+/*
+ * Copyright (c) 2021 PANTHEON.tech, s.r.o. and others. All rights reserved.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v1.0 which accompanies this distribution,
+ * and is available at http://www.eclipse.org/legal/epl-v10.html
+ */
+package org.opendaylight.yangtools.yang.common;
+
+import static java.util.Objects.requireNonNull;
+
+import com.google.common.base.MoreObjects;
+import com.google.common.collect.Interner;
+import com.google.common.collect.Interners;
+import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
+import java.io.DataInput;
+import java.io.DataOutput;
+import java.io.IOException;
+import java.util.Optional;
+import org.eclipse.jdt.annotation.NonNull;
+import org.eclipse.jdt.annotation.NonNullByDefault;
+import org.eclipse.jdt.annotation.Nullable;
+
+/**
+ * A {@link QName} equivalent which has not been resolved. There are two subclasses:
+ * <ol>
+ * <li>{@link Unqualified}, which holds only a local name available through {@link #getLocalName()}.<li>
+ * <li>{@link Qualified}, which also holds a string prefix available via {@link Qualified#getPrefix()}.</li>
+ * </ol>
+ */
+// FIXME: sealed to allow Qualified and Unqualified only when we have JDK17+
+@NonNullByDefault
+public abstract class UnresolvedQName extends AbstractQName {
+ /**
+ * An unresolved, qualified {@link QName}. It is guaranteed to hold a valid {@link #getLocalName()} bound to a
+ * namespace identified through a prefix string, but remains unresolved. A resolved {@link QName} can be obtained
+ * through {@link #bindTo(YangNamespaceContext)}.
+ */
+ public static final class Qualified extends UnresolvedQName implements Comparable<Qualified> {
+ private static final long serialVersionUID = 1L;
+ private static final Interner<Qualified> INTERNER = Interners.newWeakInterner();
+
+ private final String prefix;
+
+ private Qualified(final String prefix, final String localName) {
+ super(localName);
+ this.prefix = requireNonNull(prefix);
+ }
+
+ /**
+ * Read an QualifiedQName from a DataInput. The format is expected to match the output format of
+ * {@link #writeTo(DataOutput)}.
+ *
+ * @param in DataInput to read
+ * @return An QualifiedQName instance
+ * @throws IOException if I/O error occurs
+ */
+ public static Qualified readFrom(final DataInput in) throws IOException {
+ return qualified(in.readUTF(), in.readUTF());
+ }
+
+ @Override
+ public @NonNull String getPrefix() {
+ return prefix;
+ }
+
+ public Optional<QName> bindTo(final YangNamespaceContext namespaceContext) {
+ return namespaceContext.findNamespaceForPrefix(prefix).map(this::bindTo);
+ }
+
+ @Override
+ @SuppressFBWarnings(value = "ES_COMPARING_STRINGS_WITH_EQ", justification = "Interning identity check")
+ public Qualified intern() {
+ // Make sure to intern the string and check whether it refers to the same name as we are
+ final String name = getLocalName();
+ final String internedName = name.intern();
+ final Qualified template = internedName == name ? this : new Qualified(prefix.intern(), internedName);
+ return INTERNER.intern(template);
+ }
+
+ @Override
+ @SuppressWarnings("checkstyle:parameterName")
+ public int compareTo(final Qualified o) {
+ return getLocalName().compareTo(o.getLocalName());
+ }
+
+ @Override
+ public void writeTo(final DataOutput out) throws IOException {
+ out.writeUTF(getLocalName());
+ }
+
+ @Override
+ public int hashCode() {
+ return getLocalName().hashCode();
+ }
+
+ @Override
+ public boolean equals(final @Nullable Object obj) {
+ return this == obj || obj instanceof Qualified && getLocalName().equals(((Qualified) obj).getLocalName());
+ }
+
+ @Override
+ public String toString() {
+ return MoreObjects.toStringHelper(this).add("localName", getLocalName()).toString();
+ }
+
+ @Override
+ Object writeReplace() {
+ return new QQNv1(this);
+ }
+ }
+
+ /**
+ * An unresolved, unqualified {@link QName}. It is guaranteed to hold a valid {@link #getLocalName()}, in the
+ * default namespace, which is not resolved. A resolved {@link QName} can be constructed through
+ * {@link #bindTo(QNameModule)}.
