Make Genre a separate entity in its own right

docker/api/Dockerfile

@@ -1,4 +1,4 @@
 FROM mcr.microsoft.com/dotnet/core/aspnet:latest
-COPY musiccatalogue.api-1.14.0.0 /opt/musiccatalogue.api-1.14.0.0
-WORKDIR /opt/musiccatalogue.api-1.14.0.0/bin
+COPY musiccatalogue.api-1.15.0.0 /opt/musiccatalogue.api-1.15.0.0
+WORKDIR /opt/musiccatalogue.api-1.15.0.0/bin
 ENTRYPOINT [ "./MusicCatalogue.Api" ]

sql/Genre Migration Post-Migration Test.sql

@@ -0,0 +1,10 @@
+-- "Before" Query
+SELECT Title, Genre
+FROM ALBUMS
+ORDER BY Title ASC;
+
+-- "After" Query
+SELECT al.Title, g.Name AS "Genre"
+FROM ALBUMS al
+INNER JOIN GENRES g ON g.Id = al.GenreId
+ORDER BY al.Title ASC;

sql/Genre Migration Pre-Migration Test.sql

@@ -0,0 +1,41 @@
+-- Create a GENRES table manually
+CREATE TABLE GENRES (
+    Id int NOT NULL PRIMARY KEY,
+    Name Text NOT NULL );
+
+-- Add the Genre ID column to the ALBUMS table
+ALTER TABLE ALBUMS ADD GenreId int NULL;
+
+-- Check the WITH construct does what's required in this instance
+WITH CURRENT_GENRES ( Id, Name ) AS
+(
+    SELECT DISTINCT RANK() OVER ( ORDER BY Genre ), Genre
+    FROM ALBUMS
+    GROUP BY Genre
+)
+SELECT *
+FROM CURRENT_GENRES;
+
+-- Test the migration script to move genres to the new table
+WITH CURRENT_GENRES ( Id, Name ) AS
+(
+    SELECT DISTINCT RANK() OVER ( ORDER BY Genre ), Genre
+    FROM ALBUMS
+)
+INSERT INTO GENRES ( Id, Name )
+SELECT Id, Name
+FROM CURRENT_GENRES;
+
+-- And to update the Genre ID against the album
+UPDATE ALBUMS
+SET GenreId = ( SELECT Id FROM GENRES WHERE Name = ALBUMS.Genre );
+
+-- Cross-check - should produce 0 rows
+SELECT al.Genre, g.Name
+FROM ALBUMS al
+INNER JOIN GENRES g ON g.Id = al.GenreId
+WHERE al.Genre <> g.Name;
+
+-- Clean up
+ALTER TABLE ALBUMS DROP GenreId;
+DROP TABLE GENRES;

sql/Summarise By Genre.sql

@@ -1,9 +1,10 @@
 WITH ALBUM_SUMMARY ( Id, ArtistId, Genre, Tracks, Price, IsWishListItem ) AS
 (
-    SELECT a.Id, a.ArtistId, a.Genre, COUNT( t.Id ), IFNULL( a.Price, 0 ), IFNULL( a.IsWishListItem, 0) 
+    SELECT a.Id, a.ArtistId, g.Name, COUNT( t.Id ), IFNULL( a.Price, 0 ), IFNULL( a.IsWishListItem, 0) 
     FROM ALBUMS a
     INNER JOIN TRACKS t ON t.AlbumId = a.Id
-    GROUP BY a.Id, a.ArtistId, a.Genre, a.Price
+    INNER JOIN GENRES g ON g.Id = a.GenreId
+    GROUP BY a.Id, a.ArtistId, g.Name, a.Price
 )
 SELECT Genre, COUNT( DISTINCT ArtistId) AS "Artists", COUNT( DISTINCT Id ) AS "Albums", SUM( Tracks ) AS "Tracks", SUM( Price ) AS "Spend"
 FROM ALBUM_SUMMARY

src/MusicCatalogue.Api/Controllers/AlbumsController.cs

@@ -11,6 +11,8 @@ namespace MusicCatalogue.Api.Controllers
     [Route("[controller]")]
     public class AlbumsController : Controller
     {
+        private const string OtherGenre = "Other";
+
         private readonly IMusicCatalogueFactory _factory;
 
         public AlbumsController(IMusicCatalogueFactory factory)
@@ -77,13 +79,16 @@ public async Task<ActionResult<IEnumerable<Album>>> GetAlbumsByArtistAsync(int a
         [Route("")]
         public async Task<ActionResult<Album>> UpdateAlbumAsync([FromBody] Album template)
         {
+            // Make sure the "other" Genre exists as a fallback for album updates where no genre is given
+            var otherGenre = _factory.Genres.AddAsync(OtherGenre);
+
             // Attempt the update
             var album = await _factory.Albums.UpdateAsync(
                 template.Id,
+                template.GenreId ?? otherGenre.Id,
                 template.ArtistId,
                 template.Title,
                 template.Released,
-                template.Genre,
                 template.CoverUrl,
                 template.IsWishListItem,
                 template.Purchased,

src/MusicCatalogue.Api/MusicCatalogue.Api.csproj

@@ -2,9 +2,9 @@
 
   <PropertyGroup>
     <TargetFramework>net7.0</TargetFramework>
-    <ReleaseVersion>1.14.0.0</ReleaseVersion>
-    <FileVersion>1.14.0.0</FileVersion>
-    <ProductVersion>1.14.0</ProductVersion>
+    <ReleaseVersion>1.15.0.0</ReleaseVersion>
+    <FileVersion>1.15.0.0</FileVersion>
+    <ProductVersion>1.15.0</ProductVersion>
     <Nullable>enable</Nullable>
     <ImplicitUsings>enable</ImplicitUsings>
   </PropertyGroup>

src/MusicCatalogue.Data/MigrationUtilities.cs

@@ -0,0 +1,47 @@
+using System.Reflection;
+
+namespace MusicCatalogue.Data
+{
+    public static class MigrationUtilities
+    {
+        /// <summary>
+        /// Get the namespace for the migration SQL scripts
+        /// </summary>
+        /// <returns></returns>
+        public static string GetSqlScriptNamespace()
+        {
+            // The assumption is that there will be a SQL folder at the same level as this class
+            // where the SQL script resources are held
+            var dataAssemblyNamespace = MethodBase.GetCurrentMethod()?.DeclaringType?.Namespace ?? "";
+            var sqlScriptNamespace = $"{dataAssemblyNamespace}.Sql";
+            return sqlScriptNamespace;
+        }
+
+        /// <summary>
+        /// Read and return the contents of an embedded resource containing a SQL migration script
+        /// </summary>
+        /// <param name="name"></param>
+        /// <returns></returns>
+        public static string ReadMigrationSqlScript(string name)
+        {
+            string content = "";
+
+            // Get the resource name
+            var sqlScriptNamespace = GetSqlScriptNamespace();
+            var sqlResourceName = $"{sqlScriptNamespace}.{name}";
+
+            // Get the name of the resource and a resource stream for reading it
+            var assembly = Assembly.GetExecutingAssembly();
+            var resourceStream = assembly.GetManifestResourceStream(sqlResourceName);
+
+            // Open a stream reader to read the file content
+            using (var reader = new StreamReader(resourceStream!))
+            {
+                // Read the file content
+                content = reader.ReadToEnd();
+            }
+
+            return content;
+        }
+    }
+}