From a4a75188bd17e31b39a02511bbd6d628bab5c909 Mon Sep 17 00:00:00 2001
From: crupest <crupest@outlook.com>
Date: Sun, 25 Apr 2021 21:20:04 +0800
Subject: ...

---
 BackEnd/Timeline/Services/Api/SearchService.cs | 104 +++++++++++++++++++++++++
 1 file changed, 104 insertions(+)
 create mode 100644 BackEnd/Timeline/Services/Api/SearchService.cs

(limited to 'BackEnd/Timeline/Services/Api/SearchService.cs')

diff --git a/BackEnd/Timeline/Services/Api/SearchService.cs b/BackEnd/Timeline/Services/Api/SearchService.cs
new file mode 100644
index 00000000..eec5001f
--- /dev/null
+++ b/BackEnd/Timeline/Services/Api/SearchService.cs
@@ -0,0 +1,104 @@
+using Microsoft.EntityFrameworkCore;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using Timeline.Entities;
+
+namespace Timeline.Services.Api
+{
+    public class SearchResultItem<TItem>
+    {
+        public SearchResultItem(TItem item, int score)
+        {
+            Item = item;
+            Score = score;
+        }
+
+        public TItem Item { get; set; } = default!;
+
+        /// <summary>
+        /// Bigger is better.
+        /// </summary>
+        public int Score { get; set; }
+    }
+
+    public class SearchResult<TItem>
+    {
+#pragma warning disable CA2227 // Collection properties should be read only
+        public List<SearchResultItem<TItem>> Items { get; set; } = new();
+#pragma warning restore CA2227 // Collection properties should be read only
+    }
+
+    public interface ISearchService
+    {
+        /// <summary>
+        /// Search timelines whose name or title contains query string.
+        /// </summary>
+        /// <param name="query">String to contain.</param>
+        /// <returns>Search results.</returns>
+        /// <exception cref="ArgumentNullException">Thrown when <paramref name="query"/> is null.</exception>
+        /// <exception cref="ArgumentException">Thrown when <paramref name="query"/> is empty.</exception>
+        /// <remarks>
+        /// Implementation should promise high score is at first.
+        /// </remarks>
+        Task<SearchResult<TimelineEntity>> SearchTimeline(string query);
+
+        /// <summary>
+        /// Search users whose username or nickname contains query string.
+        /// </summary>
+        /// <param name="query">String to contain.</param>
+        /// <returns>Search results.</returns>
+        /// <exception cref="ArgumentNullException">Thrown when <paramref name="query"/> is null.</exception>
+        /// <exception cref="ArgumentException">Thrown when <paramref name="query"/> is empty.</exception>
+        /// <remarks>
+        /// Implementation should promise high score is at first.
+        /// </remarks>
+        Task<SearchResult<UserEntity>> SearchUser(string query);
+    }
+
+    public class SearchService : ISearchService
+    {
+        private readonly DatabaseContext _database;
+
+        public SearchService(DatabaseContext database)
+        {
+            _database = database;
+        }
+
+        public async Task<SearchResult<TimelineEntity>> SearchTimeline(string query)
+        {
+            if (query is null)
+                throw new ArgumentNullException(nameof(query));
+            if (query.Length == 0)
+                throw new ArgumentException("Query string can't be empty.", nameof(query));
+
+            var nameLikeTimelines = await _database.Timelines.Include(t => t.Owner).Where(t => t.Name == null ? t.Owner.Username.Contains(query) : t.Name.Contains(query)).ToListAsync();
+            var titleLikeTimelines = await _database.Timelines.Where(t => t.Title != null && t.Title.Contains(query)).ToListAsync();
+
+            var searchResult = new SearchResult<TimelineEntity>();
+            searchResult.Items.AddRange(nameLikeTimelines.Select(t => new SearchResultItem<TimelineEntity>(t, 2)));
+            searchResult.Items.AddRange(titleLikeTimelines.Select(t => new SearchResultItem<TimelineEntity>(t, 1)));
+
+            return searchResult;
+        }
+
+        public async Task<SearchResult<UserEntity>> SearchUser(string query)
+        {
+            if (query is null)
+                throw new ArgumentNullException(nameof(query));
+            if (query.Length == 0)
+                throw new ArgumentException("Query string can't be empty.", nameof(query));
+
+            var usernameLikeUsers = await _database.Users.Where(u => u.Username.Contains(query)).ToListAsync();
+            var nicknameLikeUsers = await _database.Users.Where(u => u.Nickname != null && u.Nickname.Contains(query)).ToListAsync();
+
+            var searchResult = new SearchResult<UserEntity>();
+            searchResult.Items.AddRange(usernameLikeUsers.Select(u => new SearchResultItem<UserEntity>(u, 2)));
+            searchResult.Items.AddRange(nicknameLikeUsers.Select(u => new SearchResultItem<UserEntity>(u, 1)));
+
+            return searchResult;
+
+        }
+    }
+}
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