using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Svrnty.CQRS.Events.Abstractions.Subscriptions;

namespace Svrnty.CQRS.Events.Subscriptions;

/// <summary>
/// In-memory implementation of subscription store for development and testing.
/// </summary>
public sealed class InMemorySubscriptionStore : IPersistentSubscriptionStore
{
    private readonly ConcurrentDictionary<string, PersistentSubscription> _subscriptions = new();

    public Task<PersistentSubscription> CreateAsync(
        PersistentSubscription subscription,
        CancellationToken cancellationToken = default)
    {
        if (!_subscriptions.TryAdd(subscription.Id, subscription))
        {
            throw new InvalidOperationException($"Subscription with ID {subscription.Id} already exists");
        }

        return Task.FromResult(subscription);
    }

    public Task<PersistentSubscription?> GetByIdAsync(
        string id,
        CancellationToken cancellationToken = default)
    {
        _subscriptions.TryGetValue(id, out var subscription);
        return Task.FromResult(subscription);
    }

    public Task<IReadOnlyList<PersistentSubscription>> GetBySubscriberIdAsync(
        string subscriberId,
        CancellationToken cancellationToken = default)
    {
        var subscriptions = _subscriptions.Values
            .Where(s => s.SubscriberId == subscriberId)
            .ToList();

        return Task.FromResult<IReadOnlyList<PersistentSubscription>>(subscriptions);
    }

    public Task<IReadOnlyList<PersistentSubscription>> GetByCorrelationIdAsync(
        string correlationId,
        CancellationToken cancellationToken = default)
    {
        var subscriptions = _subscriptions.Values
            .Where(s => s.CorrelationId == correlationId)
            .ToList();

        return Task.FromResult<IReadOnlyList<PersistentSubscription>>(subscriptions);
    }

    public Task<IReadOnlyList<PersistentSubscription>> GetByStatusAsync(
        SubscriptionStatus status,
        CancellationToken cancellationToken = default)
    {
        var subscriptions = _subscriptions.Values
            .Where(s => s.Status == status)
            .ToList();

        return Task.FromResult<IReadOnlyList<PersistentSubscription>>(subscriptions);
    }

    public Task<IReadOnlyList<PersistentSubscription>> GetByConnectionIdAsync(
        string connectionId,
        CancellationToken cancellationToken = default)
    {
        var subscriptions = _subscriptions.Values
            .Where(s => s.ConnectionId == connectionId)
            .ToList();

        return Task.FromResult<IReadOnlyList<PersistentSubscription>>(subscriptions);
    }

    public Task UpdateAsync(
        PersistentSubscription subscription,
        CancellationToken cancellationToken = default)
    {
        _subscriptions[subscription.Id] = subscription;
        return Task.CompletedTask;
    }

    public Task DeleteAsync(
        string id,
        CancellationToken cancellationToken = default)
    {
        _subscriptions.TryRemove(id, out _);
        return Task.CompletedTask;
    }

    public Task<IReadOnlyList<PersistentSubscription>> GetExpiredSubscriptionsAsync(
        CancellationToken cancellationToken = default)
    {
        var now = DateTimeOffset.UtcNow;
        var expired = _subscriptions.Values
            .Where(s => s.ExpiresAt.HasValue && s.ExpiresAt.Value < now && s.Status == SubscriptionStatus.Active)
            .ToList();

        return Task.FromResult<IReadOnlyList<PersistentSubscription>>(expired);
    }
}