using AsbCloudApp.Data;
using AsbCloudApp.Services;
using AsbCloudDb.Model;
using Mapster;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Caching.Memory;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

namespace AsbCloudInfrastructure.Repository
{
    public class CacheBase<TDto, TEntity> : QueryContainer<TEntity>
        where TDto : AsbCloudApp.Data.IId
        where TEntity : class, AsbCloudDb.Model.IId
    {
        protected readonly IMemoryCache memoryCache;
        protected string CacheTag = typeof(TDto).Name;
        protected TimeSpan CacheOlescence = TimeSpan.FromMinutes(5);

        public CacheBase(IAsbCloudDbContext context, IMemoryCache memoryCache) 
            : base(context)
        {
            this.memoryCache = memoryCache;
        }

        public CacheBase(IAsbCloudDbContext context, IMemoryCache memoryCache, Func<DbSet<TEntity>, IQueryable<TEntity>> makeQuery) 
            : base(context, makeQuery)
        {
            this.memoryCache = memoryCache;
        }

        protected virtual void DropCache()
            => memoryCache.Remove(CacheTag);

        protected virtual IEnumerable<TDto> GetCache()
        {
            var cache = memoryCache.GetOrCreate(CacheTag, cacheEntry =>
            {
                cacheEntry.AbsoluteExpirationRelativeToNow = CacheOlescence;
                cacheEntry.SlidingExpiration = CacheOlescence;

                var entities = this.GetQuery().ToArray();
                var dtos = entities.Select(Convert);
                return dtos.ToArray();
            });
            return cache;
        }

        protected virtual Task<IEnumerable<TDto>> GetCacheAsync(CancellationToken token)
        {
            var cache = memoryCache.GetOrCreateAsync(CacheTag, async (cacheEntry) =>
            {
                cacheEntry.AbsoluteExpirationRelativeToNow = CacheOlescence;
                cacheEntry.SlidingExpiration = CacheOlescence;

                var entities = await this.GetQuery().ToArrayAsync(token);
                var dtos = entities.Select(Convert);
                return dtos.ToArray().AsEnumerable();
            });
            return cache;
        }

        protected virtual TDto Convert(TEntity src) => src.Adapt<TDto>();

        protected virtual TEntity Convert(TDto src) => src.Adapt<TEntity>();
    }
}