X-Git-Url: https://git.opendaylight.org/gerrit/gitweb?a=blobdiff_plain;f=binding%2Fyang-binding%2Fsrc%2Fmain%2Fjava%2Forg%2Fopendaylight%2Fyangtools%2Fyang%2Fbinding%2FInstanceIdentifier.java;h=22681a4d0f13e789f541c444d117e22d76b08df2;hb=106cf943e6837e6c30d7628b7c597ee57f0bfbd3;hp=0c89142533d5c337fc8a503337f7b5b949fc8177;hpb=19a1a7c742416955cb09f6d58915b9aaa944101a;p=yangtools.git

diff --git a/binding/yang-binding/src/main/java/org/opendaylight/yangtools/yang/binding/InstanceIdentifier.java b/binding/yang-binding/src/main/java/org/opendaylight/yangtools/yang/binding/InstanceIdentifier.java
index 0c89142533..22681a4d0f 100644
--- a/binding/yang-binding/src/main/java/org/opendaylight/yangtools/yang/binding/InstanceIdentifier.java
+++ b/binding/yang-binding/src/main/java/org/opendaylight/yangtools/yang/binding/InstanceIdentifier.java
@@ -12,18 +12,21 @@ import static com.google.common.base.Verify.verify;
 import static com.google.common.base.Verify.verifyNotNull;
 import static java.util.Objects.requireNonNull;
 
+import com.google.common.annotations.Beta;
 import com.google.common.base.MoreObjects;
 import com.google.common.base.MoreObjects.ToStringHelper;
 import com.google.common.base.VerifyException;
-import com.google.common.collect.ImmutableCollection;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Iterables;
+import java.io.IOException;
+import java.io.NotSerializableException;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
 import java.io.ObjectStreamException;
 import java.io.Serializable;
 import java.util.Collections;
-import java.util.Iterator;
+import java.util.List;
 import java.util.Objects;
-import java.util.Optional;
 import org.eclipse.jdt.annotation.NonNull;
 import org.eclipse.jdt.annotation.Nullable;
 import org.opendaylight.yangtools.concepts.HierarchicalIdentifier;
@@ -34,50 +37,49 @@ import org.opendaylight.yangtools.util.HashCodeBuilder;
  *
  * <p>
  * For Example let's say you were trying to refer to a node in inventory which was modeled in YANG as follows,
+ * <pre>code{
+ *   module opendaylight-inventory {
+ *     ....
  *
- * <p>
- * <pre>
- * module opendaylight-inventory {
- *      ....
- *
- *      container nodes {
- *        list node {
- *            key "id";
- *            ext:context-instance "node-context";
- *
- *            uses node;
- *        }
- *    }
+ *     container nodes {
+ *       list node {
+ *         key "id";
+ *         ext:context-instance "node-context";
  *
- * }
- * </pre>
+ *         uses node;
+ *       }
+ *     }
+ *   }
+ * }</pre>
  *
  * <p>
  * You can create an instance identifier as follows to get to a node with id "openflow:1": {@code
- * InstanceIdentifierBuilder.builder(Nodes.class).child(Node.class, new NodeKey(new NodeId("openflow:1")).build();
+ * InstanceIdentifier.builder(Nodes.class).child(Node.class, new NodeKey(new NodeId("openflow:1")).build();
  * }
  *
  * <p>
  * This would be the same as using a path like so, "/nodes/node/openflow:1" to refer to the openflow:1 node
  */
-public class InstanceIdentifier<T extends DataObject>
-        implements HierarchicalIdentifier<InstanceIdentifier<? extends DataObject>> {
+public sealed class InstanceIdentifier<T extends DataObject>
+        implements HierarchicalIdentifier<InstanceIdentifier<? extends DataObject>>
+        permits KeyedInstanceIdentifier {
+    @java.io.Serial
     private static final long serialVersionUID = 3L;
 
     /*
      * Protected to differentiate internal and external access. Internal access is required never to modify
      * the contents. References passed to outside entities have to be wrapped in an unmodifiable view.
      */
-    final Iterable<PathArgument> pathArguments;
+    final Iterable<DataObjectStep<?>> pathArguments;
 
     private final @NonNull Class<T> targetType;
     private final boolean wildcarded;
     private final int hash;
 
-    InstanceIdentifier(final Class<T> type, final Iterable<PathArgument> pathArguments, final boolean wildcarded,
+    InstanceIdentifier(final Class<T> type, final Iterable<DataObjectStep<?>> pathArguments, final boolean wildcarded,
             final int hash) {
         this.pathArguments = requireNonNull(pathArguments);
-        this.targetType = requireNonNull(type);
+        targetType = requireNonNull(type);
         this.wildcarded = wildcarded;
         this.hash = hash;
     }
@@ -110,7 +112,7 @@ public class InstanceIdentifier<T extends DataObject>
      *
      * @return Path argument chain. Immutable and does not contain nulls.
      */
-    public final @NonNull Iterable<PathArgument> getPathArguments() {
+    public final @NonNull Iterable<DataObjectStep<?>> getPathArguments() {
         return Iterables.unmodifiableIterable(pathArguments);
     }
 
@@ -140,43 +142,24 @@ public class InstanceIdentifier<T extends DataObject>
             return false;
         }
 
-        final InstanceIdentifier<?> other = (InstanceIdentifier<?>) obj;
+        final var other = (InstanceIdentifier<?>) obj;
         if (pathArguments == other.pathArguments) {
             return true;
         }
 
         /*
-         * We could now just go and compare the pathArguments, but that
-         * can be potentially expensive. Let's try to avoid that by
-         * checking various things that we have cached from pathArguments
-         * and trying to prove the identifiers are *not* equal.
+         * We could now just go and compare the pathArguments, but that can be potentially expensive. Let's try to avoid
+         * that by checking various things that we have cached from pathArguments and trying to prove the identifiers
+         * are *not* equal.
          */
-        if (hash != other.hash) {
-            return false;
-        }
-        if (wildcarded != other.wildcarded) {
-            return false;
-        }
-        if (targetType != other.targetType) {
-            return false;
-        }
-        if (fastNonEqual(other)) {
-            return false;
-        }
-
-        // Everything checks out so far, so we have to do a full equals
-        return Iterables.elementsEqual(pathArguments, other.pathArguments);
+        return hash == other.hash && wildcarded == other.wildcarded && targetType == other.targetType
+            && keyEquals(other)
+            // Everything checks out so far, so we have to do a full equals
+            && Iterables.elementsEqual(pathArguments, other.pathArguments);
     }
 
