using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Volo.Abp.DependencyInjection;

namespace JiShe.CollectBus.Common.DeviceBalanceControl
{
    /// <summary>
    /// 设备组负载控制
    /// </summary>
    public class DeviceGroupBalanceControl
    {
        private static readonly object _syncRoot = new object();

        private static volatile CacheState _currentCache;

        /// <summary>
        /// 使用ConcurrentDictionary保证线程安全的设备分组映射
        /// </summary>
        private sealed class CacheState
        {
            public readonly ConcurrentDictionary<string, int> BalancedMapping;
            public readonly List<string>[] CachedGroups;

            public CacheState(int groupCount)
            {
                BalancedMapping = new ConcurrentDictionary<string, int>();
                CachedGroups = new List<string>[groupCount];
                for (int i = 0; i < groupCount; i++)
                {
                    CachedGroups[i] = new List<string>();
                }
            }
        }

        /// <summary>
        /// 初始化或增量更新缓存
        /// </summary>
        public static void InitializeCache(List<string> deviceList, int groupCount = 30)
        {
            if (deviceList == null || deviceList.Count <= 0)
            {
                throw new ArgumentException($"{nameof(InitializeCache)} 设备分组初始化失败，设备数据为空");
            }

            if (groupCount > 60 || groupCount <= 0)
            {
                groupCount = 60;
            }

            lock (_syncRoot)
            {
                // 首次初始化
                if (_currentCache == null)
                {
                    var newCache = new CacheState(groupCount);
                    UpdateCacheWithDevices(newCache, deviceList, groupCount);
                    _currentCache = newCache;
                }
                // 后续增量更新
                else
                {
                    if (_currentCache.CachedGroups.Length != groupCount)
                    {
                        throw new ArgumentException($"{nameof(InitializeCache)} 设备分组初始化完成以后，分组数量不能更改");
                    }

                    var clonedCache = CloneExistingCache();
                    UpdateCacheWithDevices(clonedCache, deviceList, groupCount);
                    _currentCache = clonedCache;
                }
            }
        }

        /// <summary>
        /// 带锁的缓存克隆（写入时复制）
        /// </summary>
        private static CacheState CloneExistingCache()
        {
            var oldCache = _currentCache;
            var newCache = new CacheState(oldCache.CachedGroups.Length);

            // 复制已有映射
            foreach (var kvp in oldCache.BalancedMapping)
            {
                newCache.BalancedMapping.TryAdd(kvp.Key, kvp.Value);
            }

            // 复制分组数据
            for (int i = 0; i < oldCache.CachedGroups.Length; i++)
            {
                newCache.CachedGroups[i].AddRange(oldCache.CachedGroups[i]);
            }

            return newCache;
        }

        /// <summary>
        /// 更新设备到缓存
        /// </summary>
        private static void UpdateCacheWithDevices(CacheState cache, List<string> deviceList, int groupCount)
        {
            foreach (var deviceId in deviceList)
            {
                // 原子操作：如果设备不存在则计算分组
                cache.BalancedMapping.GetOrAdd(deviceId, id =>
                {
                    int groupId = GetGroupId(id, groupCount);
                    lock (cache.CachedGroups[groupId])
                    {
                        cache.CachedGroups[groupId].Add(id);
                    }
                    return groupId;
                });
            }
        }

        /// <summary>
        /// 并行处理泛型数据集（支持动态线程分配）
        /// </summary>
        /// <typeparam name="T">已经分组的设备信息</typeparam>
        /// <param name="items">部分或者全部的已经分组的设备集合</param>
        /// <param name="deviceIdSelector">从泛型对象提取deviceId</param>
        /// <param name="processor">处理委托（参数：当前对象，线程ID）</param>
        /// <param name="maxThreads">可选线程限制</param>
        /// <returns></returns>
        /// <exception cref="InvalidOperationException"></exception>
        public static async Task ProcessGenericListAsync<T>(
            List<T> items, Func<T, string> deviceIdSelector, Action<T, int> processor, int? maxThreads = null)
        {
            var cache = _currentCache ?? throw new InvalidOperationException("缓存未初始化");

            // 创建分组任务队列
            var groupQueues = new ConcurrentQueue<T>[cache.CachedGroups.Length];
            for (int i = 0; i < groupQueues.Length; i++)
            {
                groupQueues[i] = new ConcurrentQueue<T>();
            }

