import { isString, AlertService, uniqueArray } from '@standardnotes/snjs'

const STORE_NAME = 'items'
const READ_WRITE = 'readwrite'

const OUT_OF_SPACE =
  'Unable to save changes locally because your device is out of space. ' +
  'Please free up some disk space and try again, otherwise, your data may end ' +
  'up in an inconsistent state.'

const DB_DELETION_BLOCKED =
  'Your browser is blocking Standard Notes from deleting the local database. ' +
  'Make sure there are no other open windows of this app and try again. ' +
  'If the issue persists, please manually delete app data to sign out.'

const QUOTE_EXCEEDED_ERROR = 'QuotaExceededError'

export class Database {
  private locked = true
  private db?: IDBDatabase

  constructor(public databaseName: string, private alertService?: AlertService) {}

  public deinit(): void {
    ;(this.alertService as unknown) = undefined
    this.db = undefined
  }

  /**
   * Relinquishes the lock and allows db operations to proceed
   */
  public unlock(): void {
    this.locked = false
  }

  static async getAllDatabaseNames(): Promise<string[] | undefined> {
    if (!window.indexedDB.databases) {
      return undefined
    }

    const rawDatabases = await window.indexedDB.databases()
    return rawDatabases.map((db) => db.name).filter((name) => name && name.length > 0) as string[]
  }

  static async deleteAll(databaseNames: string[]): Promise<void> {
    if (window.indexedDB.databases != undefined) {
      const idbNames = await this.getAllDatabaseNames()

      if (idbNames) {
        databaseNames = uniqueArray([...idbNames, ...databaseNames])
      }
    }

    for (const name of databaseNames) {
      const db = new Database(name)

      await db.clearAllPayloads()

      db.deinit()
    }
  }

  /**
   * Opens the database natively, or returns the existing database object if already opened.
   * @param onNewDatabase - Callback to invoke when a database has been created
   * as part of the open process. This can happen on new application sessions, or if the
   * browser deleted the database without the user being aware.
   */
  public async openDatabase(onNewDatabase?: () => void): Promise<IDBDatabase | undefined> {
    if (this.locked) {
      throw Error('Attempting to open locked database')
    }
    if (this.db) {
      return this.db
    }
    const request = window.indexedDB.open(this.databaseName, 1)
    return new Promise((resolve, reject) => {
      request.onerror = (event) => {
        const target = event.target as any
        if (target.errorCode) {
          this.showAlert('Offline database issue: ' + target.errorCode)
        } else {
          this.displayOfflineAlert()
        }
        reject(new Error('Unable to open db'))
      }
      request.onblocked = (_event) => {
        reject(Error('IndexedDB open request blocked'))
      }
      request.onsuccess = (event) => {
        const target = event.target as IDBOpenDBRequest
        const db = target.result
        db.onversionchange = () => {
          db.close()
        }
        db.onerror = (errorEvent) => {
          const target = errorEvent?.target as any
          throw Error('Database error: ' + target.errorCode)
        }
        this.db = db
        resolve(db)
      }
      request.onupgradeneeded = (event) => {
        const target = event.target as IDBOpenDBRequest
        const db = target.result
        db.onversionchange = () => {
          db.close()
        }
        /* Create an objectStore for this database */
        const objectStore = db.createObjectStore(STORE_NAME, {
          keyPath: 'uuid',
        })
        objectStore.createIndex('uuid', 'uuid', { unique: true })
        objectStore.transaction.oncomplete = () => {
          /* Ready to store values in the newly created objectStore. */
          if (db.version === 1 && onNewDatabase) {
            onNewDatabase && onNewDatabase()
          }
        }
      }
    })
  }

