#!/usr/bin/env ruby

module Snakes
  require "curses"

  Curses.init_screen
  Curses.cbreak
  Curses.noecho
  Curses.curs_set(0)  # Invisible cursor
  Curses.stdscr.keypad = true

  exit_game = lambda do
    Game.stop
    puts "Good Bye! :D"
    exit 130
  end

  trap("INT") { exit_game.call }
  at_exit { exit_game.call }

  class Game
    def initialize
      @snake_head_icon = "o"  #"*"
      @snake_node_icon = "·"  # "#"
      @food_icon = "+"  # "#"

      @game_speed = 5
      @game_update_time = 1.0 / @game_speed

      @non_block_timeout = 0.001

      @frame = nil
      @board = nil

      @window_width = nil
      @window_height = nil

      @board_width = nil
      @board_height = nil

      @pause = false
      @game_status = :RUN # :RUN ,:PAUSE, :GAME_OVER

      @direction = [:UP, :DOWN, :LEFT, :RIGHT]
      @current_direction = @direction.sample

      self.init_game_board

      @snake = (1..2).map { |i| [(@board_height / 2).to_i + i, (@board_width / 2).to_i] }

      @food = [@board_height / 2 + 2, @board_width / 2 + 2]

      @press = nil
      @score = 0
      @speed = 1
    end

    def init_game_board

      # Window Frame
      @window_height = Curses.lines
      @window_width = Curses.cols

      @board_height = (@window_height * 0.8).to_i
      @board_width = (@window_width * 0.6).to_i

      @info_board_height = (@window_height * 0.5).to_i
      @info_board_width = (@window_width * 0.3).to_i

      @frame = Curses::Window.new(@window_height, @window_width, 0, 0)

      title = "Snakes"
      @frame.setpos(0, @board_width / 2 - title.length / 2)
      @frame.addstr(title)
      @frame.refresh

      @board = @frame.subwin(@board_height, @board_width, 1, 1)
      @board.keypad = true
      @board.timeout = @non_block_timeout

      @board.box(0, 0)
      @board.refresh

      @info_board = @frame.subwin(
        @info_board_height,
        @info_board_width,
        1,
        @board_width + 1
      )
      @info_board.box(0, 0)
      @info_board.refresh
    end

    def create_food
      @food = [rand(2..@board_height - 2), rand(2..@board_width - 2)]

      unless is_safe_food?
        @food = [rand(2..@board_height - 2), rand(2..@board_width - 2)]
      end
    end

    def is_safe_food?
      return !@snake.include?(@food)
    end

    def inc_speed
      speed = @game_speed + 1
      if speed >= 30
        @game_speed = 30
      else
        @game_speed = speed
      end

      self.update_tick
    end

    def dec_speed
      speed = @game_speed - 1
      if speed <= 5
        @game_speed = 5
      else
        @game_speed = speed
      end

      self.update_tick
    end

    def render_game_info
      # Press Key
      @info_board.setpos(1, 1)
      @info_board.addstr("[Press]: #{@current_direction.to_s}")

      # score
      @info_board.setpos(3, 1)
      @info_board.addstr("[Score]: #{@score}")

      # speed
      @info_board.setpos(5, 1)
      @info_board.addstr("[Speed]: #{@game_speed}")

      # tick time
      @info_board.setpos(7, 1)
      @info_board.addstr("[Tick]: #{@game_update_time}")

      # status
      @info_board.setpos(9, 1)
      @info_board.addstr("[Status]: #{@game_status}")
    end

    def render_food
      food_y, food_x = @food
      @board.setpos(food_y, food_x)
      @board.addch(@food_icon)
    end

    def render_snake
      snake_path = @snake.dup

      head_y, head_x = snake_path.shift

      @board.setpos(head_y, head_x)
      @board.addch(@snake_head_icon)

      snake_path.each do |node_pos|
        node_y, node_x = node_pos
        @board.setpos(node_y, node_x)
        @board.addstr(@snake_node_icon)
      end
    end

