/*
 * Canvas 渲染：木色棋盘、立体棋子、悬停预览、最后一手标记、获胜连线。
 * 不持有游戏状态，每次 render(game, hover) 根据传入状态整体重绘。
 */
(function () {

  const SIZE = 15;
  const STAR_POINTS = [[3, 3], [11, 3], [3, 11], [11, 11], [7, 7]];

  function createRenderer(canvas) {
    const ctx = canvas.getContext('2d');
    let cssSize = 600;
    let margin = 0;
    let cell = 0;

    function resize() {
      const rect = canvas.getBoundingClientRect();
      cssSize = Math.max(200, Math.floor(rect.width));
      const dpr = window.devicePixelRatio || 1;
      canvas.width = Math.round(cssSize * dpr);
      canvas.height = Math.round(cssSize * dpr);
      ctx.setTransform(dpr, 0, 0, dpr, 0, 0);
      margin = cssSize / (SIZE + 1);
      cell = (cssSize - margin * 2) / (SIZE - 1);
    }

    function toPixel(x, y) {
      return { px: margin + x * cell, py: margin + y * cell };
    }

    function drawBoard() {
      const bg = ctx.createLinearGradient(0, 0, cssSize, cssSize);
      bg.addColorStop(0, '#e3b473');
      bg.addColorStop(1, '#d19a52');
      ctx.fillStyle = bg;
      ctx.fillRect(0, 0, cssSize, cssSize);

      ctx.strokeStyle = '#7a5a2e';
      ctx.lineWidth = 1;
      for (let i = 0; i < SIZE; i++) {
        const p = margin + i * cell;
        ctx.beginPath();
        ctx.moveTo(margin, p);
        ctx.lineTo(cssSize - margin, p);
        ctx.moveTo(p, margin);
        ctx.lineTo(p, cssSize - margin);
        ctx.stroke();
      }
      // 外框加粗一圈
      ctx.lineWidth = 2;
      ctx.strokeRect(margin, margin, cell * (SIZE - 1), cell * (SIZE - 1));

      ctx.fillStyle = '#5a3f1c';
      for (const [sx, sy] of STAR_POINTS) {
        const { px, py } = toPixel(sx, sy);
        ctx.beginPath();
        ctx.arc(px, py, Math.max(2.5, cell * 0.09), 0, Math.PI * 2);
        ctx.fill();
      }
    }

    function drawStone(x, y, color, alpha) {
      const { px, py } = toPixel(x, y);
      const r = cell * 0.42;
      ctx.save();
      ctx.globalAlpha = alpha;
      if (alpha === 1) {
        ctx.shadowColor = 'rgba(0, 0, 0, 0.35)';
        ctx.shadowBlur = r * 0.35;
        ctx.shadowOffsetY = r * 0.12;
      }
      const g = ctx.createRadialGradient(px - r * 0.35, py - r * 0.35, r * 0.1, px, py, r);
      if (color === 1) {
        g.addColorStop(0, '#6a6a6a');
        g.addColorStop(1, '#0d0d0d');
      } else {
        g.addColorStop(0, '#ffffff');
        g.addColorStop(1, '#c9c4ba');
      }
      ctx.fillStyle = g;
      ctx.beginPath();
      ctx.arc(px, py, r, 0, Math.PI * 2);
      ctx.fill();
      ctx.restore();
    }

    function render(game, hover) {
      drawBoard();
      for (let y = 0; y < SIZE; y++) {
        for (let x = 0; x < SIZE; x++) {
          if (game.board[y][x] !== 0) drawStone(x, y, game.board[y][x], 1);
        }
      }

      // 最后一手红点标记（有获胜连线时不画，避免遮挡）
      const last = game.moveHistory[game.moveHistory.length - 1];
      if (last && !game.winningLine) {
        const { px, py } = toPixel(last.x, last.y);
        ctx.fillStyle = '#e6493a';
        ctx.beginPath();
        ctx.arc(px, py, Math.max(2.5, cell * 0.1), 0, Math.PI * 2);
        ctx.fill();
      }

      // 获胜连线
      if (game.winningLine) {
        const a = toPixel(game.winningLine[0].x, game.winningLine[0].y);
        const b = toPixel(
          game.winningLine[game.winningLine.length - 1].x,
          game.winningLine[game.winningLine.length - 1].y
        );
        ctx.save();
        ctx.strokeStyle = 'rgba(230, 60, 45, 0.9)';
        ctx.lineWidth = cell * 0.14;
        ctx.lineCap = 'round';
        ctx.beginPath();
        ctx.moveTo(a.px, a.py);
        ctx.lineTo(b.px, b.py);
        ctx.stroke();
        ctx.restore();
      }

      // 悬停预览：半透明显示当前行棋方棋子
      if (hover && !game.gameOver && game.board[hover.y][hover.x] === 0) {
        drawStone(hover.x, hover.y, game.currentPlayer, 0.4);
      }
    }

    // 把鼠标事件换算成最近的交叉点，超出棋盘返回 null
    function cellFromEvent(evt) {
      const rect = canvas.getBoundingClientRect();
      const x = Math.round((evt.clientX - rect.left - margin) / cell);
      const y = Math.round((evt.clientY - rect.top - margin) / cell);
      if (x < 0 || x >= SIZE || y < 0 || y >= SIZE) return null;
      return { x, y };
    }

    resize();
    return { render, resize, cellFromEvent };
  }

  window.GomokuRenderer = { createRenderer };
})();