// This file is part of the 64k demo project.
// It implements the FlashEffect - brief flash on beat hits.
// Now supports parameterized color with per-frame animation.

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

// Backward compatibility constructor (delegates to parameterized constructor)
FlashEffect::FlashEffect(const GpuContext& ctx)
    : FlashEffect(ctx, FlashEffectParams{}) {
}

// Parameterized constructor
FlashEffect::FlashEffect(const GpuContext& ctx, const FlashEffectParams& params)
    : PostProcessEffect(ctx), params_(params) {
  const char* shader_code = R"(
    struct VertexOutput {
      @builtin(position) position: vec4<f32>,
      @location(0) uv: vec2<f32>,
    };

    struct Uniforms {
      flash_intensity: f32,
      intensity: f32,
      flash_color: vec3<f32>,  // Parameterized color
      _pad: 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);
      // Use parameterized flash color instead of hardcoded white
      var flashed = mix(color.rgb, uniforms.flash_color, uniforms.flash_intensity);
      return vec4<f32>(flashed, color.a);
    }
  )";

  pipeline_ =
      create_post_process_pipeline(ctx_.device, ctx_.format, shader_code);
  uniforms_.init(ctx_.device);
}

void FlashEffect::update_bind_group(WGPUTextureView input_view) {
  pp_update_bind_group(ctx_.device, pipeline_, &bind_group_, input_view,
                       uniforms_.get());
}

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

  // Trigger flash based on configured threshold
  if (intensity > params_.trigger_threshold && flash_intensity_ < 0.2f) {
    flash_intensity_ = 0.8f; // Trigger flash
  }

  // Decay based on configured rate
  flash_intensity_ *= params_.decay_rate;

  // *** PER-FRAME PARAMETER COMPUTATION ***
  // Animate color based on time and beat
  const float r = params_.color[0] * (0.5f + 0.5f * sinf(time * 0.5f));
  const float g = params_.color[1] * (0.5f + 0.5f * cosf(time * 0.7f));
  const float b = params_.color[2] * (1.0f + 0.3f * beat);

  // Update uniforms with computed (animated) values
  const FlashUniforms u = {
      .flash_intensity = flash_intensity_,
      .intensity = intensity,
      ._pad1 = {0.0f, 0.0f}, // Padding for vec3 alignment
      .color = {r, g, b},    // Time-dependent, computed every frame
      ._pad2 = 0.0f};
  uniforms_.update(ctx_.queue, u);

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