    def check_game(next_point)
      if @snake.include?(next_point)
        @game_status = :GAME_OVER
        return false
      end

      next_y, next_x = next_point

      if !(next_x > 0 && next_x < @board_width && next_y > 0 && next_y < @board_height)
        @game_status = :GAME_OVER
        return false
      end

      food_y, food_x = @food
      if food_y == next_y && food_x == next_x
        @score += 1
        @snake.unshift(@food)
        self.create_food
      end
      return true
    end

    def add_step
      head_y, head_x = @snake.first.dup

      if @current_direction == :UP
        head_y -= 1
        if head_y <= 0
          head_y = 1
        end
      elsif @current_direction == :DOWN
        head_y += 1
        if head_y >= @board_height
          head_y = @board_height - 1
        end
      elsif @current_direction == :LEFT
        head_x -= 1
        if head_x <= 0
          head_x = 1
        end
      elsif @current_direction == :RIGHT
        head_x += 1
        if head_x >= @board_width
          head_x = @board_width - 1
        end
      else
        return
      end

      next_point = [head_y, head_x]

      result = self.check_game(next_point)
      if result
        @snake.unshift(next_point)
        @snake.pop
      end
    end

    def _event_listener
      while true
        c = @board.getch
        if c
          @press = c
        end

        head_y, head_x = @snake.first.dup

        if c == Curses::KEY_UP || c == "w"
          @current_direction = :UP
        elsif c == Curses::KEY_DOWN || c == "s"
          @current_direction = :DOWN
        elsif c == Curses::KEY_LEFT || c == "a"
          @current_direction = :LEFT
        elsif c == Curses::KEY_RIGHT || c == "d"
          @current_direction = :RIGHT
        elsif c == Curses::KEY_BACKSPACE || c == "p"
          @game_status = @game_status == :PAUSE ? :RUN : :PAUSE
        elsif c == "m"
          self.inc_speed
        elsif c == "n"
          self.dec_speed
        else
          return # 这里其实断掉了。其实接住了外循环，每次读取数据
        end
      end
    end

    def reset_game
      self.initialize
    end

    def update_tick
      @game_update_time = (1.0 / @game_speed).round(2)
    end

    def check_speed
      @game_speed = @score % 5 + 5
      self.update_tick
    end

    def main_loop
      loop do
        self.init_game_board
        self.reset_game
        game_result = catch(:end_game) do
          while @game_status != :GAME_OVER
            self._event_listener

            @board.clear
            @info_board.clear
            @board.box(0, 0)
            @info_board.box(0, 0)

            if @game_status == :RUN
              self.add_step
            end
            self.check_speed
            self.render_food
            self.render_snake
            self.render_game_info

            @board.refresh
            @info_board.refresh
            sleep @game_update_time
          end

          throw :end_game, :GAME_OVER
        end

        next_status = catch(:next_action) do
          if game_result == :GAME_OVER
            @board.timeout = -1
            @board.clear
            @board.box(0, 0)
            @board.setpos(@board_height / 2, @board_width / 2 - 10)
            @board.addstr("GAME OVER")
            @board.setpos(@board_height / 2 + 2, @board_width / 2 - 10)
            @board.addstr("Play Again?")
            @board.setpos(@board_height / 2 + 3, @board_width / 2 - 10)
            @board.addstr("Y:Yes/ N: Exit")
            @board.refresh
            @board.timeout = -1

            next_goto = nil
            while next_goto != "y"
              next_goto = @board.getch
              if next_goto == "n"
                exit 0
              elsif next_goto == "y"
                @board.setpos(@board_height / 2 + 4, @board_width / 2 - 10)
                @board.addstr(next_goto)
                @board.refresh

                throw :next_action, :RUN
              end
            end
          end
        end

        @game_status = next_status
      end
    end

    def run
      self.main_loop
    end

    class << self
      def run
        @app = self.new
        @app.run
      end

      def stop
        Curses.close_screen
      end
    end
  end
end