using System.Collections.Concurrent;
using NeonSprawl.Server.Game.Rewards;

namespace NeonSprawl.Server.Game.Contracts;

/// <summary>Thread-safe in-memory append-only contract outcome audit log (NEO-146).</summary>
public sealed class InMemoryContractOutcomeStore : IContractOutcomeStore
{
    private readonly ConcurrentDictionary<string, ContractOutcomeRow> rowsById = new(StringComparer.Ordinal);

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

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

    /// <inheritdoc />
    public bool TryAppend(ContractOutcomeRow row)
    {
        if (!TryNormalizeRow(row, out var normalized))
        {
            return false;
        }

        lock (idLocks.GetOrAdd(normalized.Id, _ => new object()))
        {
            if (rowsById.ContainsKey(normalized.Id) ||
                rowIdByIdempotencyKey.ContainsKey(normalized.IdempotencyKey))
            {
                return false;
            }

            rowsById[normalized.Id] = normalized;
            rowIdByIdempotencyKey[normalized.IdempotencyKey] = normalized.Id;
            return true;
        }
    }

    /// <inheritdoc />
    public bool TryGetByIdempotencyKey(string idempotencyKey, out ContractOutcomeRow row)
    {
        row = null!;
        var key = idempotencyKey?.Trim();
        if (string.IsNullOrEmpty(key))
        {
            return false;
        }

        if (!rowIdByIdempotencyKey.TryGetValue(key, out var rowId) ||
            !rowsById.TryGetValue(rowId, out var stored))
        {
            return false;
        }

        row = stored;
        return true;
    }

    /// <inheritdoc />
    public IReadOnlyList<ContractOutcomeRow> GetOutcomesForInstance(string contractInstanceId, int? limit = null)
    {
        var instanceId = ContractInstanceIds.NormalizeContractInstanceId(contractInstanceId);
        if (instanceId.Length == 0)
        {
            return [];
        }

        IEnumerable<ContractOutcomeRow> query = rowsById.Values
            .Where(r => string.Equals(r.ContractInstanceId, instanceId, StringComparison.Ordinal))
            .OrderBy(static r => r.RecordedAt)
            .ThenBy(static r => r.Id, StringComparer.Ordinal);

        if (limit is > 0)
        {
            query = query.Take(limit.Value);
        }

        return [..query];
    }

    /// <inheritdoc />
    public bool TryClearForInstance(string contractInstanceId)
    {
        var instanceId = ContractInstanceIds.NormalizeContractInstanceId(contractInstanceId);
        if (instanceId.Length == 0)
        {
            return false;
        }

        string[] idsToRemove = [.. rowsById.Values
            .Where(row => string.Equals(row.ContractInstanceId, instanceId, StringComparison.Ordinal))
            .Select(static row => row.Id)];

        foreach (var id in idsToRemove)
        {
            if (rowsById.TryRemove(id, out var removed))
            {
                rowIdByIdempotencyKey.TryRemove(removed.IdempotencyKey, out _);
            }

            idLocks.TryRemove(id, out _);
        }

        return true;
    }

    private static bool TryNormalizeRow(ContractOutcomeRow row, out ContractOutcomeRow normalized)
    {
        normalized = null!;
        var id = row.Id.Trim();
        var playerId = ContractInstanceIds.NormalizePlayerId(row.PlayerId);
        var instanceId = ContractInstanceIds.NormalizeContractInstanceId(row.ContractInstanceId);
        var idempotencyKey = row.IdempotencyKey.Trim();
        if (id.Length == 0 ||
            playerId.Length == 0 ||
            instanceId.Length == 0 ||
            idempotencyKey.Length == 0)
        {
            return false;
        }

        normalized = row with
        {
            Id = id,
            PlayerId = playerId,
            ContractInstanceId = instanceId,
            IdempotencyKey = idempotencyKey,
            GrantedItems = [..row.GrantedItems],
            GrantedSkillXp = [..row.GrantedSkillXp],
            GrantedReputation = [..row.GrantedReputation],
        };
        return true;
    }
}