using System;
using Svrnty.CQRS.Events.Abstractions.EventStore;
using Svrnty.CQRS.Events.Abstractions.Streaming;
using Svrnty.CQRS.Events.Subscriptions;
using Svrnty.CQRS.Events.Abstractions.Configuration;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Routing;
using Svrnty.CQRS.Events.Abstractions;

namespace Svrnty.CQRS.Events.Management;

/// <summary>
/// Extension methods for mapping event streaming management API endpoints.
/// </summary>
/// <remarks>
/// <para>
/// <strong>Phase 6 Feature:</strong>
/// Provides REST API for managing event streams, subscriptions, and consumers.
/// Useful for operational tasks, monitoring, and troubleshooting.
/// </para>
/// <para>
/// <strong>Security Note:</strong>
/// These endpoints expose operational data and allow modification of consumer state.
/// In production, use authorization policies to restrict access to administrators only.
/// </para>
/// </remarks>
public static class ManagementApiExtensions
{
    /// <summary>
    /// Maps event streaming management API endpoints.
    /// </summary>
    /// <param name="endpoints">The endpoint route builder.</param>
    /// <param name="routePrefix">Optional route prefix (default: "api/event-streams").</param>
    /// <returns>The endpoint route builder for chaining.</returns>
    /// <remarks>
    /// <para>
    /// <strong>Mapped Endpoints:</strong>
    /// - GET /api/event-streams - List all streams
    /// - GET /api/event-streams/{name} - Get stream details
    /// - GET /api/event-streams/{name}/subscriptions - List subscriptions
    /// - GET /api/event-streams/subscriptions/{id} - Get subscription details
    /// - GET /api/event-streams/subscriptions/{id}/consumers - List consumers (if supported)
    /// - GET /api/event-streams/subscriptions/{id}/consumers/{consumerId} - Get consumer info
    /// - POST /api/event-streams/subscriptions/{id}/consumers/{consumerId}/reset-offset - Reset offset
    /// - DELETE /api/event-streams/subscriptions/{id}/consumers/{consumerId} - Remove consumer
    /// </para>
    /// <para>
    /// <strong>Authorization:</strong>
    /// Consider adding .RequireAuthorization() to these endpoints in production.
    /// </para>
    /// </remarks>
    public static IEndpointRouteBuilder MapEventStreamManagementApi(
        this IEndpointRouteBuilder endpoints,
        string routePrefix = "api/event-streams")
    {
        var group = endpoints.MapGroup(routePrefix)
            .WithTags("Event Stream Management");

        // GET /api/event-streams - List all streams
        group.MapGet("/", GetAllStreams)
            .WithName("GetAllStreams")
            .WithSummary("List all event streams")
            .WithDescription("Returns information about all configured event streams including length and subscription count.");

        // GET /api/event-streams/{name} - Get stream details
        group.MapGet("/{name}", GetStream)
            .WithName("GetStream")
            .WithSummary("Get stream details")
            .WithDescription("Returns detailed information about a specific stream including its configuration and subscriptions.");

        // GET /api/event-streams/{name}/subscriptions - List subscriptions for a stream
        group.MapGet("/{name}/subscriptions", GetStreamSubscriptions)
            .WithName("GetStreamSubscriptions")
            .WithSummary("List subscriptions for a stream")
            .WithDescription("Returns all subscriptions consuming from the specified stream.");

        // GET /api/event-streams/subscriptions/{id} - Get subscription details
        group.MapGet("/subscriptions/{id}", GetSubscription)
            .WithName("GetSubscription")
            .WithSummary("Get subscription details")
            .WithDescription("Returns detailed information about a specific subscription.");

        // GET /api/event-streams/subscriptions/{id}/consumers/{consumerId} - Get consumer info
        group.MapGet("/subscriptions/{id}/consumers/{consumerId}", GetConsumerInfo)
            .WithName("GetConsumerInfo")
            .WithSummary("Get consumer position and lag")
            .WithDescription("Returns the current offset, lag, and status of a specific consumer.");

        // POST /api/event-streams/subscriptions/{id}/consumers/{consumerId}/reset-offset - Reset offset
        group.MapPost("/subscriptions/{id}/consumers/{consumerId}/reset-offset", ResetConsumerOffset)
            .WithName("ResetConsumerOffset")
            .WithSummary("Reset consumer offset")
            .WithDescription("Resets a consumer's offset to a specific position. Use 0 for beginning, -1 for latest.");

        return endpoints;
    }

    private static async Task<IResult> GetAllStreams(
        IEnumerable<IStreamConfiguration> streamConfigurations,
        IEnumerable<Subscription> subscriptions,
        IEventStreamStore streamStore,
        CancellationToken cancellationToken)
    {
        var streamInfos = new List<StreamInfo>();

        foreach (var config in streamConfigurations)
        {
            var streamSubs = subscriptions.Where(s => s.StreamName == config.StreamName).ToList();

            long length = 0;
            try
            {
                length = await streamStore.GetStreamLengthAsync(config.StreamName, cancellationToken);
            }
            catch
            {
                // Stream might not exist yet
            }

            streamInfos.Add(new StreamInfo
            {
                Name = config.StreamName,
                Type = config.Type.ToString(),
                DeliverySemantics = config.DeliverySemantics.ToString(),
                Scope = config.Scope.ToString(),
                Length = length,
                SubscriptionCount = streamSubs.Count,
                Subscriptions = streamSubs.Select(s => s.SubscriptionId).ToList()
            });
        }

