using AsbCloudDb.Model;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System;
using System.Linq;
using Microsoft.EntityFrameworkCore;
using Mapster;

#nullable enable
namespace AsbCloudInfrastructure.Services.SAUB
{
    public class TelemetryDataCache<TDto, TEntity>
        where TDto : AsbCloudApp.Data.ITelemetryData
        where TEntity : class, ITelemetryData
    {
        private const int activeWellCapacity = 24 * 60 * 60;
        private const int doneWellCapacity = 65 * 60;

        private readonly ConcurrentDictionary<int, CyclycArray<TDto>> caches;
        
        public TelemetryDataCache(IAsbCloudDbContext db)
        {
            caches = new ();
            LoadCaches(db);
        }

        private void LoadCaches(IAsbCloudDbContext db)
        {
            Well[] wells = db.Set<Well>()
                .Include(well => well.Telemetry)
                .Where(well => well.IdTelemetry != null)
                .ToArray();

            foreach (Well well in wells)
            {
                var capacity = well.IdState == 1
                    ? activeWellCapacity
                    : doneWellCapacity;

                var idTelemetry = well.IdTelemetry!.Value;
                var hoursOffset = well.Timezone.Hours;

                IEnumerable<TDto> cacheItemData = GetCacheDataFromDb(db, idTelemetry, capacity, hoursOffset);
                var cacheItem = new CyclycArray<TDto>(capacity);
                cacheItem.AddRange(cacheItemData);
                caches.TryAdd(idTelemetry, cacheItem);
            }
        }

        private static IEnumerable<TDto> GetCacheDataFromDb(IAsbCloudDbContext db, int idTelemetry, int capacity, double hoursOffset)
        {
            var entities = db.Set<TEntity>()
                .Where(i => i.IdTelemetry == idTelemetry)
                .OrderByDescending(i => i.DateTime)
                .Take(capacity)
                .ToArray()
                .OrderBy(i => i.DateTime);

            var dtos = entities.Select(entity => {
                var dto = entity.Adapt<TDto>();
                dto.DateTime = entity.DateTime.ToRemoteDateTime(hoursOffset);
                return dto;
            });

            return dtos;
        }

        /// <summary>
        /// Добавить элементы в кеш
        /// </summary>
        /// <param name="idTelemetry"></param>
        /// <param name="range"></param>
        public void AddRange(int idTelemetry, IEnumerable<TDto> range) 
        {
            var cacheItem = caches.GetOrAdd(idTelemetry, _ => new CyclycArray<TDto>(activeWellCapacity));
            var newItems = range
                .OrderBy(i => i.DateTime);
            foreach (var item in newItems)
                item.IdTelemetry = idTelemetry;
            cacheItem.AddRange(newItems);
        }

        /// <summary>
        /// Получить данные из кеша. <br/>
        /// Если dateBegin меньше минимального элемента в кеше, то вернется null.
        /// Даже если intervalSec частично перекрыт данными из кеша.
        /// </summary>
        /// <param name="idTelemetry"></param>
        /// <param name="dateBegin"></param>
        /// <param name="intervalSec"></param>
        /// <param name="approxPointsCount">кол-во элементов до которых эти данные прореживаются</param>
        /// <returns></returns>
        public IEnumerable<TDto>? GetOrDefault(int idTelemetry, DateTime dateBegin, double intervalSec = 600d, int approxPointsCount = 1024)
        {
            if(!caches.TryGetValue(idTelemetry, out CyclycArray<TDto>? cacheItem))
                return null;

            if (cacheItem is null || cacheItem[0].DateTime > dateBegin)
                return null;
            
            var dateEnd = dateBegin.AddSeconds(intervalSec);
            var items = cacheItem
                .Where(i => i.DateTime >= dateBegin && i.DateTime <= dateEnd);

            var ratio = items.Count() / approxPointsCount;
            if (ratio > 1)
                items = items
                    .Where((_, index) => index % ratio == 0);

            return items;
        }
    }
}
#nullable disable