Add support for variables

CHANGELOG.md

@@ -1,5 +1,9 @@
 ## v2.0.0-beta.45 - 2025-01-14
 
+- Added variable support.
+
+## v2.0.0-beta.45 - 2025-01-14
+
 - Execute transform id after transform property.
 
 ## v2.0.0-beta.44 - 2025-01-14

src/Nexus.Sources.Transform/TransformDataSource.cs

@@ -21,7 +21,10 @@ internal record PropertyTransform(
     string? TargetProperty,
     string? TargetTemplate,
     string? Separator
-);
+)
+{
+    public bool NeedsVariableExpansion { get; set; }
+}
 
 internal record IdTransform(
     // TransformTarget target, /* (catalog vs. resource - maybe required later) */
@@ -41,7 +44,7 @@ internal record TransformSettings(
     "A data source to transform catalog properties like resources names and group memberships",
     "https://github.com/nexus-main/nexus-sources-transform",
     "https://github.com/nexus-main/nexus-sources-transform")]
-public class Transform : IDataSource
+public partial class Transform : IDataSource
 {
     private const string DEFAULT_TARGET_TEMPLATE = "$1";
 
@@ -51,13 +54,25 @@ public class Transform : IDataSource
 
     private ILogger _logger = default!;
 
+    [GeneratedRegex(@"\${(.*?)}")]
+    private partial Regex VariableExpansionRegex { get; }
+
     /// <inheritdoc/>
     public Task SetContextAsync(DataSourceContext context, ILogger logger, CancellationToken cancellationToken)
     {
         // TODO: this is not so nice
         _settings = JsonSerializer
             .Deserialize<TransformSettings>(JsonSerializer.Serialize(context.SourceConfiguration));
 
+        if (_settings is not null && _settings.PropertyTransforms is not null)
+        {
+            foreach (var propertyTransform in _settings.PropertyTransforms)
+            {
+                if (propertyTransform.TargetTemplate is not null)
+                    propertyTransform.NeedsVariableExpansion = VariableExpansionRegex.IsMatch(propertyTransform.TargetTemplate);
+            }
+        }
+
         _logger = logger;
 
         return Task.CompletedTask;
@@ -130,11 +145,17 @@ public Task<ResourceCatalog> EnrichCatalogAsync(ResourceCatalog catalog, Cancell
                     if (!isMatch)
                         continue;
 
+                    var targetTemplate = transform.TargetTemplate is null
+                        ? DEFAULT_TARGET_TEMPLATE
+                        : transform.NeedsVariableExpansion
+                            ? ExpandVariables(transform.TargetTemplate, resourceProperties)
+                            : transform.TargetTemplate;
+
                     var targetValue = Regex
                         .Replace(
                             input: sourceValue,
                             pattern: transform.SourcePattern,
-                            replacement: transform.TargetTemplate ?? DEFAULT_TARGET_TEMPLATE
+                            replacement: targetTemplate
                         );
 
                     // apply value
@@ -217,4 +238,22 @@ public Task ReadAsync(DateTime begin, DateTime end, ReadRequest[] requests, Read
     {
         return Task.CompletedTask;
     }
+
+    private string ExpandVariables(string targetTemplate, IReadOnlyDictionary<string, JsonElement>? resourceProperties)
+    {
+        return VariableExpansionRegex.Replace(targetTemplate, match =>
+        {
+            var path = match.Groups[1].Value;
+
+            if (!_pathCache.TryGetValue(path, out var pathSegments))
+            {
+                pathSegments = path.Split('/');
+                _pathCache[path] = pathSegments;
+            }
+
+            return resourceProperties is null
+                ? ""
+                : resourceProperties.GetStringValue(pathSegments) ?? "";
+        });
+    }
 }

tests/Nexus.Sources.Transform.Tests/TransformDataSourceTests.cs

@@ -393,6 +393,64 @@ string expected
         Assert.Equal(expected, actual);
     }
 
+    [Fact]
+    public async Task CanExpandVariables()
+    {
+        // Arrange
+        var expected = "my_file_source_id_foo_something_else";
+        var originalName = "foo in meters per second";
+
+        /* data source setup */
+        var transform = new PropertyTransform(
+            Operation: default,
+            SourcePath: DataModelExtensions.OriginalNameKey,
+            SourcePattern: "(.*) in.*",
+            TargetProperty: "id",
+            TargetTemplate: "${file-source-id}_$1_${something-else}",
+            Separator: default
+        );
+
+        var settings = new TransformSettings(
+            IdTransforms: [],
+            PropertyTransforms: [transform]
+        );
+
+        var sourceConfiguration = JsonSerializer
+            .Deserialize<IReadOnlyDictionary<string, JsonElement>>(JsonSerializer.SerializeToElement(settings));
+
+        var context = new DataSourceContext(
+            ResourceLocator: default,
+            SystemConfiguration: default,
+            SourceConfiguration: sourceConfiguration,
+            RequestConfiguration: default
+        );
+
+        var dataSource = new Transform();
+
+        await dataSource.SetContextAsync(context, NullLogger.Instance, CancellationToken.None);
+
+        /* catalog setup */
+        var resource = new ResourceBuilder(id: "foo")
+            .WithOriginalName(originalName)
+            .WithProperty("file-source-id", "my_file_source_id")
+            .WithProperty("something-else", "something_else")
+            .Build();
+
+        var catalog = new ResourceCatalogBuilder(id: "/bar")
+            .AddResource(resource)
+            .Build();
+
+        // Act
+        var actualCatalog = await dataSource
+            .EnrichCatalogAsync(catalog, CancellationToken.None);
+
+        // Assert
+        var actual = actualCatalog.Resources![0].Properties!
+            .GetStringValue(["id"]);
+
+        Assert.Equal(expected, actual);
+    }
+
     [Fact]
     public async Task DoesNotModifyPropertiesIfNoMatch()
     {

version.json

@@ -1,4 +1,4 @@
 {
     "version": "2.0.0",
-    "suffix": "beta.45"
+    "suffix": "beta.46"
 }