From 2f5217050dce124df9f0408c3eeab5d4f32e3a5e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thomas=20J=C3=A4ckle?= <thomas.jaeckle@beyonnex.io>
Date: Thu, 26 Oct 2023 16:23:47 +0200
Subject: [PATCH] fix that ThingFieldSelector did not allow specific paths of
 "_metadata"
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* it only allowed to select top-level "_metadata" - which does not make sense to limit, as even selecting only specific _metadata is already supported
* also add missing support for featureId wildcard when selecting e.g. "_metadata/features/*/properties"

Signed-off-by: Thomas Jäckle <thomas.jaeckle@beyonnex.io>
---
 .../things/model/ThingFieldSelector.java      |  4 +--
 .../things/model/ThingsModelFactory.java      | 35 ++++++++++++++++---
 2 files changed, 33 insertions(+), 6 deletions(-)

diff --git a/things/model/src/main/java/org/eclipse/ditto/things/model/ThingFieldSelector.java b/things/model/src/main/java/org/eclipse/ditto/things/model/ThingFieldSelector.java
index 81c3e55e8a..6dc28c152f 100644
--- a/things/model/src/main/java/org/eclipse/ditto/things/model/ThingFieldSelector.java
+++ b/things/model/src/main/java/org/eclipse/ditto/things/model/ThingFieldSelector.java
@@ -38,8 +38,8 @@ public final class ThingFieldSelector implements JsonFieldSelector {
             .withoutUrlDecoding()
             .build();
     static final List<String> SELECTABLE_FIELDS = Arrays.asList("thingId", "policyId", "definition",
-            "_namespace", "_revision", "_created", "_modified", "_metadata", "_policy", "_context", "_context(/[^,]+)?",
-            "features(/[^,]+)?", "attributes(/[^,]+)?");
+            "_namespace", "_revision", "_created", "_modified", "_metadata(/[^,]+)?", "_policy", "_context",
+            "_context(/[^,]+)?", "features(/[^,]+)?", "attributes(/[^,]+)?");
     private static final String KNOWN_FIELDS_REGEX = "/?(" + String.join("|", SELECTABLE_FIELDS) + ")";
     private static final String FIELD_SELECTION_REGEX = "^" + KNOWN_FIELDS_REGEX + "(," + KNOWN_FIELDS_REGEX + ")*$";
     private static final Pattern FIELD_SELECTION_PATTERN = Pattern.compile(FIELD_SELECTION_REGEX);
diff --git a/things/model/src/main/java/org/eclipse/ditto/things/model/ThingsModelFactory.java b/things/model/src/main/java/org/eclipse/ditto/things/model/ThingsModelFactory.java
index 4ba8534440..4938180f86 100755
--- a/things/model/src/main/java/org/eclipse/ditto/things/model/ThingsModelFactory.java
+++ b/things/model/src/main/java/org/eclipse/ditto/things/model/ThingsModelFactory.java
@@ -796,7 +796,12 @@ public static JsonFieldSelector expandFeatureIdWildcards(final Collection<JsonKe
      */
     public static Stream<JsonPointer> expandFeatureIdWildcard(final Collection<JsonKey> featureIds,
             final JsonPointer jsonPointer) {
-        if (hasFeatureIdWildcard(jsonPointer)) {
+        if (hasMetadataFeatureIdWildcard(jsonPointer)) {
+            return featureIds.stream().map(fid -> Thing.JsonFields.METADATA.getPointer()
+                    .append(Thing.JsonFields.FEATURES.getPointer())
+                    .append(JsonPointer.of(fid))
+                    .append(jsonPointer.getSubPointer(3).orElse(JsonPointer.empty())));
+        } else if (hasFeatureIdWildcard(jsonPointer)) {
             return featureIds.stream().map(fid -> Thing.JsonFields.FEATURES.getPointer()
                     .append(JsonPointer.of(fid))
                     .append(jsonPointer.getSubPointer(2).orElse(JsonPointer.empty())));
@@ -806,11 +811,33 @@ public static Stream<JsonPointer> expandFeatureIdWildcard(final Collection<JsonK
     }
 
     private static boolean hasFeatureIdWildcard(final JsonPointer pointer) {
-        return pointer.getLevelCount() > 1
-                && pointer.getRoot()
+        return pointer.getLevelCount() > 1 &&
+                isFeaturePath(pointer) && pointer.get(1).filter(FEATURE_ID_WILDCARD::equals).isPresent();
+    }
+
+    private static boolean isFeaturePath(final JsonPointer pointer) {
+        return pointer.getRoot()
                 .filter(root -> Thing.JsonFields.FEATURES.getPointer().equals(JsonPointer.of(root)))
+                .isPresent();
+    }
+
+    private static boolean hasMetadataFeatureIdWildcard(final JsonPointer pointer) {
+        return pointer.getLevelCount() > 2 &&
+                isMetadataFeaturePath(pointer) &&
+                pointer.get(2).filter(FEATURE_ID_WILDCARD::equals).isPresent();
+    }
+
+    private static boolean isMetadataFeaturePath(final JsonPointer pointer) {
+        return pointer.getRoot()
+                .filter(root -> Thing.JsonFields.METADATA.getPointer().equals(JsonPointer.of(root)))
                 .isPresent()
-                && pointer.get(1).filter(FEATURE_ID_WILDCARD::equals).isPresent();
+                &&
+                pointer.getSubPointer(1)
+                        .map(metadataRoot -> metadataRoot.getRoot()
+                                .filter(subRoot -> Thing.JsonFields.FEATURES.getPointer()
+                                        .equals(JsonPointer.of(subRoot)))
+                                .isPresent()
+                        ).orElse(false);
     }
 
 }