Merge pull request #68 from crupest/file

Unify data store.

2 files changed, 146 insertions, 21 deletions

diff --git a/Timeline/Services/DataManager.cs b/Timeline/Services/DataManager.cs
new file mode 100644
index 00000000..d447b0d5
--- /dev/null
+++ b/Timeline/Services/DataManager.cs
@@ -0,0 +1,122 @@
+using Microsoft.EntityFrameworkCore;

+using System;

+using System.Linq;

+using System.Threading.Tasks;

+using Timeline.Entities;

+

+namespace Timeline.Services

+{

+    /// <summary>

+    /// A data manager controlling data.

+    /// </summary>

+    /// <remarks>

+    /// Identical data will be saved as one copy and return the same tag.

+    /// Every data has a ref count. When data is retained, ref count increase.

+    /// When data is freed, ref count decease. If ref count is decreased

+    /// to 0, the data entry will be destroyed and no longer occupy space.

+    /// </remarks>

+    public interface IDataManager

+    {

+        /// <summary>

+        /// Saves the data to a new entry if it does not exist, 

+        /// increases its ref count and returns a tag to the entry.

+        /// </summary>

+        /// <param name="data">The data. Can't be null.</param>

+        /// <returns>The tag of the created entry.</returns>

+        /// <exception cref="ArgumentNullException">Thrown when <paramref name="data"/> is null.</exception>

+        public Task<string> RetainEntry(byte[] data);

+

+        /// <summary>

+        /// Decrease the the ref count of the entry.

+        /// Remove it if ref count is zero.

+        /// </summary>

+        /// <param name="tag">The tag of the entry.</param>

+        /// <exception cref="ArgumentNullException">Thrown when <paramref name="tag"/> is null.</exception>

+        /// <remarks>

+        /// It's no-op if entry with tag does not exist.

+        /// </remarks>

+        public Task FreeEntry(string tag);

+

+        /// <summary>

+        /// Retrieve the entry with given tag.

+        /// </summary>

+        /// <param name="tag">The tag of the entry.</param>

+        /// <returns>The data of the entry.</returns>

+        /// <exception cref="ArgumentNullException">Thrown when <paramref name="tag"/> is null.</exception>

+        /// <exception cref="InvalidOperationException">Thrown when entry with given tag does not exist.</exception>

+        public Task<byte[]> GetEntry(string tag);

+    }

+

+    public class DataManager : IDataManager

+    {

+        private readonly DatabaseContext _database;

+        private readonly IETagGenerator _eTagGenerator;

+

+        public DataManager(DatabaseContext database, IETagGenerator eTagGenerator)

+        {

+            _database = database;

+            _eTagGenerator = eTagGenerator;

+        }

+

+        public async Task<string> RetainEntry(byte[] data)

+        {

+            if (data == null)

+                throw new ArgumentNullException(nameof(data));

+

+            var tag = await _eTagGenerator.Generate(data);

+

+            var entity = await _database.Data.Where(d => d.Tag == tag).SingleOrDefaultAsync();

+

+            if (entity == null)

+            {

+                entity = new DataEntity

+                {

+                    Tag = tag,

+                    Data = data,

+                    Ref = 1

+                };

+                _database.Data.Add(entity);

+            }

+            else

+            {

+                entity.Ref += 1;

+            }

+            await _database.SaveChangesAsync();

+            return tag;

+        }

+

+        public async Task FreeEntry(string tag)

+        {

+            if (tag == null)

+                throw new ArgumentNullException(nameof(tag));

+

+            var entity = await _database.Data.Where(d => d.Tag == tag).SingleOrDefaultAsync();

+

+            if (entity != null)

+            {

+                if (entity.Ref == 1)

+                {

+                    _database.Data.Remove(entity);

+                }

+                else

+                {

+                    entity.Ref -= 1;

+                }

+                await _database.SaveChangesAsync();

+            }

+        }

+

+        public async Task<byte[]> GetEntry(string tag)

+        {

+            if (tag == null)

+                throw new ArgumentNullException(nameof(tag));

+

+            var entity = await _database.Data.Where(d => d.Tag == tag).Select(d => new { d.Data }).SingleOrDefaultAsync();

+

+            if (entity == null)

+                throw new InvalidOperationException(Resources.Services.DataManager.ExceptionEntryNotExist);

+

+            return entity.Data;

+        }

+    }

+}

diff --git a/Timeline/Services/UserAvatarService.cs b/Timeline/Services/UserAvatarService.cs
index 39b408e6..52d079a3 100644
--- a/Timeline/Services/UserAvatarService.cs
+++ b/Timeline/Services/UserAvatarService.cs
@@ -164,7 +164,7 @@ namespace Timeline.Services
         private readonly IDefaultUserAvatarProvider _defaultUserAvatarProvider;

         private readonly IUserAvatarValidator _avatarValidator;

 

-        private readonly IETagGenerator _eTagGenerator;

+        private readonly IDataManager _dataManager;

 

         private readonly IClock _clock;

 

@@ -173,20 +173,20 @@ namespace Timeline.Services
             DatabaseContext database,