-    /**
-     * Perform class-specific fast checks for non-equality. This allows subclasses to avoid iterating over the
-     * pathArguments by performing quick checks on their specific fields.
-     *
-     * @param other The other identifier, guaranteed to be the same class
-     * @return true if the other identifier cannot be equal to this one.
-     */
-    protected boolean fastNonEqual(final InstanceIdentifier<?> other) {
-        return false;
+    boolean keyEquals(final InstanceIdentifier<?> other) {
+        return true;
     }
 
     @Override
@@ -200,7 +183,7 @@ public class InstanceIdentifier<T extends DataObject>
      * <p>
      * For example let's say an instance identifier was built like so,
      * <pre>
-     *      identifier = InstanceIdentifierBuilder.builder(Nodes.class).child(Node.class,
+     *      identifier = InstanceIdentifier.builder(Nodes.class).child(Node.class,
      *                   new NodeKey(new NodeId("openflow:1")).build();
      * </pre>
      *
@@ -219,11 +202,10 @@ public class InstanceIdentifier<T extends DataObject>
     public final <I extends DataObject> @Nullable InstanceIdentifier<I> firstIdentifierOf(
             final Class<@NonNull I> type) {
         int count = 1;
-        for (final PathArgument a : pathArguments) {
-            if (type.equals(a.getType())) {
+        for (var step : pathArguments) {
+            if (type.equals(step.type())) {
                 @SuppressWarnings("unchecked")
-                final InstanceIdentifier<I> ret = (InstanceIdentifier<I>) internalCreate(
-                        Iterables.limit(pathArguments, count));
+                final var ret = (InstanceIdentifier<I>) internalCreate(Iterables.limit(pathArguments, count));
                 return ret;
             }
 
@@ -241,16 +223,15 @@ public class InstanceIdentifier<T extends DataObject>
      * @return key associated with the component, or null if the component type
      *         is not present.
      */
-    public final <N extends Identifiable<K> & DataObject, K extends Identifier<N>> @Nullable K firstKeyOf(
+    public final <N extends KeyAware<K> & DataObject, K extends Key<N>> @Nullable K firstKeyOf(
             final Class<@NonNull N> listItem) {
-        for (final PathArgument i : pathArguments) {
-            if (listItem.equals(i.getType())) {
+        for (var step : pathArguments) {
+            if (step instanceof KeyStep<?, ?> keyPredicate && listItem.equals(step.type())) {
                 @SuppressWarnings("unchecked")
-                final K ret = ((IdentifiableItem<N, K>)i).getKey();
+                final var ret = (K) keyPredicate.key();
                 return ret;
             }
         }
-
         return null;
     }
 
@@ -278,19 +259,15 @@ public class InstanceIdentifier<T extends DataObject>
     public final boolean contains(final InstanceIdentifier<? extends DataObject> other) {
         requireNonNull(other, "other should not be null");
 
-        final Iterator<?> lit = pathArguments.iterator();
-        final Iterator<?> oit = other.pathArguments.iterator();
-
-        while (lit.hasNext()) {
+        final var oit = other.pathArguments.iterator();
+        for (var step : pathArguments) {
             if (!oit.hasNext()) {
                 return false;
             }
-
-            if (!lit.next().equals(oit.next())) {
+            if (!step.equals(oit.next())) {
                 return false;
             }
         }
-
         return true;
     }
 
@@ -305,31 +282,32 @@ public class InstanceIdentifier<T extends DataObject>
     public final boolean containsWildcarded(final InstanceIdentifier<?> other) {
         requireNonNull(other, "other should not be null");
 
-        final Iterator<PathArgument> lit = pathArguments.iterator();
-        final Iterator<PathArgument> oit = other.pathArguments.iterator();
-
-        while (lit.hasNext()) {
-            if (!oit.hasNext()) {
+        final var otherSteps = other.pathArguments.iterator();
+        for (var step : pathArguments) {
+            if (!otherSteps.hasNext()) {
                 return false;
             }
 
-            final PathArgument la = lit.next();
-            final PathArgument oa = oit.next();
-
-            if (!la.getType().equals(oa.getType())) {
-                return false;
-            }
-            if (la instanceof IdentifiableItem<?, ?> && oa instanceof IdentifiableItem<?, ?> && !la.equals(oa)) {
-                return false;
+            final var otherStep = otherSteps.next();
+            if (step instanceof ExactDataObjectStep) {
+                if (!step.equals(otherStep)) {
+                    return false;
+                }
+            } else if (step instanceof KeylessStep<?> keyless) {
+                if (!keyless.matches(otherStep)) {
+                    return false;
+                }
+            } else {
+                throw new IllegalStateException("Unhandled step " + step);
             }
         }
 
         return true;
     }
 
-    private <N extends DataObject> @NonNull InstanceIdentifier<N> childIdentifier(final AbstractPathArgument<N> arg) {
+    private <N extends DataObject> @NonNull InstanceIdentifier<N> childIdentifier(final DataObjectStep<N> arg) {
         return trustedCreate(arg, Iterables.concat(pathArguments, Collections.singleton(arg)),
-            HashCodeBuilder.nextHashCode(hash, arg), isWildcarded());
+            HashCodeBuilder.nextHashCode(hash, arg), wildcarded);
     }
 
     /**
@@ -343,7 +321,7 @@ public class InstanceIdentifier<T extends DataObject>
      */
     public final <N extends ChildOf<? super T>> @NonNull InstanceIdentifier<N> child(
             final Class<@NonNull N> container) {
-        return childIdentifier(Item.of(container));
+        return childIdentifier(createStep(container));
     }
 
     /**
@@ -358,9 +336,9 @@ public class InstanceIdentifier<T extends DataObject>
      * @throws NullPointerException if any argument is null
      */
     @SuppressWarnings("unchecked")
-    public final <N extends Identifiable<K> & ChildOf<? super T>, K extends Identifier<N>>
+    public final <N extends KeyAware<K> & ChildOf<? super T>, K extends Key<N>>
             @NonNull KeyedInstanceIdentifier<N, K> child(final Class<@NonNull N> listItem, final K listKey) {
-        return (KeyedInstanceIdentifier<N, K>) childIdentifier(IdentifiableItem.of(listItem, listKey));
+        return (KeyedInstanceIdentifier<N, K>) childIdentifier(new KeyStep<>(listItem, listKey));
     }
 
