require 'set'
require 'socket'

EVENT_PORT = 9090
CLIENT_PORT = 9099

client_pool = {}
seq_no_to_message = {}
follow_registry = {}
last_seq_no = 0

thread1 = Thread.new do
  puts("Listening for events on #{EVENT_PORT}")
  server = TCPServer.open(EVENT_PORT)
  loop do
    Thread.fork(server.accept) do |event_socket|
      event_socket.each_line do |payload|
        puts("Message received: #{payload}")

        payload_parts = payload.split('|')
        seq_no_to_message[payload_parts[0].to_i] = payload_parts

        while seq_no_to_message[last_seq_no + 1]
          next_message = seq_no_to_message[last_seq_no + 1]
          next_payload = next_message.join('|')

          seq_no = next_message[0].to_i
          kind = next_message[1].strip

          case kind
          when 'F'
            from_user_id = next_message[2].to_i
            to_user_id = next_message[3].to_i

            followers = follow_registry[to_user_id] || Set.new
            followers << from_user_id
            follow_registry[to_user_id] = followers

            socket = client_pool[to_user_id]
            if socket
              socket.puts(next_payload)
              socket.flush
            end

          when 'U'
            from_user_id = next_message[2].to_i
            to_user_id = next_message[3].to_i

            followers = follow_registry[to_user_id] || Set.new
            followers.delete(from_user_id)
            follow_registry[to_user_id] = followers

          when 'P'
            to_user_id = next_message[3].to_i

            socket = client_pool[to_user_id]
            if socket
              socket.puts(next_payload)
              socket.flush
            end

          when 'B'
            client_pool.values.each do |socket|
              socket.puts(next_payload)
              socket.flush
            end

          when 'S'
            from_user_id = next_message[2].to_i

            followers = follow_registry[from_user_id] || Set.new
            followers.each do |follower|
              socket = client_pool[follower]

              if socket
                socket.puts(next_payload)
                socket.flush
              end
            end
          end

          last_seq_no = seq_no
        end
      end
      event_socket.close
    end
  end
end

thread2 = Thread.new do
  puts("Listening for client requests on #{CLIENT_PORT}")
  server = TCPServer.open(CLIENT_PORT)
  loop do
    Thread.fork(server.accept) do |socket|
      user_id_string = socket.gets
      if user_id_string
        user_id = user_id_string.to_i
        client_pool[user_id] = socket
        puts("User connected: #{user_id} (#{client_pool.size} total)")
      end
    end
  end
end

thread1.join
thread2.join