// lib/post/webgpu/bloom-selective.ts
// Selective bloom — only objects tagged via an MRT `bloomIntensity` channel
// bloom. There is no single node for this; it is an MRT composition around
// BloomNode (example: webgpu_postprocessing_bloom_selective). Pattern:
// SCENE-PASS + MRT. Set each mesh's `material.mrtNode = mrt({ bloomIntensity })`
// and give the scene pass an `output` + `bloomIntensity` MRT layout.

import { bloom } from 'three/addons/tsl/display/BloomNode.js'
import type { PassNode } from 'three/webgpu'




/** Options for {@link createBloomSelective}: bloom strength, radius, and luminance threshold. */
export interface BloomSelectiveOptions {
  strength?:  number
  radius?:    number
  threshold?: number
}

// `scenePass` must have been set up with an MRT exposing a `bloomIntensity`
// channel (see the readme wiring note). Returns { output, bloom, result } so the
// caller can inspect the masked bloom or use `result` directly as the output.


/**
 * Bloom only objects tagged via an MRT bloomIntensity channel. Set each mesh's `material.mrtNode = mrt({ bloomIntensity })`.
 *
 * @param scenePass - A {@link PassNode} configured with an MRT exposing `output` and `bloomIntensity` channels.
 * @param options.strength - Bloom intensity. Default `1`.
 * @param options.radius - Bloom spread radius. Default `0`.
 * @param options.threshold - Luminance threshold for blooming. Default `0`.
 * @returns An object `{ output, bloom, result }`. Use `result` (= output + bloom) as the output node.
 * @remarks Requires the WebGPU renderer (three/webgpu). Medium cost — one extra (low-precision) MRT attachment plus the bloom blur passes.
 */
export function createBloomSelective (scenePass: PassNode, options: BloomSelectiveOptions = {}) {
  const { strength = 1, radius = 0, threshold = 0 } = options
  const output                                      = scenePass.getTextureNode('output')
  const bloomIntensity                              = scenePass.getTextureNode('bloomIntensity')
  const bloomPass                                   = bloom(output.mul(bloomIntensity), strength, radius, threshold)
  return { output, bloom: bloomPass, result: output.add(bloomPass) }
}

// perf: medium. One extra (low-precision) MRT attachment plus the bloom blur.