, newtext, motions: [])
    buf = buf.dup
    out = ''
    nti = 0 # New Text Index
    while (nti < newtext.length) || (motions.length > 0)
      if motions.length > 0 && nti >= motions[0][:nti]
        case motions[0][:dir]
        when 'u'
          wi -= COLS
        when 'd'
          wi += COLS
        when 'l'
          wi -= 1
        when 'r'
          wi += 1
        end
        wi %= ROWS*COLS
        motions.shift # remove first motion
      end
      out << "#{VERSION[:SRV_TXT]}|"
      out << ((wi/COLS)+1).to_s + '|'
      out << ((wi%COLS)+1).to_s + '|'
      next if nti >= newtext.length
      loop do
        out << newtext[nti]
        buf[wi] = newtext[nti]
        wi += 1
        nti += 1
        break if motions.length > 0 && nti >= motions[0][:nti]
        break if nti >= newtext.length
        break if wi%COLS == 0
      end
      wi %= ROWS*COLS
      out << "\n"
    end
    [buf, wi, out]
  end

  loop do
  ready, = IO.select(sockets)
    newtext = ''

    ready.each do |sck|
      if sck == server
        client = server.accept
        sockets << client
        puts "Connection: #{client.peeraddr}"
        client.puts new_buf_wi_out(buffer,0,buffer)[2]
        if buffer.length > 1
          client.puts new_buf_wi_out(buffer,windex-1,buffer[windex-1])[2]
        end
        next
      end
      begin
        msg = sck.gets
        unless msg
          puts "Disconnect: #{sck.peeraddr}"
          sck.close
          sockets.delete(sck)
          next
        end
        ver, msg = msg.chomp.split('|',2)
        case ver
        when VERSION[:CLN_TXT]
          next unless msg != nil
          newtext << clean_chars(msg)
        when  VERSION[:CLN_ARO]
          next unless msg != nil
          dir = 'l'
          case msg
          when 'A'
            dir = 'u'
          when 'B'
            dir = 'd'
          when 'C'
            dir = 'r'
          when 'D'
            dir = 'l'
          else
            next
          end
          motions << {
            :nti => newtext.length - 1,
            :dir => dir
          }
        end
      rescue Errno::ECONNRESET, Errno::EPIPE
        puts "Disconnect (err): #{sck.peeraddr}"
        sck.close
        sockets.delete(sck)
      end
      buffer, windex, out = new_buf_wi_out(buffer,windex,newtext,motions:motions)
      motions = []
      clients = sockets - [server]
      clients.each do |c| 
        begin
          c.puts out
        rescue Errno::ECONNRESET, Errno::EPIPE
          puts "Disconnect (err): #{c.peeraddr}"
          c.close
          sockets.delete(c)
        end
      end
      #if out != ''
      #  puts "#{windex}: (#{(windex/COLS)+1},#{(windex%COLS)+1})"
      #end
    end
  end
end

def clean_chars(chars)
  out = ''
  chars.each_char do |char|
    if char.ord < 0x20 # Non printing
      out << '^'+(char.ord + 0x40).chr
    elsif char.ord == 0x7F # DEL (Non print)
      out << '^?'
    else
      out << char
    end
  end
  out
end

def do_client
  socket = TCPSocket.new(HOST, PORT)

  puts "PORT: #{PORT}"
  puts "HOST: #{HOST}"

  begin
    print "\x1b[?1049h\x1b[2J\x1b[3J" # Open and clear alternate buffer

    #reader = Thread.new do
    Thread.new do
      loop do
        msg = socket.gets
        exit 0 unless msg
        ver, msg = msg.split('|',2)
        next unless ver == VERSION[:SRV_TXT]
        next unless msg != nil
        # In message version 0.01 and lower,
        # all messages are in an assumed format...
        row,col,chars = msg.split('|',3)
        print "\x1b[#{row};#{col}H#{chars.chomp}"
      end
    end

    while (char = STDIN.noecho(&:getch))
      exit unless char != "\x04" # ^D
      if char == "\x1b" # Detect arrows
        char2 = STDIN.noecho(&:getch)
        if /[A-D]/.match? (char3 = STDIN.noecho(&:getch).upcase)
          socket.puts "#{VERSION[:CLN_ARO]}|#{char3}"
          next
        else
          char << char2+char3
        end
      elsif (char == "\x08" || # backspace
             char == "\x7F"  ) # delete
          socket.puts "#{VERSION[:CLN_ARO]}|D"
          next
      end
      socket.puts "#{VERSION[:CLN_TXT]}|#{clean_chars(char)}"
    end
  ensure
    print "\x1b[?1049l" # Back to regular buffer
  end
end

if options[:server]
  do_server
else
  do_client
end