            // 阶段1：分发数据到分组队列
            Parallel.ForEach(items, item =>
            {
                var deviceId = deviceIdSelector(item);
                if (cache.BalancedMapping.TryGetValue(deviceId, out int groupId))
                {
                    groupQueues[groupId].Enqueue(item);
                }
            });

            if ((maxThreads.HasValue && maxThreads.Value > cache.CachedGroups.Length) || maxThreads.HasValue == false)
            {
                maxThreads = cache.CachedGroups.Length;
            }

            // 阶段2：并行处理队列
            var options = new ParallelOptions
            {
                MaxDegreeOfParallelism = maxThreads.Value,
            };

            await Task.Run(() =>
            {
                Parallel.For(0, cache.CachedGroups.Length, options, async groupId =>
                {
                    var queue = groupQueues[groupId];
                    while (queue.TryDequeue(out T item))
                    {
                        processor(item, groupId);
                    }
                });
            });
        }


        /// <summary>
        /// 智能节流处理（CPU友好型）
        /// </summary>
        /// <typeparam name="T">已经分组的设备信息</typeparam>
        /// <param name="items">部分或者全部的已经分组的设备集合</param>
        /// <param name="deviceIdSelector">从泛型对象提取deviceId</param>
        /// <param name="processor">处理委托（参数：当前对象，分组ID）</param>
        /// <param name="maxConcurrency">可选最佳并发度</param>
        /// <returns></returns>
        /// <exception cref="InvalidOperationException"></exception>
        public static async Task ProcessWithThrottleAsync<T>(
            List<T> items,
            Func<T, string> deviceIdSelector,
            Action<T,int> processor,
            int? maxConcurrency = null)
        {
            var cache = _currentCache ?? throw new InvalidOperationException("缓存未初始化");

            // 自动计算最佳并发度
            int recommendedThreads = CalculateOptimalThreadCount();
            if ((maxConcurrency.HasValue && maxConcurrency.Value > cache.CachedGroups.Length) || maxConcurrency.HasValue == false)
            {
                maxConcurrency = cache.CachedGroups.Length;
            }

            int actualThreads = maxConcurrency ?? recommendedThreads;

            // 创建节流器
            using var throttler = new SemaphoreSlim(initialCount: actualThreads);

            // 使用LongRunning避免线程池饥饿
            var tasks = items.Select(async item =>
            {
                await throttler.WaitAsync();
                try
                {
                    var deviceId = deviceIdSelector(item);
                    if (cache.BalancedMapping.TryGetValue(deviceId, out int groupId))
                    {
                        // 分组级处理（保持顺序性）
                        await ProcessItemAsync(item, processor, groupId);
                    }
                }
                finally
                {
                    throttler.Release();
                }
            });

            await Task.WhenAll(tasks);
        }

        /// <summary>
        /// 自动计算最优线程数
        /// </summary>
        public static int CalculateOptimalThreadCount()
        {
            int coreCount = Environment.ProcessorCount;
            return Math.Min(
                coreCount * 2,  // 超线程优化
                _currentCache?.CachedGroups.Length ?? 60
            );
        }

        /// <summary>
        /// 分组异步处理（带节流）
        /// </summary>
        private static async Task ProcessItemAsync<T>(T item, Action<T,int> processor, int groupId)
        {
            // 使用内存缓存降低CPU负载
            await Task.Yield(); // 立即释放当前线程

            // 分组处理上下文
            var context = ExecutionContext.Capture();
            ThreadPool.QueueUserWorkItem(_ =>
            {
                ExecutionContext.Run(context!, state =>
                {
                    processor(item,groupId);
                }, null);
            });
        }


