import { Suspense, useCallback, useEffect, useMemo, useRef, useState } from "react";
import { RigidBody, TrimeshCollider } from "@react-three/rapier";
import { useThree } from "@react-three/fiber";
import {
  Mesh,
  type InstancedMesh,
  type Material,
  type Object3D,
} from "three";
import type { ResolvedDungeonAssets } from "../game/dungeonAssets";
import type { DungeonDefinition } from "../game/dungeonTypes";
import { useGameStore } from "../game/store";
import {
  collisionLineOfSightTrimeshes,
  collisionTrimeshes,
  prepareCollision,
} from "./productionDungeonCollision";
import {
  DUNGEON_PHYSICAL_COLLISION_GROUPS,
  DUNGEON_SIGHT_BLOCKER_COLLISION_GROUPS,
} from "./dungeonLineOfSight";
import { disposeObject3DResources } from "./threeResourceDisposal";
import { cacheStaticMatrices, instanceRepeatedStaticMeshes } from "./staticSceneInstancing";
import { createStaticVisibilityCells, registerStaticVisibility } from "./staticSceneVisibility";
import { useGameGLTF } from "./useGameGLTF";
import { prepareDungeonMaterial } from "./productionDungeonMaterials";
import {
  DUNGEON_COLLISION_LOAD_BATCH_SIZE,
  DUNGEON_VISUAL_LOAD_BATCH_SIZE,
  advanceDungeonAssetCount,
} from "./dungeonLoadSequencing";

function prepareVisual(root: Object3D, definition: DungeonDefinition) {
  const clone = root.clone(true);
  const clonedMaterials = new Map<string, Material>();
  clone.traverse((node) => {
    const mesh = node as Mesh;
    if (!mesh.isMesh) return;
    const sources = Array.isArray(mesh.material) ? mesh.material : [mesh.material];
    const prepared = sources.map((source) => {
      const cached = clonedMaterials.get(source.uuid);
      if (cached) return cached;
      const next = prepareDungeonMaterial(source, definition.presentation.materials, definition.environmentMode);
      clonedMaterials.set(source.uuid, next);
      return next;
    });
    mesh.material = Array.isArray(mesh.material) ? prepared : prepared[0];
    mesh.castShadow = false;
    mesh.receiveShadow = true;
    const instanced = mesh as InstancedMesh;
    if (instanced.isInstancedMesh) {
      instanced.computeBoundingBox();
      instanced.computeBoundingSphere();
    }
  });
  instanceRepeatedStaticMeshes(clone);
  const cells = createStaticVisibilityCells(clone);
  cacheStaticMatrices(clone);
  return { visual: clone, cells };
}

function VisualChunk({ url, definition }: { readonly url: string; readonly definition: DungeonDefinition }) {
  const gltf = useGameGLTF(url);
  const scene = useThree((state) => state.scene);
  const { visual, cells } = useMemo(
    () => prepareVisual(gltf.scene, definition),
    [definition, gltf.scene],
  );
  useEffect(() => registerStaticVisibility(scene, cells), [scene, cells]);
  useEffect(() => () => { disposeObject3DResources(visual); }, [visual]);
  const { position, rotation, scale } = definition.transform;
  return <primitive object={visual} position={position} rotation={rotation} scale={scale} />;
}

function AssetProbe({ url }: { readonly url: string }) {
  useGameGLTF(url);
  return null;
}

function CommitLoadedBatch({ onReady }: { readonly onReady: () => void }) {
  useEffect(() => {
    const frame = window.requestAnimationFrame(onReady);
    return () => window.cancelAnimationFrame(frame);
  }, [onReady]);
  return null;
}

/**
 * Suspends only the small batch currently being fetched. Previously prepared
 * visuals and colliders stay mounted while the next batch enters the GLTF
 * cache, avoiding one cold-start burst across the entire dungeon package.
 */
function AssetBatchLoader({
  urls,
  onReady,
}: {
  readonly urls: readonly string[];
  readonly onReady: () => void;
}) {
  if (!urls.length) return null;
  return (
    <Suspense fallback={null}>
      {urls.map((url) => <AssetProbe key={url} url={url} />)}
      <CommitLoadedBatch onReady={onReady} />
    </Suspense>
  );
}

