'use strict';

/* ---------- 1. DOM refs ---------- */
const boardEl = document.getElementById('board');
const statusEl = document.getElementById('status');
const statusTextEl = document.getElementById('status-text');
const overlayEl = document.getElementById('overlay');
const overlayTitleEl = document.getElementById('overlay-title');
const winLineEl = document.getElementById('win-line-el');
const confettiLayer = document.getElementById('confetti-layer');
const toastEl = document.getElementById('toast');

const scoreEls = {
  you: document.getElementById('score-you'),
  cpu: document.getElementById('score-cpu'),
  draws: document.getElementById('score-draws'),
};

const cells = [];

/* ---------- state ---------- */
const state = {
  board: Array(9).fill(null),
  turn: 'X',
  gameOver: false,
  scores: { you: 0, cpu: 0, draws: 0 },
};

let cpuTimer = 0;
let toastTimer = 0;

const WIN_LINES = [
  [0, 1, 2], [3, 4, 5], [6, 7, 8],
  [0, 3, 6], [1, 4, 7], [2, 5, 8],
  [0, 4, 8], [2, 4, 6],
];

const SCORES_KEY = 'ttt-scores';
const CPU_DELAY = 600;

const X_SVG =
  '<svg viewBox="0 0 100 100" class="mark mark-x" aria-hidden="true">' +
  '<line x1="24" y1="24" x2="76" y2="76"></line>' +
  '<line x1="76" y1="24" x2="24" y2="76"></line>' +
  '</svg>';

const O_SVG =
  '<svg viewBox="0 0 100 100" class="mark mark-o" aria-hidden="true">' +
  '<circle cx="50" cy="50" r="30"></circle>' +
  '</svg>';

/* ---------- 2. Win detection ---------- */
function checkWinner(board) {
  for (const line of WIN_LINES) {
    const [a, b, c] = line;
    if (board[a] && board[a] === board[b] && board[a] === board[c]) {
      return { winner: board[a], line };
    }
  }
  if (board.every((v) => v !== null)) return { winner: 'draw' };
  return null;
}

/* ---------- 3. Player move ---------- */
function onCellTap(i) {
  if (state.gameOver || state.turn !== 'X' || state.board[i]) return;
  placeMark(i, 'X');
  const result = checkWinner(state.board);
  if (result) {
    endRound(result);
    return;
  }
  state.turn = 'O';
  renderStatus('CPU is thinking…', 'thinking');
  cpuTimer = setTimeout(cpuMove, CPU_DELAY);
}

/* ---------- 4. CPU move ---------- */
function cpuMove() {
  if (state.gameOver) return;
  const empty = [];
  state.board.forEach((v, i) => {
    if (v === null) empty.push(i);
  });
  if (!empty.length) return;
  const i = empty[Math.floor(Math.random() * empty.length)];
  placeMark(i, 'O');
  const result = checkWinner(state.board);
  if (result) {
    endRound(result);
    return;
  }
  state.turn = 'X';
  renderStatus('Your turn', 'normal');
}

function placeMark(i, mark) {
  state.board[i] = mark;
  renderMark(i, mark);
}

/* ---------- 5. Render ---------- */
function renderMark(i, mark) {
  const cell = cells[i];
  cell.classList.remove('empty');
  cell.classList.add(mark === 'X' ? 'has-x' : 'has-o');
  cell.setAttribute('aria-label', mark === 'X' ? 'X' : 'O');
  cell.innerHTML = mark === 'X' ? X_SVG : O_SVG;
}

function renderStatus(text, mode) {
  mode = mode || 'normal';
  statusEl.classList.toggle('thinking', mode === 'thinking');
  if (statusTextEl.textContent === text) return;
  statusEl.classList.add('fading');
  setTimeout(() => {
    statusTextEl.textContent = text;
    statusEl.classList.remove('fading');
  }, 150);
}

function renderScores(changed) {
  for (const k of ['you', 'cpu', 'draws']) {
    scoreEls[k].textContent = state.scores[k];
    if (k === changed) {
      scoreEls[k].classList.remove('pop');
      void scoreEls[k].offsetWidth;
      scoreEls[k].classList.add('pop');
    }
  }
}

function cellCenter(i, boardRect) {
  const r = cells[i].getBoundingClientRect();
  return {
    x: r.left + r.width / 2 - boardRect.left,
    y: r.top + r.height / 2 - boardRect.top,
  };
}

function drawWinLine(line) {
  const boardRect = boardEl.getBoundingClientRect();
  const p1 = cellCenter(line[0], boardRect);
  const p2 = cellCenter(line[2], boardRect);
  const dx = p2.x - p1.x;
  const dy = p2.y - p1.y;
  const len = Math.hypot(dx, dy) || 1;
  const ext = 16;
  const ux = dx / len;
  const uy = dy / len;
  const x1 = p1.x - ux * ext;
  const y1 = p1.y - uy * ext;
  const x2 = p2.x + ux * ext;
  const y2 = p2.y + uy * ext;

  winLineEl.setAttribute('x1', x1);
  winLineEl.setAttribute('y1', y1);
  winLineEl.setAttribute('x2', x2);
  winLineEl.setAttribute('y2', y2);

  const total = Math.hypot(x2 - x1, y2 - y1);
  winLineEl.style.transition = 'none';
  winLineEl.style.strokeDasharray = total;
  winLineEl.style.strokeDashoffset = total;
  winLineEl.style.opacity = '1';
  void winLineEl.getBoundingClientRect();
  winLineEl.style.transition = 'stroke-dashoffset 400ms ease';
  winLineEl.style.strokeDashoffset = '0';
}

function clearWinLine() {
  winLineEl.style.transition = 'none';
  winLineEl.style.opacity = '0';
  winLineEl.style.strokeDashoffset = winLineEl.style.strokeDasharray;
}