     /**
@@ -377,7 +355,7 @@ public class InstanceIdentifier<T extends DataObject>
     // FIXME: add a proper caller
     public final <C extends ChoiceIn<? super T> & DataObject, N extends ChildOf<? super C>>
             @NonNull InstanceIdentifier<N> child(final Class<@NonNull C> caze, final Class<@NonNull N> container) {
-        return childIdentifier(Item.of(caze, container));
+        return childIdentifier(createStep(caze, container));
     }
 
     /**
@@ -395,10 +373,10 @@ public class InstanceIdentifier<T extends DataObject>
      */
     // FIXME: add a proper caller
     @SuppressWarnings("unchecked")
-    public final <C extends ChoiceIn<? super T> & DataObject, K extends Identifier<N>,
-        N extends Identifiable<K> & ChildOf<? super C>> @NonNull KeyedInstanceIdentifier<N, K> child(
+    public final <C extends ChoiceIn<? super T> & DataObject, K extends Key<N>,
+        N extends KeyAware<K> & ChildOf<? super C>> @NonNull KeyedInstanceIdentifier<N, K> child(
                 final Class<@NonNull C> caze, final Class<@NonNull N> listItem, final K listKey) {
-        return (KeyedInstanceIdentifier<N, K>) childIdentifier(IdentifiableItem.of(caze, listItem, listKey));
+        return (KeyedInstanceIdentifier<N, K>) childIdentifier(new KeyStep<>(listItem, requireNonNull(caze), listKey));
     }
 
     /**
@@ -412,7 +390,31 @@ public class InstanceIdentifier<T extends DataObject>
      */
     public final <N extends DataObject & Augmentation<? super T>> @NonNull InstanceIdentifier<N> augmentation(
             final Class<@NonNull N> container) {
-        return childIdentifier(Item.of(container));
+        return childIdentifier(new NodeStep<>(container));
+    }
+
+    @java.io.Serial
+    Object writeReplace() throws ObjectStreamException {
+        return new IIv4<>(this);
+    }
+
+    @java.io.Serial
+    private void readObject(final ObjectInputStream stream) throws IOException, ClassNotFoundException {
+        throwNSE();
+    }
+
+    @java.io.Serial
+    private void readObjectNoData() throws ObjectStreamException {
+        throwNSE();
+    }
+
+    @java.io.Serial
+    private void writeObject(final ObjectOutputStream stream) throws IOException {
+        throwNSE();
+    }
+
+    private void throwNSE() throws NotSerializableException {
+        throw new NotSerializableException(getClass().getName());
     }
 
     /**
@@ -421,59 +423,58 @@ public class InstanceIdentifier<T extends DataObject>
      * @return A builder instance
      */
     // FIXME: rename this method to 'toBuilder()'
-    public @NonNull InstanceIdentifierBuilder<T> builder() {
-        return new InstanceIdentifierBuilderImpl<>(Item.of(targetType), pathArguments, hash, isWildcarded());
+    public @NonNull Builder<T> builder() {
+        return new RegularBuilder<>(this);
     }
 
     /**
-     * Create an InstanceIdentifierBuilder for a specific type of InstanceIdentifier as specified by container.
+     * Create a {@link Builder} for a specific type of InstanceIdentifier as specified by container.
      *
      * @param container Base container
      * @param <T> Type of the container
-     * @return A new {@link InstanceIdentifierBuilder}
+     * @return A new {@link Builder}
      * @throws NullPointerException if {@code container} is null
      */
-    public static <T extends ChildOf<? extends DataRoot>> @NonNull InstanceIdentifierBuilder<T> builder(
+    public static <T extends ChildOf<? extends DataRoot>> @NonNull Builder<T> builder(
             final Class<T> container) {
-        return new InstanceIdentifierBuilderImpl<T>().addWildNode(Item.of(container));
+        return new RegularBuilder<>(createStep(container));
     }
 
     /**
-     * Create an InstanceIdentifierBuilder for a specific type of InstanceIdentifier as specified by container in
+     * Create a {@link Builder} for a specific type of InstanceIdentifier as specified by container in
      * a {@code grouping} used in the {@code case} statement.
      *
      * @param caze Choice case class
      * @param container Base container
      * @param <C> Case type
      * @param <T> Type of the container
-     * @return A new {@link InstanceIdentifierBuilder}
+     * @return A new {@link Builder}
      * @throws NullPointerException if any argument is null
      */
     public static <C extends ChoiceIn<? extends DataRoot> & DataObject, T extends ChildOf<? super C>>
-            @NonNull InstanceIdentifierBuilder<T> builder(final Class<C> caze, final Class<T> container) {
-        return new InstanceIdentifierBuilderImpl<T>().addWildNode(Item.of(caze, container));
+            @NonNull Builder<T> builder(final Class<C> caze, final Class<T> container) {
+        return new RegularBuilder<>(createStep(caze, container));
     }
 
     /**
-     * Create an InstanceIdentifierBuilder for a specific type of InstanceIdentifier which represents an
-     * {@link IdentifiableItem}.
+     * Create a {@link Builder} for a specific type of InstanceIdentifier which represents an {@link IdentifiableItem}.
      *
      * @param listItem list item class
      * @param listKey key value
      * @param <N> List type
      * @param <K> List key
-     * @return A new {@link InstanceIdentifierBuilder}
+     * @return A new {@link Builder}
      * @throws NullPointerException if any argument is null
      */
-    public static <N extends Identifiable<K> & ChildOf<? extends DataRoot>,
-            K extends Identifier<N>> @NonNull InstanceIdentifierBuilder<N> builder(final Class<N> listItem,
+    public static <N extends KeyAware<K> & ChildOf<? extends DataRoot>,
+            K extends Key<N>> @NonNull KeyedBuilder<N, K> builder(final Class<N> listItem,
                     final K listKey) {
-        return new InstanceIdentifierBuilderImpl<N>().addNode(IdentifiableItem.of(listItem, listKey));
+        return new KeyedBuilder<>(new KeyStep<>(listItem, listKey));
     }
 
