using NeonSprawl.Server.Game.PositionState;

namespace NeonSprawl.Server.Game.Encounters;

/// <summary>Maps <c>GET /game/players/{{id}}/encounter-progress</c> (NEO-108).</summary>
public static class EncounterProgressApi
{
    public const string StateInactive = "inactive";
    public const string StateActive = "active";
    public const string StateCompleted = "completed";

    public static WebApplication MapEncounterProgressApi(this WebApplication app)
    {
        app.MapGet(
            "/game/players/{id}/encounter-progress",
            (string id, IPositionStateStore positions, IEncounterDefinitionRegistry encounterRegistry,
                IEncounterProgressStore progressStore, IEncounterCompletionStore completionStore,
                IEncounterCompleteEventStore completeEventStore) =>
            {
                var trimmedId = id.Trim();
                if (trimmedId.Length == 0 || !positions.TryGetPosition(trimmedId, out _))
                {
                    return Results.NotFound();
                }

                return Results.Json(
                    BuildSnapshot(
                        trimmedId,
                        encounterRegistry,
                        progressStore,
                        completionStore,
                        completeEventStore));
            });

        return app;
    }

    internal static EncounterProgressListResponse BuildSnapshot(
        string playerId,
        IEncounterDefinitionRegistry encounterRegistry,
        IEncounterProgressStore progressStore,
        IEncounterCompletionStore completionStore,
        IEncounterCompleteEventStore completeEventStore)
    {
        var defs = encounterRegistry.GetDefinitionsInIdOrder();
        var rows = new List<EncounterProgressRowJson>(defs.Count);
        foreach (var def in defs)
        {
            rows.Add(
                MapRow(
                    playerId,
                    def.Id,
                    progressStore,
                    completionStore,
                    completeEventStore));
        }

        return new EncounterProgressListResponse
        {
            PlayerId = playerId,
            Encounters = rows,
            SchemaVersion = EncounterProgressListResponse.CurrentSchemaVersion,
        };
    }

    private static EncounterProgressRowJson MapRow(
        string playerId,
        string encounterId,
        IEncounterProgressStore progressStore,
        IEncounterCompletionStore completionStore,
        IEncounterCompleteEventStore completeEventStore)
    {
        var hasProgress = progressStore.TryGetProgress(playerId, encounterId, out var progress);
        var defeatedTargetIds = hasProgress
            ? [.. progress.DefeatedNpcInstanceIds.OrderBy(static id => id, StringComparer.Ordinal)]
            : Array.Empty<string>();

        if (completionStore.IsCompleted(playerId, encounterId))
        {
            if (!completionStore.TryGetCompletedAt(playerId, encounterId, out var completedAt))
            {
                throw new InvalidOperationException(
                    $"Encounter '{encounterId}' is completed for player '{playerId}' but completedAt is missing.");
            }

            if (!completeEventStore.TryGet(playerId, encounterId, out var completeEvent))
            {
                throw new InvalidOperationException(
                    $"Encounter '{encounterId}' is completed for player '{playerId}' but EncounterCompleteEvent is missing.");
            }

            return new EncounterProgressRowJson
            {
                EncounterId = encounterId,
                State = StateCompleted,
                DefeatedTargetIds = defeatedTargetIds,
                CompletedAt = completedAt,
                RewardGrantSummary = MapGrantSummary(completeEvent.GrantedItems),
            };
        }

        if (hasProgress && progress.Started)
        {
            return new EncounterProgressRowJson
            {
                EncounterId = encounterId,
                State = StateActive,
                DefeatedTargetIds = defeatedTargetIds,
            };
        }

        return new EncounterProgressRowJson
        {
            EncounterId = encounterId,
            State = StateInactive,
            DefeatedTargetIds = defeatedTargetIds,
        };
    }

    /// <summary>Preserves commit-time grant order from <see cref="EncounterCompleteEvent.GrantedItems"/> (reward-table apply order).</summary>
    private static List<EncounterRewardGrantJson> MapGrantSummary(IReadOnlyList<EncounterGrantApplied> grants)
    {
        var summary = new List<EncounterRewardGrantJson>(grants.Count);
        foreach (var grant in grants)
        {
            summary.Add(
                new EncounterRewardGrantJson
                {
                    ItemId = grant.ItemId,
                    Quantity = grant.Quantity,
                });
        }

        return summary;
    }
}