(#102) FileCache: improve the workarounds for the older versions of W…

…indows

Emulsion.ContentProxy/FileCache.fs

@@ -36,6 +36,26 @@ module FileCache =
         with
         | :? ArgumentException -> None
 
+    let IsMoveAndDeleteModeEnabled =
+        // NOTE: On older versions of Windows (known to reproduce on windows-2019 GitHub Actions image), the following
+        // scenario may be defunct:
+        //
+        // - open a file with FileShare.Delete (i.e. for download)
+        // - delete a file (i.e. during the cache cleanup)
+        // - try to create a file with the same name again
+        //
+        // According to this article
+        // (https://boostgsoc13.github.io/boost.afio/doc/html/afio/FAQ/deleting_open_files.html), it is impossible to do
+        // since file will occupy its disk name until the last handle is closed.
+        //
+        // In practice, this is allowed (checked at least on Windows 10 20H2 and windows-2022 GitHub Actions image), but
+        // some tests are known to be broken on older versions of Windows (windows-2019).
+        //
+        // As a workaround, let's rename the file to a random name before deleting it.
+        //
+        // This workaround may be removed after these older versions of Windows goes out of support.
+        OperatingSystem.IsWindows()
+
 type FileCache(logger: ILogger,
                settings: FileCacheSettings,
                httpClientFactory: IHttpClientFactory,
@@ -61,12 +81,27 @@ type FileCache(logger: ILogger,
                 None
     }
 
+    let enumerateCacheFiles() =
+        let entries = Directory.EnumerateFileSystemEntries settings.Directory
+        if FileCache.IsMoveAndDeleteModeEnabled then
+            entries |> Seq.filter(fun p -> not(p.EndsWith ".deleted"))
+        else
+            entries
+
+    let deleteFileSafe (fileInfo: FileInfo) = async {
+        if FileCache.IsMoveAndDeleteModeEnabled then
+            fileInfo.MoveTo(Path.Combine(fileInfo.DirectoryName, $"{Guid.NewGuid().ToString()}.deleted"))
+            fileInfo.Delete()
+        else
+            fileInfo.Delete()
+    }
+
     let assertCacheDirectoryExists() = async {
         Directory.CreateDirectory settings.Directory |> ignore
     }
 
     let assertCacheValid() = async {
-        Directory.EnumerateFileSystemEntries settings.Directory
+        enumerateCacheFiles()
         |> Seq.iter(fun entry ->
             let entryName = Path.GetFileName entry
 
@@ -83,40 +118,14 @@ type FileCache(logger: ILogger,
         )
     }
 
-    let deleteFileSafe (fileInfo: FileInfo) = async {
-        if OperatingSystem.IsWindows() then
-            // NOTE: On older versions of Windows (known to reproduce on windows-2019 GitHub Actions image), the
-            // following scenario may be defunct:
-            // - open a file with FileShare.Delete (i.e. for download)
-            // - delete a file (i.e. during the cache cleanup)
-            // - try to create a file with the same name again
-            //
-            // According to this article
-            // (https://boostgsoc13.github.io/boost.afio/doc/html/afio/FAQ/deleting_open_files.html), it is impossible
-            // to do since file will occupy its disk name until the last handle is closed.
-            //
-            // In practice, this is allowed (checked at least on Windows 10 20H2 and windows-2022 GitHub Actions image),
-            // but is known to be broken on older versions of Windows (windows-2019).
-            //
-            // As a workaround, let's rename the file to a random name before deleting it.
-            //
-            // This workaround may be removed after these older versions of Windows goes out of support.
-            fileInfo.MoveTo(Path.Combine(fileInfo.DirectoryName, $"{Guid.NewGuid().ToString()}.deleted"))
-            fileInfo.Delete()
-        else
-            fileInfo.Delete()
-    }
-
     let ensureFreeCache size = async {
         if size > settings.FileSizeLimitBytes || size > settings.TotalCacheSizeLimitBytes then
             return false
         else
             do! assertCacheDirectoryExists()
             do! assertCacheValid()
 
-            let allEntries =
-                Directory.EnumerateFileSystemEntries settings.Directory
-                |> Seq.map FileInfo
+            let allEntries = enumerateCacheFiles() |> Seq.map FileInfo
 
             // Now, sort the entries from newest to oldest, and start deleting if required at a point when we understand
             // that there are too much files:

Emulsion.Database/Migrations/20220828132228_UpdatedUniqueContentIndex.fs

@@ -0,0 +1,63 @@
+// <auto-generated />
+namespace Emulsion.Database.Migrations
+
+open System
+open Emulsion.Database
+open Microsoft.EntityFrameworkCore
+open Microsoft.EntityFrameworkCore.Infrastructure
+open Microsoft.EntityFrameworkCore.Migrations
+
+[<DbContext(typeof<EmulsionDbContext>)>]
+[<Migration("20220828132228_UpdatedUniqueContentIndex")>]
+type UpdatedUniqueContentIndex() =
+    inherit Migration()
+
+    override this.Up(migrationBuilder:MigrationBuilder) =
+        migrationBuilder.Sql @"
+            drop index TelegramContents_Unique
+
+            create unique index TelegramContents_Unique
+            on TelegramContents(ChatUserName, MessageId, FileId, FileName, MimeType)
+        " |> ignore
+
+    override this.Down(migrationBuilder:MigrationBuilder) =
+        migrationBuilder.Sql @"
+            drop index TelegramContents_Unique
+
+            create unique index TelegramContents_Unique
+            on TelegramContents(ChatUserName, MessageId, FileId)
+        " |> ignore
+
+    override this.BuildTargetModel(modelBuilder: ModelBuilder) =
+        modelBuilder
+            .HasAnnotation("ProductVersion", "5.0.10")
+            |> ignore
+
+        modelBuilder.Entity("Emulsion.Database.Entities.TelegramContent", (fun b ->
+
+            b.Property<Int64>("Id")
+                .IsRequired(true)
+                .ValueGeneratedOnAdd()
+                .HasColumnType("INTEGER") |> ignore
+            b.Property<string>("ChatUserName")
+                .IsRequired(false)
+                .HasColumnType("TEXT") |> ignore
+            b.Property<string>("FileId")
+                .IsRequired(false)
+                .HasColumnType("TEXT") |> ignore
+            b.Property<string option>("FileName")
+                .IsRequired(false)
+                .HasColumnType("TEXT") |> ignore
+            b.Property<Int64>("MessageId")
+                .IsRequired(true)
+                .HasColumnType("INTEGER") |> ignore
+            b.Property<string option>("MimeType")
+                .IsRequired(false)
+                .HasColumnType("TEXT") |> ignore
+
+            b.HasKey("Id") |> ignore
+
+            b.ToTable("TelegramContents") |> ignore
+
+        )) |> ignore
+

Emulsion.Tests/ContentProxy/FileCacheTests.fs

@@ -25,6 +25,10 @@ type FileCacheTests(outputHelper: ITestOutputHelper) =
     let assertCacheState(entries: (string * byte[]) seq) =
         let files =
             Directory.EnumerateFileSystemEntries(cacheDirectory.Value)
+            |> Seq.filter(fun f ->
+                if FileCache.IsMoveAndDeleteModeEnabled then not(f.EndsWith ".deleted")
+                else true
+            )
             |> Seq.map(fun file ->
                 let name = Path.GetFileName file
                 let content = File.ReadAllBytes file