// This file is part of the 64k demo project.
// It implements the FadeEffect - fades to/from black based on time.

#include "gpu/effects/fade_effect.h"
#include "gpu/effects/post_process_helper.h"
#include <cmath>

FadeEffect::FadeEffect(WGPUDevice device, WGPUQueue queue,
                       WGPUTextureFormat format)
    : PostProcessEffect(device, queue) {
  const char* shader_code = R"(
    struct VertexOutput {
      @builtin(position) position: vec4<f32>,
      @location(0) uv: vec2<f32>,
    };

    struct Uniforms {
      fade_amount: f32,
      _pad0: f32,
      _pad1: f32,
      _pad2: f32,
    };

    @group(0) @binding(0) var inputSampler: sampler;
    @group(0) @binding(1) var inputTexture: texture_2d<f32>;
    @group(0) @binding(2) var<uniform> uniforms: Uniforms;

    @vertex
    fn vs_main(@builtin(vertex_index) vertexIndex: u32) -> VertexOutput {
      var output: VertexOutput;
      var pos = array<vec2<f32>, 3>(
        vec2<f32>(-1.0, -1.0),
        vec2<f32>(3.0, -1.0),
        vec2<f32>(-1.0, 3.0)
      );
      output.position = vec4<f32>(pos[vertexIndex], 0.0, 1.0);
      output.uv = pos[vertexIndex] * 0.5 + 0.5;
      return output;
    }

    @fragment
    fn fs_main(input: VertexOutput) -> @location(0) vec4<f32> {
      let color = textureSample(inputTexture, inputSampler, input.uv);
      // Fade to black: 0.0 = black, 1.0 = full color
      return vec4<f32>(color.rgb * uniforms.fade_amount, color.a);
    }
  )";

  pipeline_ = create_post_process_pipeline(device, format, shader_code);
  uniforms_ = gpu_create_buffer(device, 16, WGPUBufferUsage_Uniform | WGPUBufferUsage_CopyDst);
}

void FadeEffect::update_bind_group(WGPUTextureView input_view) {
  pp_update_bind_group(device_, pipeline_, &bind_group_, input_view, uniforms_);
}

void FadeEffect::render(WGPURenderPassEncoder pass, float time,
                        float beat, float intensity, float aspect_ratio) {
  (void)beat;
  (void)intensity;
  (void)aspect_ratio;

  // Example fade pattern: fade in at start, fade out at end
  // Customize this based on your needs
  float fade_amount = 1.0f;
  if (time < 2.0f) {
    // Fade in from black over first 2 seconds
    fade_amount = time / 2.0f;
  } else if (time > 36.0f) {
    // Fade out to black after 36 seconds
    fade_amount = 1.0f - ((time - 36.0f) / 4.0f);
    fade_amount = fmaxf(fade_amount, 0.0f);
  }

  float uniforms[4] = {fade_amount, 0.0f, 0.0f, 0.0f};
  wgpuQueueWriteBuffer(queue_, uniforms_.buffer, 0, uniforms, sizeof(uniforms));

  wgpuRenderPassEncoderSetPipeline(pass, pipeline_);
  wgpuRenderPassEncoderSetBindGroup(pass, 0, bind_group_, 0, nullptr);
  wgpuRenderPassEncoderDraw(pass, 3, 1, 0, 0);
}