using System.Collections.Concurrent;
using Microsoft.Extensions.Options;
using NeonSprawl.Server.Game.PositionState;

namespace NeonSprawl.Server.Game.Factions;

/// <summary>Thread-safe in-memory faction standing; seeds the configured dev player (NEO-135).</summary>
public sealed class InMemoryFactionStandingStore(
    IOptions<GamePositionOptions> options,
    IFactionDefinitionRegistry factionRegistry) : IFactionStandingStore
{
    private readonly HashSet<string> knownPlayers = CreateKnownPlayers(options.Value);

    private readonly ConcurrentDictionary<string, int> standingByKey = new(StringComparer.Ordinal);

    private readonly ConcurrentDictionary<string, object> keyLocks = new(StringComparer.Ordinal);

    private static HashSet<string> CreateKnownPlayers(GamePositionOptions o)
    {
        var id = FactionStandingIds.NormalizePlayerId(o.DevPlayerId);
        if (id.Length == 0)
        {
            throw new InvalidOperationException("Game:DevPlayerId must be non-empty.");
        }

        return new HashSet<string>(StringComparer.OrdinalIgnoreCase) { id };
    }

    /// <inheritdoc />
    public bool CanWritePlayer(string playerId)
    {
        var player = FactionStandingIds.NormalizePlayerId(playerId);
        return player.Length > 0 && knownPlayers.Contains(player);
    }

    /// <inheritdoc />
    public FactionStandingReadOutcome TryGetStanding(string playerId, string factionId)
    {
        var player = FactionStandingIds.NormalizePlayerId(playerId);
        var faction = FactionStandingIds.NormalizeFactionId(factionId);
        if (player.Length == 0)
        {
            return DenyRead(FactionStandingReasonCodes.PlayerNotWritable);
        }

        if (faction.Length == 0)
        {
            return DenyRead(FactionStandingReasonCodes.UnknownFaction);
        }

        if (!factionRegistry.TryGetDefinition(faction, out var definition) || definition is null)
        {
            return DenyRead(FactionStandingReasonCodes.UnknownFaction);
        }

        if (!CanWritePlayer(player))
        {
            return DenyRead(FactionStandingReasonCodes.PlayerNotWritable);
        }

        var key = FactionStandingIds.MakeStandingKey(player, faction);
        var raw = standingByKey.GetValueOrDefault(key, 0);
        return new FactionStandingReadOutcome(true, null, FactionStandingIds.ClampStanding(raw, definition));
    }

    /// <inheritdoc />
    public FactionStandingMutationOutcome TryApplyStandingDelta(string playerId, string factionId, int deltaAmount)
    {
        var player = FactionStandingIds.NormalizePlayerId(playerId);
        var faction = FactionStandingIds.NormalizeFactionId(factionId);
        if (player.Length == 0)
        {
            return DenyMutation(FactionStandingReasonCodes.PlayerNotWritable);
        }

        if (faction.Length == 0)
        {
            return DenyMutation(FactionStandingReasonCodes.UnknownFaction);
        }

        if (!factionRegistry.TryGetDefinition(faction, out var definition) || definition is null)
        {
            return DenyMutation(FactionStandingReasonCodes.UnknownFaction);
        }

        if (!CanWritePlayer(player))
        {
            return DenyMutation(FactionStandingReasonCodes.PlayerNotWritable);
        }

        var key = FactionStandingIds.MakeStandingKey(player, faction);
        lock (keyLocks.GetOrAdd(key, _ => new object()))
        {
            var raw = standingByKey.GetValueOrDefault(key, 0);
            var previousStanding = FactionStandingIds.ClampStanding(raw, definition);
            var newStanding = FactionStandingIds.ClampStanding(raw + deltaAmount, definition);
            standingByKey[key] = newStanding;
            return new FactionStandingMutationOutcome(true, null, previousStanding, newStanding);
        }
    }

    private static FactionStandingReadOutcome DenyRead(string reasonCode) =>
        new(false, reasonCode, 0);

    private static FactionStandingMutationOutcome DenyMutation(string reasonCode) =>
        new(false, reasonCode, 0, 0);

    /// <summary>Test-only seed of raw standing before read-clamp (NEO-135 unit tests).</summary>
    internal void SeedRawStandingForTests(string playerId, string factionId, int rawStanding)
    {
        var player = FactionStandingIds.NormalizePlayerId(playerId);
        var faction = FactionStandingIds.NormalizeFactionId(factionId);
        if (player.Length == 0 || faction.Length == 0 || !CanWritePlayer(player))
        {
            return;
        }

        var key = FactionStandingIds.MakeStandingKey(player, faction);
        lock (keyLocks.GetOrAdd(key, _ => new object()))
        {
            standingByKey[key] = rawStanding;
        }
    }
}