import 'package:postgres/postgres.dart';

import 'market_history_config.dart';
import 'market_history_prospective_questions.dart';
import 'market_history_session_slot.dart';
import 'sync_run_recorder.dart';

/// Outcome of a [MarketDataRetention] cleanup pass.
class MarketDataRetentionResult {
  MarketDataRetentionResult({
    required this.rowsRemoved,
    required this.startedAt,
    required this.finishedAt,
    this.error,
  });

  final int rowsRemoved;
  final DateTime startedAt;
  final DateTime finishedAt;
  final String? error;

  bool get succeeded => error == null;
}

/// Prunes [market_data_snapshots] older than the rolling window.
///
/// Phase 1 ([runCleanup]): hard-delete in batches.
/// Phase 2 ([runArchiveAndCleanup]): copy expired rows into
/// [market_data_archive] inside the same transaction, then delete.
class MarketDataRetention {
  MarketDataRetention({
    required Connection connection,
    this.windowDays = MarketHistoryConfig.windowDays,
    this.batchSize = MarketHistoryConfig.retentionBatchSize,
    void Function(String sql)? onExecute,
  })  : _connection = connection,
        _recorder = SyncRunRecorder(connection),
        _onExecute = onExecute;

  final Connection _connection;
  final SyncRunRecorder _recorder;
  final void Function(String sql)? _onExecute;

  final int windowDays;
  final int batchSize;

  static const String kind = 'cleanup';

  /// Hard-delete rows older than the [windowDays] trading-day sync window.
  Future<MarketDataRetentionResult> runCleanup({DateTime? now}) {
    return run(archive: false, now: now);
  }

  /// Archive-then-delete for rows older than the [windowDays] trading-day window.
  Future<MarketDataRetentionResult> runArchiveAndCleanup({DateTime? now}) {
    return run(archive: true, now: now);
  }

  /// Dispatches to hard-delete or archive mode.
  Future<MarketDataRetentionResult> run({
    bool archive = false,
    DateTime? now,
    int? windowDays,
  }) async {
    final DateTime tick = (now ?? DateTime.now()).toUtc();
    final int effectiveWindow = windowDays ?? this.windowDays;

    final SyncRunOutcome outcome = await _recorder.record(
      kind,
      () => _cleanupBody(
        now: tick,
        windowDays: effectiveWindow,
        archive: archive,
      ),
      now: tick,
    );

    return MarketDataRetentionResult(
      rowsRemoved: outcome.rowsRemoved,
      startedAt: outcome.startedAt,
      finishedAt: outcome.finishedAt,
      error: outcome.error,
    );
  }

  Future<SyncRunCounts> _cleanupBody({
    required DateTime now,
    required int windowDays,
    required bool archive,
  }) async {
    final DateTime cutoff =
        MarketHistorySessionSlot.windowFirstSlotStart(now, windowDays);
    int totalRemoved = 0;

    while (true) {
      final int removed = archive
          ? await _archiveAndDeleteBatch(cutoff)
          : await _deleteBatch(cutoff);
      if (removed == 0) {
        break;
      }
      totalRemoved += removed;
    }

    totalRemoved += await MarketHistoryProspectiveQuestions(
      connection: _connection,
    ).deleteExpiredBefore(cutoff);

    return SyncRunCounts(rowsRemoved: totalRemoved);
  }

  Future<int> _deleteBatch(DateTime cutoff) async {
    const String sql = '''
        WITH doomed AS (
          SELECT id
          FROM market_data_snapshots
          WHERE as_of < @cutoff
          LIMIT @batch_size
        )
        DELETE FROM market_data_snapshots
        WHERE id IN (SELECT id FROM doomed)
        RETURNING id
        ''';
    _onExecute?.call(sql);
    final Result result = await _connection.execute(
      Sql.named(sql),
      parameters: <String, dynamic>{
        'cutoff': cutoff,
        'batch_size': batchSize,
      },
    );
    return result.length;
  }

  Future<int> _archiveAndDeleteBatch(DateTime cutoff) async {
    const String sql = '''
          WITH doomed AS (
            SELECT id, symbol, asset_class, feed, metric, timeframe,
                   price, volume, as_of, raw
            FROM market_data_snapshots
            WHERE as_of < @cutoff
            LIMIT @batch_size
          ),
          inserted AS (
            INSERT INTO market_data_archive (
              symbol, asset_class, feed, metric, timeframe,
              price, volume, as_of, raw, archived_at
            )
            SELECT symbol, asset_class, feed, metric, timeframe,
                   price, volume, as_of, raw, now()
            FROM doomed
            RETURNING id
          )
          DELETE FROM market_data_snapshots m
          USING doomed d
          WHERE m.id = d.id
          RETURNING m.id
          ''';
    int removed = 0;
    await _connection.runTx((TxSession tx) async {
      _onExecute?.call(sql);
      final Result archived = await tx.execute(
        Sql.named(sql),
        parameters: <String, dynamic>{
          'cutoff': cutoff,
          'batch_size': batchSize,
        },
      );
      removed = archived.length;
    });
    return removed;
  }
}