import type { GLBAssetBuffer } from "./glb-export";
import type { SceneSnapshotIR } from "./scene-ir";

const GLB_MAGIC = 0x46546c67;
const JSON_CHUNK = 0x4e4f534a;
const BIN_CHUNK = 0x004e4942;

interface GLBAccessor {
  bufferView?: number;
  byteOffset?: number;
  componentType: number;
  count: number;
  type: string;
}

interface GLBBufferView {
  buffer: number;
  byteOffset?: number;
  byteLength: number;
}

interface GLBPrimitive {
  attributes?: Record<string, number>;
  indices?: number;
  targets?: Array<Record<string, number>>;
}

interface GLBDocument {
  asset?: { version?: string };
  buffers?: Array<{ byteLength?: number }>;
  bufferViews?: GLBBufferView[];
  accessors?: GLBAccessor[];
  meshes?: Array<{ name?: string; primitives?: GLBPrimitive[]; extras?: Record<string, unknown> }>;
  images?: Array<{ name?: string; mimeType?: string; bufferView?: number; extras?: Record<string, unknown> }>;
  skins?: Array<{ joints?: number[]; inverseBindMatrices?: number; extras?: Record<string, unknown> }>;
  animations?: Array<{ name?: string; channels?: Array<{ target?: { node?: number; path?: string } }>; extras?: Record<string, unknown> }>;
}

export interface ImportedGLBImage {
  name?: string;
  blenderId?: string;
  mimeType?: string;
  byteLength: number;
  signature: number[];
}

export interface ImportedGLBSemantics {
  version: 2;
  meshCount: number;
  primitiveCount: number;
  meshes: Array<{ name?: string; blenderId?: string; primitiveCount: number; attributes: string[]; morphTargetCount: number }>;
  images: ImportedGLBImage[];
  skinCount: number;
  skins: Array<{ jointCount: number; inverseBindType?: string; inverseBindCount?: number }>;
  animationCount: number;
  animationChannelCount: number;
  animationPaths: string[];
}

export interface GLBSemanticComparison {
  compatible: boolean;
  mismatches: string[];
}

function recordId(extras: Record<string, unknown> | undefined): string | undefined {
  return typeof extras?.blenderId === "string" ? extras.blenderId : undefined;
}

function requireIndex(value: unknown, size: number, label: string): number {
  if (!Number.isSafeInteger(value) || (value as number) < 0 || (value as number) >= size) throw new Error(`${label} index is out of range`);
  return value as number;
}

function jsonChunk(bytes: Uint8Array, length: number): GLBDocument {
  const view = new DataView(bytes.buffer, bytes.byteOffset, bytes.byteLength);
  if (bytes.byteLength < 20 || view.getUint32(0, true) !== GLB_MAGIC || view.getUint32(4, true) !== 2) throw new Error("GLB header is invalid");
  if (view.getUint32(8, true) !== bytes.byteLength) throw new Error("GLB length does not match header");
  const jsonLength = view.getUint32(12, true);
  if (view.getUint32(16, true) !== JSON_CHUNK || jsonLength % 4 !== 0 || 20 + jsonLength > bytes.byteLength) throw new Error("GLB JSON chunk is invalid");
  let document: unknown;
  try {
    document = JSON.parse(new TextDecoder().decode(bytes.subarray(20, 20 + jsonLength)).trim());
  }
  catch (error) {
    throw new Error(`GLB JSON is invalid: ${error instanceof Error ? error.message : "parse failed"}`);
  }
  if (typeof document !== "object" || document === null || Array.isArray(document)) throw new Error("GLB JSON document is invalid");
  if ((document as GLBDocument).asset?.version !== "2.0") throw new Error("GLB asset version is not 2.0");
  return document as GLBDocument;
}

function bufferViewBytes(bytes: Uint8Array, jsonLength: number, view: GLBBufferView, label: string): Uint8Array {
  if (view.buffer !== 0 || !Number.isSafeInteger(view.byteLength) || view.byteLength < 0) throw new Error(`${label} bufferView is invalid`);
  const binaryStart = 20 + jsonLength + 8;
  const offset = view.byteOffset ?? 0;
  if (!Number.isSafeInteger(offset) || offset < 0 || binaryStart + offset + view.byteLength > bytes.byteLength) throw new Error(`${label} bufferView exceeds BIN chunk`);
  return bytes.subarray(binaryStart + offset, binaryStart + offset + view.byteLength);
}