+ */
+ public static final class Unqualified extends UnresolvedQName implements Comparable<Unqualified> {
+ private static final long serialVersionUID = 1L;
+ private static final Interner<Unqualified> INTERNER = Interners.newWeakInterner();
+
+ private Unqualified(final String localName) {
+ super(localName);
+ }
+
+ /**
+ * Read an UnqualifiedQName from a DataInput. The format is expected to match the output format of
+ * {@link #writeTo(DataOutput)}.
+ *
+ * @param in DataInput to read
+ * @return An UnqualifiedQName instance
+ * @throws IOException if I/O error occurs
+ */
+ public static Unqualified readFrom(final DataInput in) throws IOException {
+ return unqualified(in.readUTF());
+ }
+
+ @Override
+ @SuppressFBWarnings(value = "ES_COMPARING_STRINGS_WITH_EQ", justification = "Interning identity check")
+ public Unqualified intern() {
+ // Make sure to intern the string and check whether it refers to the same name as we are
+ final String name = getLocalName();
+ final String internedName = name.intern();
+ final Unqualified template = internedName == name ? this : new Unqualified(internedName);
+ return INTERNER.intern(template);
+ }
+
+ @Override
+ @SuppressFBWarnings(value = "NP_NONNULL_RETURN_VIOLATION", justification = "Non-grok of @Nullable")
+ public @Nullable String getPrefix() {
+ return null;
+ }
+
+ @Override
+ @SuppressWarnings("checkstyle:parameterName")
+ public int compareTo(final Unqualified o) {
+ return getLocalName().compareTo(o.getLocalName());
+ }
+
+ @Override
+ public void writeTo(final DataOutput out) throws IOException {
+ out.writeUTF(getLocalName());
+ }
+
+ @Override
+ public int hashCode() {
+ return getLocalName().hashCode();
+ }
+
+ @Override
+ public boolean equals(final @Nullable Object obj) {
+ return this == obj || obj instanceof Unqualified
+ && getLocalName().equals(((AbstractQName) obj).getLocalName());
+ }
+
+ @Override
+ public String toString() {
+ return MoreObjects.toStringHelper(this).add("localName", getLocalName()).toString();
+ }
+
+ @Override
+ Object writeReplace() {
+ return new UQNv1(this);
+ }
+ }
+
+ private static final long serialVersionUID = 1L;
+
+ private UnresolvedQName(final String localName) {
+ super(localName);
+ }
+
+ /**
+ * Create a new qualified unresolved QName.
+ *
+ * @param prefix The prefix on this qualified QName
+ * @param localName The local name of this qualified QName
+ * @return An UnqualifiedQName instance
+ * @throws NullPointerException if any argument is {@code null}
+ * @throws IllegalArgumentException if {@code localName} is not a valid YANG identifier
+ */
+ public static Qualified qualified(final String prefix, final String localName) {
+ return new Qualified(checkLocalName(prefix), checkLocalName(localName));
+ }
+
+ /**
+ * Create a new unqualified unresolved QName.
+ *
+ * @param localName The local name of this unqualified QName
+ * @return An UnqualifiedQName instance
+ * @throws NullPointerException if localName is {@code null}
+ * @throws IllegalArgumentException if {@code localName} is not a valid YANG identifier
+ */
+ public static Unqualified unqualified(final String localName) {
+ return new Unqualified(checkLocalName(localName));
+ }
+
+ /**
+ * Try to create a new unqualified QName.
+ *
+ * @param localName The local name of this unqualified QName
+ * @return An UnqualifiedQName instance, or null if localName is not valid
+ */
+ @SuppressFBWarnings(value = "NP_NONNULL_RETURN_VIOLATION", justification = "Non-grok of @Nullable")
+ public static @Nullable Unqualified tryLocalName(final String localName) {
+ return isValidLocalName(localName) ? new Unqualified(localName) : null;
+ }
+
+ @Override
+ public abstract UnresolvedQName intern();
+
+ /**
+ * Return the prefix of this unresolved QName.
+ *
+ * @return This QName's prefix
+ */
+ public abstract @Nullable String getPrefix();
+}