     /**
-     * Create an InstanceIdentifierBuilder for a specific type of InstanceIdentifier which represents an
-     * {@link IdentifiableItem} in a {@code grouping} used in the {@code case} statement.
+     * Create a {@link Builder} for a specific type of InstanceIdentifier which represents an {@link IdentifiableItem}
+     *  in a {@code grouping} used in the {@code case} statement.
      *
      * @param caze Choice case class
      * @param listItem list item class
@@ -481,44 +482,56 @@ public class InstanceIdentifier<T extends DataObject>
      * @param <C> Case type
      * @param <N> List type
      * @param <K> List key
-     * @return A new {@link InstanceIdentifierBuilder}
+     * @return A new {@link Builder}
      * @throws NullPointerException if any argument is null
      */
     public static <C extends ChoiceIn<? extends DataRoot> & DataObject,
-            N extends Identifiable<K> & ChildOf<? super C>, K extends Identifier<N>>
-            @NonNull InstanceIdentifierBuilder<N> builder(final Class<C> caze, final Class<N> listItem,
+            N extends KeyAware<K> & ChildOf<? super C>, K extends Key<N>>
+            @NonNull KeyedBuilder<N, K> builder(final Class<C> caze, final Class<N> listItem,
                     final K listKey) {
-        return new InstanceIdentifierBuilderImpl<N>().addNode(IdentifiableItem.of(caze, listItem, listKey));
+        return new KeyedBuilder<>(new KeyStep<>(listItem, requireNonNull(caze), listKey));
     }
 
     public static <R extends DataRoot & DataObject, T extends ChildOf<? super R>>
-            @NonNull InstanceIdentifierBuilder<T> builderOfInherited(final Class<R> root, final Class<T> container) {
+            @NonNull Builder<T> builderOfInherited(final Class<R> root, final Class<T> container) {
         // FIXME: we are losing root identity, hence namespaces may not work correctly
-        return new InstanceIdentifierBuilderImpl<T>().addWildNode(Item.of(container));
+        return new RegularBuilder<>(createStep(container));
     }
 
     public static <R extends DataRoot & DataObject, C extends ChoiceIn<? super R> & DataObject,
             T extends ChildOf<? super C>>
-            @NonNull InstanceIdentifierBuilder<T> builderOfInherited(final Class<R> root,
+            @NonNull Builder<T> builderOfInherited(final Class<R> root,
                 final Class<C> caze, final Class<T> container) {
         // FIXME: we are losing root identity, hence namespaces may not work correctly
-        return new InstanceIdentifierBuilderImpl<T>().addWildNode(Item.of(caze, container));
+        return new RegularBuilder<>(createStep(caze, container));
     }
 
-    public static <R extends DataRoot & DataObject, N extends Identifiable<K> & ChildOf<? super R>,
-            K extends Identifier<N>>
-            @NonNull InstanceIdentifierBuilder<N> builderOfInherited(final Class<R> root,
+    public static <R extends DataRoot & DataObject, N extends KeyAware<K> & ChildOf<? super R>,
+            K extends Key<N>>
+            @NonNull KeyedBuilder<N, K> builderOfInherited(final Class<R> root,
                 final Class<N> listItem, final K listKey) {
         // FIXME: we are losing root identity, hence namespaces may not work correctly
-        return new InstanceIdentifierBuilderImpl<N>().addNode(IdentifiableItem.of(listItem, listKey));
+        return new KeyedBuilder<>(new KeyStep<>(listItem, listKey));
     }
 
     public static <R extends DataRoot & DataObject, C extends ChoiceIn<? super R> & DataObject,
-            N extends Identifiable<K> & ChildOf<? super C>, K extends Identifier<N>>
-            @NonNull InstanceIdentifierBuilder<N> builderOfInherited(final Class<R> root,
+            N extends KeyAware<K> & ChildOf<? super C>, K extends Key<N>>
+            @NonNull KeyedBuilder<N, K> builderOfInherited(final Class<R> root,
                 final Class<C> caze, final Class<N> listItem, final K listKey) {
         // FIXME: we are losing root identity, hence namespaces may not work correctly
-        return new InstanceIdentifierBuilderImpl<N>().addNode(IdentifiableItem.of(caze, listItem, listKey));
+        return new KeyedBuilder<>(new KeyStep<>(listItem, requireNonNull(caze), listKey));
+    }
+
+    @Beta
+    @SuppressWarnings({ "rawtypes", "unchecked" })
+    public static <T extends DataObject, C extends ChoiceIn<?> & DataObject> @NonNull DataObjectStep<T> createStep(
+            final Class<C> caze, final Class<T> type) {
+        return KeyAware.class.isAssignableFrom(type) ? new KeylessStep(type, caze) : new NodeStep<>(type, caze);
+    }
+
+    @Beta
+    public static <T extends DataObject> @NonNull DataObjectStep<T> createStep(final Class<T> type) {
+        return createStep(null, type);
     }
 
     /**
@@ -530,24 +543,24 @@ public class InstanceIdentifier<T extends DataObject>
      * @throws IllegalArgumentException if pathArguments is empty or contains a null element.
      * @throws NullPointerException if {@code pathArguments} is null
      */
-    private static @NonNull InstanceIdentifier<?> internalCreate(final Iterable<PathArgument> pathArguments) {
+    private static @NonNull InstanceIdentifier<?> internalCreate(final Iterable<DataObjectStep<?>> pathArguments) {
         final var it = requireNonNull(pathArguments, "pathArguments may not be null").iterator();
         checkArgument(it.hasNext(), "pathArguments may not be empty");
 
-        final HashCodeBuilder<PathArgument> hashBuilder = new HashCodeBuilder<>();
+        final var hashBuilder = new HashCodeBuilder<DataObjectStep<?>>();
         boolean wildcard = false;
-        PathArgument arg;
+        DataObjectStep<?> arg;
 
         do {
             arg = it.next();
             // Non-null is implied by our callers
-            final var type = verifyNotNull(arg).getType();
+            final var type = verifyNotNull(arg).type();
             checkArgument(ChildOf.class.isAssignableFrom(type) || Augmentation.class.isAssignableFrom(type),
                 "%s is not a valid path argument", type);
 
             hashBuilder.addArgument(arg);
 
