import { parseUdimTilePatch, type UdimTilePatchIR } from "./paint";

export const TEXTURE_PAINT_ASSET_SCHEMA_VERSION = 1 as const;

export type TexturePaintTileKind = "PACKED" | "UDIM";
export type TexturePaintTileFault = "before-asset-write" | "after-asset-write" | "before-binding-commit";

export interface TexturePaintTileTargetIR {
  schemaVersion: typeof TEXTURE_PAINT_ASSET_SCHEMA_VERSION;
  projectId: string;
  imageId: string;
  textureAssetId: string;
  kind: TexturePaintTileKind;
  tile: number;
  revision: number;
  width: number;
  height: number;
  mimeType: "image/png";
  colorSpace: "SRGB" | "LINEAR";
  sourcePath: string;
  baseAssetSha256: string;
}

export interface TexturePaintTileCommitIR {
  schemaVersion: typeof TEXTURE_PAINT_ASSET_SCHEMA_VERSION;
  target: TexturePaintTileTargetIR;
  patch: UdimTilePatchIR;
  faultAt?: TexturePaintTileFault;
}

export interface TexturePaintTileBindingRequestIR {
  schemaVersion: typeof TEXTURE_PAINT_ASSET_SCHEMA_VERSION;
  projectId: string;
  textureAssetId: string;
  tile: number;
}

export interface TexturePaintTileBindingIR {
  schemaVersion: typeof TEXTURE_PAINT_ASSET_SCHEMA_VERSION;
  projectId: string;
  imageId: string;
  textureAssetId: string;
  kind: TexturePaintTileKind;
  tile: number;
  revision: number;
  generation: number;
  width: number;
  height: number;
  mimeType: "image/png";
  colorSpace: "SRGB" | "LINEAR";
  sourcePath: string;
  assetId: string;
  assetSha256: string;
  pixelSha256: string;
  bytes: number;
  path: string;
  updatedAt: string;
}

export interface TexturePaintTileCommitResultIR {
  projectId: string;
  persisted: true;
  binding: TexturePaintTileBindingIR;
  previousAssetSha256: string;
  orphanedAssetPossible: boolean;
}

export interface TexturePaintTileBindingResultIR {
  projectId: string;
  binding?: TexturePaintTileBindingIR;
}

const SHA256 = /^[a-f0-9]{64}$/;
const TARGET_FIELDS = new Set(["schemaVersion", "projectId", "imageId", "textureAssetId", "kind", "tile", "revision", "width", "height", "mimeType", "colorSpace", "sourcePath", "baseAssetSha256"]);
const COMMIT_FIELDS = new Set(["schemaVersion", "target", "patch", "faultAt"]);
const BINDING_REQUEST_FIELDS = new Set(["schemaVersion", "projectId", "textureAssetId", "tile"]);
const encoder = new TextEncoder();

function fail(message: string): never {
  throw new Error(`PAINT_SCHEMA_INVALID: ${message}`);
}

function record(value: unknown, label: string): Record<string, unknown> {
  if (typeof value !== "object" || value === null || Array.isArray(value)) fail(`${label} must be an object`);
  return value as Record<string, unknown>;
}

function exact(value: Record<string, unknown>, fields: ReadonlySet<string>, label: string): void {
  if (Object.keys(value).some((field) => !fields.has(field))) fail(`${label} contains undeclared fields`);
}

function boundedString(value: unknown, label: string, prefix?: string, maxBytes = 512): string {
  if (typeof value !== "string" || value.length === 0 || (prefix !== undefined && !value.startsWith(prefix)) || encoder.encode(value).byteLength > maxBytes) {
    fail(`${label} is outside the bounded identity range`);
  }
  return value;
}

function integer(value: unknown, label: string): number {
  if (typeof value !== "number" || !Number.isSafeInteger(value) || value < 0) fail(`${label} must be a non-negative safe integer`);
  return value;
}

function tileNumber(value: unknown): number {
  const tile = integer(value, "tile");
  if (tile < 1001 || tile > 1999) fail("tile must be in [1001,1999]");
  return tile;
}

