// This file is part of the 64k demo project.
// It implements theme modulation (bright/dark alternation).

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

ThemeModulationEffect::ThemeModulationEffect(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 {
      theme_brightness: 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;
      // Large triangle trick for fullscreen coverage
      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);
      // Apply theme brightness modulation
      return vec4<f32>(color.rgb * uniforms.theme_brightness, color.a);
    }
  )";

  pipeline_ = create_post_process_pipeline(device, format, shader_code);

  // Create uniform buffer (4 floats: brightness + padding)
  uniforms_ = gpu_create_buffer(device, 16, WGPUBufferUsage_Uniform | WGPUBufferUsage_CopyDst);
}

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

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

  // Alternate between bright and dark every 4 seconds (2 pattern changes)
  // Music patterns change every 2 seconds at 120 BPM
  float cycle_time = fmodf(time, 8.0f);  // 8 second cycle (4 patterns)
  bool is_dark_section = (cycle_time >= 4.0f);  // Dark for second half

  // Smooth transition between themes using a sine wave
  float transition = (std::sin(time * 3.14159f / 4.0f) + 1.0f) * 0.5f;  // 0.0 to 1.0
  float bright_value = 1.0f;
  float dark_value = 0.35f;
  float theme_brightness = bright_value + (dark_value - bright_value) * transition;

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

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