using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;

namespace Svrnty.CQRS.Events.Abstractions.Sagas;

/// <summary>
/// Persistent storage for saga state.
/// </summary>
public interface ISagaStateStore
{
    /// <summary>
    /// Save saga state.
    /// </summary>
    /// <param name="state">The saga state to save.</param>
    /// <param name="cancellationToken">Cancellation token.</param>
    Task SaveStateAsync(SagaStateSnapshot state, CancellationToken cancellationToken = default);

    /// <summary>
    /// Load saga state.
    /// </summary>
    /// <param name="sagaId">The saga ID.</param>
    /// <param name="cancellationToken">Cancellation token.</param>
    /// <returns>The saga state, or null if not found.</returns>
    Task<SagaStateSnapshot?> LoadStateAsync(string sagaId, CancellationToken cancellationToken = default);

    /// <summary>
    /// Get all sagas for a correlation ID.
    /// </summary>
    /// <param name="correlationId">The correlation ID.</param>
    /// <param name="cancellationToken">Cancellation token.</param>
    /// <returns>List of saga states.</returns>
    Task<List<SagaStateSnapshot>> GetByCorrelationIdAsync(
        string correlationId,
        CancellationToken cancellationToken = default);

    /// <summary>
    /// Get sagas by state.
    /// </summary>
    /// <param name="state">The saga state to filter by.</param>
    /// <param name="cancellationToken">Cancellation token.</param>
    /// <returns>List of saga states.</returns>
    Task<List<SagaStateSnapshot>> GetByStateAsync(
        SagaState state,
        CancellationToken cancellationToken = default);

    /// <summary>
    /// Delete saga state.
    /// </summary>
    /// <param name="sagaId">The saga ID to delete.</param>
    /// <param name="cancellationToken">Cancellation token.</param>
    Task DeleteStateAsync(string sagaId, CancellationToken cancellationToken = default);
}

/// <summary>
/// Snapshot of saga state for persistence.
/// </summary>
public sealed record SagaStateSnapshot
{
    /// <summary>
    /// Saga instance ID.
    /// </summary>
    public required string SagaId { get; init; }

    /// <summary>
    /// Correlation ID.
    /// </summary>
    public required string CorrelationId { get; init; }

    /// <summary>
    /// Saga type name.
    /// </summary>
    public required string SagaName { get; init; }

    /// <summary>
    /// Current state.
    /// </summary>
    public SagaState State { get; init; }

    /// <summary>
    /// Current step index.
    /// </summary>
    public int CurrentStep { get; init; }

    /// <summary>
    /// Total number of steps.
    /// </summary>
    public int TotalSteps { get; init; }

    /// <summary>
    /// Completed steps (for compensation tracking).
    /// </summary>
    public List<string> CompletedSteps { get; init; } = new();

    /// <summary>
    /// When the saga started.
    /// </summary>
    public DateTimeOffset StartedAt { get; init; }

    /// <summary>
    /// When the saga was last updated.
    /// </summary>
    public DateTimeOffset LastUpdated { get; init; }

    /// <summary>
    /// When the saga completed (if completed).
    /// </summary>
    public DateTimeOffset? CompletedAt { get; init; }

    /// <summary>
    /// Error message (if failed).
    /// </summary>
    public string? ErrorMessage { get; init; }

    /// <summary>
    /// Saga data (serialized as JSON or similar).
    /// </summary>
    public Dictionary<string, object> Data { get; init; } = new();
}