  public async getAllPayloads(): Promise<any[]> {
    const db = (await this.openDatabase()) as IDBDatabase
    return new Promise((resolve) => {
      const objectStore = db.transaction(STORE_NAME).objectStore(STORE_NAME)
      const payloads: any = []
      const cursorRequest = objectStore.openCursor()
      cursorRequest.onsuccess = (event) => {
        const target = event.target as any
        const cursor = target.result
        if (cursor) {
          payloads.push(cursor.value)
          cursor.continue()
        } else {
          resolve(payloads)
        }
      }
    })
  }

  public async getAllKeys(): Promise<string[]> {
    const db = (await this.openDatabase()) as IDBDatabase

    return new Promise((resolve) => {
      const objectStore = db.transaction(STORE_NAME).objectStore(STORE_NAME)
      const getAllKeysRequest = objectStore.getAllKeys()
      getAllKeysRequest.onsuccess = function () {
        const result = getAllKeysRequest.result

        const strings = result.map((key) => {
          if (isString(key)) {
            return key
          } else {
            return JSON.stringify(key)
          }
        })

        resolve(strings)
      }
    })
  }

  public async savePayload(payload: any): Promise<void> {
    return this.savePayloads([payload])
  }

  public async savePayloads(payloads: any[]): Promise<void> {
    if (payloads.length === 0) {
      return
    }
    const db = (await this.openDatabase()) as IDBDatabase
    const transaction = db.transaction(STORE_NAME, READ_WRITE)
    return new Promise((resolve, reject) => {
      // eslint-disable-next-line @typescript-eslint/no-empty-function
      transaction.oncomplete = () => {}
      transaction.onerror = (event) => {
        const target = event.target as any
        this.showGenericError(target.error)
      }
      transaction.onabort = (event) => {
        const target = event.target as any
        const error = target.error
        if (error.name === QUOTE_EXCEEDED_ERROR) {
          this.showAlert(OUT_OF_SPACE)
        } else {
          this.showGenericError(error)
        }
        reject(error)
      }
      const objectStore = transaction.objectStore(STORE_NAME)
      this.putItems(objectStore, payloads).then(resolve).catch(console.error)
    })
  }

  private async putItems(objectStore: IDBObjectStore, items: any[]): Promise<void> {
    await Promise.all(
      items.map((item) => {
        return new Promise((resolve) => {
          const request = objectStore.put(item)
          request.onerror = resolve
          request.onsuccess = resolve
        })
      }),
    )
  }

  public async deletePayload(uuid: string): Promise<void> {
    const db = (await this.openDatabase()) as IDBDatabase
    return new Promise((resolve, reject) => {
      const request = db.transaction(STORE_NAME, READ_WRITE).objectStore(STORE_NAME).delete(uuid)
      request.onsuccess = () => {
        resolve()
      }
      request.onerror = reject
    })
  }

  public async clearAllPayloads(): Promise<void> {
    const deleteRequest = window.indexedDB.deleteDatabase(this.databaseName)
    return new Promise((resolve, reject) => {
      deleteRequest.onerror = () => {
        reject(Error('Error deleting database.'))
      }
      deleteRequest.onsuccess = () => {
        this.db = undefined
        resolve()
      }
      deleteRequest.onblocked = (_event) => {
        this.showAlert(DB_DELETION_BLOCKED)
        reject(Error('Delete request blocked'))
      }
    })
  }

  private showAlert(message: string) {
    if (this.alertService) {
      this.alertService.alert(message).catch(console.error)
    } else {
      window.alert(message)
    }
  }

  private showGenericError(error: { code: number; name: string }) {
    const message =
      'Unable to save changes locally due to an unknown system issue. ' +
      `Issue Code: ${error.code} Issue Name: ${error.name}.`

    this.showAlert(message)
  }

  private displayOfflineAlert() {
    const message =
      'There was an issue loading your offline database. This could happen for two reasons:' +
      "\n\n1. You're in a private window in your browser. We can't save your data without " +
      'access to the local database. Please use a non-private window.' +
      '\n\n2. You have two windows of the app open at the same time. ' +
      'Please close any other app instances and reload the page.'

    this.showAlert(message)
  }
}