props/Props/Services/Modules/LiveMetricsManager.cs

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Logging;
using Props.Data;
using Props.Models.Search;
using Props.Options;
using Props.Shop.Framework;

namespace Props.Services.Modules
{
    public class LiveMetricsManager : IMetricsManager
    {
        private MetricsOptions metricsOptions;
        private ILogger<LiveMetricsManager> logger;
        private ApplicationDbContext dbContext;
        private IQueryable<ProductListingInfo> leastPopularProductListings;
        private IQueryable<QueryWordInfo> leastPopularQueryWords;
        public LiveMetricsManager(ApplicationDbContext dbContext, ILogger<LiveMetricsManager> logger, IConfiguration configuration)
        {
            this.metricsOptions = configuration.GetSection(MetricsOptions.Metrics).Get<MetricsOptions>();
            this.logger = logger;
            this.dbContext = dbContext;
            leastPopularProductListings = from listing in dbContext.ProductListingInfos orderby listing.Hits ascending select listing;
            leastPopularQueryWords = from word in dbContext.QueryWords orderby word.Hits ascending select word;
        }
        public IEnumerable<ProductListingInfo> RetrieveTopListings(int max)
        {
            if (dbContext.ProductListingInfos == null) return null;
            return (from l in dbContext.ProductListingInfos
                    orderby l.Hits descending
                    select l).Take(max);
        }

        public IEnumerable<string> RetrieveCommonKeywords(int max)
        {
            if (dbContext.QueryWords == null) return null;
            return (from k in dbContext.QueryWords
                    orderby k.Hits descending
                    select k.Word).Take(max);
        }

        public void RegisterSearchQuery(string query)
        {
            query = query.ToLower();
            string[] tokens = query.Split(' ');
            QueryWordInfo[] wordInfos = new QueryWordInfo[tokens.Length];
            for (int wordIndex = 0; wordIndex < tokens.Length; wordIndex++)
            {
                QueryWordInfo queryWordInfo = dbContext.QueryWords.Where((k) => k.Word.ToLower().Equals(tokens[wordIndex])).SingleOrDefault() ?? new QueryWordInfo();
                if (queryWordInfo.Hits == 0)
                {
                    queryWordInfo.Word = tokens[wordIndex];
                    dbContext.QueryWords.Add(queryWordInfo);
                }
                queryWordInfo.Hits += 1;
                wordInfos[wordIndex] = queryWordInfo;
            }
            for (int wordIndex = 0; wordIndex < tokens.Length; wordIndex++)
            {
                for (int beforeIndex = 0; beforeIndex < wordIndex; beforeIndex++)
                {
                    wordInfos[wordIndex].Preceding.Add(wordInfos[beforeIndex]);
                }
                for (int afterIndex = wordIndex; afterIndex < tokens.Length; afterIndex++)
                {
                    wordInfos[wordIndex].Following.Add(wordInfos[afterIndex]);
                }
            }

            CullQueryWords();
            dbContext.SaveChanges();
        }

        public void RegisterProductListing(ProductListing productListing, string shopName)
        {
            ProductListingInfo productListingInfo =
                (from info in dbContext.ProductListingInfos
                 where info.ProductListingIdentifier.Equals(productListing.Identifier)
                 select info).SingleOrDefault() ?? new ProductListingInfo();
            if (productListingInfo.Hits == 0)
            {
                dbContext.Add(productListingInfo);
            }
            productListingInfo.ShopName = shopName;
            productListingInfo.ProductListing = productListing;
            productListingInfo.ProductListingIdentifier = productListing.Identifier;
            productListingInfo.Hits += 1;

            CullProductListings();
            dbContext.SaveChanges();
        }

        private void CullProductListings()
        {
            int surplus = dbContext.ProductListingInfos.Count() - metricsOptions.MaxProductListings;
            if (surplus > 0)
            {
                dbContext.RemoveRange(leastPopularProductListings.Take(surplus));
            }
        }

        private void CullQueryWords()
        {
            int surplus = dbContext.QueryWords.Count() - metricsOptions.MaxQueryWords;
            if (surplus > 0)
            {
                dbContext.RemoveRange(leastPopularQueryWords.Take(surplus));
            }
        }
    }
}