-            if (Identifiable.class.isAssignableFrom(type) && !(arg instanceof IdentifiableItem)) {
+            if (!(arg instanceof ExactDataObjectStep)) {
                 wildcard = true;
             }
         } while (it.hasNext());
@@ -556,29 +569,26 @@ public class InstanceIdentifier<T extends DataObject>
     }
 
     /**
-     * Create an instance identifier for a very specific object type.
+     * Create an instance identifier for a sequence of {@link DataObjectStep} steps. The steps are required to be formed
+     * of classes extending either {@link ChildOf} or {@link Augmentation} contracts. This method does not check whether
+     * or not the sequence is structurally sound, for example that an {@link Augmentation} follows an
+     * {@link Augmentable} step. Furthermore the compile-time indicated generic type of the returned object does not
+     * necessarily match the contained state.
      *
      * <p>
-     * Example:
-     * <pre>
-     *  List&lt;PathArgument&gt; path = Arrays.asList(new Item(Nodes.class))
-     *  new InstanceIdentifier(path);
-     * </pre>
+     * Failure to observe precautions to validate the list's contents may yield an object which mey be rejected at
+     * run-time or lead to undefined behaviour.
      *
      * @param pathArguments The path to a specific node in the data tree
      * @return InstanceIdentifier instance
-     * @throws IllegalArgumentException if pathArguments is empty or
-     *         contains a null element.
+     * @throws NullPointerException if {@code pathArguments} is, or contains an item which is, {@code null}
+     * @throws IllegalArgumentException if {@code pathArguments} is empty or contains an item which does not represent
+     *                                  a valid addressing step.
      */
-    // FIXME: rename to 'unsafeOf()'
-    public static @NonNull InstanceIdentifier<?> create(final Iterable<? extends PathArgument> pathArguments) {
-        if (pathArguments instanceof ImmutableCollection) {
-            @SuppressWarnings("unchecked")
-            final var immutableArguments = (ImmutableCollection<PathArgument>) pathArguments;
-            return internalCreate(immutableArguments);
-        }
-
-        return internalCreate(ImmutableList.copyOf(pathArguments));
+    @SuppressWarnings("unchecked")
+    public static <T extends DataObject> @NonNull InstanceIdentifier<T> unsafeOf(
+            final List<? extends DataObjectStep<?>> pathArguments) {
+        return (InstanceIdentifier<T>) internalCreate(ImmutableList.copyOf(pathArguments));
     }
 
     /**
@@ -598,7 +608,7 @@ public class InstanceIdentifier<T extends DataObject>
     @SuppressWarnings("unchecked")
     public static <T extends ChildOf<? extends DataRoot>> @NonNull InstanceIdentifier<T> create(
             final Class<@NonNull T> type) {
-        return (InstanceIdentifier<T>) internalCreate(ImmutableList.of(Item.of(type)));
+        return (InstanceIdentifier<T>) internalCreate(ImmutableList.of(createStep(type)));
     }
 
     /**
@@ -610,7 +620,7 @@ public class InstanceIdentifier<T extends DataObject>
      * @throws NullPointerException if id is null.
      */
     // FIXME: reconsider naming and design of this method
-    public static <N extends Identifiable<K> & DataObject, K extends Identifier<N>> K keyOf(
+    public static <N extends KeyAware<K> & DataObject, K extends Key<N>> K keyOf(
             final InstanceIdentifier<N> id) {
         requireNonNull(id);
         checkArgument(id instanceof KeyedInstanceIdentifier, "%s does not have a key", id);
@@ -621,99 +631,90 @@ public class InstanceIdentifier<T extends DataObject>
     }
 
     @SuppressWarnings({ "unchecked", "rawtypes" })
-    static <N extends DataObject> @NonNull InstanceIdentifier<N> trustedCreate(final PathArgument arg,
-            final Iterable<PathArgument> pathArguments, final int hash, boolean wildcarded) {
-        if (Identifiable.class.isAssignableFrom(arg.getType()) && !wildcarded) {
-            Identifier<?> key = null;
-            if (arg instanceof IdentifiableItem) {
-                key = ((IdentifiableItem<?, ?>)arg).getKey();
-            } else {
-                wildcarded = true;
-            }
-
-            return new KeyedInstanceIdentifier(arg.getType(), pathArguments, wildcarded, hash, key);
+    static <N extends DataObject> @NonNull InstanceIdentifier<N> trustedCreate(final DataObjectStep<?> lastStep,
+            final Iterable<DataObjectStep<?>> pathArguments, final int hash, final boolean wildcarded) {
+        if (lastStep instanceof NodeStep) {
+            return new InstanceIdentifier(lastStep.type(), pathArguments, wildcarded, hash);
+        } else if (lastStep instanceof KeyStep<?, ?> predicate) {
+            return new KeyedInstanceIdentifier(predicate, pathArguments, wildcarded, hash);
+        } else if (lastStep instanceof KeylessStep) {
+            return new InstanceIdentifier(lastStep.type(), pathArguments, true, hash);
+        } else {
+            throw new IllegalStateException("Unhandled step " + lastStep);
         }
-
-        return new InstanceIdentifier(arg.getType(), pathArguments, wildcarded, hash);
     }
 
-    /**
-     * Path argument of {@link InstanceIdentifier}. Interface which implementations are used as path components of the
-     * path in overall data tree.
-     */
-    public interface PathArgument extends Comparable<PathArgument> {
+    @Deprecated(since = "13.0.0", forRemoval = true)
+    private abstract static sealed class AbstractPathArgument<T extends DataObject>
+            implements Comparable<AbstractPathArgument<?>>, Serializable {
+        @java.io.Serial
+        private static final long serialVersionUID = 1L;
+
+        private final @NonNull Class<T> type;
+
+        AbstractPathArgument(final Class<T> type) {
+            this.type = requireNonNull(type, "Type may not be null.");
+        }
+
         /**
          * Return the data object type backing this PathArgument.
          *
          * @return Data object type.
          */
-        @NonNull Class<? extends DataObject> getType();
+        final @NonNull Class<T> type() {
+            return type;
+        }
 