        /// <summary>
        /// 通过 deviceId 获取所在的分组集合
        /// </summary>
        public static List<string> GetGroup(string deviceId)
        {
            var cache = _currentCache;
            if (cache == null)
                throw new InvalidOperationException("缓存未初始化");

            return cache.CachedGroups[cache.BalancedMapping[deviceId]];
        }

        /// <summary>
        /// 通过 deviceId 获取分组Id
        /// </summary>
        public static int GetDeviceGroupId(string deviceId)
        {
            var cache = _currentCache;
            if (cache == null)
                throw new InvalidOperationException("缓存未初始化");

            return cache.BalancedMapping[deviceId];
        }


        /// <summary>
        /// 创建均衡映射表
        /// </summary>
        /// <param name="deviceList">数据集合</param>
        /// <param name="groupCount">分组数量</param>
        /// <param name="maxDeviation">允许的最大偏差百分比</param>
        /// <returns></returns>
        public static Dictionary<string, int> CreateBalancedMapping(List<string> deviceList, int groupCount, int maxDeviation = 5)
        {
            var mapping = new Dictionary<string, int>();
            int targetPerGroup = deviceList.Count / groupCount;
            int maxAllowed = (int)(targetPerGroup * (1 + maxDeviation / 100.0));

            // 初始化分组计数器
            int[] groupCounters = new int[groupCount];

            foreach (var deviceId in deviceList)
            {
                int preferredGroup = GetGroupId(deviceId, groupCount);

                // 如果首选分组未满，直接分配
                if (groupCounters[preferredGroup] < maxAllowed)
                {
                    mapping[deviceId] = preferredGroup;
                    groupCounters[preferredGroup]++;
                }
                else
                {
                    // 寻找当前最空闲的分组
                    int fallbackGroup = Array.IndexOf(groupCounters, groupCounters.Min());
                    mapping[deviceId] = fallbackGroup;
                    groupCounters[fallbackGroup]++;
                }
            }

            return mapping;
        }

        /// <summary>
        /// 分析分组分布
        /// </summary>
        /// <param name="deviceList"></param>
        /// <param name="groupCount"></param>
        /// <returns></returns>
        public static Dictionary<int, int> AnalyzeDistribution(List<string> deviceList, int groupCount)
        {
            Dictionary<int, int> distribution = new Dictionary<int, int>();
            foreach (var deviceId in deviceList)
            {
                int groupId = GetGroupId(deviceId, groupCount);
                distribution[groupId] = distribution.TryGetValue(groupId, out var count) ? count + 1 : 1;
            }
            return distribution;
        }

        /// <summary>
        /// 获取设备ID对应的分组ID
        /// </summary>
        /// <param name="deviceId"></param>
        /// <param name="groupCount"></param>
        /// <returns></returns>
        public static int GetGroupId(string deviceId, int groupCount)
        {
            int hash = Fnv1aHash(deviceId);
            // 双重取模确保分布均匀
            return (hash % groupCount + groupCount) % groupCount;
        }

        /// <summary>
        /// FNV-1a哈希算法
        /// </summary>
        /// <param name="input"></param>
        /// <returns></returns>
        public static int Fnv1aHash(string input)
        {
            const uint fnvPrime = 16777619;
            const uint fnvOffsetBasis = 2166136261;

            uint hash = fnvOffsetBasis;
            foreach (char c in input)
            {
                hash ^= (byte)c;
                hash *= fnvPrime;
            }
            return (int)hash;
        }

        /// <summary>
        /// CRC16算法实现
        /// </summary>
        /// <param name="bytes"></param>
        /// <returns></returns>
        public static ushort CRC16Hash(byte[] bytes)
        {
            ushort crc = 0xFFFF;
            for (int i = 0; i < bytes.Length; i++)
            {
                crc ^= bytes[i];
                for (int j = 0; j < 8; j++)
                {
                    if ((crc & 0x0001) == 1)
                    {
                        crc = (ushort)((crc >> 1) ^ 0xA001);
                    }
                    else
                    {
                        crc >>= 1;
                    }
                }
            }
            return crc;
        }

        /// <summary>
        /// 打印分组统计数据
        /// </summary>
        public static void PrintDistributionStats()
        {
            var cache = _currentCache;
            if (cache == null)
            {
                Console.WriteLine("缓存未初始化");
                return;
            }

            var stats = cache.CachedGroups
                .Select((group, idx) => new { GroupId = idx, Count = group.Count })
                .OrderBy(x => x.GroupId);

            Console.WriteLine("分组数据量统计:");
            foreach (var stat in stats)
            {
                Console.WriteLine($"Group {stat.GroupId}: {stat.Count} 条数据");
            }

            Console.WriteLine($"总共: {stats.Sum(d=>d.Count)} 条数据");
        }

    }
}