import { createReadStream, createWriteStream } from 'node:fs';
import { mkdir, readFile, rename, rm, stat, writeFile } from 'node:fs/promises';
import { join } from 'node:path';
import { Readable } from 'node:stream';
import { pipeline } from 'node:stream/promises';

import {
  remoteBundleId,
  remoteBundleName,
  type BackupEnv,
  type BackupRemoteStatus,
} from '@dorfteich/shared';
import {
  webdavCheck,
  webdavDelete,
  webdavGet,
  webdavList,
  webdavPut,
  type WebDavTarget,
} from '@dorfteich/shared/webdav';

import { createArchiveOfFiles, extractArchiveTo } from './archive.js';
import { archiveFileName, backupIdTime, dumpFileName } from './backup-set.js';
import { sendUploadFailureMail } from './mail.js';
import { NEXTCLOUD_PASSWORD_SECRET_KEY, type BackupDbSettings } from './settings.js';

/**
 * Off-host half of a backup run (issue #103): bundle a complete local set
 * into ONE self-contained archive, upload it to the admin-configured
 * Nextcloud folder via WebDAV, and prune expired remote bundles — never the
 * newest one, mirroring the local guarantee (#83).
 */

export interface RemoteLogger {
  info(details: object, message: string): void;
  warn(details: object, message: string): void;
  error(details: object, message: string): void;
}

/**
 * The effective WebDAV target, or null when the feature is off or not fully
 * configured. The app password comes from the wizard-written secret store
 * (never the database); base URL and username from instance settings.
 */
export function resolveRemoteTarget(
  settings: BackupDbSettings,
  secrets: Record<string, string>,
): WebDavTarget | null {
  const { enabled, baseUrl, username, folder } = settings.nextcloud;
  const password = secrets[NEXTCLOUD_PASSWORD_SECRET_KEY] ?? '';
  if (!enabled || !baseUrl || !username || !password) return null;
  return { baseUrl, username, password, folder };
}

/**
 * Whether a scheduled run should upload: `off` never (manual trigger only),
 * `daily` after every successful set, `weekly` when the last remote copy is
 * at least ~a week old (half a day of slack so a slightly early nightly run
 * does not skip its week).
 */
export function uploadDue(
  schedule: BackupDbSettings['nextcloud']['uploadSchedule'],
  lastSuccessfulUploadAt: string | null,
  now: Date,
): boolean {
  if (schedule === 'off') return false;
  if (schedule === 'daily') return true;
  if (!lastSuccessfulUploadAt) return true;
  const ageMs = now.getTime() - new Date(lastSuccessfulUploadAt).getTime();
  return ageMs >= 6.5 * 24 * 60 * 60 * 1000;
}

/** Contents of the bundle's manifest.json — the self-description a rebuild
 * after total loss relies on (documented in the restore runbook). */
export interface BundleManifest {
  schemaVersion: 1;
  backupId: string;
  createdAt: string;
  files: string[];
}

/**
 * Packs one complete local set into `dorfteich-backup-<id>.tar.gz` next to
 * the set (staged as `.partial`, like every other artifact). Returns the
 * bundle path; the caller uploads and then deletes it — bundles are derived
 * data and would double the volume's footprint.
 */
export async function buildBundle(
  backupsDir: string,
  backupId: string,
  now: Date,
): Promise<{ path: string; sizeBytes: number }> {
  const files = [dumpFileName(backupId), archiveFileName(backupId)];
  const manifest: BundleManifest = {
    schemaVersion: 1,
    backupId,
    createdAt: now.toISOString(),
    files,
  };
  const manifestName = 'manifest.json';
  await writeFile(join(backupsDir, manifestName), JSON.stringify(manifest, null, 2) + '\n');

  const bundlePath = join(backupsDir, remoteBundleName(backupId));
  await createArchiveOfFiles(`${bundlePath}.partial`, backupsDir, [...files, manifestName]);
  await rename(`${bundlePath}.partial`, bundlePath);
  await rm(join(backupsDir, manifestName), { force: true });
  return { path: bundlePath, sizeBytes: (await stat(bundlePath)).size };
}

/**
 * Uploads the bundle for `backupId` and prunes expired remote bundles.
 * Returns the new remote status; an upload failure alerts by mail (the
 * local run stays succeeded — the admin card and readyz surface the gap).
 */
export async function uploadSet(deps: {
  env: BackupEnv;
  backupsDir: string;
  target: WebDavTarget;
  remoteRetentionDays: number;
  backupId: string;
  previous: BackupRemoteStatus | undefined;
  now(): Date;
  log: RemoteLogger;
}): Promise<BackupRemoteStatus> {
  const { backupId, target } = deps;
  const previousSuccess = deps.previous?.lastSuccessfulUpload ?? null;
  let bundle: { path: string; sizeBytes: number } | null = null;
  try {
    const check = await webdavCheck(target);
    if (!check.ok) throw new Error(check.error);

