using System;
using Svrnty.CQRS.Events.Abstractions.Replay;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
using Svrnty.CQRS.Events.Abstractions.Models;

namespace Svrnty.CQRS.Events.Abstractions.Replay;

/// <summary>
/// Service for replaying historical events from persistent streams.
/// Enables rebuilding projections, reprocessing events, and time-travel debugging.
/// </summary>
public interface IEventReplayService
{
    /// <summary>
    /// Replay events from a specific offset.
    /// </summary>
    /// <param name="streamName">Stream to replay from.</param>
    /// <param name="startOffset">Starting offset (inclusive).</param>
    /// <param name="options">Replay options.</param>
    /// <param name="cancellationToken">Cancellation token.</param>
    /// <returns>Async enumerable of events.</returns>
    /// <remarks>
    /// Events are returned in offset order (oldest first).
    /// Use ReplayOptions to control batch size, rate limiting, and filtering.
    /// </remarks>
    IAsyncEnumerable<StoredEvent> ReplayFromOffsetAsync(
        string streamName,
        long startOffset,
        ReplayOptions? options = null,
        CancellationToken cancellationToken = default);

    /// <summary>
    /// Replay events from a specific timestamp.
    /// </summary>
    /// <param name="streamName">Stream to replay from.</param>
    /// <param name="startTime">Starting timestamp (UTC, inclusive).</param>
    /// <param name="options">Replay options.</param>
    /// <param name="cancellationToken">Cancellation token.</param>
    /// <returns>Async enumerable of events.</returns>
    /// <remarks>
    /// Finds the first event at or after the specified timestamp.
    /// All subsequent events are returned in order.
    /// </remarks>
    IAsyncEnumerable<StoredEvent> ReplayFromTimeAsync(
        string streamName,
        DateTimeOffset startTime,
        ReplayOptions? options = null,
        CancellationToken cancellationToken = default);

    /// <summary>
    /// Replay events within a time range.
    /// </summary>
    /// <param name="streamName">Stream to replay from.</param>
    /// <param name="startTime">Starting timestamp (UTC, inclusive).</param>
    /// <param name="endTime">Ending timestamp (UTC, exclusive).</param>
    /// <param name="options">Replay options.</param>
    /// <param name="cancellationToken">Cancellation token.</param>
    /// <returns>Async enumerable of events.</returns>
    /// <remarks>
    /// Only events with stored_at >= startTime AND stored_at < endTime are returned.
    /// Useful for replaying specific time periods.
    /// </remarks>
    IAsyncEnumerable<StoredEvent> ReplayTimeRangeAsync(
        string streamName,
        DateTimeOffset startTime,
        DateTimeOffset endTime,
        ReplayOptions? options = null,
        CancellationToken cancellationToken = default);

    /// <summary>
    /// Replay all events in a stream from the beginning.
    /// </summary>
    /// <param name="streamName">Stream to replay from.</param>
    /// <param name="options">Replay options.</param>
    /// <param name="cancellationToken">Cancellation token.</param>
    /// <returns>Async enumerable of events.</returns>
    /// <remarks>
    /// Equivalent to ReplayFromOffsetAsync(streamName, 0, options).
    /// Use for complete stream replay when rebuilding projections.
    /// </remarks>
    IAsyncEnumerable<StoredEvent> ReplayAllAsync(
        string streamName,
        ReplayOptions? options = null,
        CancellationToken cancellationToken = default);

    /// <summary>
    /// Get the total count of events that would be replayed.
    /// </summary>
    /// <param name="streamName">Stream to count events for.</param>
    /// <param name="startOffset">Starting offset (optional).</param>
    /// <param name="startTime">Starting timestamp (optional).</param>
    /// <param name="endTime">Ending timestamp (optional).</param>
    /// <param name="options">Replay options (for event type filtering).</param>
    /// <param name="cancellationToken">Cancellation token.</param>
    /// <returns>Count of events matching the criteria.</returns>
    /// <remarks>
    /// Useful for estimating replay duration and showing progress.
    /// Counts only events matching the event type filter if specified.
    /// </remarks>
    Task<long> GetReplayCountAsync(
        string streamName,
        long? startOffset = null,
        DateTimeOffset? startTime = null,
        DateTimeOffset? endTime = null,
        ReplayOptions? options = null,
        CancellationToken cancellationToken = default);
}