/* ---------- 6. Round end ---------- */
function endRound(result) {
  state.gameOver = true;
  let title;
  let key;
  if (result.winner === 'X') {
    key = 'you';
    title = 'You Win! 🎉';
    renderStatus('You win! 🎉', 'normal');
  } else if (result.winner === 'O') {
    key = 'cpu';
    title = 'CPU Wins';
    renderStatus('CPU wins', 'normal');
    boardEl.classList.add('shake');
  } else {
    key = 'draws';
    title = "It's a Draw";
    renderStatus("It's a draw", 'normal');
    boardEl.classList.add('pulse');
  }

  state.scores[key]++;
  persistScores();
  renderScores(key);

  if (result.line) drawWinLine(result.line);

  setTimeout(() => {
    overlayTitleEl.textContent = title;
    overlayEl.classList.add('show');
    if (result.winner === 'X') burstConfetti();
  }, result.winner === 'draw' ? 400 : 600);
}

/* ---------- 7. Confetti ---------- */
const CONFETTI_COLORS = ['#22d3ee', '#f472b6', '#a78bfa', '#fbbf24', '#34d399', '#ffffff'];

function burstConfetti() {
  const pieces = [];
  for (let i = 0; i < 40; i++) {
    const el = document.createElement('div');
    el.className = 'confetti';
    const size = 6 + Math.random() * 8;
    el.style.width = size + 'px';
    el.style.height = size * 1.4 + 'px';
    el.style.left = Math.random() * 100 + 'vw';
    el.style.background = CONFETTI_COLORS[Math.floor(Math.random() * CONFETTI_COLORS.length)];
    el.style.setProperty('--drift', (Math.random() * 160 - 80) + 'px');
    el.style.setProperty('--spin', (360 + Math.random() * 720) + 'deg');
    el.style.animationDuration = 1.3 + Math.random() * 0.5 + 's';
    el.style.animationDelay = Math.random() * 0.25 + 's';
    confettiLayer.appendChild(el);
    pieces.push(el);
  }
  setTimeout(() => pieces.forEach((p) => p.remove()), 2200);
}

/* ---------- 8. Reset ---------- */
function newRound() {
  clearTimeout(cpuTimer);
  state.board = Array(9).fill(null);
  state.turn = 'X';
  state.gameOver = false;
  cells.forEach((cell) => {
    cell.innerHTML = '';
    cell.classList.add('empty');
    cell.classList.remove('has-x', 'has-o');
    cell.setAttribute('aria-label', 'Empty cell');
  });
  clearWinLine();
  boardEl.classList.remove('shake', 'pulse');
  overlayEl.classList.remove('show');
  confettiLayer.innerHTML = '';
  renderStatus('Your turn', 'normal');
}

function resetScores() {
  state.scores = { you: 0, cpu: 0, draws: 0 };
  persistScores();
  renderScores();
  showToast('Scores reset');
}

function persistScores() {
  try {
    localStorage.setItem(SCORES_KEY, JSON.stringify(state.scores));
  } catch (e) {
    /* storage unavailable */
  }
}

function loadScores() {
  try {
    const raw = localStorage.getItem(SCORES_KEY);
    if (raw) {
      const s = JSON.parse(raw);
      state.scores = {
        you: Number(s.you) || 0,
        cpu: Number(s.cpu) || 0,
        draws: Number(s.draws) || 0,
      };
    }
  } catch (e) {
    /* corrupted storage — keep defaults */
  }
}

function showToast(msg) {
  toastEl.textContent = msg;
  toastEl.classList.add('show');
  clearTimeout(toastTimer);
  toastTimer = setTimeout(() => toastEl.classList.remove('show'), 1600);
}

/* ---------- 9. Init ---------- */
function buildBoard() {
  for (let i = 0; i < 9; i++) {
    const cell = document.createElement('button');
    cell.type = 'button';
    cell.className = 'cell empty';
    cell.dataset.index = String(i);
    cell.setAttribute('aria-label', 'Empty cell');
    cell.addEventListener('click', () => onCellTap(i));
    boardEl.appendChild(cell);
    cells.push(cell);
  }
}

function init() {
  buildBoard();
  loadScores();
  renderScores();
  document.getElementById('btn-new').addEventListener('click', newRound);
  document.getElementById('btn-reset').addEventListener('click', resetScores);
  document.getElementById('btn-again').addEventListener('click', newRound);
  renderStatus('Your turn', 'normal');
}

init();