using Newtonsoft.Json;
using System.Collections.Concurrent;
using System.Reflection;
using HealthMonitor.Util.Entities.Interfaces;

namespace HealthMonitor.Core.Cache
{
    public class EntityCacheHandler : IEntityCacheHandler
    {
        /// <summary>
        /// 结构示例
        /// {
        ///		"id_xxx":  //实体的id值
        ///		[
        ///			"key_yyy_1",  //缓存有该实体的缓存键
        ///			"key_yyy_2",
        ///			...
        ///		],
        ///		...
        /// }
        /// </summary>
        private ConcurrentDictionary<string, List<Tuple<string, DateTime>>> _mapper;
        private readonly MethodInfo _m_GetPrimaryKey;

        public int DurableSecond { get; private set; }
        public Type EntityType { get; private set; }

        public EntityCacheHandler(Type entityType, int durableSeconds)
        {
            EntityType = entityType;
            DurableSecond = durableSeconds;

            _mapper = new ConcurrentDictionary<string, List<Tuple<string, DateTime>>>();
            _m_GetPrimaryKey = entityType.GetMethod(nameof(IEntity.GetPrimaryKey))!;
        }

        public IEnumerable<object>? GetEntitiesCache(string key)
        {
            string json = RedisHelper.Get(key);
            if (string.IsNullOrEmpty(json)) return null;

            var t = typeof(IEnumerable<>);
            return JsonConvert.DeserializeObject(json, t.MakeGenericType(EntityType)) as IEnumerable<object>;
        }

        public void SetEntityCache(string key, object param, bool isEnumerable = false)
        {
            if (param == null) return;
            IEnumerable<object> value;
            if (isEnumerable) value = (param as IEnumerable<object>)!;
            else value = new List<object> { param };

            RedisHelper.SetAsync(key, value, DurableSecond);

            MapKeyToEntity(key, value!);
        }

        public void DeleteEntityCache(string key)
        {
            RedisHelper.DelAsync(key);
        }

        public IEnumerable<string>? UnmapKeyFromEntity(object entity)
        {
            if (entity == null) return null;

            string id = _m_GetPrimaryKey.Invoke(entity, null) + "";
            //if (!_mapper.TryRemove(id, out List<Tuple<string, DateTime>> rels)) return null;
            if (!_mapper.TryRemove(id, out var rels)) return null;
            return rels.Select(e => e.Item1).Distinct();
        }

        public void CleanUpExpiredMapper()
        {
            if (_mapper.Keys.Count == 0)
            {
                //释放内存
                _mapper.Clear();
                _mapper = new ConcurrentDictionary<string, List<Tuple<string, DateTime>>>();
                return;
            }
            foreach (var id in _mapper.Keys)
            {
                // if (!_mapper.TryRemove(id, out List<Tuple<string, DateTime>> rels)) continue;
                if (!_mapper.TryRemove(id, out var rels)) continue;
                var availableList = rels.Where(t => DateTime.Now.Subtract(t.Item2).TotalSeconds < DurableSecond).ToList();
                _mapper.AddOrUpdate(id,
                    _ => availableList,
                    (_, _presentValue) =>
                    {
                        _presentValue.AddRange(availableList);
                        return _presentValue;
                    });
            }
        }

        /// <summary>
        /// 附加缓存键和实体主键（或实体主键列表）的映射关系
        /// </summary>
        /// <param name="key"></param>
        /// <param name="entities">实体列表</param>
        private void MapKeyToEntity(string key, IEnumerable<object> entities)
        {
            if (entities == null || entities.Count() == 0) return;

            foreach (var entity in entities)
            {
                string id = _m_GetPrimaryKey.Invoke(entity, null) + "";

                _mapper.AddOrUpdate(id,
                    _ => new List<Tuple<string, DateTime>> { new Tuple<string, DateTime>(key, DateTime.Now) },
                    (_, _presentValue) =>
                    {
                        _presentValue.Add(new Tuple<string, DateTime>(key, DateTime.Now));
                        return _presentValue;
                    });
            }
        }
    }
}