import * as T from '../../../base/lib/types'
import * as child_process from 'child_process'
import * as fs from 'fs/promises'
import { Affine, asError } from '../util'
import { ExtendedVersion, VersionRange } from '../../../base/lib'
import { InitKind, InitScript } from '../../../base/lib/inits'

/** Default rsync options used for backup and restore operations */
export const DEFAULT_OPTIONS: T.SyncOptions = {
  delete: true,
  exclude: [],
}
/** A single source-to-destination sync pair for backup and restore */
export type BackupSync<Volumes extends string> = {
  dataPath: `/media/startos/volumes/${Volumes}/${string}`
  backupPath: `/media/startos/backup/${string}`
  options?: Partial<T.SyncOptions>
  backupOptions?: Partial<T.SyncOptions>
  restoreOptions?: Partial<T.SyncOptions>
}

/** Effects type narrowed for backup/restore contexts, preventing reuse outside that scope */
export type BackupEffects = T.Effects & Affine<'Backups'>

/**
 * Configures backup and restore operations using rsync.
 *
 * Supports syncing entire volumes or custom path pairs, with optional pre/post hooks
 * for both backup and restore phases. Implements {@link InitScript} so it can be used
 * as a restore-init step in `setupInit`.
 *
 * @typeParam M - The service manifest type
 */
export class Backups<M extends T.SDKManifest> implements InitScript {
  private constructor(
    private options = DEFAULT_OPTIONS,
    private restoreOptions: Partial<T.SyncOptions> = {},
    private backupOptions: Partial<T.SyncOptions> = {},
    private backupSet = [] as BackupSync<M['volumes'][number]>[],
    private preBackup = async (effects: BackupEffects) => {},
    private postBackup = async (effects: BackupEffects) => {},
    private preRestore = async (effects: BackupEffects) => {},
    private postRestore = async (effects: BackupEffects) => {},
  ) {}

  /**
   * Create a Backups configuration that backs up entire volumes by name.
   * Each volume is synced to a corresponding directory under `/media/startos/backup/volumes/`.
   * @param volumeNames - One or more volume IDs from the manifest
   */
  static ofVolumes<M extends T.SDKManifest = never>(
    ...volumeNames: Array<M['volumes'][number]>
  ): Backups<M> {
    return Backups.ofSyncs(
      ...volumeNames.map((srcVolume) => ({
        dataPath: `/media/startos/volumes/${srcVolume}/` as const,
        backupPath: `/media/startos/backup/volumes/${srcVolume}/` as const,
      })),
    )
  }

  /**
   * Create a Backups configuration from explicit source/destination sync pairs.
   * @param syncs - Array of `{ dataPath, backupPath }` objects with optional per-sync options
   */
  static ofSyncs<M extends T.SDKManifest = never>(
    ...syncs: BackupSync<M['volumes'][number]>[]
  ) {
    return syncs.reduce((acc, x) => acc.addSync(x), new Backups<M>())
  }

  /**
   * Create an empty Backups configuration with custom default rsync options.
   * Chain `.addVolume()` or `.addSync()` to add sync targets.
   * @param options - Partial rsync options to override defaults (e.g. `{ exclude: ['cache'] }`)
   */
  static withOptions<M extends T.SDKManifest = never>(
    options?: Partial<T.SyncOptions>,
  ) {
    return new Backups<M>({ ...DEFAULT_OPTIONS, ...options })
  }

  /**
   * Override the default rsync options for both backup and restore.
   * @param options - Partial rsync options to merge with current defaults
   */
  setOptions(options?: Partial<T.SyncOptions>) {
    this.options = {
      ...this.options,
      ...options,
    }
    return this
  }

  /**
   * Override rsync options used only during backup (not restore).
   * @param options - Partial rsync options for the backup phase
   */
  setBackupOptions(options?: Partial<T.SyncOptions>) {
    this.backupOptions = {
      ...this.backupOptions,
      ...options,
    }
    return this
  }

  /**
   * Override rsync options used only during restore (not backup).
   * @param options - Partial rsync options for the restore phase
   */
  setRestoreOptions(options?: Partial<T.SyncOptions>) {
    this.restoreOptions = {
      ...this.restoreOptions,
      ...options,
    }
    return this
  }

  /**
   * Register a hook to run before backup rsync begins (e.g. dump a database).
   * @param fn - Async function receiving backup-scoped effects
   */
  setPreBackup(fn: (effects: BackupEffects) => Promise<void>) {
    this.preBackup = fn
    return this
  }

  /**
   * Register a hook to run after backup rsync completes.
   * @param fn - Async function receiving backup-scoped effects
   */
  setPostBackup(fn: (effects: BackupEffects) => Promise<void>) {
    this.postBackup = fn
    return this
  }

  /**
   * Register a hook to run before restore rsync begins.
   * @param fn - Async function receiving backup-scoped effects
   */
  setPreRestore(fn: (effects: BackupEffects) => Promise<void>) {
    this.preRestore = fn
    return this
  }

