const canvas = document.getElementById('game');
const ctx = canvas.getContext('2d');
const scoreEl = document.getElementById('score');
const heartsEl = document.getElementById('hearts');

const keys = new Set();
const gravity = 1900;
const groundY = 420;
const worldWidth = 6000;

const waterGaps = [
  { x: 700, width: 130 },
  { x: 1300, width: 150 },
  { x: 2100, width: 170 },
  { x: 3000, width: 140 },
  { x: 3900, width: 200 }
];

const state = {
  running: true,
  dead: false,
  deadReason: '',
  lastTs: performance.now(),
  score: 0,
  stepCarry: 0,
  cameraX: 0,
  hearts: 3,
  player: {
    x: 160,
    y: 0,
    width: 64,
    height: 76,
    standingHeight: 76,
    duckHeight: 48,
    vx: 0,
    vy: 0,
    speed: 300,
    jumpPower: 760,
    onGround: true,
    ducking: false
  }
};
state.player.y = groundY - state.player.height;

window.addEventListener('keydown', (e) => {
  if (["ArrowUp", "ArrowDown", "ArrowLeft", "ArrowRight"].includes(e.key)) {
    e.preventDefault();
  }
  keys.add(e.key);
  if (e.key === 'ArrowUp' && state.player.onGround) {
    state.player.vy = -state.player.jumpPower;
    state.player.onGround = false;
  }
});
window.addEventListener('keyup', (e) => keys.delete(e.key));

function drawBackground() {
  ctx.fillStyle = '#8ddcff';
  ctx.fillRect(0, 0, canvas.width, canvas.height);
  ctx.fillStyle = '#88d34f';
  ctx.fillRect(0, groundY, canvas.width, canvas.height - groundY);

  // Water gaps
  for (const gap of waterGaps) {
    const sx = gap.x - state.cameraX;
    if (sx + gap.width < 0 || sx > canvas.width) continue;
    ctx.fillStyle = '#2e8bcf';
    ctx.fillRect(sx, groundY, gap.width, canvas.height - groundY);
  }
}

function drawTRex(p) {
  const sx = p.x - state.cameraX;
  ctx.fillStyle = '#35535f';
  ctx.fillRect(sx, p.y, p.width, p.height);
  ctx.fillStyle = '#27404a';
  ctx.fillRect(sx + p.width - 12, p.y + 14, 7, 7);
  ctx.fillRect(sx + 10, p.y + p.height - 8, 14, 8);
  ctx.fillRect(sx + p.width - 24, p.y + p.height - 8, 14, 8);
}

function updateHeartsUI() {
  heartsEl.textContent = '❤'.repeat(state.hearts) + '🖤'.repeat(Math.max(0, 3 - state.hearts));
}

function kill(reason) {
  state.running = false;
  state.dead = true;
  state.deadReason = reason;
}

function isOverWater(player) {
  const centerX = player.x + player.width / 2;
  return waterGaps.some((g) => centerX >= g.x && centerX <= g.x + g.width);
}

function updatePlayer(dt) {
  const p = state.player;
  let move = 0;
  if (keys.has('ArrowLeft')) move -= 1;
  if (keys.has('ArrowRight')) move += 1;

  p.ducking = keys.has('ArrowDown') && p.onGround;
  const targetHeight = p.ducking ? p.duckHeight : p.standingHeight;
  if (targetHeight !== p.height) {
    p.y += p.height - targetHeight;
    p.height = targetHeight;
  }

  p.vx = move * p.speed;
  const oldX = p.x;
  p.x += p.vx * dt;
  p.x = Math.max(0, Math.min(worldWidth - p.width, p.x));

  if (p.x > oldX) {
    state.stepCarry += p.x - oldX;
    while (state.stepCarry >= 8) {
      state.score += 1;
      state.stepCarry -= 8;
    }
  }

  p.vy += gravity * dt;
  p.y += p.vy * dt;

  if (p.y + p.height >= groundY) {
    p.y = groundY - p.height;
    p.vy = 0;
    p.onGround = true;

    if (isOverWater(p)) {
      kill('SPLASH! Water is instant death.');
    }
  } else {
    p.onGround = false;
  }

  state.cameraX = Math.max(0, Math.min(worldWidth - canvas.width, p.x - 240));
}

function drawDeathText() {
  if (!state.dead) return;
  ctx.fillStyle = 'rgba(0,0,0,0.55)';
  ctx.fillRect(0, 0, canvas.width, canvas.height);
  ctx.fillStyle = '#fff';
  ctx.font = 'bold 42px Arial';
  ctx.fillText('Game Over', 360, 220);
  ctx.font = '24px Arial';
  ctx.fillText(state.deadReason, 280, 270);
}

function tick(ts) {
  const dt = Math.min((ts - state.lastTs) / 1000, 0.05);
  state.lastTs = ts;

  if (state.running) updatePlayer(dt);

  ctx.clearRect(0, 0, canvas.width, canvas.height);
  drawBackground();
  drawTRex(state.player);
  drawDeathText();

  scoreEl.textContent = `Score: ${state.score}`;
  updateHeartsUI();

  requestAnimationFrame(tick);
}

requestAnimationFrame((ts) => {
  state.lastTs = ts;
  updateHeartsUI();
  requestAnimationFrame(tick);
});