/**
 * 封装的方法以及用法
 * 打开数据库
 */
export function openDB(dbName, storeName, version = 1) {
    return new Promise((resolve, reject) => {
      let indexedDB = window.indexedDB
      let db
      const request = indexedDB.open(dbName, version)
      request.onsuccess = function(event) {
        db = event.target.result // 数据库对象
        resolve(db)
      }
   
      request.onerror = function(event) {
        reject(event)
      }
   
      request.onupgradeneeded = function(event) {
        // 数据库创建或升级的时候会触发
        console.log('onupgradeneeded')
        db = event.target.result // 数据库对象
        let objectStore
        if (!db.objectStoreNames.contains(storeName)) {
          objectStore = db.createObjectStore(storeName, { keyPath: 'id' }) // 创建表
          // objectStore.createIndex('name', 'name', { unique: true }) // 创建索引 可以让你搜索任意字段
        }
      }
    })
  }
   
  /**
   * 新增数据
   */
  export function addData(db, storeName, data) {
    return new Promise((resolve, reject) => {
      let request = db.transaction([storeName], 'readwrite') // 事务对象 指定表格名称和操作模式（"只读"或"读写"）
        .objectStore(storeName) // 仓库对象
        .add(data)
   
      request.onsuccess = function(event) {
        resolve(event)
      }
   
      request.onerror = function(event) {
        throw new Error(event.target.error)
        reject(event)
      }
    })
  }
   
  /**
   * 通过主键读取数据
   */
  export function getDataByKey(db, storeName, key) {
    return new Promise((resolve, reject) => {
      let transaction = db.transaction([storeName]) // 事务
      let objectStore = transaction.objectStore(storeName) // 仓库对象
      let request = objectStore.get(key)
   
      request.onerror = function(event) {
        reject(event)
      }
   
      request.onsuccess = function(event) {
        resolve(request.result)
      }
    })
  }
   
  /**
   * 通过游标读取数据
   */
  export function cursorGetData(db, storeName) {
    let list = []
    let store = db.transaction(storeName, 'readwrite') // 事务
      .objectStore(storeName) // 仓库对象
    let request = store.openCursor() // 指针对象
    return new Promise((resolve, reject) => {
      request.onsuccess = function(e) {
        let cursor = e.target.result
        if (cursor) {
          // 必须要检查
          list.push(cursor.value)
          cursor.continue() // 遍历了存储对象中的所有内容
        } else {
          resolve(list)
        }
      }
      request.onerror = function(e) {
        reject(e)
      }
    })
  }
   
  /**
   * 通过索引读取数据
   */
  export function getDataByIndex(db, storeName, indexName, indexValue) {
    let store = db.transaction(storeName, 'readwrite').objectStore(storeName)
    let request = store.index(indexName).get(indexValue)
    return new Promise((resolve, reject) => {
      request.onerror = function(e) {
        reject(e)
      }
      request.onsuccess = function(e) {
        resolve(e.target.result)
      }
    })
  }
   
  /**
   * 通过索引和游标查询记录
   */
  export function cursorGetDataByIndex(db, storeName, indexName, indexValue) {
    let list = []
    let store = db.transaction(storeName, 'readwrite').objectStore(storeName) // 仓库对象
    let request = store.index(indexName) // 索引对象
      .openCursor(IDBKeyRange.only(indexValue)) // 指针对象
    return new Promise((resolve, reject) => {
      request.onsuccess = function(e) {
        let cursor = e.target.result
        if (cursor) {
          list.push(cursor.value)
          cursor.continue() // 遍历了存储对象中的所有内容
        } else {
          resolve(list)
        }
      }
      request.onerror = function(ev) {
        reject(ev)
      }
    })
  }
   
  /**
   * 更新数据
   */
  export function updateDB(db, storeName, data) {
    let request = db.transaction([storeName], 'readwrite') // 事务对象
      .objectStore(storeName) // 仓库对象
      .put(data)
   
    return new Promise((resolve, reject) => {
      request.onsuccess = function(ev) {
        resolve(ev)
      }
   
      request.onerror = function(ev) {
        resolve(ev)
      }
    })
  }
   
  /**
   * 删除数据
   */
  export function deleteDB(db, storeName, id) {
    let request = db.transaction([storeName], 'readwrite').objectStore(storeName).delete(id)
   
    return new Promise((resolve, reject) => {
      request.onsuccess = function(ev) {
        resolve(ev)
      }
   
      request.onerror = function(ev) {
        resolve(ev)
      }
    })
  }
   
  /**
   * 删除数据库
   */
  export function deleteDBAll(dbName) {
    console.log(dbName)
    let deleteRequest = window.indexedDB.deleteDatabase(dbName)
    return new Promise((resolve, reject) => {
      deleteRequest.onerror = function(event) {
        console.log('删除失败')
      }
      deleteRequest.onsuccess = function(event) {
        console.log('删除成功')
      }
    })
  }
   
  /**
   * 关闭数据库
   */
  export function closeDB(db) {
    db.close()
    console.log('数据库已关闭')
  }
   
  export default {
    openDB,
    addData,
    getDataByKey,
    cursorGetData,
    getDataByIndex,
    cursorGetDataByIndex,
    updateDB,
    deleteDB,
    deleteDBAll,
    closeDB
  }