domain: add Media Catalog ports and MetadataResolver service

crates/domain/tests/services/metadata_resolver.rs

@@ -0,0 +1,45 @@
+use domain::entities::{AssetMetadata, MetadataSource};
+use domain::services::metadata_resolver::{get_field_source, resolve_metadata};
+use domain::value_objects::{MetadataValue, StructuredData, SystemId};
+
+fn layer(source: MetadataSource, entries: &[(&str, &str)]) -> AssetMetadata {
+    let mut data = StructuredData::new();
+    for (k, v) in entries {
+        data.insert(*k, MetadataValue::String(v.to_string()));
+    }
+    AssetMetadata::new(SystemId::new(), source, data)
+}
+
+#[test]
+fn user_edited_overrides_exif() {
+    let exif = layer(MetadataSource::ExifExtracted, &[("title", "DSC_0001")]);
+    let user = layer(MetadataSource::UserEdited, &[("title", "Sunset")]);
+    let result = resolve_metadata(&[exif, user]);
+    assert_eq!(result.get_string("title"), Some("Sunset"));
+}
+
+#[test]
+fn ai_overrides_exif_but_not_user() {
+    let exif = layer(MetadataSource::ExifExtracted, &[("desc", "raw"), ("camera", "Nikon")]);
+    let ai = layer(MetadataSource::AiGenerated, &[("desc", "ai-desc")]);
+    let user = layer(MetadataSource::UserEdited, &[("desc", "user-desc")]);
+    let result = resolve_metadata(&[exif, ai, user]);
+    assert_eq!(result.get_string("desc"), Some("user-desc"));
+    assert_eq!(result.get_string("camera"), Some("Nikon"));
+}
+
+#[test]
+fn get_field_source_returns_highest_priority() {
+    let exif = layer(MetadataSource::ExifExtracted, &[("iso", "100")]);
+    let ai = layer(MetadataSource::AiGenerated, &[("iso", "200")]);
+    let layers = [exif, ai];
+    let (src, val) = get_field_source(&layers, "iso").unwrap();
+    assert_eq!(src, MetadataSource::AiGenerated);
+    assert_eq!(val, &MetadataValue::String("200".to_string()));
+}
+
+#[test]
+fn empty_layers_returns_empty() {
+    let result = resolve_metadata(&[]);
+    assert!(result.is_empty());
+}

crates/domain/tests/services/mod.rs

@@ -1,2 +1,3 @@
 mod permission_service;
 mod quota_checker;
+mod metadata_resolver;