class Input {
  constructor() {
    this.left = false;
    this.right = false;
    this.up = false;
    this.down = false;
    this.a = false;
    this.b = false;
    this.x = false;
    this.y = false;
    this.l = false;
    this.r = false;
    this.select = false;
    this.start = false;

    window.addEventListener('gamepadconnected', this.gamepadConnected);
    window.addEventListener('gamepaddisconnected', this.gamepadDisconnected);
  }

  update() {
    // TODO: have a config screen instead of hard-coding the 8Bitdo SNES30 pad.
    // TODO: handle connects / disconnects more correctly.
    const gamepad = navigator.getGamepads()[0];
    if (gamepad == null || !gamepad.connected || gamepad.axes.length < 2 ||
        gamepad.buttons.length < 12) {
      return;
    }

    this.left = gamepad.axes[0] < 0;
    this.right = gamepad.axes[0] > 0;
    this.up = gamepad.axes[1] < 0;
    this.down = gamepad.axes[1] > 0;
    this.a = gamepad.buttons[0].pressed;
    this.b = gamepad.buttons[1].pressed;
    this.x = gamepad.buttons[3].pressed;
    this.y = gamepad.buttons[4].pressed;
    this.l = gamepad.buttons[6].pressed;
    this.r = gamepad.buttons[7].pressed;
    this.select = gamepad.buttons[10].pressed;
    this.start = gamepad.buttons[11].pressed;
    debug(this.toString());
  }

  gamepadConnected(e) {
    debug('gamepad connected! :)');
    console.log('gamepad connected @ index %d: %d buttons, %d axes\n[%s]',
        e.gamepad.index, e.gamepad.buttons.length, e.gamepad.axes.length,
        e.gamepad.id);
  }

  gamepadDisconnected(e) {
    debug('gamepad disconnected :(');
    console.log('gamepad disconnected @ index %d:\n[%s]', e.gamepad.index,
        e.gamepad.id);
  }

  toString() {
    let result = '';

    if (this.up) {
      result += '^';
    } else if (this.down) {
      result += 'v';
    } else {
      result += '-';
    }

    if (this.left) {
      result += '<';
    } else if (this.right) {
      result += '>';
    } else {
      result += '-';
    }

    result += ' ';

    if (this.a) {
      result += 'A';
    }
    if (this.b) {
      result += 'B';
    }
    if (this.x) {
      result += 'X';
    }
    if (this.y) {
      result += 'Y';
    }
    if (this.l) {
      result += 'L';
    }
    if (this.r) {
      result += 'R';
    }
    if (this.select) {
      result += 's';
    }
    if (this.start) {
      result += 'S';
    }
    return result;
  }
}

const input = new Input();

class Graphics {
  constructor(canvas) {
    this.canvas_ = canvas;
    this.ctx_ = canvas.getContext('2d');
  }

  get width() {
    return this.canvas_.width;
  }

  get height() {
    return this.canvas_.height;
  }

  fill(color) {
    this.ctx_.fillStyle = color;
    this.ctx_.beginPath();
    this.ctx_.rect(0, 0, this.canvas_.width, this.canvas_.height);
    this.ctx_.fill();
    this.ctx_.closePath();
  }

  circle(x, y, radius, color) {
    this.ctx_.fillStyle = color;
    this.ctx_.beginPath();
    this.ctx_.arc(x, y, radius, 0, 2 * Math.PI)
    this.ctx_.fill();
    this.ctx_.closePath();
  }

  // TODO: replace with custom sprite-based text rendering.
  text(string, x, y, size, color) {
    this.ctx_.imageSmoothingEnabled = false;
    this.ctx_.fillStyle = color;
    this.ctx_.font = '' + size + 'px monospace';
    this.ctx_.fillText(string, x, y);
  }
}

class FpsCounter {
  constructor() {
    this.fps = 0;
    this.frameTimes_ = new Array(60);
    this.idx_ = 0;
  }

  update(timestampMs) {
    if (this.frameTimes_[this.idx_]) {
      const timeElapsed = (timestampMs - this.frameTimes_[this.idx_]) / 1000;
      this.fps = this.frameTimes_.length / timeElapsed;
    }
    this.frameTimes_[this.idx_] = timestampMs;
    this.idx_++;
    if (this.idx_ == this.frameTimes_.length) {
      this.idx_ = 0;
    }
  }

  draw(gfx) {
    gfx.text('FPS: ' + Math.round(this.fps), 8, 16, 16, 'yellow');
  }
}

class World {
  constructor() {
    this.state_ = null;
    this.fpsCounter_ = new FpsCounter();
    this.input_ = new Input();
    this.gamepadRenderer_ = new GamepadRenderer();
  }

  update(timestampMs) {
    this.fpsCounter_.update(timestampMs);
    this.input_.update();
  }

  draw(gfx) {
    this.gamepadRenderer_.draw(gfx, this.input_);
    this.fpsCounter_.draw(gfx);
  }
}

class GamepadRenderer {
  draw(gfx, input) {
    const centerX = gfx.width / 2;
    const centerY = gfx.height / 2;

    gfx.fill('black');

    // Select & Start
    gfx.circle(centerX + 12, centerY, 8, input.start ? 'cyan' : 'grey');
    gfx.circle(centerX - 12, centerY, 8, input.select ? 'cyan' : 'grey');

    // Y X B A
    gfx.circle(centerX + 48, centerY, 8, input.y ? 'cyan' : 'grey');
    gfx.circle(centerX + 64, centerY - 16, 8, input.x ? 'cyan' : 'grey');
    gfx.circle(centerX + 64, centerY + 16, 8, input.b ? 'cyan' : 'grey');
    gfx.circle(centerX + 80, centerY, 8, input.a ? 'cyan' : 'grey');

    // dpad
    gfx.circle(centerX - 48, centerY, 8, input.right ? 'cyan' : 'grey');
    gfx.circle(centerX - 64, centerY - 16, 8, input.up ? 'cyan' : 'grey');
    gfx.circle(centerX - 64, centerY + 16, 8, input.down ? 'cyan' : 'grey');
    gfx.circle(centerX - 80, centerY, 8, input.left ? 'cyan' : 'grey');

    // L & R
    gfx.circle(centerX + 30, centerY - 32, 8, input.r ? 'cyan' : 'grey');
    gfx.circle(centerX - 30, centerY - 32, 8, input.l ? 'cyan' : 'grey');
  }
}

function debug(message) {
  const debugDiv = document.getElementById('debug');
  debugDiv.innerText = message;
}

function loop(world, gfx) {
  return timestampMs => {
    world.update(timestampMs);
    world.draw(gfx);
    window.requestAnimationFrame(loop(world, gfx));
  };
}

function setCanvasScale(scale) {
  const snesWidth = 256;
  const snesHeight = 224;
  const canvas = document.getElementById('canvas');
  canvas.style.width = '' + snesWidth * scale + 'px';
  canvas.style.height = '' + snesHeight * scale + 'px';
}

function init() {
  const world = new World();
  const gfx = new Graphics(document.getElementById('canvas'));

  document.getElementById('1x').onclick = () => setCanvasScale(1);
  document.getElementById('2x').onclick = () => setCanvasScale(2);
  document.getElementById('3x').onclick = () => setCanvasScale(3);
  document.getElementById('4x').onclick = () => setCanvasScale(4);
  document.getElementById('5x').onclick = () => setCanvasScale(5);
  setCanvasScale(4);
  window.requestAnimationFrame(loop(world, gfx));
  debug('initialized!');
}

init();