// services/s3.service.js
//
// S3-compatible storage service targeting Garage (self-hosted).
// Exposes the same interface as chibisafe.service.js:
//   uploadFile({ buffer, originalname, mimetype, ownerType }) → { url, uuid }
//   deleteFile(key)
//
// Required .env vars:
//   S3_ENDPOINT    – http://127.0.0.1:3900 (internal — always used for uploads/deletes)
//   S3_REGION      – garage
//   S3_ACCESS_KEY
//   S3_SECRET_KEY
//   S3_BUCKET      – your-bucket-name
//   S3_PUBLIC_URL  – https://cdn.yourdomain.com (used for browser-facing URLs
//                    whenever S3_ENDPOINT isn't reachable from this machine —
//                    see resolvePublicHost() below)

const { S3Client, PutObjectCommand, DeleteObjectCommand, GetObjectCommand, HeadBucketCommand } = require("@aws-sdk/client-s3");
const { getSignedUrl } = require("@aws-sdk/s3-request-presigner");
const crypto = require("crypto");
const path = require("path");

// ─── Clients ──────────────────────────────────────────────────────────────────

const credentials = {
  accessKeyId:     process.env.S3_ACCESS_KEY,
  secretAccessKey: process.env.S3_SECRET_KEY,
};

// Internal client — uploads, deletes, direct streams from the server itself.
// Always targets S3_ENDPOINT: these calls originate from this machine, so the
// internal address is the correct (and only) one to use.
const s3 = new S3Client({
  endpoint:       process.env.S3_ENDPOINT,
  region:         process.env.S3_REGION || "garage",
  credentials,
  forcePathStyle: true,
});

const DEFAULT_BUCKET = process.env.S3_BUCKET;

// ─── Public host resolution ───────────────────────────────────────────────────
//
// URLs handed to browsers (file_url, presigned GET links) need a host reachable
// from wherever the client sits. S3_ENDPOINT (e.g. 127.0.0.1:3900) only works
// from the machine running Garage itself; S3_PUBLIC_URL is the externally
// reachable address (tunnel/CDN/domain).
//
// Rather than always preferring one, probe S3_ENDPOINT and use it when it's
// actually reachable (same-machine dev setup — no extra hop through the
// tunnel), falling back to S3_PUBLIC_URL when it isn't (any other machine).
//
// The probe runs once at startup and then on a background timer — never on
// the request path itself. A machine without Garage would otherwise pay the
// full HeadBucket timeout on whichever upload/asset request happens to land
// right after the cache expires; polling in the background means every
// request just reads the last known-good host instantly.
const PROBE_TIMEOUT_MS = 1500;
const PROBE_CACHE_MS   = 15000;

let hostCache = { host: process.env.S3_PUBLIC_URL || process.env.S3_ENDPOINT || "" };

async function probeEndpoint(endpoint) {
  const probe = new S3Client({
    endpoint,
    region:         process.env.S3_REGION || "garage",
    credentials,
    forcePathStyle: true,
  });
  await Promise.race([
    probe.send(new HeadBucketCommand({ Bucket: DEFAULT_BUCKET })),
    new Promise((_, reject) => setTimeout(() => reject(new Error("timeout")), PROBE_TIMEOUT_MS)),
  ]);
}

async function refreshHostCache() {
  const endpoint  = process.env.S3_ENDPOINT;
  const publicUrl = process.env.S3_PUBLIC_URL || "";

  if (!endpoint)  { hostCache = { host: publicUrl }; return; }
  if (!publicUrl) { hostCache = { host: endpoint };   return; }

  try {
    await probeEndpoint(endpoint);
    hostCache = { host: endpoint };
  } catch {
    hostCache = { host: publicUrl };
  }
}

// Kick off the first probe immediately so the cache is populated before any
// request needs it, then keep it fresh in the background. unref() so this
// timer alone doesn't keep the process (or a test run) alive.
const initialProbe = refreshHostCache();
const refreshTimer = setInterval(refreshHostCache, PROBE_CACHE_MS);
refreshTimer.unref?.();

async function resolvePublicHost() {
  await initialProbe; // no-op after the first call — already resolved
  return hostCache.host;
}

// Public client — lazily built against whichever host resolvePublicHost()
// picks, so it follows the reachability check instead of a fixed endpoint.
async function getPublicClient() {
  const endpoint = await resolvePublicHost();
  return new S3Client({
    endpoint,
    region:         process.env.S3_REGION || "garage",
    credentials,
    forcePathStyle: true,
  });
}

