using System.Diagnostics;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using StackExchange.Redis;
using TakeoutSaaS.Application.Dictionary.Abstractions;
using TakeoutSaaS.Domain.Dictionary.Entities;
using TakeoutSaaS.Domain.Dictionary.Enums;
using TakeoutSaaS.Domain.Dictionary.Repositories;
using TakeoutSaaS.Shared.Abstractions.Security;

namespace TakeoutSaaS.Infrastructure.Dictionary.Caching;

/// <summary>
/// 两级缓存封装：L1 内存 + L2 Redis。
/// </summary>
public sealed class HybridCacheService : IDictionaryHybridCache
{
    private static readonly RedisChannel InvalidationChannel = RedisChannel.Literal("dictionary:cache:invalidate");

    private readonly MemoryCacheService _memoryCache;
    private readonly RedisCacheService _redisCache;
    private readonly ISubscriber? _subscriber;
    private readonly ILogger<HybridCacheService>? _logger;
    private readonly CacheMetricsCollector? _metrics;
    private readonly IServiceScopeFactory? _scopeFactory;

    /// <summary>
    /// 初始化两级缓存服务。
    /// </summary>
    public HybridCacheService(
        MemoryCacheService memoryCache,
        RedisCacheService redisCache,
        IConnectionMultiplexer? multiplexer = null,
        ILogger<HybridCacheService>? logger = null,
        CacheMetricsCollector? metrics = null,
        IServiceScopeFactory? scopeFactory = null)
    {
        _memoryCache = memoryCache;
        _redisCache = redisCache;
        _logger = logger;
        _subscriber = multiplexer?.GetSubscriber();
        _metrics = metrics;
        _scopeFactory = scopeFactory;

        if (_subscriber != null)
        {
            _subscriber.Subscribe(InvalidationChannel, (_, value) =>
            {
                var prefix = value.ToString();
                if (!string.IsNullOrWhiteSpace(prefix))
                {
                    _memoryCache.RemoveByPrefix(prefix);
                }
            });
        }
    }

    /// <summary>
    /// 获取缓存，如果不存在则创建并回填。
    /// </summary>
    public async Task<T?> GetOrCreateAsync<T>(
        string key,
        TimeSpan ttl,
        Func<CancellationToken, Task<T?>> factory,
        CancellationToken cancellationToken = default)
    {
        var stopwatch = Stopwatch.StartNew();
        var dictionaryCode = CacheMetricsCollector.ExtractDictionaryCode(key);
        var l1Hit = false;
        var l2Hit = false;

        var cached = await _memoryCache.GetAsync<T>(key, cancellationToken);
        if (cached != null)
        {
            l1Hit = true;
            _metrics?.RecordHit("L1", dictionaryCode);
            _metrics?.RecordDuration(dictionaryCode, stopwatch.Elapsed.TotalMilliseconds);
            _metrics?.RecordQuery(dictionaryCode, l1Hit, l2Hit, stopwatch.Elapsed.TotalMilliseconds);
            return cached;
        }

        _metrics?.RecordMiss("L1", dictionaryCode);

        try
        {
            cached = await _redisCache.GetAsync<T>(key, cancellationToken);
            if (cached != null)
            {
                l2Hit = true;
                _metrics?.RecordHit("L2", dictionaryCode);
                await _memoryCache.SetAsync(key, cached, ttl, cancellationToken);
                _metrics?.RecordDuration(dictionaryCode, stopwatch.Elapsed.TotalMilliseconds);
                _metrics?.RecordQuery(dictionaryCode, l1Hit, l2Hit, stopwatch.Elapsed.TotalMilliseconds);
                return cached;
            }

            _metrics?.RecordMiss("L2", dictionaryCode);
        }
        catch (Exception ex)
        {
            _metrics?.RecordMiss("L2", dictionaryCode);
            _logger?.LogWarning(ex, "读取 Redis 缓存失败，降级为数据库查询。");
        }

        var created = await factory(cancellationToken);
        if (created == null)
        {
            _metrics?.RecordDuration(dictionaryCode, stopwatch.Elapsed.TotalMilliseconds);
            _metrics?.RecordQuery(dictionaryCode, l1Hit, l2Hit, stopwatch.Elapsed.TotalMilliseconds);
            return default;
        }

        await _memoryCache.SetAsync(key, created, ttl, cancellationToken);
        try
        {
            await _redisCache.SetAsync(key, created, ttl, cancellationToken);
        }
        catch (Exception ex)
        {
            _logger?.LogWarning(ex, "写入 Redis 缓存失败。");
        }