         /**
-         * Return an optional enclosing case type. This is used only when {@link #getType()} references a node defined
+         * Return an optional enclosing case type. This is used only when {@link #type()} references a node defined
          * in a {@code grouping} which is reference inside a {@code case} statement in order to safely reference the
          * node.
          *
-         * @return Optional case class.
+         * @return case class or {@code null}
          */
-        default Optional<? extends Class<? extends DataObject>> getCaseType() {
-            return Optional.empty();
-        }
-    }
-
-    private abstract static class AbstractPathArgument<T extends DataObject> implements PathArgument, Serializable {
-        private static final long serialVersionUID = 1L;
-
-        private final @NonNull Class<T> type;
-
-        AbstractPathArgument(final Class<T> type) {
-            this.type = requireNonNull(type, "Type may not be null.");
-        }
-
-        @Override
-        public final Class<T> getType() {
-            return type;
+        Class<? extends DataObject> caseType() {
+            return null;
         }
 
-        Object getKey() {
+        @Nullable Object key() {
             return null;
         }
 
         @Override
         public final int hashCode() {
-            return Objects.hash(type, getCaseType(), getKey());
+            return Objects.hash(type, caseType(), key());
         }
 
         @Override
         public final boolean equals(final Object obj) {
-            if (this == obj) {
-                return true;
-            }
-            if (!(obj instanceof AbstractPathArgument)) {
-                return false;
-            }
-            final AbstractPathArgument<?> other = (AbstractPathArgument<?>) obj;
-            return type.equals(other.type) && Objects.equals(getKey(), other.getKey())
-                    && getCaseType().equals(other.getCaseType());
+            return this == obj || obj instanceof AbstractPathArgument<?> other && type.equals(other.type)
+                && Objects.equals(key(), other.key()) && Objects.equals(caseType(), other.caseType());
         }
 
         @Override
-        public final int compareTo(final PathArgument arg) {
-            final int cmp = compareClasses(type, arg.getType());
+        public final int compareTo(final AbstractPathArgument<?> arg) {
+            final int cmp = compareClasses(type, arg.type());
             if (cmp != 0) {
                 return cmp;
             }
-            final Optional<? extends Class<?>> caseType = getCaseType();
-            if (!caseType.isPresent()) {
-                return arg.getCaseType().isPresent() ? -1 : 1;
+            final var caseType = caseType();
+            final var argCaseType = arg.caseType();
+            if (caseType == null) {
+                return argCaseType == null ? 1 : -1;
             }
-            final Optional<? extends Class<?>> argCaseType = getCaseType();
-            return argCaseType.isPresent() ? compareClasses(caseType.get(), argCaseType.get()) : 1;
+            return argCaseType == null ? 1 : compareClasses(caseType, argCaseType);
         }
 
         private static int compareClasses(final Class<?> first, final Class<?> second) {
             return first.getCanonicalName().compareTo(second.getCanonicalName());
         }
+
+        @java.io.Serial
+        final Object readResolve() throws ObjectStreamException {
+            return toStep();
+        }
+
+        abstract DataObjectStep<?> toStep();
     }
 
     /**
@@ -722,44 +723,24 @@ public class InstanceIdentifier<T extends DataObject>
      *
      * @param <T> Item type
      */
-    public static class Item<T extends DataObject> extends AbstractPathArgument<T> {
+    @Deprecated(since = "13.0.0", forRemoval = true)
+    private static sealed class Item<T extends DataObject> extends AbstractPathArgument<T> {
+        @java.io.Serial
         private static final long serialVersionUID = 1L;
 
         Item(final Class<T> type) {
             super(type);
         }
 
-        /**
-         * Return a PathArgument instance backed by the specified class.
-         *
-         * @param type Backing class
-         * @param <T> Item type
-         * @return A new PathArgument
-         * @throws NullPointerException if {@code} is null.
-         */
-        public static <T extends DataObject> @NonNull Item<T> of(final Class<T> type) {
-            return new Item<>(type);
-        }
-
-        /**
-         * Return a PathArgument instance backed by the specified class, which in turn is defined in a {@code grouping}
-         * used in a corresponding {@code case} statement.
-         *
-         * @param caseType defining case class
-         * @param type Backing class
-         * @param <C> Case type
-         * @param <T> Item type
-         * @return A new PathArgument
-         * @throws NullPointerException if any argument is null.
-         */
-        public static <C extends ChoiceIn<?> & DataObject, T extends ChildOf<? super C>> @NonNull Item<T> of(
-                final Class<C> caseType, final Class<T> type) {
-            return new CaseItem<>(caseType, type);
+        @Override
+        @SuppressWarnings({ "rawtypes", "unchecked" })
+        final DataObjectStep<?> toStep() {
+            return createStep((Class) caseType(), type());
         }
 
         @Override
         public String toString() {
-            return getType().getName();
+            return type().getName();
         }
     }
 
@@ -770,8 +751,10 @@ public class InstanceIdentifier<T extends DataObject>
      * @param <I> An object that is identifiable by an identifier
      * @param <T> The identifier of the object
      */
-    public static class IdentifiableItem<I extends Identifiable<T> & DataObject, T extends Identifier<I>>
+    @Deprecated(since = "13.0.0", forRemoval = true)
+    private static sealed class IdentifiableItem<I extends KeyAware<T> & DataObject, T extends Key<I>>
             extends AbstractPathArgument<I> {
+        @java.io.Serial
         private static final long serialVersionUID = 1L;
 
         private final @NonNull T key;
@@ -781,57 +764,31 @@ public class InstanceIdentifier<T extends DataObject>
             this.key = requireNonNull(key, "Key may not be null.");
         }
 
