Proof-of-concept of write-reporting collection wrappers

Author: PeteGillinElastic

server/src/main/java/org/elasticsearch/ingest/WriteReportingList.java

@@ -0,0 +1,334 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the "Elastic License
+ * 2.0", the "GNU Affero General Public License v3.0 only", and the "Server Side
+ * Public License v 1"; you may not use this file except in compliance with, at
+ * your election, the "Elastic License 2.0", the "GNU Affero General Public
+ * License v3.0 only", or the "Server Side Public License, v 1".
+ */
+
+package org.elasticsearch.ingest;
+
+import java.util.Collection;
+import java.util.Comparator;
+import java.util.Iterator;
+import java.util.List;
+import java.util.ListIterator;
+import java.util.Spliterator;
+import java.util.function.Consumer;
+import java.util.function.IntFunction;
+import java.util.function.Predicate;
+import java.util.function.UnaryOperator;
+import java.util.stream.Stream;
+
+import static java.util.Objects.requireNonNull;
+
+/**
+ * {@link List} implementation for use in {@link WriteReportingWrapper}. This reports write mutations directly on this list, or on derived
+ * objects such as those returned by calling {@link #iterator} or {@link #subList}. It does <strong>not</strong> report mutations on
+ * elements contained within the list — although the caller may populate the wrapped list with elements which report their own mutations.
+ */
+class WriteReportingList<E> implements List<E> {
+
+    private final List<E> delegate;
+    private final Consumer<String> reporter;
+    private final String label;
+
+    WriteReportingList(List<E> delegate, Consumer<String> reporter, String label) {
+        this.delegate = requireNonNull(delegate);
+        this.reporter = requireNonNull(reporter);
+        this.label = label;
+    }
+
+    @Override
+    public int size() {
+        return delegate.size();
+    }
+
+    @Override
+    public boolean isEmpty() {
+        return delegate.isEmpty();
+    }
+
+    @Override
+    public boolean contains(Object o) {
+        return delegate.contains(o);
+    }
+
+    @Override
+    public Iterator<E> iterator() {
+        return new WriteReportingIterator(delegate.iterator());
+    }
+
+    @Override
+    public void forEach(Consumer<? super E> action) {
+        delegate.forEach(action);
+    }
+
+    @Override
+    public Object[] toArray() {
+        return delegate.toArray();
+    }
+
+    @Override
+    public <E1> E1[] toArray(E1[] a) {
+        return delegate.toArray(a);
+    }
+
+    @Override
+    public <E1> E1[] toArray(IntFunction<E1[]> generator) {
+        return delegate.toArray(generator);
+    }
+
+    @Override
+    public boolean add(E t) {
+        reporter.accept(label + ".add(E)");
+        return delegate.add(t);
+    }
+
+    @Override
+    public boolean remove(Object o) {
+        reporter.accept(label + ".remove(Object)");
+        return delegate.remove(o);
+    }
+
+    @Override
+    public boolean containsAll(Collection<?> c) {
+        return delegate.containsAll(c);
+    }
+
+    @Override
+    public boolean addAll(Collection<? extends E> c) {
+        reporter.accept(label + ".addAll(Collection<? extends E>)");
+        return delegate.addAll(c);
+    }
+
+    @Override
+    public boolean addAll(int index, Collection<? extends E> c) {
+        reporter.accept(label + ".addAll(int, Collection<? extends E>)");
+        return delegate.addAll(index, c);
+    }
+
+    @Override
+    public boolean removeAll(Collection<?> c) {
+        reporter.accept(label + ".removeAll(Collection<?>)");
+        return delegate.removeAll(c);
+    }
+
+    @Override
+    public boolean removeIf(Predicate<? super E> filter) {
+        reporter.accept(label + ".removeIf(Predicate<? super E>)");
+        return delegate.removeIf(filter);
+    }
+
+    @Override
+    public boolean retainAll(Collection<?> c) {
+        reporter.accept(label + ".retainAll(Collection<?>)");
+        return delegate.retainAll(c);
+    }
+
+    @Override
+    public void replaceAll(UnaryOperator<E> operator) {
+        reporter.accept(label + ".replaceAll(UnaryOperator<E>)");
+        delegate.replaceAll(operator);
+    }
+
+    @Override
+    public void sort(Comparator<? super E> c) {
+        reporter.accept(label + ".sort(Comparator<? super E>)");
+        delegate.sort(c);
+    }
+
+    @Override
+    public void clear() {
+        reporter.accept(label + ".clear()");
+        delegate.clear();
+    }
+
+    @Override
+    public E get(int index) {
+        return delegate.get(index);
+    }
+
+    @Override
+    public E set(int index, E element) {
