/* 贪蛇出动 - 输入控制：左摇杆 + 右加速按钮 + 桌面键盘 */
(function () {
  'use strict';
  window.GS = window.GS || {};

  class Input {
    constructor() {
      this.angle = -Math.PI / 2;   // 目标方向
      this.boost = false;
      this.enabled = false;
      this._joyId = null;
      this._joyBase = { x: 0, y: 0 };
      this._keys = new Set();
      this._bind();
    }

    _bind() {
      const joy = document.getElementById('gs-joystick');
      const knob = document.getElementById('gs-joystick-knob');
      const boostBtn = document.getElementById('gs-boost');
      this.joyEl = joy; this.knobEl = knob; this.boostEl = boostBtn;

      // 摇杆：触摸左下区域
      joy.addEventListener('touchstart', e => {
        e.preventDefault();
        const t = e.changedTouches[0];
        this._joyId = t.identifier;
        const r = joy.getBoundingClientRect();
        this._joyBase = { x: r.left + r.width / 2, y: r.top + r.height / 2 };
        this._moveKnob(t.clientX, t.clientY);
      }, { passive: false });
      joy.addEventListener('touchmove', e => {
        e.preventDefault();
        for (const t of e.changedTouches) if (t.identifier === this._joyId) this._moveKnob(t.clientX, t.clientY);
      }, { passive: false });
      const endJoy = e => {
        for (const t of e.changedTouches) if (t.identifier === this._joyId) {
          this._joyId = null;
          this.knobEl.style.transform = 'translate(-50%, -50%)';
        }
      };
      joy.addEventListener('touchend', endJoy);
      joy.addEventListener('touchcancel', endJoy);

      // 桌面鼠标拖拽摇杆
      let mouseDown = false;
      joy.addEventListener('mousedown', e => {
        mouseDown = true;
        const r = joy.getBoundingClientRect();
        this._joyBase = { x: r.left + r.width / 2, y: r.top + r.height / 2 };
        this._moveKnob(e.clientX, e.clientY);
      });
      window.addEventListener('mousemove', e => { if (mouseDown) this._moveKnob(e.clientX, e.clientY); });
      window.addEventListener('mouseup', () => { mouseDown = false; this.knobEl.style.transform = 'translate(-50%, -50%)'; });

      // 加速按钮：按住加速
      const boostOn = e => { e.preventDefault(); this.boost = true; boostBtn.classList.add('active'); };
      const boostOff = () => { this.boost = false; boostBtn.classList.remove('active'); };
      boostBtn.addEventListener('touchstart', boostOn, { passive: false });
      boostBtn.addEventListener('touchend', boostOff);
      boostBtn.addEventListener('touchcancel', boostOff);
      boostBtn.addEventListener('mousedown', boostOn);
      boostBtn.addEventListener('mouseup', boostOff);
      boostBtn.addEventListener('mouseleave', boostOff);

      // 键盘（桌面调试）：方向键/WSAD 转向，空格加速
      window.addEventListener('keydown', e => {
        this._keys.add(e.code);
        if (e.code === 'Space') { this.boost = true; boostBtn.classList.add('active'); }
        this._applyKeys();
      });
      window.addEventListener('keyup', e => {
        this._keys.delete(e.code);
        if (e.code === 'Space') { this.boost = false; boostBtn.classList.remove('active'); }
        this._applyKeys();
      });

      // 阻止页面滚动/双击缩放
      document.addEventListener('touchmove', e => { e.preventDefault(); }, { passive: false });
      document.addEventListener('gesturestart', e => e.preventDefault());
    }

    _applyKeys() {
      let dx = 0, dy = 0;
      if (this._keys.has('ArrowLeft') || this._keys.has('KeyA')) dx -= 1;
      if (this._keys.has('ArrowRight') || this._keys.has('KeyD')) dx += 1;
      if (this._keys.has('ArrowUp') || this._keys.has('KeyW')) dy -= 1;
      if (this._keys.has('ArrowDown') || this._keys.has('KeyS')) dy += 1;
      if (dx || dy) this.angle = Math.atan2(dy, dx);
    }

    _moveKnob(cx, cy) {
      const maxR = 40;
      let dx = cx - this._joyBase.x, dy = cy - this._joyBase.y;
      const d = Math.sqrt(dx * dx + dy * dy);
      if (d > maxR) { dx = dx / d * maxR; dy = dy / d * maxR; }
      this.knobEl.style.transform = `translate(calc(-50% + ${dx}px), calc(-50% + ${dy}px))`;
      if (d > 8) this.angle = Math.atan2(dy, dx);
    }

    setVisible(v) {
      this.enabled = v;
      this.joyEl.classList.toggle('gs-hidden', !v);
      this.boostEl.classList.toggle('gs-hidden', !v);
    }
  }

  GS.Input = Input;
})();