// ─── Key prefix map ───────────────────────────────────────────────────────────
//
// ownerType mirrors what the controller already passes to chibisafe
// (image, video, audio, document, avatar, thumbnail).
// Maps to folder prefixes inside the bucket.
//
const PREFIX_MAP = {
  image:     "images",
  video:     "videos",
  audio:     "audios",
  document:  "documents",
  avatar:    "avatars",
  thumbnail: "thumbnails",
  badge:     "badges",
};

function resolvePrefix(ownerType = "image") {
  return PREFIX_MAP[ownerType] || "others";
}

function resolveExtension(originalname = "") {
  return path.extname(originalname).replace(".", "").toLowerCase() || "bin";
}

// ─── Helpers ──────────────────────────────────────────────────────────────────

// Builds the S3 object key: {prefix}/{uuid}.{ext}
// e.g. images/3f2a1b4c-uuid.jpg
function buildKey(originalname, ownerType) {
  const prefix = resolvePrefix(ownerType);
  const ext    = resolveExtension(originalname);
  const uuid   = crypto.randomUUID();
  return `${prefix}/${uuid}.${ext}`;
}

// Builds the public URL for a stored object.
// Garage path-style: {host}/{bucket}/{key}
// e.g. https://cdn.yourdomain.com/your-bucket/images/uuid.jpg
async function buildPublicUrl(key, bucket = DEFAULT_BUCKET) {
  const host = (await resolvePublicHost()).replace(/\/$/, "");
  return `${host}/${bucket}/${key}`;
}

// ─── uploadFile ───────────────────────────────────────────────────────────────
//
// Matches chibisafe.service.js interface exactly.
// input:  { buffer, originalname, mimetype, ownerType? }
// output: { url, uuid }  ← uuid = the S3 key, stored as storage_key in DB
//
async function uploadFile({ buffer, originalname, mimetype, ownerType = "image" }) {
  if (!buffer) {
    throw Object.assign(new Error("File buffer is required for S3 uploads."), { status: 400 });
  }

  const bucket = DEFAULT_BUCKET;
  const key    = buildKey(originalname, ownerType);

  await s3.send(new PutObjectCommand({
    Bucket:      bucket,
    Key:         key,
    Body:        buffer,
    ContentType: mimetype,
  }));

  return {
    url:  await buildPublicUrl(key, bucket),
    uuid: key, // used as storage_key in DB — mirrors chibi_uuid usage
  };
}

// ─── deleteFile ───────────────────────────────────────────────────────────────
//
// Matches chibisafe.service.js interface.
// input: key — the value stored in storage_key column (e.g. "images/uuid.jpg")
//
async function deleteFile(key) {
  if (!key) return;
  await s3.send(new DeleteObjectCommand({
    Bucket: DEFAULT_BUCKET,
    Key:    key,
  }));
}

// ─── getSignedDownloadUrl ─────────────────────────────────────────────────────
//
// Generates a short-lived pre-signed GET URL against whichever host
// resolvePublicHost() picks, so the URL is resolvable from wherever the
// request is served (browser or proxy server), not just the one running
// Garage locally.
//
async function getSignedDownloadUrl(key, expiresInSeconds = 3600) {
  const client = await getPublicClient();
  return getSignedUrl(
    client,
    new GetObjectCommand({ Bucket: DEFAULT_BUCKET, Key: key }),
    { expiresIn: expiresInSeconds }
  );
}

// ─── getObjectStream ────────────────────────────────────────────────────────
//
// Fetches an S3 object and returns its readable stream + metadata, for use
// in a server-side download proxy (Content-Disposition: attachment).
//
// input:  key — the storage_key (e.g. "images/uuid.jpg")
// output: { stream, contentType, contentLength }
//
async function getObjectStream(key) {
    if (!key) {
        throw Object.assign(new Error("Storage key is required."), { status: 400 });
    }
 
    const result = await s3.send(new GetObjectCommand({
        Bucket: DEFAULT_BUCKET,
        Key:    key,
    }));
 
    return {
        stream:        result.Body,          // Node.js Readable stream
        contentType:   result.ContentType,
        contentLength: result.ContentLength,
    };
}

async function ping() {
  const client = await getPublicClient();
  await client.send(new HeadBucketCommand({ Bucket: DEFAULT_BUCKET }));
}

module.exports = { uploadFile, deleteFile, getSignedDownloadUrl, getObjectStream, ping };