-        /**
-         * Return an IdentifiableItem instance backed by the specified class with specified key.
-         *
-         * @param type Backing class
-         * @param key Key
-         * @param <T> List type
-         * @param <I> Key type
-         * @return An IdentifiableItem
-         * @throws NullPointerException if any argument is null.
-         */
-        public static <T extends Identifiable<I> & DataObject, I extends Identifier<T>>
-                @NonNull IdentifiableItem<T, I> of(final Class<T> type, final I key) {
-            return new IdentifiableItem<>(type, key);
-        }
-
-        /**
-         * Return an IdentifiableItem instance backed by the specified class with specified key. The class is in turn
-         * defined in a {@code grouping} used in a corresponding {@code case} statement.
-         *
-         * @param caseType defining case class
-         * @param type Backing class
-         * @param <C> Case type
-         * @param <T> List type
-         * @param <I> Key type
-         * @return A new PathArgument
-         * @throws NullPointerException if any argument is null.
-         */
-        public static <C extends ChoiceIn<?> & DataObject, T extends ChildOf<? super C> & Identifiable<I>,
-                I extends Identifier<T>> @NonNull IdentifiableItem<T, I> of(final Class<C> caseType,
-                        final Class<T> type, final I key) {
-            return new CaseIdentifiableItem<>(caseType, type, key);
-        }
-
         /**
          * Return the data object type backing this PathArgument.
          *
          * @return Data object type.
          */
         @Override
-        public final @NonNull T getKey() {
+        final @NonNull T key() {
             return key;
         }
 
+        @Override
+        final KeyStep<?, ?> toStep() {
+            return new KeyStep<>(type(), caseType(), key);
+        }
+
         @Override
         public String toString() {
-            return getType().getName() + "[key=" + key + "]";
+            return type().getName() + "[key=" + key + "]";
         }
     }
 
+    @Deprecated(since = "13.0.0", forRemoval = true)
     private static final class CaseItem<C extends ChoiceIn<?> & DataObject, T extends ChildOf<? super C>>
             extends Item<T> {
+        @java.io.Serial
         private static final long serialVersionUID = 1L;
 
         private final Class<C> caseType;
@@ -842,13 +799,15 @@ public class InstanceIdentifier<T extends DataObject>
         }
 
         @Override
-        public Optional<Class<C>> getCaseType() {
-            return Optional.of(caseType);
+        Class<C> caseType() {
+            return caseType;
         }
     }
 
+    @Deprecated(since = "13.0.0", forRemoval = true)
     private static final class CaseIdentifiableItem<C extends ChoiceIn<?> & DataObject,
-            T extends ChildOf<? super C> & Identifiable<K>, K extends Identifier<T>> extends IdentifiableItem<T, K> {
+            T extends ChildOf<? super C> & KeyAware<K>, K extends Key<T>> extends IdentifiableItem<T, K> {
+        @java.io.Serial
         private static final long serialVersionUID = 1L;
 
         private final Class<C> caseType;
@@ -859,14 +818,65 @@ public class InstanceIdentifier<T extends DataObject>
         }
 
         @Override
-        public Optional<Class<C>> getCaseType() {
-            return Optional.of(caseType);
+        Class<C> caseType() {
+            return caseType;
         }
     }
 
-    // FIXME: rename to 'Builder'
-    // FIXME: introduce KeyedBuilder with specialized build() method
-    public interface InstanceIdentifierBuilder<T extends DataObject> {
+    /**
+     * A builder of {@link InstanceIdentifier} objects.
+     *
+     * @param <T> Instance identifier target type
+     */
+    public abstract static sealed class Builder<T extends DataObject> {
+        private final ImmutableList.Builder<DataObjectStep<?>> pathBuilder;
+        private final HashCodeBuilder<DataObjectStep<?>> hashBuilder;
+        private final Iterable<? extends DataObjectStep<?>> basePath;
+
+        private boolean wildcard;
+
+        Builder(final Builder<?> prev, final DataObjectStep<?> item) {
+            pathBuilder = prev.pathBuilder;
+            hashBuilder = prev.hashBuilder;
+            basePath = prev.basePath;
+            wildcard = prev.wildcard;
+            appendItem(item);
+        }
+
+        Builder(final InstanceIdentifier<T> identifier) {
+            pathBuilder = ImmutableList.builder();
+            hashBuilder = new HashCodeBuilder<>(identifier.hashCode());
+            wildcard = identifier.isWildcarded();
+            basePath = identifier.pathArguments;
+        }
+
+        Builder(final DataObjectStep<?> item, final boolean wildcard) {
+            pathBuilder = ImmutableList.builder();
+            hashBuilder = new HashCodeBuilder<>();
+            basePath = null;
+            hashBuilder.addArgument(item);
+            pathBuilder.add(item);
+            this.wildcard = wildcard;
+        }
+
+        final boolean wildcard() {
+            return wildcard;
+        }
+
+        /**
+         * Build an identifier which refers to a specific augmentation of the current InstanceIdentifier referenced by
+         * the builder.
+         *
+         * @param container augmentation class
+         * @param <N> augmentation type
+         * @return this builder
+         * @throws NullPointerException if {@code container} is null
+         */
+        public final <N extends DataObject & Augmentation<? super T>> Builder<N> augmentation(
+                final Class<N> container) {
+            return append(new NodeStep<>(container));
+        }
+
         /**
          * Append the specified container as a child of the current InstanceIdentifier referenced by the builder. This
          * method should be used when you want to build an instance identifier by appending top-level elements, for
@@ -884,7 +894,9 @@ public class InstanceIdentifier<T extends DataObject>
          * @return this builder
          * @throws NullPointerException if {@code container} is null
          */
-        <N extends ChildOf<? super T>> @NonNull InstanceIdentifierBuilder<N> child(Class<N> container);
+        public final <N extends ChildOf<? super T>> Builder<N> child(final Class<N> container) {
+            return append(createStep(container));
+        }
 
         /**
          * Append the specified container as a child of the current InstanceIdentifier referenced by the builder. This
@@ -898,8 +910,10 @@ public class InstanceIdentifier<T extends DataObject>
          * @return this builder
          * @throws NullPointerException if {@code container} is null
          */
-        <C extends ChoiceIn<? super T> & DataObject, N extends ChildOf<? super C>>
-                @NonNull InstanceIdentifierBuilder<N> child(Class<C> caze, Class<N> container);
+        public final <C extends ChoiceIn<? super T> & DataObject, N extends ChildOf<? super C>> Builder<N> child(
+                final Class<C> caze, final Class<N> container) {
+            return append(createStep(caze, container));
+        }
 
