Add avatar service.

1 files changed, 181 insertions, 0 deletions

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();

+            }

+        }

+    }

+}