using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Svrnty.CQRS.Sagas.Abstractions;
using Svrnty.CQRS.Sagas.Abstractions.Persistence;

namespace Svrnty.CQRS.Sagas.Persistence;

/// <summary>
/// In-memory saga state store for development and testing.
/// </summary>
public class InMemorySagaStateStore : ISagaStateStore
{
    private readonly ConcurrentDictionary<Guid, SagaState> _states = new();

    /// <inheritdoc />
    public Task<SagaState> CreateAsync(SagaState state, CancellationToken cancellationToken = default)
    {
        if (!_states.TryAdd(state.SagaId, state))
        {
            throw new InvalidOperationException($"Saga with ID {state.SagaId} already exists.");
        }
        return Task.FromResult(state);
    }

    /// <inheritdoc />
    public Task<SagaState?> GetByIdAsync(Guid sagaId, CancellationToken cancellationToken = default)
    {
        _states.TryGetValue(sagaId, out var state);
        return Task.FromResult(state);
    }

    /// <inheritdoc />
    public Task<SagaState?> GetByCorrelationIdAsync(Guid correlationId, CancellationToken cancellationToken = default)
    {
        var state = _states.Values.FirstOrDefault(s => s.CorrelationId == correlationId);
        return Task.FromResult(state);
    }

    /// <inheritdoc />
    public Task<SagaState> UpdateAsync(SagaState state, CancellationToken cancellationToken = default)
    {
        state.UpdatedAt = DateTimeOffset.UtcNow;
        _states[state.SagaId] = state;
        return Task.FromResult(state);
    }

    /// <inheritdoc />
    public Task<IReadOnlyList<SagaState>> GetPendingSagasAsync(CancellationToken cancellationToken = default)
    {
        var pending = _states.Values
            .Where(s => s.Status == SagaStatus.InProgress || s.Status == SagaStatus.Compensating)
            .ToList();
        return Task.FromResult<IReadOnlyList<SagaState>>(pending);
    }

    /// <inheritdoc />
    public Task<IReadOnlyList<SagaState>> GetSagasByStatusAsync(SagaStatus status, CancellationToken cancellationToken = default)
    {
        var sagas = _states.Values
            .Where(s => s.Status == status)
            .ToList();
        return Task.FromResult<IReadOnlyList<SagaState>>(sagas);
    }
}