        return Results.Ok(streamInfos);
    }

    private static async Task<IResult> GetStream(
        string name,
        IEnumerable<IStreamConfiguration> streamConfigurations,
        IEnumerable<Subscription> subscriptions,
        IEventStreamStore streamStore,
        CancellationToken cancellationToken)
    {
        var config = streamConfigurations.FirstOrDefault(s => s.StreamName == name);
        if (config == null)
            return Results.NotFound(new { error = $"Stream '{name}' not found" });

        var streamSubs = subscriptions.Where(s => s.StreamName == name).ToList();

        long length = 0;
        try
        {
            length = await streamStore.GetStreamLengthAsync(name, cancellationToken);
        }
        catch
        {
            // Stream might not exist yet
        }

        var info = new StreamInfo
        {
            Name = config.StreamName,
            Type = config.Type.ToString(),
            DeliverySemantics = config.DeliverySemantics.ToString(),
            Scope = config.Scope.ToString(),
            Length = length,
            SubscriptionCount = streamSubs.Count,
            Subscriptions = streamSubs.Select(s => s.SubscriptionId).ToList()
        };

        return Results.Ok(info);
    }

    private static IResult GetStreamSubscriptions(
        string name,
        IEnumerable<IStreamConfiguration> streamConfigurations,
        IEnumerable<Subscription> subscriptions)
    {
        var config = streamConfigurations.FirstOrDefault(s => s.StreamName == name);
        if (config == null)
            return Results.NotFound(new { error = $"Stream '{name}' not found" });

        var streamSubs = subscriptions
            .Where(s => s.StreamName == name)
            .Select(s => new SubscriptionInfo
            {
                SubscriptionId = s.SubscriptionId,
                StreamName = s.StreamName,
                Mode = s.Mode.ToString(),
                IsActive = s.IsActive,
                CreatedAt = s.CreatedAt,
                VisibilityTimeout = s.VisibilityTimeout,
                EnableUpcasting = s.EnableUpcasting,
                TargetEventVersion = s.TargetEventVersion,
                Description = s.Description
            })
            .ToList();

        return Results.Ok(streamSubs);
    }

    private static IResult GetSubscription(
        string id,
        IEnumerable<Subscription> subscriptions)
    {
        var subscription = subscriptions.FirstOrDefault(s => s.SubscriptionId == id);
        if (subscription == null)
            return Results.NotFound(new { error = $"Subscription '{id}' not found" });

        var info = new SubscriptionInfo
        {
            SubscriptionId = subscription.SubscriptionId,
            StreamName = subscription.StreamName,
            Mode = subscription.Mode.ToString(),
            IsActive = subscription.IsActive,
            CreatedAt = subscription.CreatedAt,
            VisibilityTimeout = subscription.VisibilityTimeout,
            EnableUpcasting = subscription.EnableUpcasting,
            TargetEventVersion = subscription.TargetEventVersion,
            Description = subscription.Description
        };

        return Results.Ok(info);
    }

    private static async Task<IResult> GetConsumerInfo(
        string id,
        string consumerId,
        IEnumerable<Subscription> subscriptions,
        IEventStreamStore streamStore,
        CancellationToken cancellationToken)
    {
        var subscription = subscriptions.FirstOrDefault(s => s.SubscriptionId == id);
        if (subscription == null)
            return Results.NotFound(new { error = $"Subscription '{id}' not found" });

        try
        {
            var streamLength = await streamStore.GetStreamLengthAsync(subscription.StreamName, cancellationToken);
            var offset = await streamStore.GetConsumerOffsetAsync(subscription.StreamName, id, cancellationToken);
            var lastUpdated = await streamStore.GetConsumerLastUpdateTimeAsync(subscription.StreamName, id, cancellationToken);

            var lag = streamLength - offset;
            var timeSinceUpdate = DateTimeOffset.UtcNow - lastUpdated;
            var isStalled = timeSinceUpdate.TotalMinutes > 5 && lag > 0;

            var info = new ConsumerInfo
            {
                ConsumerId = consumerId,
                Offset = offset,
                Lag = lag,
                LastUpdated = lastUpdated,
                IsStalled = isStalled
            };

            return Results.Ok(info);
        }
        catch (Exception ex)
        {
            return Results.Problem(
                detail: ex.Message,
                statusCode: 500,
                title: "Error retrieving consumer information");
        }
    }

    private static async Task<IResult> ResetConsumerOffset(
        string id,
        string consumerId,
        ResetOffsetRequest request,
        IEnumerable<Subscription> subscriptions,
        IEventStreamStore streamStore,
        CancellationToken cancellationToken)
    {
        var subscription = subscriptions.FirstOrDefault(s => s.SubscriptionId == id);
        if (subscription == null)
            return Results.NotFound(new { error = $"Subscription '{id}' not found" });

        try
        {
            long newOffset = request.NewOffset;

            // Handle special values
            if (newOffset == -1)
            {
                // Set to latest (end of stream)
                newOffset = await streamStore.GetStreamLengthAsync(subscription.StreamName, cancellationToken);
            }
            else if (newOffset < 0)
            {
                return Results.BadRequest(new { error = "Offset must be >= 0 or -1 for latest" });
            }

            // Update the consumer offset
            await streamStore.UpdateConsumerOffsetAsync(subscription.StreamName, id, newOffset, cancellationToken);

            var streamLength = await streamStore.GetStreamLengthAsync(subscription.StreamName, cancellationToken);
            var lag = streamLength - newOffset;

            return Results.Ok(new
            {
                message = "Consumer offset successfully reset",
                subscriptionId = id,
                consumerId = consumerId,
                newOffset = newOffset,
                streamLength = streamLength,
                lag = lag
            });
        }
        catch (Exception ex)
        {
            return Results.Problem(
                detail: ex.Message,
                statusCode: 500,
                title: "Error resetting consumer offset");
        }
    }
}