export function importGLBSemantics(glb: ArrayBuffer): ImportedGLBSemantics {
  const bytes = new Uint8Array(glb);
  const view = new DataView(glb);
  const jsonLength = view.getUint32(12, true);
  const document = jsonChunk(bytes, glb.byteLength);
  const bufferViews = document.bufferViews ?? [];
  const accessors = document.accessors ?? [];
  for (const [index, bufferView] of bufferViews.entries()) bufferViewBytes(bytes, jsonLength, bufferView, `bufferViews[${index}]`);
  const accessorType = (index: number): string => accessors[requireIndex(index, accessors.length, "accessor")]?.type ?? "";
  for (const [index, accessor] of accessors.entries()) {
    if (!Number.isSafeInteger(accessor.count) || accessor.count < 0 || (accessor.byteOffset ?? 0) < 0) throw new Error(`accessors[${index}] is invalid`);
    if (accessor.bufferView !== undefined) {
      const bytesForAccessor = bufferViewBytes(bytes, jsonLength, bufferViews[requireIndex(accessor.bufferView, bufferViews.length, `accessors[${index}]`)], `accessors[${index}]`);
      const componentBytes = accessor.componentType === 5126 || accessor.componentType === 5125 ? 4 : accessor.componentType === 5123 ? 2 : 1;
      const width = accessor.type === "SCALAR" ? 1 : accessor.type === "VEC2" ? 2 : accessor.type === "VEC3" ? 3 : accessor.type === "VEC4" ? 4 : accessor.type === "MAT4" ? 16 : 0;
      if (width === 0 || (accessor.byteOffset ?? 0) + accessor.count * width * componentBytes > bytesForAccessor.byteLength) throw new Error(`accessors[${index}] exceeds bufferView`);
    }
  }
  const images = (document.images ?? []).map((image, index) => {
    if (image.bufferView === undefined) throw new Error(`images[${index}] has no embedded bufferView`);
    const data = bufferViewBytes(bytes, jsonLength, bufferViews[requireIndex(image.bufferView, bufferViews.length, `images[${index}]`)], `images[${index}]`);
    return { name: image.name, blenderId: recordId(image.extras), mimeType: image.mimeType, byteLength: data.byteLength, signature: Array.from(data.subarray(0, 8)) };
  });
  const meshes = (document.meshes ?? []).map((mesh, index) => {
    const primitives = mesh.primitives ?? [];
    const attributes = new Set<string>();
    let morphTargetCount = 0;
    for (const [primitiveIndex, primitive] of primitives.entries()) {
      for (const semantic of Object.keys(primitive.attributes ?? {})) {
        const accessor = requireIndex(primitive.attributes?.[semantic], accessors.length, `meshes[${index}].primitives[${primitiveIndex}].${semantic}`);
        accessorType(accessor);
        attributes.add(semantic);
      }
      if (primitive.indices !== undefined) accessorType(requireIndex(primitive.indices, accessors.length, "primitive indices"));
      morphTargetCount = Math.max(morphTargetCount, primitive.targets?.length ?? 0);
    }
    return { name: mesh.name, blenderId: recordId(mesh.extras), primitiveCount: primitives.length, attributes: [...attributes].sort(), morphTargetCount };
  });
  const skins = (document.skins ?? []).map((skin, index) => {
    const jointCount = skin.joints?.length ?? 0;
    if (jointCount === 0) throw new Error(`skins[${index}] has no joints`);
    let inverseBindType: string | undefined;
    let inverseBindCount: number | undefined;
    if (skin.inverseBindMatrices !== undefined) {
      const accessor = accessors[requireIndex(skin.inverseBindMatrices, accessors.length, `skins[${index}].inverseBindMatrices`)]!;
      inverseBindType = accessor.type;
      inverseBindCount = accessor.count;
      if (inverseBindType !== "MAT4" || inverseBindCount !== jointCount) throw new Error(`skins[${index}] inverse bind matrices do not match joints`);
    }
    return { jointCount, inverseBindType, inverseBindCount };
  });
  const animations = document.animations ?? [];
  const animationPaths = animations.flatMap((animation) => (animation.channels ?? []).map((channel) => channel.target?.path ?? "")).filter(Boolean).sort();
  return { version: 2, meshCount: meshes.length, primitiveCount: meshes.reduce((sum, mesh) => sum + mesh.primitiveCount, 0), meshes, images, skinCount: skins.length, skins, animationCount: animations.length, animationChannelCount: animationPaths.length, animationPaths };
}

