class FileDownloader {
  constructor({url, fileName, chunkSize = 2 * 1024 * 1024, cb}) {
    this.url = url;
    this.fileName = fileName;
    this.chunkSize = chunkSize;
    this.fileSize = 0;
    this.totalChunks = 0;
    this.currentChunk = 0;
    this.downloadedSize = 0;
    this.chunks = [];
    this.abortController = new AbortController();
    this.paused = false;
    this.cb = cb
  }

  async getFileSize() {
    const response = await fetch(this.url, { signal: this.abortController.signal });
    const contentLength = response.headers.get("content-length");
    this.fileSize = parseInt(contentLength);
    this.totalChunks = Math.ceil(this.fileSize / this.chunkSize);
  }

  async downloadChunk(chunkIndex) {
    const start = chunkIndex * this.chunkSize;
    const end = Math.min(this.fileSize, (chunkIndex + 1) * this.chunkSize - 1);

    const response = await fetch(this.url, {
      headers: { Range: `bytes=${start}-${end}` },
      signal: this.abortController.signal
    });

    const blob = await response.blob();
    this.chunks[chunkIndex] = blob;
    this.downloadedSize += blob.size;

    if (!this.paused && this.currentChunk < this.totalChunks - 1) {
      this.currentChunk++;
      this.downloadChunk(this.currentChunk);
    } else if (this.currentChunk === this.totalChunks - 1) {
      this.mergeChunks();
    }
  }

  async startDownload() {
    if (this.chunks.length === 0) {
      await this.getFileSize();
    }
    this.downloadChunk(this.currentChunk);
  }

  pauseDownload() {
    this.paused = true;
  }

  resumeDownload() {
    this.paused = false;
    this.downloadChunk(this.currentChunk);
  }

  cancelDownload() {
    this.abortController.abort();
    this.reset();
  }

  async mergeChunks() {
    const blob = new Blob(this.chunks, { type: "application/octet-stream" });
    const url = window.URL.createObjectURL(blob);
    const a = document.createElement("a");
    a.href = url;
    a.download = this.fileName;
    document.body.appendChild(a);
    a.click();
    setTimeout(() => {
      this.cb && this.cb({
        downState: 1
      })
      this.reset();
      document.body.removeChild(a);
      window.URL.revokeObjectURL(url);
    }, 0);
  }
  
  reset() {
    this.chunks = [];
    this.fileName = '';
    this.fileSize = 0;
    this.totalChunks = 0;
    this.currentChunk = 0;
    this.downloadedSize = 0;
  }
}


// 使用示例
const url = "https://example.com/largefile.zip";
const fileName = "largefile.zip";

const downloader = new FileDownloader({url, fileName, cb: this.updateData});

// 更新?tīng)顟B(tài)
updateData(res) {
  const {downState} = res
  this.downState = downState
}

// 開(kāi)始下載
downloader.startDownload();

// 暫停下載
// downloader.pauseDownload();

// 繼續(xù)下載
// downloader.resumeDownload();

// 取消下載
// downloader.cancelDownload();

class IndexedDBWrapper {
  constructor(dbName, storeName) {
    this.dbName = dbName;
    this.storeName = storeName;
    this.db = null;
  }

  openDatabase() {
    return new Promise((resolve, reject) => {
      const request = indexedDB.open(this.dbName);
      
      request.onerror = () => {
        console.error("Failed to open database");
        reject();
      };

      request.onsuccess = () => {
        this.db = request.result;
        resolve();
      };

      request.onupgradeneeded = () => {
        this.db = request.result;
        
        if (!this.db.objectStoreNames.contains(this.storeName)) {
          this.db.createObjectStore(this.storeName, { keyPath: "id" });
        }
      };
    });
  }

  addData(data) {
    return new Promise((resolve, reject) => {
      const transaction = this.db.transaction([this.storeName], "readwrite");
      const objectStore = transaction.objectStore(this.storeName);
      const request = objectStore.add(data);

      request.onsuccess = () => {
        resolve();
      };

      request.onerror = () => {
        console.error("Failed to add data");
        reject();
      };
    });
  }

  getDataById(id) {
    return new Promise((resolve, reject) => {
      const transaction = this.db.transaction([this.storeName], "readonly");
      const objectStore = transaction.objectStore(this.storeName);
      const request = objectStore.get(id);

