# frozen_string_literal: true

require 'json'
require_relative './world.rb'
require_relative './serialiser.rb'

# This class handles sending/receiving network data + the "game loop" timing.
class App
  FRAMES_PER_SECOND = 60

  def initialize
    @connections = {}
    @messages = []
    @world = World.new
    @mutex = Mutex.new
    Thread.new { main_loop }
  end

  def connect(cid, &socket)
    @mutex.synchronize do
      @connections[cid] = { socket: socket }
      @messages.append({ from: cid, type: :join })
    end
  end

  def disconnect(cid)
    @mutex.synchronize do
      @connections.delete(cid)
      @messages.append({ from: cid, type: :quit })
    end
  end

  def receive(cid, text)
    json = JSON.parse(text)
    @mutex.synchronize { @messages.append({ from: cid, data: json }) }
  rescue JSON::ParserError => e
    puts("ERROR: #{e}")
  end

  private

  def main_loop
    timer = milliseconds

    loop do
      updated = false
      while timer <= milliseconds
        updated = update_world_state
        timer += 1000.0 / FRAMES_PER_SECOND
      end
      update_frame_count if updated

      sleep(0.001) # Avoid constantly using 100% CPU.
    end
  end

  def update_world_state
    @mutex.synchronize do
      @world.update(@messages)
      @messages = []
    end
    true
  end

  def update_frame_count
    @frame ||= 0
    @frame = (@frame + 1) % 120
    update_clients(full: @frame.zero?) if (@frame % 6).zero?
  end

  def update_clients(full: false)
    @mutex.synchronize do
      @connections.each do |cid, data|
        data[:serialiser] ||= Serialiser.new(cid)
        state = data[:serialiser].snapshot(@world, full: full)
        data[:socket].call(state) unless state.nil? # nil = Nothing to send.
      end
    end
  end

  def milliseconds
    (Process.clock_gettime(Process::CLOCK_MONOTONIC) * 1000).to_i
  end
end