import 'dart:math';

import 'package:postgres/postgres.dart';

import 'market_data_db.dart' show MarketDataDb;
import 'market_history_bar_placeholder.dart';
import 'market_history_config.dart';
import 'market_history_session_slot.dart';
import 'tradable_assets_db.dart';

/// One symbol's rolling-window 4-hour bar summary for the guessing game.
class WeeklyMover {
  WeeklyMover({
    required this.symbol,
    required this.openClose,
    required this.currentClose,
    required this.days,
  });

  final String symbol;
  final num openClose;
  final num currentClose;

  /// Number of 4-hour bars in the window (≥ [MarketHistoryConfig.minBarsForGuess]).
  final int days;
}

/// Read-side queries over 4-hour history bars for question rules.
class MarketHistoryQuery {
  MarketHistoryQuery({
    required Connection connection,
    TradableAssetsDb? tradableAssetsDb,
  })  : _connection = connection,
        _tradableAssetsDb = tradableAssetsDb ?? TradableAssetsDb(connection);

  final Connection _connection;
  final TradableAssetsDb _tradableAssetsDb;

  /// Symbols with ≥ [minBars] 4-hour closes in [`asOf` − window, `asOf`), whose
  /// newest bar is not older than [maxStalenessDays] before [asOf].
  ///
  /// When [random] is set, eligible rows are sorted by symbol then shuffled for
  /// a stable pick order across runs with the same seed.
  Future<List<WeeklyMover>> weeklyMovers({
    required DateTime asOf,
    int minBars = MarketHistoryConfig.minBarsForGuess,
    int windowDays = MarketHistoryConfig.windowDays,
    int maxStalenessDays = 2,
    Random? random,
  }) async {
    final DateTime until = asOf.toUtc();
    final DateTime since =
        MarketHistorySessionSlot.windowFirstSlotStart(until, windowDays);
    final DateTime freshSince =
        until.subtract(Duration(days: maxStalenessDays));

    final List<String> active =
        await _tradableAssetsDb.listActiveTradableSymbols();
    if (active.isEmpty) {
      return <WeeklyMover>[];
    }

    final Result rows = await _connection.execute(
      Sql.named(
        '''
        WITH bars AS (
          SELECT symbol, as_of, price
          FROM market_data_snapshots
          WHERE metric = 'bar'
            AND timeframe = @timeframe
            AND as_of >= @since
            AND as_of < @until
            AND symbol = ANY(@symbols)
            AND ${MarketHistoryBarPlaceholder.sqlExcludePlaceholders}
            AND price IS NOT NULL
        ),
        agg AS (
          SELECT
            symbol,
            COUNT(*)::int AS bar_count,
            MIN(as_of) AS oldest_as_of,
            MAX(as_of) AS newest_as_of
          FROM bars
          GROUP BY symbol
          HAVING COUNT(*) >= @min_bars
            AND MAX(as_of) >= @fresh_since
        )
        SELECT
          a.symbol,
          a.bar_count,
          (
            SELECT b.price
            FROM bars b
            WHERE b.symbol = a.symbol AND b.as_of = a.oldest_as_of
            LIMIT 1
          ) AS open_close,
          (
            SELECT b.price
            FROM bars b
            WHERE b.symbol = a.symbol AND b.as_of = a.newest_as_of
            LIMIT 1
          ) AS current_close
        FROM agg a
        ORDER BY a.symbol ASC
        ''',
      ),
      parameters: <String, dynamic>{
        'since': since,
        'until': until,
        'symbols': active,
        'timeframe': MarketHistoryConfig.barTimeframe,
        'min_bars': minBars,
        'fresh_since': freshSince,
      },
    );

    final List<WeeklyMover> movers = <WeeklyMover>[];
    for (final ResultRow row in rows) {
      final num? openClose = MarketDataDb.readOptionalNumeric(row[2]);
      final num? currentClose = MarketDataDb.readOptionalNumeric(row[3]);
      if (openClose == null || currentClose == null) {
        continue;
      }
      movers.add(
        WeeklyMover(
          symbol: row[0]! as String,
          openClose: openClose,
          currentClose: currentClose,
          days: (row[1]! as num).toInt(),
        ),
      );
    }

    if (random != null && movers.length > 1) {
      movers.shuffle(random);
    }
    return movers;
  }
}