+        reporter.accept(label + ".set(int, E)");
+        return delegate.set(index, element);
+    }
+
+    @Override
+    public void add(int index, E element) {
+        reporter.accept(label + ".add(int, E)");
+        delegate.add(index, element);
+    }
+
+    @Override
+    public E remove(int index) {
+        reporter.accept(label + ".remove(index)");
+        return delegate.remove(index);
+    }
+
+    @Override
+    public int indexOf(Object o) {
+        return delegate.indexOf(o);
+    }
+
+    @Override
+    public int lastIndexOf(Object o) {
+        return delegate.lastIndexOf(o);
+    }
+
+    @Override
+    public ListIterator<E> listIterator() {
+        return new WriteReportingListIterator(delegate.listIterator());
+    }
+
+    @Override
+    public ListIterator<E> listIterator(int index) {
+        return new WriteReportingListIterator(delegate.listIterator(index));
+    }
+
+    @Override
+    public List<E> subList(int fromIndex, int toIndex) {
+        return new WriteReportingList<>(delegate.subList(fromIndex, toIndex), reporter, label + ".subList(int, int)");
+    }
+
+    @Override
+    public Spliterator<E> spliterator() {
+        return delegate.spliterator();
+    }
+
+    @Override
+    public Stream<E> stream() {
+        return delegate.stream();
+    }
+
+    @Override
+    public Stream<E> parallelStream() {
+        return delegate.parallelStream();
+    }
+
+    @Override
+    public void addFirst(E t) {
+        reporter.accept(label + ".addFirst(E)");
+        delegate.addFirst(t);
+    }
+
+    @Override
+    public void addLast(E t) {
+        reporter.accept(label + ".addLast(E)");
+        delegate.addLast(t);
+    }
+
+    @Override
+    public E getFirst() {
+        return delegate.getFirst();
+    }
+
+    @Override
+    public E getLast() {
+        return delegate.getLast();
+    }
+
+    @Override
+    public E removeFirst() {
+        reporter.accept(label + ".removeFirst()");
+        return delegate.removeFirst();
+    }
+
+    @Override
+    public E removeLast() {
+        reporter.accept(label + ".removeLast()");
+        return delegate.removeLast();
+    }
+
+    @Override
+    public List<E> reversed() {
+        return new WriteReportingList<>(delegate.reversed(), reporter, label + ".reversed()");
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        return delegate.equals(o);
+    }
+
+    @Override
+    public int hashCode() {
+        return delegate.hashCode();
+    }
+
+    @Override
+    public String toString() {
+        return delegate.toString();
+    }
+
+    private class WriteReportingIterator implements Iterator<E> {
+
+        protected final Iterator<E> iteratorDelegate;
+
+        WriteReportingIterator(Iterator<E> iteratorDelegate) {
+            this.iteratorDelegate = iteratorDelegate;
+        }
+
+        @Override
+        public boolean hasNext() {
+            return iteratorDelegate.hasNext();
+        }
+
+        @Override
+        public E next() {
+            return iteratorDelegate.next();
+        }
+
+        @Override
+        public void remove() {
+            reporter.accept(label + ".iterator()...remove()");
+            iteratorDelegate.remove();
+        }
+
+        @Override
+        public void forEachRemaining(Consumer<? super E> action) {
+            iteratorDelegate.forEachRemaining(action);
+        }
+    }
+
+    private class WriteReportingListIterator extends WriteReportingIterator implements ListIterator<E> {
+
+        // N.B. This constructor means we can safely downcast iteratorDelegate to ListIterator<E>:
+        WriteReportingListIterator(ListIterator<E> iteratorDelegate) {
+            super(iteratorDelegate);
+        }
+
+        @Override
+        public boolean hasPrevious() {
+            return ((ListIterator<E>) iteratorDelegate).hasPrevious();
+        }
+
+        @Override
+        public E previous() {
+            return ((ListIterator<E>) iteratorDelegate).previous();
+        }
+
+        @Override
+        public int nextIndex() {
+            return ((ListIterator<E>) iteratorDelegate).nextIndex();
+        }
+
+        @Override
+        public int previousIndex() {
+            return ((ListIterator<E>) iteratorDelegate).previousIndex();
+        }
+
+        @Override
+        public void set(E t) {
+            reporter.accept(label + ".listIterator()...set(E)");
+            ((ListIterator<E>) iteratorDelegate).set(t);
+        }
+
+        @Override
+        public void add(E t) {
+            reporter.accept(label + ".listIterator()...add(E)");
+            ((ListIterator<E>) iteratorDelegate).add(t);
+        }
+    }
+}