refactor: Refactor data services.

1 files changed, 49 insertions, 0 deletions

diff --git a/BackEnd/Timeline/Services/Data/IDataManager.cs b/BackEnd/Timeline/Services/Data/IDataManager.cs
new file mode 100644
index 00000000..6a87c1b2
--- /dev/null
+++ b/BackEnd/Timeline/Services/Data/IDataManager.cs
@@ -0,0 +1,49 @@
+using System;

+using System.Threading;

+using System.Threading.Tasks;

+

+namespace Timeline.Services.Data

+{

+    /// <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>

+        /// <param name="cancellationToken">Cancellation token.</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, CancellationToken cancellationToken = default);

+

+        /// <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>

+        /// <param name="cancellationToken">Cancellation token.</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, CancellationToken cancellationToken = default);

+

+        /// <summary>

+        /// Retrieve the entry with given tag. If not exist, returns null.

+        /// </summary>

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

+        /// <param name="cancellationToken">Cancellation token.</param>

+        /// <returns>The data of the entry. If not exist, returns null.</returns>

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

+        public Task<byte[]?> GetEntry(string tag, CancellationToken cancellationToken = default);

+    }

+}