import { readFile, writeFile, readdir } from 'fs/promises';
import path from 'path';
import { fileURLToPath } from 'url';
import { nanoid } from 'nanoid'
import { LibraryItem_v1, LibraryItem, LibraryItems } from '@excalidraw/excalidraw/types'

// 合并素材库
// 由于官方不支持多素材库文件，只能将其合并成一个文件

type LibraryItems_v1 = readonly LibraryItem_v1[];

interface ImportedLibraryData extends Partial<ExportedLibraryData> {
  /** @compatible v1 */
  library?: LibraryItems;
}

interface ExportedLibraryData {
  type: string;
  version: number;
  source: string;
  libraryItems: LibraryItems;
}

/**
 * checks if library item does not exist already in current library
 */
const isUniqueItem = (
  existingLibraryItems: LibraryItems,
  targetLibraryItem: LibraryItem,
) => {
  return !existingLibraryItems.find((libraryItem) => {
    if (libraryItem.elements.length !== targetLibraryItem.elements.length) {
      return false;
    }

    // detect z-index difference by checking the excalidraw elements
    // are in order
    return libraryItem.elements.every((libItemExcalidrawItem, idx) => {
      return (
        libItemExcalidrawItem.id === targetLibraryItem.elements[idx].id &&
        libItemExcalidrawItem.versionNonce ===
          targetLibraryItem.elements[idx].versionNonce
      );
    });
  });
};

const isUniqueItemV1 = (
  existingLibraryItems: LibraryItems,
  targetLibraryItem: LibraryItem_v1,
) => {
  return !existingLibraryItems.find((libraryItem) => {
    if (libraryItem.elements.length !== targetLibraryItem.length) {
      return false;
    }

    // detect z-index difference by checking the excalidraw elements
    // are in order
    return libraryItem.elements.every((libItemExcalidrawItem, idx) => {
      return (
        libItemExcalidrawItem.id === targetLibraryItem[idx].id &&
        libItemExcalidrawItem.versionNonce ===
          targetLibraryItem[idx].versionNonce
      );
    });
  });
};

/** Merges otherItems into localItems. Unique items in otherItems array are
    sorted first. */
const mergeLibraryItems = (
  localItems: LibraryItems,
  otherItems: LibraryItems | LibraryItems_v1,
  version: number
): LibraryItems => {
  const newItems: LibraryItem[] = [];
  otherItems.map(item => {
    if (version === 1 && isUniqueItemV1(localItems, item)) {
      newItems.push({
        status: "published",
        elements: [...item],
        id: nanoid(),
        created: Date.now()
      });
    } else if (isUniqueItem(localItems, item)) {
      newItems.push({...item});
    }
  })

  return [...newItems, ...localItems];
};

const __filename = fileURLToPath(import.meta.url);
const __dirname = path.dirname(__filename);

const inputDir = path.resolve(__dirname, '../lib'); // 输入目录
const outputFile = path.resolve(__dirname, '../library.excalidrawlib'); // 输出文件路径

function isExcalidrawlibFile(fileName: string): boolean {
  return fileName.endsWith('.excalidrawlib');
}

function positionError(obj: any, msg?: string): false {
  console.error({
    error_msg: msg,
    error_obj: obj
  })
  return false
}

function isLibraryItem(obj: any): obj is LibraryItem {
  if (!obj) return positionError(obj, "LibraryItem obj does not exist")
  if (!obj.id || !obj.status || !obj.elements || !obj.created) return positionError(obj, "obj missing fields")
  if (typeof obj.id !== 'string') return positionError(obj, "obj.id type is not string")
  if (obj.status !== "published" && obj.status !== "unpublished") return positionError(obj, "obj.status value is wrong")
  if (!Array.isArray(obj.elements))  return positionError(obj, "obj.elements is not an array")
  if (typeof obj.created !== 'number') return positionError(obj, "obj.created type is not number")
  return true
}

function isLibrary(obj: any): obj is LibraryItem {
  if (!obj) return positionError(obj, "Library obj does not exist")
  if (!Array.isArray(obj))  return positionError(obj, "obj.elements is not an array")
  return true
}

function isLibraryItems(obj: any): obj is LibraryItems {
  if (!obj) return positionError(obj, "LibraryItems obj does not exist")
  if (!Array.isArray(obj)) return positionError(obj, "obj is not an array")
  for (const item of obj) {
    if (!isLibraryItem(item)) return positionError(obj, "LibraryItems is not an array")
  }
  return true
}

function isImportedLibraryData(obj: any): obj is ImportedLibraryData {
  if (!obj) return positionError(obj, "ImportedLibraryData obj does not exist")
  if (obj.type !== "excalidrawlib") return positionError(obj, "obj.type value is not excalidrawlib")
  if (typeof obj.version !== "number") return positionError(obj, "obj.version type is not number")
  if ((!obj.libraryItems || !isLibraryItems(obj.libraryItems))
    && (!obj.library || !isLibrary(obj.library))
  ) return positionError(obj, "The library array does not exist or is wrong")
  return true
}

async function readExcalidrawlibFile(filePath: string): Promise<ImportedLibraryData> {
  const content = await readFile(filePath, 'utf-8');
  const parsed = JSON.parse(content);

  if (!isImportedLibraryData(parsed)) {
    console.error({filePath, parsed})
    throw new Error(`Invalid excalidrawlib file: ${filePath}`);
  }

  return parsed;
}

async function mergeExcalidrawlibFiles(dir: string): Promise<ImportedLibraryData | undefined> {
  const files = (await readdir(dir)).filter(isExcalidrawlibFile);
  let libraryItems: LibraryItems = []
  let mianLibData: ExportedLibraryData | undefined = undefined

  for (const file of files) {
    const fullPath = path.join(dir, file);
    const data = await readExcalidrawlibFile(fullPath);
    if (file === "library.excalidrawlib") {
      mianLibData = {
        type: data.type ?? "excalidrawlib",
        version: data.version ?? 2,
        source: data.source ?? "https://marketplace.visualstudio.com/items?itemName=pomdtr.excalidraw-editor",
        libraryItems: data.libraryItems ?? data.library ?? []
      }
    } else {
      libraryItems = mergeLibraryItems(libraryItems, data.libraryItems ?? data.library ?? [], data.version ?? 1)
    }
  }

  if (mianLibData === undefined) return undefined

  mianLibData.libraryItems = mergeLibraryItems(mianLibData.libraryItems, libraryItems)
  return mianLibData;
}

async function saveMergedExcalidrawlib(data: ImportedLibraryData, filePath: string) {
  const jsonString = JSON.stringify(data, null, 2); // 缩进美化
  await writeFile(filePath, jsonString, 'utf-8');
  console.log(`✅ 合并完成，已保存到 ${filePath}`);
}

// 执行流程
const merged = await mergeExcalidrawlibFiles(inputDir);
if (merged !== undefined) {
  saveMergedExcalidrawlib(merged, outputFile);
}