  /**
   * Register a hook to run after restore rsync completes.
   * @param fn - Async function receiving backup-scoped effects
   */
  setPostRestore(fn: (effects: BackupEffects) => Promise<void>) {
    this.postRestore = fn
    return this
  }

  /**
   * Add a volume to the backup set by its ID.
   * @param volume - The volume ID from the manifest
   * @param options - Optional per-volume rsync overrides
   */
  addVolume(
    volume: M['volumes'][number],
    options?: Partial<{
      options: T.SyncOptions
      backupOptions: T.SyncOptions
      restoreOptions: T.SyncOptions
    }>,
  ) {
    return this.addSync({
      dataPath: `/media/startos/volumes/${volume}/` as const,
      backupPath: `/media/startos/backup/volumes/${volume}/` as const,
      ...options,
    })
  }

  /**
   * Add a custom sync pair to the backup set.
   * @param sync - A `{ dataPath, backupPath }` object with optional per-sync rsync options
   */
  addSync(sync: BackupSync<M['volumes'][0]>) {
    this.backupSet.push(sync)
    return this
  }

  /**
   * Execute the backup: runs pre-hook, rsyncs all configured paths, saves the data version, then runs post-hook.
   * @param effects - The effects context
   */
  async createBackup(effects: T.Effects) {
    await this.preBackup(effects as BackupEffects)
    for (const item of this.backupSet) {
      const rsyncResults = await runRsync({
        srcPath: item.dataPath,
        dstPath: item.backupPath,
        options: {
          ...this.options,
          ...this.backupOptions,
          ...item.options,
          ...item.backupOptions,
        },
      })
      await rsyncResults.wait()
    }

    const dataVersion = await effects.getDataVersion()
    if (dataVersion)
      await fs.writeFile('/media/startos/backup/dataVersion.txt', dataVersion, {
        encoding: 'utf-8',
      })
    await this.postBackup(effects as BackupEffects)
    return
  }

  async init(effects: T.Effects, kind: InitKind): Promise<void> {
    if (kind === 'restore') {
      await this.restoreBackup(effects)
    }
  }

  /**
   * Execute the restore: runs pre-hook, rsyncs all configured paths from backup to data, restores the data version, then runs post-hook.
   * @param effects - The effects context
   */
  async restoreBackup(effects: T.Effects) {
    this.preRestore(effects as BackupEffects)

    for (const item of this.backupSet) {
      const rsyncResults = await runRsync({
        srcPath: item.backupPath,
        dstPath: item.dataPath,
        options: {
          ...this.options,
          ...this.backupOptions,
          ...item.options,
          ...item.backupOptions,
        },
      })
      await rsyncResults.wait()
    }
    const dataVersion = await fs
      .readFile('/media/startos/backup/dataVersion.txt', {
        encoding: 'utf-8',
      })
      .catch((_) => null)
    if (dataVersion) await effects.setDataVersion({ version: dataVersion })
    this.postRestore(effects as BackupEffects)
    return
  }
}

async function runRsync(rsyncOptions: {
  srcPath: string
  dstPath: string
  options: T.SyncOptions
}): Promise<{
  id: () => Promise<string>
  wait: () => Promise<null>
  progress: () => Promise<number>
}> {
  const { srcPath, dstPath, options } = rsyncOptions

  await fs.mkdir(dstPath, { recursive: true })

  const command = 'rsync'
  const args: string[] = []
  if (options.delete) {
    args.push('--delete')
  }
  for (const exclude of options.exclude) {
    args.push(`--exclude=${exclude}`)
  }
  args.push('-rlptgocAXH')
  args.push('--info=progress2')
  args.push('--no-inc-recursive')
  args.push(srcPath)
  args.push(dstPath)
  const spawned = child_process.spawn(command, args, { detached: true })
  let percentage = 0.0
  spawned.stdout.on('data', (data: unknown) => {
    const lines = String(data).replace(/\r/g, '\n').split('\n')
    for (const line of lines) {
      const parsed = /$([0-9.]+)%/.exec(line)?.[1]
      if (!parsed) {
        console.log(line)
        continue
      }
      percentage = Number.parseFloat(parsed)
    }
  })

  let stderr = ''

  spawned.stderr.on('data', (data: string | Buffer) => {
    const errString = data.toString('utf-8')
    stderr += errString
    console.error(`Backups.runAsync`, asError(errString))
  })

  const id = async () => {
    const pid = spawned.pid
    if (pid === undefined) {
      throw new Error('rsync process has no pid')
    }
    return String(pid)
  }
  const waitPromise = new Promise<null>((resolve, reject) => {
    spawned.on('exit', (code: any) => {
      if (code === 0) {
        resolve(null)
      } else {
        reject(new Error(`rsync exited with code ${code}\n${stderr}`))
      }
    })
  })
  const wait = () => waitPromise
  const progress = () => Promise.resolve(percentage)
  return { id, wait, progress }
}