import 'trading_config.dart';

/// Why a trade was rejected. `null` means the guardrails passed.
enum GuardrailRejectionReason {
  tradingDisabled,
  blocklistedSymbol,
  symbolNotInWatchlist,
  maxOrdersPerDayExceeded,
  maxNotionalUsdPer4hExceeded,
  serverMaxNotionalUsdExceeded,
  questionRequired,
  unansweredQuestion,
  livePaperMismatch,
}

/// Outcome of a guardrail check.
class GuardrailDecision {
  GuardrailDecision._({required this.allowed, this.reason, this.detail});

  factory GuardrailDecision.allow() =>
      GuardrailDecision._(allowed: true);

  factory GuardrailDecision.reject(
    GuardrailRejectionReason reason, {
    String? detail,
  }) =>
      GuardrailDecision._(allowed: false, reason: reason, detail: detail);

  final bool allowed;
  final GuardrailRejectionReason? reason;
  final String? detail;

  @override
  String toString() => allowed
      ? 'GuardrailDecision.allow'
      : 'GuardrailDecision.reject(${reason!.name}${detail == null ? '' : ': $detail'})';
}

/// Pre-trade safety checks executed before any Alpaca POST.
///
/// Guardrails take precedence over user-supplied config: even if config sets
/// `max_notional_usd_per_4h` higher than [serverMaxNotionalUsd], the server
/// ceiling wins.
///
/// The notional cap is a **rolling 4-hour window** — not a calendar-day cap —
/// so a strategy can "double down" later in the day when a thesis continues
/// to look attractive, while still bounding the blast radius of a runaway
/// rule. Order-count is still a calendar-day cap.
class Guardrails {
  Guardrails({
    this.serverMaxNotionalUsd = 50,
    this.allowLive = false,
    this.windowDuration = const Duration(hours: 4),
  });

  /// Hard server-side ceiling per order regardless of user config.
  final num serverMaxNotionalUsd;

  /// Server-wide live-trading allow flag (mirrors `ALPACA_ALLOW_LIVE`).
  final bool allowLive;

  /// Width of the rolling window used for [maxNotionalUsdPer4h]. Callers must
  /// compute [notionalUsdInWindow] using this same duration (typically a
  /// `SELECT … WHERE submitted_at >= now() - INTERVAL '4 hours'` on
  /// `trade_orders`).
  final Duration windowDuration;

  GuardrailDecision check({
    required EffectiveTradingConfig config,
    required String symbol,
    required num notionalUsd,
    required int dailyOrderCount,
    required num notionalUsdInWindow,
    required bool hasUnansweredQuestion,
    required bool questionAnswered,
  }) {
    if (!config.enabled) {
      return GuardrailDecision.reject(
        GuardrailRejectionReason.tradingDisabled,
        detail: 'user trading config is disabled',
      );
    }

    if (config.mode == 'live' && !allowLive) {
      return GuardrailDecision.reject(
        GuardrailRejectionReason.livePaperMismatch,
        detail: 'live mode requires ALPACA_ALLOW_LIVE=true',
      );
    }

    if (config.guardrails.symbolsBlocklist.contains(symbol)) {
      return GuardrailDecision.reject(
        GuardrailRejectionReason.blocklistedSymbol,
        detail: symbol,
      );
    }

    final Set<String> watchlist = <String>{
      for (final DataInputConfig input in config.dataInputs) ...input.symbols,
    };
    if (watchlist.isNotEmpty && !watchlist.contains(symbol)) {
      return GuardrailDecision.reject(
        GuardrailRejectionReason.symbolNotInWatchlist,
        detail: symbol,
      );
    }

    if (notionalUsd > serverMaxNotionalUsd) {
      return GuardrailDecision.reject(
        GuardrailRejectionReason.serverMaxNotionalUsdExceeded,
        detail: '$notionalUsd > server ceiling $serverMaxNotionalUsd',
      );
    }

    if (dailyOrderCount >= config.guardrails.maxOrdersPerDay) {
      return GuardrailDecision.reject(
        GuardrailRejectionReason.maxOrdersPerDayExceeded,
        detail:
            '$dailyOrderCount >= ${config.guardrails.maxOrdersPerDay}',
      );
    }

    if (notionalUsdInWindow + notionalUsd >
        config.guardrails.maxNotionalUsdPer4h) {
      return GuardrailDecision.reject(
        GuardrailRejectionReason.maxNotionalUsdPer4hExceeded,
        detail:
            '${notionalUsdInWindow + notionalUsd} > ${config.guardrails.maxNotionalUsdPer4h} in ${windowDuration.inHours}h window',
      );
    }

    if (config.guardrails.requireQuestionBeforeOrder) {
      if (!questionAnswered) {
        return GuardrailDecision.reject(
          GuardrailRejectionReason.questionRequired,
          detail: 'no confirming answer on file',
        );
      }
      if (hasUnansweredQuestion) {
        return GuardrailDecision.reject(
          GuardrailRejectionReason.unansweredQuestion,
          detail: 'resolve open question before submitting order',
        );
      }
    }

    return GuardrailDecision.allow();
  }
}