function digest(value: unknown, label: string): string {
  if (typeof value !== "string" || !SHA256.test(value)) fail(`${label} must be a lowercase SHA-256 digest`);
  return value;
}

export function validateTexturePaintTileTarget(value: unknown): TexturePaintTileTargetIR {
  const target = record(value, "Texture paint target");
  exact(target, TARGET_FIELDS, "Texture paint target");
  if (target.schemaVersion !== TEXTURE_PAINT_ASSET_SCHEMA_VERSION) fail("Texture paint asset schema is unsupported");
  if (target.kind !== "PACKED" && target.kind !== "UDIM") fail("Texture paint target kind is invalid");
  if (target.mimeType !== "image/png") fail("Texture paint atomic tile currently requires packed PNG bytes");
  if (target.colorSpace !== "SRGB" && target.colorSpace !== "LINEAR") fail("Texture paint color space is invalid");
  const width = integer(target.width, "width");
  const height = integer(target.height, "height");
  if (width < 1 || height < 1 || width > 16_384 || height > 16_384 || width * height * 4 > 256 * 1024 * 1024) {
    throw new Error("PAINT_BUDGET_EXCEEDED: Texture paint tile dimensions exceed the RGBA8 budget");
  }
  const sourcePath = boundedString(target.sourcePath, "sourcePath", undefined, 1024);
  if (sourcePath.includes("\\") || sourcePath.split("/").includes("..")) fail("Texture paint source path escapes the project");
  return {
    schemaVersion: TEXTURE_PAINT_ASSET_SCHEMA_VERSION,
    projectId: boundedString(target.projectId, "projectId", undefined, 128),
    imageId: boundedString(target.imageId, "imageId", "image:", 256),
    textureAssetId: boundedString(target.textureAssetId, "textureAssetId", undefined, 256),
    kind: target.kind,
    tile: tileNumber(target.tile),
    revision: integer(target.revision, "revision"),
    width,
    height,
    mimeType: "image/png",
    colorSpace: target.colorSpace,
    sourcePath,
    baseAssetSha256: digest(target.baseAssetSha256, "baseAssetSha256"),
  };
}

export function validateTexturePaintTileCommit(value: unknown): TexturePaintTileCommitIR {
  const input = record(value, "Texture paint commit");
  exact(input, COMMIT_FIELDS, "Texture paint commit");
  if (input.schemaVersion !== TEXTURE_PAINT_ASSET_SCHEMA_VERSION) fail("Texture paint asset schema is unsupported");
  const target = validateTexturePaintTileTarget(input.target);
  const patch = parseUdimTilePatch(input.patch);
  if (patch.textureAssetId !== target.textureAssetId || patch.tile !== target.tile || patch.revision !== target.revision ||
      patch.width !== target.width || patch.height !== target.height || patch.colorSpace !== target.colorSpace) {
    fail("Texture paint patch does not match its packed tile target");
  }
  const faultAt = input.faultAt;
  if (faultAt !== undefined && faultAt !== "before-asset-write" && faultAt !== "after-asset-write" && faultAt !== "before-binding-commit") {
    fail("Texture paint fault injection point is invalid");
  }
  return { schemaVersion: TEXTURE_PAINT_ASSET_SCHEMA_VERSION, target, patch, faultAt };
}

export function validateTexturePaintTileBindingRequest(value: unknown): TexturePaintTileBindingRequestIR {
  const input = record(value, "Texture paint binding request");
  exact(input, BINDING_REQUEST_FIELDS, "Texture paint binding request");
  if (input.schemaVersion !== TEXTURE_PAINT_ASSET_SCHEMA_VERSION) fail("Texture paint asset schema is unsupported");
  return {
    schemaVersion: TEXTURE_PAINT_ASSET_SCHEMA_VERSION,
    projectId: boundedString(input.projectId, "projectId", undefined, 128),
    textureAssetId: boundedString(input.textureAssetId, "textureAssetId", undefined, 256),
    tile: tileNumber(input.tile),
  };
}

export function texturePaintTileBindingKey(request: TexturePaintTileBindingRequestIR): string {
  return `texture-paint:v1:${request.projectId}:${encodeURIComponent(request.textureAssetId)}:${request.tile}`;
}