namespace NeonSprawl.Server.Game.Quests;

/// <summary>
/// Server-authoritative quest accept, step advance, and complete with reason codes (NEO-117).
/// Objective wiring: E7M1-07 (NEO-118). HTTP: E7M1-08/09 (NEO-119/NEO-120).
/// </summary>
public static class QuestStateOperations
{
    /// <summary>
    /// Validates quest id and prerequisites, then activates at step 0 when not started.
    /// </summary>
    public static QuestStateOperationResult TryAccept(
        string playerId,
        string questId,
        IQuestDefinitionRegistry questRegistry,
        IPlayerQuestStateStore progressStore)
    {
        if (!questRegistry.TryNormalizeKnown(questId, out var normalizedQuestId) ||
            !questRegistry.TryGetDefinition(normalizedQuestId, out var definition))
        {
            return Deny(QuestStateReasonCodes.UnknownQuest);
        }

        if (progressStore.TryGetProgress(playerId, normalizedQuestId, out var existing))
        {
            return existing.Status switch
            {
                QuestProgressStatus.Completed => Deny(QuestStateReasonCodes.AlreadyCompleted, existing),
                QuestProgressStatus.Active => Deny(QuestStateReasonCodes.AlreadyActive, existing),
                _ => Deny(QuestStateReasonCodes.UnknownQuest),
            };
        }

        foreach (var prerequisiteId in definition.PrerequisiteQuestIds)
        {
            if (!progressStore.TryGetProgress(playerId, prerequisiteId, out var prerequisite) ||
                prerequisite.Status != QuestProgressStatus.Completed)
            {
                return Deny(QuestStateReasonCodes.PrerequisiteIncomplete);
            }
        }

        if (progressStore.TryActivate(playerId, normalizedQuestId, out var snapshot))
        {
            return Success(snapshot);
        }

        return Deny(QuestStateReasonCodes.UnknownPlayer);
    }

    /// <summary>
    /// Advances an active quest to <paramref name="newStepIndex"/> when within catalog bounds.
    /// </summary>
    public static QuestStateOperationResult TryAdvanceStep(
        string playerId,
        string questId,
        int newStepIndex,
        IQuestDefinitionRegistry questRegistry,
        IPlayerQuestStateStore progressStore)
    {
        if (!questRegistry.TryNormalizeKnown(questId, out var normalizedQuestId) ||
            !questRegistry.TryGetDefinition(normalizedQuestId, out var definition))
        {
            return Deny(QuestStateReasonCodes.UnknownQuest);
        }

        if (!progressStore.TryGetProgress(playerId, normalizedQuestId, out var existing))
        {
            return Deny(QuestStateReasonCodes.NotActive);
        }

        if (existing.Status == QuestProgressStatus.Completed)
        {
            return Deny(QuestStateReasonCodes.AlreadyCompleted, existing);
        }

        if (existing.Status != QuestProgressStatus.Active)
        {
            return Deny(QuestStateReasonCodes.NotActive);
        }

        if (newStepIndex <= existing.CurrentStepIndex || newStepIndex >= definition.Steps.Count)
        {
            return Deny(QuestStateReasonCodes.InvalidStepIndex, existing);
        }

        if (progressStore.TryAdvanceStep(playerId, normalizedQuestId, newStepIndex, out var snapshot))
        {
            return Success(snapshot);
        }

        return Deny(QuestStateReasonCodes.UnknownPlayer, existing);
    }

    /// <summary>
    /// Marks a quest complete. Idempotent: replays return success with the existing snapshot.
    /// </summary>
    public static QuestStateOperationResult TryMarkComplete(
        string playerId,
        string questId,
        IQuestDefinitionRegistry questRegistry,
        IPlayerQuestStateStore progressStore,
        TimeProvider timeProvider)
    {
        if (!questRegistry.TryNormalizeKnown(questId, out var normalizedQuestId) ||
            !questRegistry.TryGetDefinition(normalizedQuestId, out _))
        {
            return Deny(QuestStateReasonCodes.UnknownQuest);
        }

        if (progressStore.TryGetProgress(playerId, normalizedQuestId, out var existing) &&
            existing.Status == QuestProgressStatus.Completed)
        {
            return Success(existing);
        }

        if (!progressStore.TryGetProgress(playerId, normalizedQuestId, out var active) ||
            active.Status != QuestProgressStatus.Active)
        {
            return Deny(QuestStateReasonCodes.NotActive);
        }

        if (progressStore.TryMarkComplete(playerId, normalizedQuestId, timeProvider.GetUtcNow(), out var snapshot))
        {
            return Success(snapshot);
        }

        if (progressStore.TryGetProgress(playerId, normalizedQuestId, out var afterAttempt) &&
            afterAttempt.Status == QuestProgressStatus.Completed)
        {
            return Success(afterAttempt);
        }

        return Deny(QuestStateReasonCodes.UnknownPlayer);
    }

    private static QuestStateOperationResult Success(QuestStepState snapshot) =>
        new(Success: true, ReasonCode: null, Snapshot: snapshot);

    private static QuestStateOperationResult Deny(string reasonCode, QuestStepState? snapshot = null) =>
        new(Success: false, ReasonCode: reasonCode, Snapshot: snapshot);
}