             IDefaultUserAvatarProvider defaultUserAvatarProvider,

             IUserAvatarValidator avatarValidator,

-            IETagGenerator eTagGenerator,

+            IDataManager dataManager,

             IClock clock)

         {

             _logger = logger;

             _database = database;

             _defaultUserAvatarProvider = defaultUserAvatarProvider;

             _avatarValidator = avatarValidator;

-            _eTagGenerator = eTagGenerator;

+            _dataManager = dataManager;

             _clock = clock;

         }

 

         public async Task<string> GetAvatarETag(long id)

         {

-            var eTag = (await _database.UserAvatars.Where(a => a.UserId == id).Select(a => new { a.ETag }).SingleOrDefaultAsync())?.ETag;

+            var eTag = (await _database.UserAvatars.Where(a => a.UserId == id).Select(a => new { a.DataTag }).SingleOrDefaultAsync())?.DataTag;

             if (eTag == null)

                 return await _defaultUserAvatarProvider.GetDefaultAvatarETag();

             else

@@ -195,25 +195,27 @@ namespace Timeline.Services
 

         public async Task<AvatarInfo> GetAvatar(long id)

         {

-            var avatarEntity = await _database.UserAvatars.Where(a => a.UserId == id).Select(a => new { a.Type, a.Data, a.LastModified }).SingleOrDefaultAsync();

+            var avatarEntity = await _database.UserAvatars.Where(a => a.UserId == id).Select(a => new { a.Type, a.DataTag, a.LastModified }).SingleOrDefaultAsync();

 

             if (avatarEntity != null)

             {

-                if (!LanguageHelper.AreSame(avatarEntity.Data == null, avatarEntity.Type == null))

+                if (!LanguageHelper.AreSame(avatarEntity.DataTag == null, avatarEntity.Type == null))

                 {

                     var message = Resources.Services.UserAvatarService.ExceptionDatabaseCorruptedDataAndTypeNotSame;

                     _logger.LogCritical(message);

                     throw new DatabaseCorruptedException(message);

                 }

 

-                if (avatarEntity.Data != null)

+

+                if (avatarEntity.DataTag != null)

                 {

+                    var data = await _dataManager.GetEntry(avatarEntity.DataTag);

                     return new AvatarInfo

                     {

                         Avatar = new Avatar

                         {

                             Type = avatarEntity.Type!,

-                            Data = avatarEntity.Data

+                            Data = data

                         },

                         LastModified = avatarEntity.LastModified

                     };

@@ -239,15 +241,15 @@ namespace Timeline.Services
 

             if (avatar == null)

             {

-                if (avatarEntity == null || avatarEntity.Data == null)

+                if (avatarEntity == null || avatarEntity.DataTag == null)

                 {

                     return;

                 }

                 else

                 {

-                    avatarEntity.Data = null;

+                    await _dataManager.FreeEntry(avatarEntity.DataTag);

+                    avatarEntity.DataTag = null;

                     avatarEntity.Type = null;

-                    avatarEntity.ETag = null;

                     avatarEntity.LastModified = _clock.GetCurrentTime();

                     await _database.SaveChangesAsync();

                     _logger.LogInformation(Resources.Services.UserAvatarService.LogUpdateEntity);

@@ -256,24 +258,26 @@ namespace Timeline.Services
             else

             {

                 await _avatarValidator.Validate(avatar);

+                var tag = await _dataManager.RetainEntry(avatar.Data);

+                var oldTag = avatarEntity?.DataTag;

                 var create = avatarEntity == null;

-                if (create)

+                if (avatarEntity == null)

                 {

                     avatarEntity = new UserAvatarEntity();

+                    _database.UserAvatars.Add(avatarEntity);

                 }

-                avatarEntity!.Type = avatar.Type;

-                avatarEntity.Data = avatar.Data;

-                avatarEntity.ETag = await _eTagGenerator.Generate(avatar.Data);

+                avatarEntity.DataTag = tag;

+                avatarEntity.Type = avatar.Type;

                 avatarEntity.LastModified = _clock.GetCurrentTime();

                 avatarEntity.UserId = id;

-                if (create)

-                {

-                    _database.UserAvatars.Add(avatarEntity);

-                }

                 await _database.SaveChangesAsync();

                 _logger.LogInformation(create ?

                     Resources.Services.UserAvatarService.LogCreateEntity

                     : Resources.Services.UserAvatarService.LogUpdateEntity);

+                if (oldTag != null)

+                {

+                    await _dataManager.FreeEntry(oldTag);

+                }

             }

         }

     }

@@ -282,9 +286,8 @@ namespace Timeline.Services
     {

         public static void AddUserAvatarService(this IServiceCollection services)

         {

-            services.TryAddTransient<IETagGenerator, ETagGenerator>();

             services.AddScoped<IUserAvatarService, UserAvatarService>();

-            services.AddSingleton<IDefaultUserAvatarProvider, DefaultUserAvatarProvider>();

+            services.AddScoped<IDefaultUserAvatarProvider, DefaultUserAvatarProvider>();

             services.AddTransient<IUserAvatarValidator, UserAvatarValidator>();

         }

     }