/**
 * Sia-backed storage for scan-clean uploads.
 *
 * When the service is configured with S3 credentials pointing at the
 * sidecar s3d, every clean upload is pushed to Sia and the public download
 * URL — hosted by Prometheus itself on `/dl/<sha256>` — is handed back to
 * the submit UI. The publisher no longer has to self-host.
 *
 * Design notes
 * ------------
 * - Writes go to `s3://${bucket}/${prefix}<sha256>.bin` by content hash.
 *   The bucket is created on first use if missing, so a fresh s3d data
 *   folder bootstraps itself.
 * - The returned URL is a Prometheus-hosted URL (`${publicBase}/dl/<sha256>`),
 *   NOT the raw s3d endpoint. The service's `/dl` handler streams from s3d
 *   on the back end; the s3d itself stays off the public network.
 * - If storage is not configured, isConfigured() returns false and the
 *   service falls back to its old behavior (publisher provides their own
 *   download_url). That keeps dev loops working without creds.
 *
 * Env
 * ---
 *   PROMETHEUS_S3_ENDPOINT     write-side endpoint, e.g. http://s3d:8000
 *   PROMETHEUS_S3_ACCESS_KEY   access key minted by `s3d keys create <user>`
 *   PROMETHEUS_S3_SECRET       matching secret
 *   PROMETHEUS_S3_BUCKET       default: prometheus
 *   PROMETHEUS_S3_PREFIX       default: apps/
 *   PROMETHEUS_PUBLIC_BASE     default: https://prometheus.x  — origin for
 *                              the public /dl URL readers follow
 */

import { createReadStream } from 'node:fs';
import { stat } from 'node:fs/promises';
import { S3Client, S3Error } from './s3.js';

const CFG = {
  endpoint: process.env.PROMETHEUS_S3_ENDPOINT || '',
  accessKey: process.env.PROMETHEUS_S3_ACCESS_KEY || '',
  secret: process.env.PROMETHEUS_S3_SECRET || '',
  bucket: process.env.PROMETHEUS_S3_BUCKET || 'prometheus',
  prefix: normalizePrefix(process.env.PROMETHEUS_S3_PREFIX || 'apps/'),
  publicBase: (process.env.PROMETHEUS_PUBLIC_BASE || 'https://prometheus.x').replace(/\/+$/, ''),
};

let client = null;
let bucketReady = false;

export function isConfigured() {
  return Boolean(CFG.endpoint && CFG.accessKey && CFG.secret);
}

export function describe() {
  if (!isConfigured()) return { configured: false };
  return {
    configured: true,
    endpoint: CFG.endpoint,
    bucket: CFG.bucket,
    prefix: CFG.prefix,
    publicBase: CFG.publicBase,
  };
}

function getClient() {
  if (!isConfigured()) return null;
  if (!client) {
    client = new S3Client({
      endpoint: CFG.endpoint,
      accessKeyId: CFG.accessKey,
      secretKey: CFG.secret,
    });
  }
  return client;
}

/** Make sure the bucket exists; called once lazily, idempotent on error. */
async function ensureBucket(c) {
  if (bucketReady) return;
  try {
    await c.createBucket(CFG.bucket);
  } catch (err) {
    // BucketAlreadyOwnedByYou / BucketAlreadyExists → done. Anything else
    // is a real failure the caller should see.
    if (err instanceof S3Error && /already/i.test(err.code || '')) {
      // noop
    } else if (err?.status === 409) {
      // noop
    } else {
      throw err;
    }
  }
  bucketReady = true;
}

/**
 * Upload a scan-clean file to Sia and return the public URL readers can fetch.
 *
 * Idempotent: if an object with the same key already exists (same sha256 →
 * same bytes), the PUT overwrites with identical content and the URL is the
 * same. The returned URL is stable across reruns.
 *
 * @param {object} args
 * @param {string} args.localPath — absolute path to the file on disk
 * @param {string} args.sha256    — content hash, used as the object key
 * @param {string} args.name      — original filename (for display suffix, unused server-side)
 * @param {string} args.mime      — content-type for the stored object
 * @returns {Promise<{ downloadUrl: string, key: string, bytes: number }>}
 */
export async function uploadScannedFile({ localPath, sha256, name, mime }) {
  const c = getClient();
  if (!c) throw new Error('storage not configured — set PROMETHEUS_S3_*');

  await ensureBucket(c);

  const { size } = await stat(localPath);
  const key = `${CFG.prefix}${sha256}.bin`;
  const body = createReadStream(localPath);
  const contentType = mime || 'application/octet-stream';

  // s3d wants a Content-Length on streaming PUTs; chunked encoding does not
  // round-trip cleanly for large bodies in its current gateway.
  await c.putObject(CFG.bucket, key, body, {
    contentType,
    contentLength: size,
  });

  return { downloadUrl: publicUrlFor(sha256), key, bytes: size };
}

/**
 * Open a read stream from s3d for a given sha256. Returns the raw HTTP
 * response so callers can stream it straight back to the browser and
 * forward content-type / content-length / etag / accept-ranges. Supports
 * Range requests via the optional `range` header.
 */
export async function getObjectStream(sha256, { range } = {}) {
  const c = getClient();
  if (!c) throw new Error('storage not configured');
  const key = `${CFG.prefix}${sha256}.bin`;
  return c.getObject(CFG.bucket, key, range ? { range } : {});
}

export function publicUrlFor(sha256) {
  return `${CFG.publicBase}/dl/${sha256}`;
}

function normalizePrefix(p) {
  const t = String(p || '').replace(/^\/+/, '');
  return t.endsWith('/') || t === '' ? t : t + '/';
}