import { createWriteStream, promises as fs } from 'node:fs'
import { basename, join } from 'node:path'
import { pipeline } from 'node:stream/promises'
import * as tar from 'tar'
import { getImageTotals, listAllImageIndexRows } from '../image-index'
import type { ImageIndexRow } from '../image-index'
import {
  listStorageBackendRows
} from '../storage-backends'
import { parseS3Config } from '../storage/s3'
import { parseTelegramConfig } from '../storage/telegram'
import { createImageStream } from '../storage'
import { copyDatabaseSnapshot } from './db-snapshot'
import { markJobDone, markJobFailed, updateBackupJob } from './jobs'
import { BACKUP_FORMAT_VERSION, type BackupManifest, type StorageBackendMetaExport } from './manifest'
import {
  BACKUP_ARCHIVE_EXT,
  getBackupStagingDir,
  getBackupsDir
} from './paths'
import type { StorageBackendRow } from '../storage/types'

function formatArchiveName(jobId: string): string {
  return `pichost-${jobId}${BACKUP_ARCHIVE_EXT}`
}

function buildStorageBackendsMeta(): StorageBackendMetaExport[] {
  return listStorageBackendRows().map((row: StorageBackendRow) => ({
    id: row.id,
    name: row.name,
    type: row.type,
    config: row.type === 's3'
      ? (parseS3Config(row.config_json) ?? {})
      : row.type === 'telegram'
        ? (parseTelegramConfig(row.config_json) ?? {})
        : {},
    servingMode: row.serving_mode,
    publicUrl: row.public_url,
    quotaBytes: row.quota_bytes,
    enabled: row.enabled === 1,
    isDefault: row.is_default === 1,
    sortOrder: row.sort_order
  }))
}

async function writeStreamToFile(stream: NodeJS.ReadableStream, filePath: string): Promise<void> {
  await fs.mkdir(join(filePath, '..'), { recursive: true })
  await pipeline(stream, createWriteStream(filePath))
}

async function streamToString(stream: NodeJS.ReadableStream): Promise<string> {
  const chunks: Buffer[] = []
  for await (const chunk of stream) {
    chunks.push(Buffer.from(chunk as Uint8Array))
  }
  return Buffer.concat(chunks).toString('utf8')
}

/**
 * 源文件已按设计删除（转码完成）时，导出 HLS 播放列表、分片与封面。
 * 恢复端会遍历 blobs 目录原样还原，因此这里只需把附属文件写进去。
 */
async function exportVideoSidecars(row: ImageIndexRow, stagingRoot: string): Promise<void> {
  const keys: string[] = []
  if (row.thumb_key) keys.push(row.thumb_key)

  if (row.hls_key) {
    keys.push(row.hls_key)
    const dir = row.hls_key.slice(0, row.hls_key.lastIndexOf('/'))
    const text = await streamToString(await createImageStream(row.hls_key))
    for (const line of text.split('\n')) {
      const name = line.trim()
      if (!name || name.startsWith('#')) continue
      keys.push(`${dir}/${basename(name)}`)
    }
  }

  for (const key of keys) {
    await writeStreamToFile(
      await createImageStream(key),
      join(stagingRoot, 'blobs', key)
    )
  }
}

export async function runFullExportJob(jobId: string, appVersion: string): Promise<void> {
  const stagingRoot = getBackupStagingDir(jobId)
  const archiveName = formatArchiveName(jobId)
  const archivePath = join(getBackupsDir(), archiveName)

  try {
    await fs.rm(stagingRoot, { recursive: true, force: true })
    await fs.mkdir(stagingRoot, { recursive: true })
    await fs.mkdir(getBackupsDir(), { recursive: true })

    const totals = getImageTotals()
    const rows = listAllImageIndexRows()
    updateBackupJob(jobId, {
      total: totals.count + 1,
      message: '正在备份数据库…'
    })

    await copyDatabaseSnapshot(join(stagingRoot, 'database', 'pichost.sqlite'))
    updateBackupJob(jobId, { progress: 1, message: '正在写入备份元数据…' })

    const manifest: BackupManifest = {
      formatVersion: BACKUP_FORMAT_VERSION,
      appVersion,
      createdAt: new Date().toISOString(),
      imageCount: totals.count,
      imageBytes: totals.bytes,
      includesDatabase: true
    }
    await fs.writeFile(
      join(stagingRoot, 'manifest.json'),
      JSON.stringify(manifest, null, 2),
      'utf8'
    )

    const metaDir = join(stagingRoot, 'meta')
    await fs.mkdir(metaDir, { recursive: true })
    await fs.writeFile(
      join(metaDir, 'storage_backends.json'),
      JSON.stringify(buildStorageBackendsMeta(), null, 2),
      'utf8'
    )
    await fs.writeFile(
      join(metaDir, 'readme.txt'),
      [
        'PicHost site backup package.',
        'Restore via Storage → Backup & migration in the admin UI.',
        'Object storage secrets are not included; re-enter keys after restore.'
      ].join('\n'),
      'utf8'
    )

    let processed = 1
    for (const row of rows) {
      updateBackupJob(jobId, {
        progress: processed,
        message: `正在导出图片 ${processed}/${totals.count + 1}…`
      })

      if (Number(row.source_deleted ?? 0) === 1) {
        // 转码完成的视频只有 HLS 产物与封面
        await exportVideoSidecars(row, stagingRoot)
      } else {
        const blobPath = join(stagingRoot, 'blobs', row.key)
        const stream = await createImageStream(row.key)
        await writeStreamToFile(stream, blobPath)
      }
      processed += 1
      updateBackupJob(jobId, { progress: processed })
    }

    updateBackupJob(jobId, { message: '正在压缩备份包…' })
    await tar.c(
      {
        gzip: true,
        file: archivePath,
        cwd: stagingRoot,
        portable: true
      },
      ['.']
    )

    await fs.rm(stagingRoot, { recursive: true, force: true })

    markJobDone(jobId, {
      message: '备份完成',
      outputPath: archivePath,
      payload: { archiveName }
    })
  } catch (error) {
    await fs.rm(stagingRoot, { recursive: true, force: true }).catch(() => {})
    const message = error instanceof Error ? error.message : '导出失败'
    markJobFailed(jobId, message)
    throw error
  }
}