    bundle = await buildBundle(deps.backupsDir, backupId, deps.now());
    const put = await webdavPut(
      target,
      remoteBundleName(backupId),
      Readable.toWeb(createReadStream(bundle.path)) as ReadableStream<Uint8Array>,
      { contentLength: bundle.sizeBytes },
    );
    if (!put.ok) throw new Error(put.error);

    await pruneRemote(target, deps.remoteRetentionDays, deps.now(), deps.log);
    const finishedAt = deps.now().toISOString();
    deps.log.info({ backupId, sizeBytes: bundle.sizeBytes }, 'remote upload succeeded');
    return {
      lastUpload: { backupId, finishedAt, outcome: 'succeeded', sizeBytes: bundle.sizeBytes },
      lastSuccessfulUpload: { backupId, finishedAt, sizeBytes: bundle.sizeBytes },
    };
  } catch (error) {
    const message = error instanceof Error ? error.message : String(error);
    deps.log.error({ backupId, error: message }, 'remote upload failed');
    try {
      const sent = await sendUploadFailureMail(deps.env, {
        backupId,
        error: message,
        lastSuccessAt: previousSuccess?.finishedAt ?? null,
      });
      if (!sent) deps.log.warn({ backupId }, 'no BACKUP_MAIL_TO configured, upload alert not sent');
    } catch (mailError) {
      deps.log.error({ backupId, error: String(mailError) }, 'upload alert could not be sent');
    }
    return {
      lastUpload: {
        backupId,
        finishedAt: deps.now().toISOString(),
        outcome: 'failed',
        error: message,
      },
      lastSuccessfulUpload: previousSuccess,
    };
  } finally {
    if (bundle) await rm(bundle.path, { force: true });
    await rm(join(deps.backupsDir, 'manifest.json'), { force: true });
  }
}

/**
 * Deletes remote bundles older than the retention window — never the newest
 * one, even when expired (same guarantee as the local prune, #83). Foreign
 * files in the folder are never touched. Prune failures are logged, not
 * thrown: the upload itself succeeded and must count.
 */
export async function pruneRemote(
  target: WebDavTarget,
  retentionDays: number,
  now: Date,
  log: RemoteLogger,
): Promise<void> {
  const listed = await webdavList(target);
  if (!listed.ok) {
    log.warn({ error: listed.error }, 'remote prune skipped: listing failed');
    return;
  }
  const bundles = listed.value
    .filter((entry) => !entry.isCollection)
    .map((entry) => ({ name: entry.name, id: remoteBundleId(entry.name) }))
    .filter((entry): entry is { name: string; id: string } => entry.id !== null)
    .sort((a, b) => a.id.localeCompare(b.id));
  const cutoff = now.getTime() - retentionDays * 24 * 60 * 60 * 1000;
  const newest = bundles.at(-1);
  for (const bundle of bundles) {
    if (bundle === newest) continue;
    const time = backupIdTime(bundle.id);
    if (!time || time.getTime() >= cutoff) continue;
    const deleted = await webdavDelete(target, bundle.name);
    if (deleted.ok) log.info({ name: bundle.name }, 'pruned expired remote bundle');
    else log.warn({ name: bundle.name, error: deleted.error }, 'remote prune of bundle failed');
  }
}

/**
 * Downloads a remote bundle and unpacks its set artifacts into the backups
 * directory (the in-app restore path, and documented for operators in the
 * runbook). Verifies the manifest matches the requested id.
 */
export async function fetchRemoteSet(deps: {
  backupsDir: string;
  target: WebDavTarget;
  backupId: string;
  log: RemoteLogger;
}): Promise<void> {
  const name = remoteBundleName(deps.backupId);
  const response = await webdavGet(deps.target, name);
  if (!response.ok) throw new Error(response.error);
  if (!response.value.body) throw new Error(`download ${name}: empty response body`);

  const downloadPath = join(deps.backupsDir, `${name}.download`);
  const scratchDir = join(deps.backupsDir, `.restore-${deps.backupId}`);
  try {
    await pipeline(
      Readable.fromWeb(response.value.body as import('node:stream/web').ReadableStream),
      createWriteStream(downloadPath),
    );
    await mkdir(scratchDir, { recursive: true });
    await extractArchiveTo(downloadPath, scratchDir);

    const manifest = JSON.parse(
      await readFile(join(scratchDir, 'manifest.json'), 'utf8'),
    ) as BundleManifest;
    if (manifest.backupId !== deps.backupId) {
      throw new Error(
        `bundle manifest mismatch: requested ${deps.backupId}, bundle contains ${manifest.backupId}`,
      );
    }
    for (const file of [dumpFileName(deps.backupId), archiveFileName(deps.backupId)]) {
      await rename(join(scratchDir, file), join(deps.backupsDir, file));
    }
    deps.log.info({ backupId: deps.backupId }, 'remote set downloaded and unpacked');
  } finally {
    await rm(downloadPath, { force: true });
    await rm(scratchDir, { recursive: true, force: true });
  }
}