From 36a5a7c81569bbc4fa76b77e9823767d951944b4 Mon Sep 17 00:00:00 2001
From: 杨宇千 <crupest@outlook.com>
Date: Sun, 18 Aug 2019 18:07:50 +0800
Subject: Add avatar service.

---
 Timeline/Services/UserAvatarService.cs | 181 +++++++++++++++++++++++++++++++++
 1 file changed, 181 insertions(+)
 create mode 100644 Timeline/Services/UserAvatarService.cs

(limited to 'Timeline/Services/UserAvatarService.cs')

diff --git a/Timeline/Services/UserAvatarService.cs b/Timeline/Services/UserAvatarService.cs
new file mode 100644
index 00000000..21153575
--- /dev/null
+++ b/Timeline/Services/UserAvatarService.cs
@@ -0,0 +1,181 @@
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging;
+using System;
+using System.IO;
+using System.Linq;
+using System.Threading.Tasks;
+using Timeline.Entities;
+
+namespace Timeline.Services
+{
+    public class Avatar
+    {
+        public string Type { get; set; }
+        public byte[] Data { get; set; }
+    }
+
+    /// <summary>
+    /// Thrown when avatar is of bad format.
+    /// </summary>
+    [Serializable]
+    public class AvatarDataException : Exception
+    {
+        public AvatarDataException(Avatar avatar, string message) : base(message) { Avatar = avatar; }
+        public AvatarDataException(Avatar avatar, string message, Exception inner) : base(message, inner) { Avatar = avatar; }
+        protected AvatarDataException(
+          System.Runtime.Serialization.SerializationInfo info,
+          System.Runtime.Serialization.StreamingContext context) : base(info, context) { }
+
+        public Avatar Avatar { get; set; }
+    }
+
+    /// <summary>
+    /// Provider for default user avatar.
+    /// </summary>
+    /// <remarks>
+    /// Mainly for unit tests.
+    /// </remarks>
+    public interface IDefaultUserAvatarProvider
+    {
+        /// <summary>
+        /// Get the default avatar.
+        /// </summary>
+        Task<Avatar> GetDefaultAvatar();
+    }
+
+    public interface IUserAvatarService
+    {
+        /// <summary>
+        /// Get avatar of a user. If the user has no avatar, a default one is returned.
+        /// </summary>
+        /// <param name="username">The username of the user to get avatar of.</param>
+        /// <returns>The avatar.</returns>
+        /// <exception cref="ArgumentException">Thrown if <paramref name="username"/> is null or empty.</exception>
+        /// <exception cref="UserNotExistException">Thrown if the user does not exist.</exception>
+        Task<Avatar> GetAvatar(string username);
+
+        /// <summary>
+        /// Set avatar for a user.
+        /// </summary>
+        /// <param name="username">The username of the user to set avatar for.</param>
+        /// <param name="avatar">The avatar. Can be null to delete the saved avatar.</param>
+        /// <exception cref="ArgumentException">Throw if <paramref name="username"/> is null or empty.
+        /// Or thrown if <paramref name="avatar"/> is not null but <see cref="Avatar.Type"/> is null or empty or <see cref="Avatar.Data"/> is null.</exception>
+        /// <exception cref="UserNotExistException">Thrown if the user does not exist.</exception>
+        /// <exception cref="AvatarDataException">Thrown if avatar is of bad format.</exception>
+        Task SetAvatar(string username, Avatar avatar);
+    }
+
+    public class DefaultUserAvatarProvider : IDefaultUserAvatarProvider
+    {
+        private readonly IHostingEnvironment _environment;
+
+        public DefaultUserAvatarProvider(IHostingEnvironment environment)
+        {
+            _environment = environment;
+        }
+
+        public async Task<Avatar> GetDefaultAvatar()
+        {
+            return new Avatar
+            {
+                Type = "image/png",
+                Data = await File.ReadAllBytesAsync(Path.Combine(_environment.ContentRootPath, "default-avatar.png"))
+            };
+        }
+    }
+
+    public class UserAvatarService : IUserAvatarService
+    {
+
+        private readonly ILogger<UserAvatarService> _logger;
+
+        private readonly DatabaseContext _database;
+
+        private readonly IDefaultUserAvatarProvider _defaultUserAvatarProvider;
+
+        public UserAvatarService(ILogger<UserAvatarService> logger, DatabaseContext database, IDefaultUserAvatarProvider defaultUserAvatarProvider)
+        {
+            _logger = logger;
+            _database = database;
+            _defaultUserAvatarProvider = defaultUserAvatarProvider;
+        }
+
+        public async Task<Avatar> GetAvatar(string username)
+        {
+            if (string.IsNullOrEmpty(username))
+                throw new ArgumentException("Username is null or empty.", nameof(username));
+
+            var user = await _database.Users.Where(u => u.Name == username).SingleOrDefaultAsync();
+            if (user == null)
+                throw new UserNotExistException(username);
+
+            await _database.Entry(user).Reference(u => u.Avatar).LoadAsync();
+            var avatar = user.Avatar;
+
+            if (avatar == null)
+            {
+                return await _defaultUserAvatarProvider.GetDefaultAvatar();
+            }
+            else
+            {
+                return new Avatar
+                {
+                    Type = avatar.Type,
+                    Data = avatar.Data
+                };
+            }
+        }
+
+        public async Task SetAvatar(string username, Avatar avatar)
+        {
+            if (string.IsNullOrEmpty(username))
+                throw new ArgumentException("Username is null or empty.", nameof(username));
+
+            if (avatar != null)
+            {
+                if (string.IsNullOrEmpty(avatar.Type))
+                    throw new ArgumentException("Type of avatar is null or empty.", nameof(avatar));
+                if (avatar.Data == null)
+                    throw new ArgumentException("Data of avatar is null.", nameof(avatar));
+            }
+
+            var user = await _database.Users.Where(u => u.Name == username).SingleOrDefaultAsync();
+            if (user == null)
+                throw new UserNotExistException(username);
+
+            await _database.Entry(user).Reference(u => u.Avatar).LoadAsync();
+            var avatarEntity = user.Avatar;
+
+            if (avatar == null)
+            {
+                if (avatarEntity == null)
+                    return;
+                else
+                {
+                    _database.UserAvatars.Remove(avatarEntity);
+                    await _database.SaveChangesAsync();
+                }
+            }
+            else
+            {
+                // TODO: Use image library to check the format to prohibit bad data.
+                if (avatarEntity == null)
+                {
+                    user.Avatar = new UserAvatar
+                    {
+                        Type = avatar.Type,
+                        Data = avatar.Data
+                    };
+                }
+                else
+                {
+                    avatarEntity.Type = avatar.Type;
+                    avatarEntity.Data = avatar.Data;
+                }
+                await _database.SaveChangesAsync();
+            }
+        }
+    }
+}
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