      request.onsuccess = () => {
        resolve(request.result);
      };

      request.onerror = () => {
        console.error(`Failed to get data with id: ${id}`);
        reject();
      };
    });
  }

  getAllData() {
    return new Promise((resolve, reject) => {
      const transaction = this.db.transaction([this.storeName], "readonly");
      const objectStore = transaction.objectStore(this.storeName);
      const request = objectStore.getAll();

      request.onsuccess = () => {
        resolve(request.result);
      };

      request.onerror = () => {
        console.error("Failed to get all data");
        reject();
      };
    });
  }

  updateData(data) {
    return new Promise((resolve, reject) => {
      const transaction = this.db.transaction([this.storeName], "readwrite");
      const objectStore = transaction.objectStore(this.storeName);
      const request = objectStore.put(data);

      request.onsuccess = () => {
        resolve();
      };

      request.onerror = () => {
        console.error("Failed to update data");
        reject();
      };
    });
  }

  deleteDataById(id) {
    return new Promise((resolve, reject) => {
      const transaction = this.db.transaction([this.storeName], "readwrite");
      const objectStore = transaction.objectStore(this.storeName);
      const request = objectStore.delete(id);

      request.onsuccess = () => {
        resolve();
      };

      request.onerror = () => {
        console.error(`Failed to delete data with id: ${id}`);
        reject();
      };
    });
  }

  deleteStore() {
    return new Promise((resolve, reject) => {
      const version = this.db.version + 1;
      this.db.close();

      const request = indexedDB.open(this.dbName, version);

      request.onupgradeneeded = () => {
        this.db = request.result;
        this.db.deleteObjectStore(this.storeName);
        resolve();
      };

      request.onsuccess = () => {
        resolve();
      };

      request.onerror = () => {
        console.error("Failed to delete object store");
        reject();
      };
    });
  }
}

const dbName = "myDatabase";
const storeName = "myStore";

const dbWrapper = new IndexedDBWrapper(dbName, storeName);

dbWrapper.openDatabase().then(() => {
  const data = { id: 1, name: "John Doe", age: 30 };

  dbWrapper.addData(data).then(() => {
    console.log("Data added successfully");

    dbWrapper.getDataById(1).then((result) => {
      console.log("Data retrieved:", result);

      const updatedData = { id: 1, name: "Jane Smith", age: 35 };
      dbWrapper.updateData(updatedData).then(() => {
        console.log("Data updated successfully");

        dbWrapper.getDataById(1).then((updatedResult) => {
          console.log("Updated data retrieved:", updatedResult);

          dbWrapper.deleteDataById(1).then(() => {
            console.log("Data deleted successfully");

            dbWrapper.getAllData().then((allData) => {
              console.log("All data:", allData);

              dbWrapper.deleteStore().then(() => {
                console.log("Object store deleted successfully");
              });
            });
          });
        });
      });
    });
  });
});

const localforage = require('localforage');

// 配置 LocalForage
localforage.config({
  driver: localforage.INDEXEDDB, // 使用 IndexedDB 存儲(chǔ)引擎
  name: 'myApp', // 數(shù)據(jù)庫(kù)名稱
  version: 1.0, // 數(shù)據(jù)庫(kù)版本
  storeName: 'myData' // 存儲(chǔ)表名稱
});

// 使用 async/await 進(jìn)行異步操作
(async () => {
  try {
    // 存儲(chǔ)數(shù)據(jù)
    await localforage.setItem('key', 'value');
    console.log('數(shù)據(jù)保存成功');

    // 獲取數(shù)據(jù)
    const value = await localforage.getItem('key');
    console.log('獲取到的數(shù)據(jù)為:', value);

    // 移除數(shù)據(jù)
    await localforage.removeItem('key');
    console.log('數(shù)據(jù)移除成功');
    
    // 關(guān)閉 IndexedDB 連接
    await localforage.close();
    console.log('IndexedDB 已關(guān)閉');
  } catch (err) {
    console.error('操作失敗', err);
  }
})();

import localforage from 'localforage';

// 使用 clear() 方法刪除所有數(shù)據(jù)
localforage.clear()
  .then(() => {
    console.log('IndexedDB 中的所有數(shù)據(jù)已刪除');
  })
  .catch((error) => {
    console.error('刪除 IndexedDB 數(shù)據(jù)時(shí)出錯(cuò)：', error);
  });