Implement data manager.

3 files changed, 107 insertions, 39 deletions

diff --git a/Timeline/Entities/DataEntity.cs b/Timeline/Entities/DataEntity.cs
new file mode 100644
index 00000000..b21e2dbf
--- /dev/null
+++ b/Timeline/Entities/DataEntity.cs
@@ -0,0 +1,23 @@
+using System.ComponentModel.DataAnnotations;

+using System.ComponentModel.DataAnnotations.Schema;

+

+namespace Timeline.Entities

+{

+    [Table("data")]

+    public class DataEntity

+    {

+        [Column("id"), Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]

+        public long Id { get; set; }

+

+        [Column("tag"), Required]

+        public string Tag { get; set; } = default!;

+

+        [Column("data"), Required]

+#pragma warning disable CA1819 // Properties should not return arrays

+        public byte[] Data { get; set; } = default!;

+#pragma warning restore CA1819 // Properties should not return arrays

+

+        [Column("ref"), Required]

+        public int Ref { get; set; }

+    }

+}

diff --git a/Timeline/Entities/DatabaseContext.cs b/Timeline/Entities/DatabaseContext.cs
index 039cbd51..3ed61b71 100644
--- a/Timeline/Entities/DatabaseContext.cs
+++ b/Timeline/Entities/DatabaseContext.cs
@@ -21,5 +21,6 @@ namespace Timeline.Entities
         public DbSet<TimelinePostEntity> TimelinePosts { get; set; } = default!;

         public DbSet<TimelineMemberEntity> TimelineMembers { get; set; } = default!;

         public DbSet<JwtTokenEntity> JwtToken { get; set; } = default!;

+        public DbSet<DataEntity> Data { get; set; } = default!;

     }

 }

diff --git a/Timeline/Services/DataManager.cs b/Timeline/Services/DataManager.cs
index 005ad23c..66aa6f81 100644
--- a/Timeline/Services/DataManager.cs
+++ b/Timeline/Services/DataManager.cs
@@ -1,37 +1,19 @@
-using System;

-using System.Collections.Generic;

+using Microsoft.EntityFrameworkCore;

+using System;

 using System.Linq;

 using System.Threading.Tasks;

+using Timeline.Entities;

 

 namespace Timeline.Services

 {

-    public class DataEntry

-    {

-#pragma warning disable CA1819 // Properties should not return arrays

-        public byte[] Data { get; set; } = default!;

-#pragma warning restore CA1819 // Properties should not return arrays

-        public DataInfo Info { get; set; } = default!;

-    }

-

-    public class DataInfo

-    {

-        public DateTime Time { get; set; }

-        public string Type { get; set; } = default!;

-    }

-

     /// <summary>

-    /// A data manager controling data.

+    /// A data manager controlling data.

     /// </summary>

     /// <remarks>

-    /// All data to be saved will be checked identity.

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

-    /// Every data has a ref count. When data is saved, ref count increase.

-    /// When data is removed, ref count decease. If ref count is decreased

+    /// 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.

-    /// 

-    /// Type is just an attached attribute for convenience and not participate

-    /// in identity verification. This should be only used to save blobs but not

-    /// strings. It will be rare for identity blob with different type, I think.

     /// </remarks>

     public interface IDataManager

     {

@@ -40,11 +22,9 @@ namespace Timeline.Services
         /// increases its ref count and returns a tag to the entry.

         /// </summary>

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

-        /// <param name="type">The type of the data. Can't be null.</param>

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

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

-        /// <exception cref="InvalidOperationException">Thrown when a saved copy of data already exists but type is different.</exception>

-        public Task<string> RetainEntry(byte[] data, string type);

+        /// <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.

@@ -61,19 +41,83 @@ namespace Timeline.Services
         /// Retrieve the entry with given tag.

         /// </summary>

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

-        /// <returns>The entry.</returns>

+        /// <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<DataEntry> GetEntry(string tag);

-

-        /// <summary>

-        /// Retrieve info of the entry with given tag.

-        /// </summary>

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

-        /// <returns>The entry info.</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<DataInfo> GetEntryInfo(string tag);

+        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);

+                await _database.SaveChangesAsync();

+            }

+            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("Entry with given tag does not exist.");

+

+            return entity.Data;

+        }

+    }

 }