// Cocos Creator 2.x 兼容的纸牌翻转Shader
CCEffect %{
  techniques:
  - passes:
    - vert: card-flip-vs
      frag: card-flip-fs
      blendState:
        targets:
        - blend: true
          blendSrc: src_alpha
          blendDst: one_minus_src_alpha
      rasterizerState:
        cullMode: none
      depthStencilState:
        depthTest: false
        depthWrite: false
      properties:
        texture: { value: white }
        flipProgress: { value: 0, editor: { type: slider, min: 0, max: 1 } }
        bendStrength: { value: 0.2, editor: { type: slider, min: 0, max: 1 } }
        enableShadow: { value: 1, editor: { type: boolean } }
}%

CCProgram card-flip-vs %{
  precision highp float;
  #include <cc-global>
  
  in vec3 a_position;
  in vec4 a_color;
  out vec4 v_color;
  
  #if USE_TEXTURE
  in vec2 a_uv0;
  out vec2 v_uv0;
  uniform sampler2D texture;
  #endif
  
  uniform Properties {
    float flipProgress;
    float bendStrength;
    float enableShadow;
  };
  
  void main () {
    vec4 pos = vec4(a_position, 1);
    
    // 计算翻转角度 (从对应30%展示状态的角度到0度，实现从30%展示到完全展示的翻转)
    // 30%展示状态对应的角度约为π * 0.7
    float adjustedProgress = (flipProgress - 0.1) / 0.7; // 将0.1-1.0范围映射到0-1
    adjustedProgress = clamp(adjustedProgress, 0.0, 1.0);
    float flipAngle = (1.0 - adjustedProgress) * 3.14159; // 从π到0
    
    // 计算当前y坐标相对于中心的位置 (-0.5到0.5)
    float relativeY = pos.y - 0.5;
    
    // 应用弯曲效果，使卡片看起来有厚度
    float bend = sin(flipAngle) * bendStrength * relativeY;
    
    // 应用X轴旋转
    pos.y = 0.5 + relativeY * cos(flipAngle);
    pos.z = relativeY * sin(flipAngle) + bend;
    
    // 限制Z轴范围，防止卡片在父节点移动时消失
    pos.z = clamp(pos.z, -0.5, 0.5);
    
    // 应用阴影效果
    if (enableShadow > 0.5 && flipProgress > 0.1 && flipProgress < 0.9) {
      float shadowIntensity = sin(flipAngle) * 0.5;
      v_color = vec4(a_color.rgb * (1.0 - shadowIntensity * 0.5), a_color.a);
    } else {
      v_color = a_color;
    }
    
    #if USE_TEXTURE
    v_uv0 = a_uv0;
    #endif
    
    gl_Position = cc_matViewProj * pos;
  }
}%

CCProgram card-flip-fs %{
  precision highp float;
  
  #include <cc-global>
  
  in vec4 v_color;
  
  #if USE_TEXTURE
  in vec2 v_uv0;
  uniform sampler2D texture;
  #endif
  
  uniform Properties {
    float flipProgress;
    float bendStrength;
    float enableShadow;
  };
  
  void main () {
    vec4 o = vec4(1, 1, 1, 1);
    
    #if USE_TEXTURE
      o *= texture2D(texture, v_uv0);
    #endif
    
    o *= v_color;
    
    // 当卡片背面朝向相机时，使其透明（翻转开始时30%展示，结束时完全展示）
    // 计算调整后的进度，将0.1-1.0范围映射到0-1
    float adjustedProgress = (flipProgress - 0.1) / 0.7;
    adjustedProgress = clamp(adjustedProgress, 0.0, 1.0);
    
    if (adjustedProgress < 0.3) {
      float backFaceAlpha = (0.5 - adjustedProgress) * 2.0;
      o.a *= (1.0 - backFaceAlpha * 0.7); // 调整透明度，使初始状态为30%展示
    }
    
    gl_FragColor = o;
  }
}%