function CollisionChunk({
  url,
  definition,
  registerPrepared,
}: {
  readonly url: string;
  readonly definition: DungeonDefinition;
  readonly registerPrepared: (url: string, ready: boolean) => void;
}) {
  const gltf = useGameGLTF(url);
  const collision = useMemo(
    () => prepareCollision(gltf.scene, definition.traversalRamps),
    [definition.traversalRamps, gltf.scene],
  );
  const trimeshes = useMemo(() => collisionTrimeshes(collision), [collision]);
  const sightBlockers = useMemo(() => collisionLineOfSightTrimeshes(collision), [collision]);
  useEffect(() => () => {
    disposeObject3DResources(collision, {
      materials: false,
      textures: false,
      skeletons: false,
    });
  }, [collision]);
  useEffect(() => {
    registerPrepared(url, trimeshes.length > 0);
    return () => registerPrepared(url, false);
  }, [registerPrepared, trimeshes.length, url]);
  const { position, rotation, scale } = definition.transform;
  return (
    <RigidBody
      type="fixed"
      colliders={false}
      name={`${definition.id}-collision`}
      position={position}
      rotation={rotation}
      scale={scale}
    >
      {trimeshes.map((trimesh) => (
        <TrimeshCollider
          key={trimesh.id}
          args={[trimesh.vertices, trimesh.indices]}
          collisionGroups={DUNGEON_PHYSICAL_COLLISION_GROUPS}
        />
      ))}
      {sightBlockers.map((trimesh) => (
        <TrimeshCollider
          key={trimesh.id}
          args={[trimesh.vertices, trimesh.indices]}
          collisionGroups={DUNGEON_SIGHT_BLOCKER_COLLISION_GROUPS}
          sensor
        />
      ))}
      <primitive object={collision} />
    </RigidBody>
  );
}

export function ProductionDungeon({
  definition,
  assets,
  onReady,
}: {
  readonly definition: DungeonDefinition;
  readonly assets: ResolvedDungeonAssets;
  readonly onReady?: () => void;
}) {
  if (!assets.visual.length || !assets.collision.length) {
    throw new Error(`${definition.title} mounted without its required visual and collision GLBs.`);
  }
  const [loadedVisualCount, setLoadedVisualCount] = useState(0);
  const [loadedCollisionCount, setLoadedCollisionCount] = useState(0);
  const preparedCollisions = useRef(new Set<string>());
  const signalledFirstFrame = useRef(false);
  const pendingVisuals = assets.visual.slice(
    loadedVisualCount,
    advanceDungeonAssetCount(
      loadedVisualCount,
      assets.visual.length,
      DUNGEON_VISUAL_LOAD_BATCH_SIZE,
    ),
  );
  const visualsLoaded = loadedVisualCount >= assets.visual.length;
  const pendingCollisions = visualsLoaded
    ? assets.collision.slice(
      loadedCollisionCount,
      advanceDungeonAssetCount(
        loadedCollisionCount,
        assets.collision.length,
        DUNGEON_COLLISION_LOAD_BATCH_SIZE,
      ),
    )
    : [];
  const pendingUrls = pendingVisuals.length ? pendingVisuals : pendingCollisions;
  const commitLoadedBatch = useCallback(() => {
    if (!visualsLoaded) {
      setLoadedVisualCount((current) => advanceDungeonAssetCount(
        current,
        assets.visual.length,
        DUNGEON_VISUAL_LOAD_BATCH_SIZE,
      ));
      return;
    }
    setLoadedCollisionCount((current) => advanceDungeonAssetCount(
      current,
      assets.collision.length,
      DUNGEON_COLLISION_LOAD_BATCH_SIZE,
    ));
  }, [assets.collision.length, assets.visual.length, visualsLoaded]);

  useEffect(() => {
    useGameStore.getState().setAssetStatus(
      "loading",
      `Preparing ${loadedVisualCount}/${assets.visual.length} visual and ${loadedCollisionCount}/${assets.collision.length} collision chunks.`,
    );
  }, [assets.collision.length, assets.visual.length, loadedCollisionCount, loadedVisualCount]);

  const registerPrepared = useCallback((url: string, ready: boolean) => {
    if (!ready) {
      preparedCollisions.current.delete(url);
      return;
    }
    preparedCollisions.current.add(url);
    if (signalledFirstFrame.current) return;
    if (preparedCollisions.current.size < assets.collision.length) return;
    signalledFirstFrame.current = true;
    onReady?.();
  }, [assets.collision.length, onReady]);

  return (
    <group name={`${definition.id}-production`}>
      {assets.visual.slice(0, loadedVisualCount).map((url) => (
        <VisualChunk key={url} url={url} definition={definition} />
      ))}
      {assets.collision.slice(0, loadedCollisionCount).map((url) => (
        <CollisionChunk
          key={url}
          url={url}
          definition={definition}
          registerPrepared={registerPrepared}
        />
      ))}
      <AssetBatchLoader
        key={`${loadedVisualCount}:${loadedCollisionCount}:${pendingUrls.join("|")}`}
        urls={pendingUrls}
        onReady={commitLoadedBatch}
      />
    </group>
  );
}