/**
 * SQLite blob store (logical S3 keys → rows in `blobs`).
 */

const crypto = require('crypto');
const { openDatabase } = require('../db/sqliteDb');

function sha256Etag(buf) {
  const h = crypto.createHash('sha256').update(buf).digest('hex');
  return `"${h}"`;
}

function namespaceFromKey(objectKey) {
  const k = String(objectKey || '');
  if (k.startsWith('ping-cache/') || k.startsWith('speed-test-cache/') || k.startsWith('network-map-cache/') ||
      k.startsWith('uptime-monitor-cache/') || k.startsWith('ping-services/')) {
    return 'cache';
  }
  if (k.startsWith('filter-manager/config-') || k.startsWith('filter-manager/server-filters-')) {
    return 'per_server';
  }
  if (k === 'mikrotik-frouting-config.txt') {
    return 'derived';
  }
  return 'config';
}

function isVersionedKey(db, objectKey) {
  const row = db.prepare('SELECT 1 FROM versioned_keys WHERE object_key = ?').get(objectKey);
  return Boolean(row);
}

function trimVersions(db, objectKey, keep = 50) {
  db.prepare(
    `DELETE FROM blob_versions WHERE object_key = ? AND id NOT IN (
       SELECT id FROM blob_versions WHERE object_key = ? ORDER BY created_at DESC, id DESC LIMIT ?
     )`
  ).run(objectKey, objectKey, keep);
}

/**
 * @param {Buffer|string} body
 */
function writeBlobTx(db, objectKey, body, contentType) {
  const buf = Buffer.isBuffer(body) ? body : Buffer.from(String(body), 'utf8');
  const ns = namespaceFromKey(objectKey);
  const etag = sha256Etag(buf);
  const now = Date.now();
  const size = buf.length;

  const existing = db.prepare('SELECT body, content_type, etag, updated_at, created_at FROM blobs WHERE object_key = ?').get(objectKey);

  const run = () => {
    if (existing && isVersionedKey(db, objectKey)) {
      const oldBuf = existing.body;
      db.prepare(
        `INSERT INTO blob_versions (object_key, body, byte_size, etag, created_at)
         VALUES (?, ?, ?, ?, ?)`
      ).run(objectKey, oldBuf, oldBuf.length, existing.etag, existing.updated_at);
      trimVersions(db, objectKey);
    }

    if (existing) {
      db.prepare(
        `UPDATE blobs SET namespace = ?, content_type = ?, body = ?, byte_size = ?, etag = ?, updated_at = ?
         WHERE object_key = ?`
      ).run(ns, contentType, buf, size, etag, now, objectKey);
    } else {
      db.prepare(
        `INSERT INTO blobs (object_key, namespace, content_type, body, byte_size, etag, updated_at, created_at)
         VALUES (?, ?, ?, ?, ?, ?, ?, ?)`
      ).run(objectKey, ns, contentType, buf, size, etag, now, now);
    }
  };

  db.transaction(run)();
  return {
    etag,
    lastModified: new Date(now).toISOString(),
    contentLength: size,
  };
}

function readBlob(objectKey) {
  const db = openDatabase();
  const row = db.prepare(
    'SELECT body, etag, updated_at, byte_size FROM blobs WHERE object_key = ?'
  ).get(objectKey);
  if (!row) return null;
  const bodyStr = row.body.toString('utf8');
  return {
    body: bodyStr,
    etag: row.etag,
    lastModified: new Date(row.updated_at).toISOString(),
    contentLength: row.byte_size,
  };
}

function headMetaRow(objectKey) {
  const db = openDatabase();
  const row = db.prepare('SELECT etag, updated_at, byte_size FROM blobs WHERE object_key = ?').get(objectKey);
  if (!row) {
    return { etag: null, lastModified: null, contentLength: null };
  }
  return {
    etag: row.etag,
    lastModified: new Date(row.updated_at).toISOString(),
    contentLength: row.byte_size,
  };
}

function headEtag(objectKey) {
  const m = headMetaRow(objectKey);
  return m.etag || undefined;
}

function deleteBlob(objectKey) {
  const db = openDatabase();
  db.prepare('DELETE FROM blobs WHERE object_key = ?').run(objectKey);
}

function listByPrefix(prefix, maxKeys = 100) {
  const db = openDatabase();
  const rows = db.prepare(
    `SELECT object_key AS key, byte_size AS size, updated_at, etag FROM blobs
     WHERE object_key >= ? AND object_key < ? ORDER BY object_key LIMIT ?`
  ).all(prefix, prefix + '\uffff', maxKeys);
  return rows.map((r) => ({
    key: r.key,
    size: r.size,
    lastModified: new Date(r.updated_at).toISOString(),
    etag: r.etag,
  }));
}

function listVersions(objectKey, maxKeys = 50) {
  const db = openDatabase();
  return db.prepare(
    `SELECT id, object_key, byte_size, etag, created_at FROM blob_versions
     WHERE object_key = ? ORDER BY created_at DESC, id DESC LIMIT ?`
  ).all(objectKey, maxKeys);
}

function rollbackToVersionId(objectKey, versionId) {
  const db = openDatabase();
  const vid = Number(versionId);
  if (!Number.isFinite(vid)) throw new Error('Invalid versionId');
  const ver = db.prepare('SELECT body, etag, created_at FROM blob_versions WHERE id = ? AND object_key = ?').get(vid, objectKey);
  if (!ver) throw new Error('Version not found');
  const buf = ver.body;
  const contentType = objectKey.endsWith('.json') ? 'application/json' : 'text/plain';
  writeBlobTx(db, objectKey, buf, contentType);
  return headMetaRow(objectKey);
}

module.exports = {
  namespaceFromKey,
  writeBlobTx,
  readBlob,
  headMetaRow,
  headEtag,
  deleteBlob,
  listByPrefix,
  listVersions,
  rollbackToVersionId,
  sha256Etag,
};