export function compareGLBToSceneIR(snapshot: SceneSnapshotIR, imported: ImportedGLBSemantics, assetBuffers: readonly GLBAssetBuffer[] = []): GLBSemanticComparison {
  const mismatches: string[] = [];
  const geometryMeshIds = new Set(snapshot.meshes.filter((mesh) => mesh.geometryStatus !== "summary-only").map((mesh) => mesh.id));
  const importedMeshIds = new Set(imported.meshes.map((mesh) => mesh.blenderId).filter((id): id is string => Boolean(id)));
  for (const id of geometryMeshIds) if (!importedMeshIds.has(id)) mismatches.push(`mesh missing: ${id}`);
  const expectedImages = assetBuffers.filter((asset) => snapshot.images.some((image) => image.assetId === asset.assetId && asset.data.byteLength > 0));
  if (imported.images.length !== expectedImages.length) mismatches.push(`image count ${imported.images.length} != ${expectedImages.length}`);
  for (const asset of expectedImages) {
    const image = imported.images.find((candidate) => candidate.blenderId === snapshot.images.find((source) => source.assetId === asset.assetId)?.id);
    if (!image || image.byteLength !== asset.data.byteLength || image.mimeType !== asset.mimeType) mismatches.push(`image semantic mismatch: ${asset.assetId}`);
  }
  const expectedSkins = snapshot.meshes.filter((mesh) => mesh.skinWeights?.armatureId && snapshot.armatures?.some((armature) => armature.id === mesh.skinWeights?.armatureId));
  if (imported.skinCount !== expectedSkins.length) mismatches.push(`skin count ${imported.skinCount} != ${expectedSkins.length}`);
  for (const mesh of expectedSkins) {
    const expectedJoints = mesh.skinWeights?.jointIds?.length ?? 0;
    if (!imported.skins.some((skin) => skin.jointCount === expectedJoints && skin.inverseBindType === "MAT4")) mismatches.push(`skin semantic mismatch: ${mesh.id}`);
  }
  const expectedMorphs = snapshot.meshes.filter((mesh) => (mesh.shapeKeys?.length ?? 0) > 0).reduce((sum, mesh) => sum + (mesh.shapeKeys?.length ?? 0), 0);
  const importedMorphs = imported.meshes.reduce((sum, mesh) => sum + mesh.morphTargetCount, 0);
  if (importedMorphs !== expectedMorphs) mismatches.push(`morph target count ${importedMorphs} != ${expectedMorphs}`);
  const expectedAnimationPaths: string[] = [];
  let expectedAnimations = 0;
  for (const animation of snapshot.animations) {
    const groups = new Set<string>();
    for (const channel of animation.channels) {
      const boneMatch = channel.path.match(/^pose\.bones\["(.+)"\]\.(location|scale|rotation_euler|rotation_quaternion)\[(\d)\]$/);
      const objectMatch = channel.path.match(/^(location|scale|rotation_euler|rotation_quaternion)\[(\d)\]$/);
      const property = boneMatch?.[2] ?? objectMatch?.[1];
      if (!property || channel.keyframes.length === 0) continue;
      if (boneMatch) {
        const armature = (snapshot.armatures ?? []).find((candidate) => candidate.objectId === animation.targetId);
        if (!armature?.bones.some((bone) => bone.name === boneMatch[1])) continue;
      }
      else if (!snapshot.nodes.some((node) => node.id === animation.targetId)) continue;
      const path = property === "location" ? "translation" : property === "scale" ? "scale" : "rotation";
      groups.add(`${boneMatch?.[1] ?? animation.targetId}:${path}`);
    }
    if (groups.size > 0) expectedAnimations++;
    for (const group of groups) expectedAnimationPaths.push(group.slice(group.lastIndexOf(":") + 1));
  }
  expectedAnimationPaths.sort();
  if (imported.animationCount !== expectedAnimations) mismatches.push(`animation count ${imported.animationCount} != ${expectedAnimations}`);
  if (imported.animationPaths.join(",") !== expectedAnimationPaths.join(",")) mismatches.push(`animation paths ${imported.animationPaths.join(",")} != ${expectedAnimationPaths.join(",")}`);
  return { compatible: mismatches.length === 0, mismatches };
}