         /**
          * Append the specified listItem as a child of the current InstanceIdentifier referenced by the builder. This
@@ -913,8 +927,10 @@ public class InstanceIdentifier<T extends DataObject>
          * @return this builder
          * @throws NullPointerException if any argument is null
          */
-        <N extends Identifiable<K> & ChildOf<? super T>, K extends Identifier<N>>
-                @NonNull InstanceIdentifierBuilder<N> child(Class<@NonNull N> listItem, K listKey);
+        public final <N extends KeyAware<K> & ChildOf<? super T>, K extends Key<N>> KeyedBuilder<N, K> child(
+                final Class<@NonNull N> listItem, final K listKey) {
+            return append(new KeyStep<>(listItem, listKey));
+        }
 
         /**
          * Append the specified listItem as a child of the current InstanceIdentifier referenced by the builder. This
@@ -930,31 +946,128 @@ public class InstanceIdentifier<T extends DataObject>
          * @return this builder
          * @throws NullPointerException if any argument is null
          */
-        <C extends ChoiceIn<? super T> & DataObject, K extends Identifier<N>,
-                N extends Identifiable<K> & ChildOf<? super C>> @NonNull InstanceIdentifierBuilder<N> child(
-                        Class<C> caze, Class<N> listItem, K listKey);
+        public final <C extends ChoiceIn<? super T> & DataObject, K extends Key<N>,
+                N extends KeyAware<K> & ChildOf<? super C>> KeyedBuilder<N, K> child(final Class<C> caze,
+                    final Class<N> listItem, final K listKey) {
+            return append(new KeyStep<>(listItem, requireNonNull(caze), listKey));
+        }
 
         /**
-         * Build an identifier which refers to a specific augmentation of the current InstanceIdentifier referenced by
-         * the builder.
+         * Build the instance identifier.
          *
-         * @param container augmentation class
-         * @param <N> augmentation type
-         * @return this builder
-         * @throws NullPointerException if {@code container} is null
+         * @return Resulting {@link InstanceIdentifier}.
          */
-        <N extends DataObject & Augmentation<? super T>> @NonNull InstanceIdentifierBuilder<N> augmentation(
-                Class<N> container);
+        public abstract @NonNull InstanceIdentifier<T> build();
+
+        @Override
+        public final int hashCode() {
+            return hashBuilder.build();
+        }
+
+        @Override
+        public final boolean equals(final Object obj) {
+            return this == obj || obj instanceof Builder<?> other
+                && wildcard == other.wildcard && hashCode() == other.hashCode()
+                && Iterables.elementsEqual(pathArguments(), other.pathArguments());
+        }
+
+        final Iterable<DataObjectStep<?>> pathArguments() {
+            final var args = pathBuilder.build();
+            return basePath == null ? args : Iterables.concat(basePath, args);
+        }
+
+        final void appendItem(final DataObjectStep<?> item) {
+            hashBuilder.addArgument(item);
+            pathBuilder.add(item);
+            if (!(item instanceof ExactDataObjectStep)) {
+                wildcard = true;
+            }
+        }
+
+        abstract <X extends DataObject> @NonNull RegularBuilder<X> append(DataObjectStep<X> step);
+
+        abstract <X extends DataObject & KeyAware<Y>, Y extends Key<X>> @NonNull KeyedBuilder<X, Y> append(
+            KeyStep<Y, X> step);
+    }
+
+    public static final class KeyedBuilder<T extends DataObject & KeyAware<K>, K extends Key<T>>
+            extends Builder<T> {
+        private @NonNull KeyStep<K, T> lastStep;
+
+        KeyedBuilder(final KeyStep<K, T> firstStep) {
+            super(firstStep, false);
+            lastStep = requireNonNull(firstStep);
+        }
+
+        KeyedBuilder(final KeyedInstanceIdentifier<T, K> identifier) {
+            super(identifier);
+            lastStep = identifier.lastStep();
+        }
+
+        private KeyedBuilder(final RegularBuilder<?> prev, final KeyStep<K, T> lastStep) {
+            super(prev, lastStep);
+            this.lastStep = requireNonNull(lastStep);
+        }
 
         /**
          * Build the instance identifier.
          *
-         * @return Resulting instance identifier.
+         * @return Resulting {@link KeyedInstanceIdentifier}.
          */
-        @NonNull InstanceIdentifier<T> build();
+        @Override
+        public @NonNull KeyedInstanceIdentifier<T, K> build() {
+            return new KeyedInstanceIdentifier<>(lastStep, pathArguments(), wildcard(), hashCode());
+        }
+
+        @Override
+        <X extends DataObject> @NonNull RegularBuilder<X> append(final DataObjectStep<X> step) {
+            return new RegularBuilder<>(this, step);
+        }
+
+        @Override
+        @SuppressWarnings("unchecked")
+        <X extends DataObject & KeyAware<Y>, Y extends Key<X>> KeyedBuilder<X, Y> append(final KeyStep<Y, X> step) {
+            appendItem(step);
+            lastStep = (KeyStep<K, T>) requireNonNull(step);
+            return (KeyedBuilder<X, Y>) this;
+        }
     }
 
-    private Object writeReplace() throws ObjectStreamException {
-        return new InstanceIdentifierV3<>(this);
+    private static final class RegularBuilder<T extends DataObject> extends Builder<T> {
+        private @NonNull Class<T> type;
+
+        RegularBuilder(final DataObjectStep<T> item) {
+            super(item, !(item instanceof ExactDataObjectStep));
+            type = item.type();
+        }
+
+        RegularBuilder(final InstanceIdentifier<T> identifier) {
+            super(identifier);
+            type = identifier.getTargetType();
+        }
+
+        private RegularBuilder(final KeyedBuilder<?, ?> prev, final DataObjectStep<T> item) {
+            super(prev, item);
+            type = item.type();
+        }
+
+        @Override
+        public InstanceIdentifier<T> build() {
+            return new InstanceIdentifier<>(type, pathArguments(), wildcard(), hashCode());
+        }
+
+        @Override
+        @SuppressWarnings({ "rawtypes", "unchecked" })
+        <X extends DataObject> RegularBuilder<X> append(final DataObjectStep<X> step) {
+            appendItem(step);
+            type = (Class) step.type();
+            return (RegularBuilder<X>) this;
+        }
+
+        @Override
+        <X extends DataObject & KeyAware<Y>, Y extends Key<X>> KeyedBuilder<X, Y> append(
+                final KeyStep<Y, X> item) {
+            return new KeyedBuilder<>(this, item);
+        }
     }
 }