tetris.rb

require 'ffi-ncurses'

class Tetris
  Curses = FFI::NCurses

  PIECES = [
    [ # O
      [[-1, 0], [0, 0], [-1, 1], [0, 1]]
    ],
    [ # I
      [[-2, 0], [-1, 0], [0, 0], [1, 0]],
      [[0, -1], [0, 0], [0, 1], [0, 2]]
    ],
    [ # S
      [[0, 0], [1, 0], [-1, 1], [0, 1]],
      [[0, -1], [0, 0], [1, 0], [1, 1]]
    ],
    [ # Z
      [[-1, 0], [0, 0], [0, 1], [1, 1]],
      [[1, -1], [0, 0], [1, 0], [0, 1]]
    ],
    [ # L
      [[-1, 0], [0, 0], [1, 0], [-1, 1]],
      [[0, -1], [0, 0], [0, 1], [1, 1]],
      [[1, -1], [-1, 0], [0, 0], [1, 0]],
      [[-1, -1], [0, -1], [0, 0], [0, 1]]
    ],
    [ # J
      [[-1, 0], [0, 0], [1, 0], [1, 1]],
      [[0, -1], [1, -1], [0, 0], [0, 1]],
      [[-1, -1], [-1, 0], [0, 0], [1, 0]],
      [[0, -1], [0, 0], [-1, 1], [0, 1]]
    ],
    [ # T
      [[-1, 0], [0, 0], [1, 0], [0, 1]],
      [[0, -1], [0, 0], [1, 0], [0, 1]],
      [[0, -1], [-1, 0], [0, 0], [1, 0]],
      [[0, -1], [-1, 0], [0, 0], [0, 1]]
    ]
  ]

  def self.run
    new.run
  end

  def initialize
    @pile = Array.new(20) { Array.new(10, false) }
    @piece = nil
    @x = nil
    @y = nil
    @completed_lines = 0
    @level = 0
    @delay = 0
  end

  def run
    Curses.initscr
    Curses.clear
    Curses.cbreak
    Curses.noecho
    Curses.timeout(0)
    Curses.move(0, 0)
    Curses.vline('|'.ord, 21)
    Curses.move(0, 21)
    Curses.vline('|'.ord, 21)
    Curses.move(20, 0)
    Curses.hline('-'.ord, 22)
    Curses.move(1, 24)
    Curses.addstr('Score:')
    Curses.move(4, 24)
    Curses.addstr('Keys:')
    Curses.move(5, 24)
    Curses.addstr('h,l: Left, Right')
    Curses.move(6, 24)
    Curses.addstr('j,k: Down, Rotate')
    Curses.move(7, 24)
    Curses.addstr("' ': Drop")
    Curses.move(8, 24)
    Curses.addstr('  q: Quit')

    catch(:quit) do
      prev = nil
      loop do
        now = Time.now
        if !prev || now - prev > @delay
          fall
          prev = now
        end

        while (c = Curses.getch) != -1
          c = c.chr rescue ''
          if @piece
            case c
            when 'h'
              @x -= 1
              @x += 1 if overlapped?
            when 'j'
              @y += 1
              @y -= 1 if overlapped?
            when 'k'
              @piece.rotate!(1)
              @piece.rotate!(-1) if overlapped?
            when 'l'
              @x += 1
              @x -= 1 if overlapped?
            when ' '
              fall while @piece
            end
          end
          throw :quit if c == 'q'
        end

        render

        sleep 0.05
      end
    end
  ensure
    Curses.endwin
  end

  private

  def fall
    if @piece
      @y += 1

      if overlapped?
        @piece[0].each do |x, y|
          @pile[@y+y-1][@x+x] = true
        end
        @piece = nil
        @pile.reject! {|line| line.all? }
        while @pile.length < 20
          @pile.unshift(Array.new(10, false))
          @completed_lines += 1
        end
      end
    else
      @x, @y = 5, 0
      @piece = PIECES.sample.dup
      @level = [@completed_lines / 10, 10].min
      @delay = (11 - @level) * 0.05
      Curses.move(2, 27)
      Curses.addstr('%06d' % @completed_lines)

      if overlapped?
        Curses.timeout(-1)
        Curses.move(8, 6)
        Curses.addstr('GAME OVER')
        Curses.move(0, 0)
        Curses.refresh
        c = Curses.getch
        throw :quit if c == 'q'.ord
        Curses.timeout(0)
        initialize
      end
    end
  end

  def overlapped?
    if @piece
      @piece[0].any? do |x, y|
        x += @x
        y += @y
        x < 0 || 10 <= x || y < 0 || 20 <= y || @pile[y][x]
      end
    end
  end

  def render
    20.times do |y|
      10.times do |x|
        Curses.move(y, x*2+1)
        if @pile[y][x]
          Curses.addstr('[]')
        else
          Curses.addstr('  ')
        end
      end
    end
    if @piece
      @piece[0].each do |x, y|
        Curses.move(@y+y, (@x+x)*2+1)
        Curses.addstr('[]')
      end
    end
    Curses.move(0, 0)
    Curses.refresh
  end
end

if __FILE__ == $0
  Tetris.run
end