import { ContentType } from '@standardnotes/common'
import { EncryptionProviderInterface } from '@standardnotes/encryption'
import { PayloadEmitSource, FileItem, CreateEncryptedBackupFileContextPayload } from '@standardnotes/models'
import { ClientDisplayableError } from '@standardnotes/responses'
import {
  FilesApiInterface,
  FileBackupMetadataFile,
  FileBackupsDevice,
  FileBackupsMapping,
  FileBackupRecord,
  OnChunkCallback,
  BackupServiceInterface,
} from '@standardnotes/files'
import { InternalEventBusInterface } from '../Internal/InternalEventBusInterface'
import { ItemManagerInterface } from '../Item/ItemManagerInterface'
import { AbstractService } from '../Service/AbstractService'
import { StatusServiceInterface } from '../Status/StatusServiceInterface'
import { PureCryptoInterface } from '@standardnotes/sncrypto-common'
import { log, LoggingDomain } from '../Logging'

export class FilesBackupService extends AbstractService implements BackupServiceInterface {
  private itemsObserverDisposer: () => void
  private pendingFiles = new Set<string>()
  private mappingCache?: FileBackupsMapping['files']

  constructor(
    private items: ItemManagerInterface,
    private api: FilesApiInterface,
    private encryptor: EncryptionProviderInterface,
    private device: FileBackupsDevice,
    private status: StatusServiceInterface,
    private crypto: PureCryptoInterface,
    protected override internalEventBus: InternalEventBusInterface,
  ) {
    super(internalEventBus)

    this.itemsObserverDisposer = items.addObserver<FileItem>(ContentType.File, ({ changed, inserted, source }) => {
      const applicableSources = [
        PayloadEmitSource.LocalDatabaseLoaded,
        PayloadEmitSource.RemoteSaved,
        PayloadEmitSource.RemoteRetrieved,
      ]

      if (applicableSources.includes(source)) {
        void this.handleChangedFiles([...changed, ...inserted])
      }
    })
  }

  override deinit() {
    super.deinit()
    this.itemsObserverDisposer()
    ;(this.items as unknown) = undefined
    ;(this.api as unknown) = undefined
    ;(this.encryptor as unknown) = undefined
    ;(this.device as unknown) = undefined
    ;(this.status as unknown) = undefined
    ;(this.crypto as unknown) = undefined
  }

  public isFilesBackupsEnabled(): Promise<boolean> {
    return this.device.isFilesBackupsEnabled()
  }

  public async enableFilesBackups(): Promise<void> {
    await this.device.enableFilesBackups()

    if (!(await this.isFilesBackupsEnabled())) {
      return
    }

    this.backupAllFiles()
  }

  private backupAllFiles(): void {
    const files = this.items.getItems<FileItem>(ContentType.File)

    void this.handleChangedFiles(files)
  }

  public disableFilesBackups(): Promise<void> {
    return this.device.disableFilesBackups()
  }

  public changeFilesBackupsLocation(): Promise<string | undefined> {
    return this.device.changeFilesBackupsLocation()
  }

  public getFilesBackupsLocation(): Promise<string> {
    return this.device.getFilesBackupsLocation()
  }

  public openFilesBackupsLocation(): Promise<void> {
    return this.device.openFilesBackupsLocation()
  }

  private async getBackupsMappingFromDisk(): Promise<FileBackupsMapping['files']> {
    const result = (await this.device.getFilesBackupsMappingFile()).files

    this.mappingCache = result

    return result
  }

  private invalidateMappingCache(): void {
    this.mappingCache = undefined
  }

  private async getBackupsMappingFromCache(): Promise<FileBackupsMapping['files']> {
    return this.mappingCache ?? (await this.getBackupsMappingFromDisk())
  }

  public async getFileBackupInfo(file: { uuid: string }): Promise<FileBackupRecord | undefined> {
    const mapping = await this.getBackupsMappingFromCache()
    const record = mapping[file.uuid]
    return record
  }

  public async openFileBackup(record: FileBackupRecord): Promise<void> {
    await this.device.openFileBackup(record)
  }

  private async handleChangedFiles(files: FileItem[]): Promise<void> {
    if (files.length === 0) {
      return
    }

    if (!(await this.isFilesBackupsEnabled())) {
      return
    }

    const mapping = await this.getBackupsMappingFromDisk()

    for (const file of files) {
      if (this.pendingFiles.has(file.uuid)) {
        continue
      }

      const record = mapping[file.uuid]

      if (record == undefined) {
        this.pendingFiles.add(file.uuid)

        await this.performBackupOperation(file)

        this.pendingFiles.delete(file.uuid)
      }
    }

    this.invalidateMappingCache()
  }

  async readEncryptedFileFromBackup(uuid: string, onChunk: OnChunkCallback): Promise<'success' | 'failed' | 'aborted'> {
    const fileBackup = await this.getFileBackupInfo({ uuid })

    if (!fileBackup) {
      return 'failed'
    }

    const token = await this.device.getFileBackupReadToken(fileBackup)

    let readMore = true
    let index = 0

    while (readMore) {
      const { chunk, isLast, progress } = await this.device.readNextChunk(token)

      await onChunk({ data: chunk, index, isLast, progress })

      readMore = !isLast

      index++
    }

    return 'success'
  }

  private async performBackupOperation(file: FileItem): Promise<'success' | 'failed' | 'aborted'> {
    log(LoggingDomain.FilesBackups, 'Backing up file locally', file.uuid)

    const messageId = this.status.addMessage(`Backing up file ${file.name}...`)

    const encryptedFile = await this.encryptor.encryptSplitSingle({
      usesItemsKeyWithKeyLookup: {
        items: [file.payload],
      },
    })

    const itemsKey = this.items.getDisplayableItemsKeys().find((k) => k.uuid === encryptedFile.items_key_id)

    if (!itemsKey) {
      return 'failed'
    }

    const encryptedItemsKey = await this.encryptor.encryptSplitSingle({
      usesRootKeyWithKeyLookup: {
        items: [itemsKey.payload],
      },
    })

    const token = await this.api.createFileValetToken(file.remoteIdentifier, 'read')

    if (token instanceof ClientDisplayableError) {
      return 'failed'
    }

    const metaFile: FileBackupMetadataFile = {
      info: {
        warning: 'Do not edit this file.',
        information: 'The file and key data below is encrypted with your account password.',
        instructions:
          'Drag and drop this metadata file into the File Backups preferences pane in the Standard Notes desktop or web application interface.',
      },
      file: CreateEncryptedBackupFileContextPayload(encryptedFile.ejected()),
      itemsKey: CreateEncryptedBackupFileContextPayload(encryptedItemsKey.ejected()),
      version: '1.0.0',
    }

    const metaFileAsString = JSON.stringify(metaFile, null, 2)

    const result = await this.device.saveFilesBackupsFile(file.uuid, metaFileAsString, {
      chunkSizes: file.encryptedChunkSizes,
      url: this.api.getFilesDownloadUrl(),
      valetToken: token,
    })

    this.status.removeMessage(messageId)

    if (result === 'failed') {
      const failMessageId = this.status.addMessage(`Failed to back up ${file.name}...`)
      setTimeout(() => {
        this.status.removeMessage(failMessageId)
      }, 2000)
    }

    return result
  }
}