import 'dart:convert';

import 'package:drift/drift.dart';
import 'package:drift_flutter/drift_flutter.dart';

part 'response_cache.g.dart';

/// The last successful body of one GET, keyed by endpoint+params exactly as
/// [CacheInterceptor] builds the key. See `docs/ai/offline-cache.md` for the
/// whole contract this table is part of.
class CachedResponses extends Table {
  TextColumn get requestKey => text()();
  TextColumn get body => text()();
  DateTimeColumn get fetchedAt => dateTime()();

  @override
  Set<Column> get primaryKey => {requestKey};
}

/// A cached body plus when it was fetched — what [CacheInterceptor] needs to
/// rebuild a synthetic [Response] when the network itself is unreachable.
///
/// Not named `CachedResponse`: drift already generates a row class with that
/// name for the `CachedResponses` table above.
class CacheEntry {
  const CacheEntry(this.body, this.fetchedAt);
  final Object? body;
  final DateTime fetchedAt;
}

@DriftDatabase(tables: [CachedResponses])
class ResponseCacheDatabase extends _$ResponseCacheDatabase {
  ResponseCacheDatabase() : super(_openConnection());
  ResponseCacheDatabase.forTesting(super.executor);

  @override
  int get schemaVersion => 1;

  /// Replaces whatever was cached for [requestKey] — one row per endpoint+params,
  /// never a history.
  Future<void> put(String requestKey, Object? body) =>
      into(cachedResponses).insertOnConflictUpdate(
        CachedResponsesCompanion.insert(
          requestKey: requestKey,
          body: jsonEncode(body),
          fetchedAt: DateTime.now(),
        ),
      );

  /// Drops every cached body — on sign-out, so the next account (or nobody) never sees them.
  Future<void> clear() => delete(cachedResponses).go();

  /// The body last stored for [requestKey], or null if this endpoint+params was
  /// never fetched successfully on this device.
  Future<CacheEntry?> get(String requestKey) async {
    final row = await (select(
      cachedResponses,
    )..where((t) => t.requestKey.equals(requestKey))).getSingleOrNull();
    if (row == null) return null;
    return CacheEntry(jsonDecode(row.body), row.fetchedAt);
  }
}

/// One sqlite file via native FFI on Android/iOS/desktop; wasm+OPFS (falling
/// back to IndexedDB) on web — `driftDatabase` from `package:drift_flutter`
/// picks the right backend, `web/sqlite3.wasm` and `web/drift_worker.js` are
/// the compiled assets it loads there (regenerate with `just app-web-assets`
/// whenever the `drift`/`sqlite3` package versions change).
QueryExecutor _openConnection() => driftDatabase(
  name: 'response_cache',
  web: DriftWebOptions(
    sqlite3Wasm: Uri.parse('sqlite3.wasm'),
    driftWorker: Uri.parse('drift_worker.js'),
  ),
);