import * as THREE from "three";
import { EffectComposer } from "three/examples/jsm/postprocessing/EffectComposer.js";
import { RenderPass } from "three/examples/jsm/postprocessing/RenderPass.js";
import { UnrealBloomPass } from "three/examples/jsm/postprocessing/UnrealBloomPass.js";
import { LensFinishPass, type LensState } from "@/scene/cinematic-grade";
import type {
  GpuRenderTargetAllocation,
  GpuRenderTargetReporter,
  SceneResourceBag,
} from "@/scene/resources";

export interface PostProcessor extends GpuRenderTargetReporter {
  resize(width: number, height: number, pixelRatio: number): void;
  /** dawn (END OF SHIFT, 0..1) lowers the bloom threshold up to 10%. */
  setDynamics(acceleration: number, dawn?: number): void;
  setLens(state: LensState): void;
  render(scene: unknown, camera: unknown): void;
  /**
   * The off-screen target the scene pass draws into. Bind it while compiling
   * scene programs: three keys tone mapping and output colour space on it.
   */
  sceneTarget(): unknown;
  dispose(): void;
}

interface RenderTargetLike {
  width: number;
  height: number;
  samples?: number;
  depthBuffer?: boolean;
}

interface ComposerLike {
  renderTarget1?: RenderTargetLike;
  renderTarget2?: RenderTargetLike;
  /** RenderPass (needsSwap false) draws the scene into this target. */
  readBuffer?: unknown;
  addPass(pass: unknown): void;
  setPixelRatio(pixelRatio: number): void;
  setSize(width: number, height: number): void;
  render(): void;
  dispose(): void;
}

interface RenderPassLike {
  scene: unknown;
  camera: unknown;
  dispose(): void;
}

interface BloomPassLike {
  strength: number;
  radius: number;
  threshold: number;
  materialHighPassFilter?: { dispose(): void };
  renderTargetBright?: RenderTargetLike;
  renderTargetsHorizontal?: readonly RenderTargetLike[];
  renderTargetsVertical?: readonly (RenderTargetLike & { texture?: unknown })[];
  dispose(): void;
}

interface OutputPassLike {
  setStreakSource?(texture: unknown, strength?: number): void;
  setLens?(state: LensState): void;
  dispose(): void;
}

export interface PostProcessingFactories {
  createComposer(renderer: unknown): ComposerLike;
  createRenderPass(scene: unknown, camera: unknown): RenderPassLike;
  createBloomPass(): BloomPassLike;
  createOutputPass(): OutputPassLike;
}

// Lights read as light: a lower threshold lets lamps, trails and the sun's limb
// bloom, while the asphalt and the panels' surroundings stay below it.
const BLOOM_REST = { strength: 0.58, radius: 0.58, threshold: 0.85 } as const;

const productionFactories: PostProcessingFactories = {
  createComposer: (renderer) => new EffectComposer(renderer),
  createRenderPass: (scene, camera) => new RenderPass(scene, camera),
  createBloomPass: () => {
    const bloom = new UnrealBloomPass(
      new THREE.Vector2(1, 1),
      BLOOM_REST.strength,
      BLOOM_REST.radius,
      BLOOM_REST.threshold,
    );
    // These fullscreen passes overwrite every color pixel. No pass samples
    // their depth, and scene depth lives in the composer's separate targets.
    for (const target of [
      bloom.renderTargetBright,
      ...bloom.renderTargetsHorizontal,
      ...bloom.renderTargetsVertical,
    ]) {
      target.depthBuffer = false;
    }
    return bloom;
  },
  // The lens pass replaces OutputPass one for one: last pass, straight to the
  // canvas, no swap. Neither RenderPass nor bloom swaps buffers, so swapping
  // here would only alternate two identical full-resolution GPU targets.
  createOutputPass: () => new LensFinishPass(),
};