        _metrics?.RecordDuration(dictionaryCode, stopwatch.Elapsed.TotalMilliseconds);
        _metrics?.RecordQuery(dictionaryCode, l1Hit, l2Hit, stopwatch.Elapsed.TotalMilliseconds);
        return created;
    }

    /// <summary>
    /// 失效指定前缀的缓存键。
    /// </summary>
    public async Task InvalidateAsync(
        string prefix,
        CacheInvalidationOperation operation = CacheInvalidationOperation.Update,
        CancellationToken cancellationToken = default)
    {
        var dictionaryCode = CacheMetricsCollector.ExtractDictionaryCode(prefix);
        _metrics?.RecordInvalidation(dictionaryCode);

        var removedCount = _memoryCache.RemoveByPrefixWithCount(prefix);
        long redisRemoved = 0;
        try
        {
            redisRemoved = await _redisCache.RemoveByPrefixWithCountAsync(prefix, cancellationToken);
        }
        catch (Exception ex)
        {
            _logger?.LogWarning(ex, "删除 Redis 缓存失败。");
        }

        var totalRemoved = removedCount + (int)Math.Min(redisRemoved, int.MaxValue);

        if (_subscriber != null && !string.IsNullOrWhiteSpace(prefix))
        {
            await _subscriber.PublishAsync(InvalidationChannel, prefix);
        }

        _ = WriteInvalidationLogAsync(prefix, dictionaryCode, totalRemoved, operation);
    }

    private async Task WriteInvalidationLogAsync(
        string prefix,
        string dictionaryCode,
        int removedCount,
        CacheInvalidationOperation operation)
    {
        if (_scopeFactory == null)
        {
            return;
        }

        try
        {
            using var scope = _scopeFactory.CreateScope();
            var repo = scope.ServiceProvider.GetService<ICacheInvalidationLogRepository>();
            if (repo == null)
            {
                return;
            }

            var currentUser = scope.ServiceProvider.GetService<ICurrentUserAccessor>();
            var tenantId = TryExtractTenantId(prefix) ?? 0;
            var scopeType = tenantId == 0 ? DictionaryScope.System : DictionaryScope.Business;

            var log = new CacheInvalidationLog
            {
                TenantId = tenantId,
                Timestamp = DateTime.UtcNow,
                DictionaryCode = dictionaryCode,
                Scope = scopeType,
                AffectedCacheKeyCount = removedCount,
                OperatorId = currentUser?.IsAuthenticated == true ? currentUser.UserId : 0,
                Operation = operation
            };

            await repo.AddAsync(log);
            await repo.SaveChangesAsync();
        }
        catch (Exception ex)
        {
            _logger?.LogWarning(ex, "写入缓存失效日志失败。");
        }
    }

    private static long? TryExtractTenantId(string prefix)
    {
        if (string.IsNullOrWhiteSpace(prefix))
        {
            return null;
        }

        if (prefix.StartsWith("dict:groups:", StringComparison.Ordinal))
        {
            var token = prefix.Replace("dict:groups:", string.Empty, StringComparison.Ordinal).Trim(':');
            return long.TryParse(token.Split(':', StringSplitOptions.RemoveEmptyEntries).FirstOrDefault(), out var tenantId)
                ? tenantId
                : null;
        }

        if (prefix.StartsWith("dict:", StringComparison.Ordinal) && !prefix.StartsWith("dict:items:", StringComparison.Ordinal))
        {
            var token = prefix.Replace("dict:", string.Empty, StringComparison.Ordinal);
            return long.TryParse(token.Split(':', StringSplitOptions.RemoveEmptyEntries).FirstOrDefault(), out var tenantId)
                ? tenantId
                : null;
        }

        return null;
    }
}