Toolbox/public/tools/greedy_snake/js/ai.js

/* 贪蛇出动 - AI 蛇控制器：觅食/避障/边界回避/随机加速 */
(function () {
  'use strict';
  window.GS = window.GS || {};
  const U = GS.U;

  class AI {
    constructor(snake) {
      this.s = snake;
      this.decideTimer = U.rand(0, 0.3);
      this.wanderAngle = snake.angle;
      this.boostTimer = 0;
    }

    update(dt, world, snakes) {
      const s = this.s;
      if (s.dead) return;
      this.decideTimer -= dt;
      this.boostTimer -= dt;
      if (this.decideTimer > 0) {
        s.boosting = this.boostTimer > 0;
        return;
      }
      this.decideTimer = 0.15;

      const h = s.head;
      const look = 90 + s.radius * 3;
      const aheadX = h.x + Math.cos(s.angle) * look;
      const aheadY = h.y + Math.sin(s.angle) * look;

      // 1) 边界回避
      const margin = 220;
      let avoid = null;
      if (aheadX < margin || aheadY < margin || aheadX > world.size - margin || aheadY > world.size - margin) {
        avoid = Math.atan2(world.size / 2 - h.y, world.size / 2 - h.x);
      }

      // 2) 蛇身回避：检查前方采样点是否撞上其他蛇
      if (avoid == null) {
        for (const o of snakes) {
          if (o === s || o.dead) continue;
          const segs = o.segments();
          const rr = (s.radius + o.radius + 26);
          for (let i = 0; i < segs.length; i += 2) {
            if (U.dist2(aheadX, aheadY, segs[i].x, segs[i].y) < rr * rr) {
              // 向左或向右转，选更开阔的一侧
              const left = s.angle - Math.PI / 2, right = s.angle + Math.PI / 2;
              avoid = this._clearer(left, right, h, snakes, s);
              break;
            }
          }
          if (avoid != null) break;
        }
      }

      if (avoid != null) {
        s.targetAngle = avoid;
        s.boosting = false;
        return;
      }

      // 3) 觅食：找最近金币
      let best = null, bestD = 520 * 520;
      const near = world.grid.query(h.x, h.y, 520);
      for (const c of near) {
        const d2 = U.dist2(h.x, h.y, c.x, c.y);
        if (d2 < bestD) { bestD = d2; best = c; }
      }
      if (best) {
        s.targetAngle = Math.atan2(best.y - h.y, best.x - h.x);
      } else {
        // 漫游：小幅随机偏转
        this.wanderAngle += U.rand(-0.6, 0.6);
        s.targetAngle = this.wanderAngle;
      }

      // 4) 随机加速：追食或逃跑时小概率冲刺
      if (Math.random() < 0.06 && s.score > 30) this.boostTimer = U.rand(0.4, 1.0);
      s.boosting = this.boostTimer > 0;
    }

    _clearer(a1, a2, h, snakes, s) {
      const score = a => {
        const px = h.x + Math.cos(a) * 160, py = h.y + Math.sin(a) * 160;
        let d = 1e9;
        for (const o of snakes) {
          if (o === s || o.dead) continue;
          const segs = o.segments();
          for (let i = 0; i < segs.length; i += 3) {
            const dd = U.dist2(px, py, segs[i].x, segs[i].y);
            if (dd < d) d = dd;
          }
        }
        return d;
      };
      return score(a1) >= score(a2) ? a1 : a2;
    }
  }

  GS.AI = AI;
})();