export function createPostProcessor(
  resources: SceneResourceBag,
  renderer: unknown,
  factories: PostProcessingFactories = productionFactories,
): PostProcessor {
  const composer = factories.createComposer(renderer);
  const renderPass = factories.createRenderPass(
    new THREE.Scene(),
    new THREE.Camera(),
  );
  const bloomPass = factories.createBloomPass();
  const outputPass = factories.createOutputPass();
  composer.addPass(renderPass);
  composer.addPass(bloomPass);
  composer.addPass(outputPass);
  // A quarter-resolution bloom mip is already blurred: sampling it sideways
  // gives anamorphic streaks without a target of their own.
  outputPass.setStreakSource?.(bloomPass.renderTargetsVertical?.[1]?.texture ?? null, 0.22);
  let disposed = false;

  const processor: PostProcessor = {
    gpuRenderTargets() {
      return collectRenderTargetAllocations(composer, bloomPass);
    },
    resize(width, height, pixelRatio) {
      if (disposed) return;
      composer.setPixelRatio(clamp(pixelRatio, 0.5, 2));
      composer.setSize(
        Math.max(1, Math.floor(finiteOr(width, 1))),
        Math.max(1, Math.floor(finiteOr(height, 1))),
      );
    },
    setDynamics(acceleration, dawn = 0) {
      if (disposed) return;
      const energy = clamp(acceleration, 0, 1);
      const daybreak = clamp(dawn, 0, 1);
      bloomPass.strength = BLOOM_REST.strength + energy * 0.16;
      bloomPass.radius = BLOOM_REST.radius + energy * 0.06;
      bloomPass.threshold = (BLOOM_REST.threshold - energy * 0.05) * (1 - 0.1 * daybreak);
    },
    setLens(state) {
      if (disposed) return;
      outputPass.setLens?.(state);
    },
    render(scene, camera) {
      if (disposed) return;
      renderPass.scene = scene;
      renderPass.camera = camera;
      composer.render();
    },
    sceneTarget() {
      return composer.readBuffer ?? composer.renderTarget2 ?? null;
    },
    dispose() {
      if (disposed) return;
      disposed = true;
      renderPass.dispose();
      // Three r185 omits this material from UnrealBloomPass.dispose().
      bloomPass.materialHighPassFilter?.dispose();
      bloomPass.dispose();
      outputPass.dispose();
      composer.dispose();
    },
  };
  return resources.own("pass", processor);
}

function collectRenderTargetAllocations(
  composer: ComposerLike,
  bloomPass: BloomPassLike,
): readonly GpuRenderTargetAllocation[] {
  const candidates: ReadonlyArray<
    readonly [string, RenderTargetLike | undefined]
  > = [
    ["composer-target-1", composer.renderTarget1],
    ["composer-target-2", composer.renderTarget2],
    ["bloom-bright", bloomPass.renderTargetBright],
    ...(bloomPass.renderTargetsHorizontal ?? []).map(
      (target, index) => [`bloom-horizontal-${index}`, target] as const,
    ),
    ...(bloomPass.renderTargetsVertical ?? []).map(
      (target, index) => [`bloom-vertical-${index}`, target] as const,
    ),
  ];
  const seen = new Set<RenderTargetLike>();
  return candidates.flatMap(([id, target]) => {
    if (target === undefined || seen.has(target)) return [];
    seen.add(target);
    return [
      {
        id,
        width: Math.max(1, Math.floor(finiteOr(target.width, 1))),
        height: Math.max(1, Math.floor(finiteOr(target.height, 1))),
        bytesPerPixel: 4,
        attachments: target.depthBuffer === false ? 1 : 2,
        samples: Math.max(1, Math.floor(finiteOr(target.samples ?? 1, 1))),
      },
    ];
  });
}

function finiteOr(value: number, fallback: number): number {
  return Number.isFinite(value) ? value : fallback;
}

function clamp(value: number, minimum: number, maximum: number): number {
  return THREE.MathUtils.clamp(finiteOr(value, minimum), minimum, maximum);
}