// Copyright (C) 2012 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package com.google.gerrit.extensions.registration;
import com.google.inject.Binder;
import com.google.inject.Key;
import com.google.inject.Provider;
import com.google.inject.Scopes;
import com.google.inject.TypeLiteral;
import com.google.inject.binder.LinkedBindingBuilder;
import com.google.inject.internal.UniqueAnnotations;
import com.google.inject.name.Named;
import com.google.inject.util.Providers;
import com.google.inject.util.Types;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.atomic.AtomicReference;
/**
* A set of members that can be modified as plugins reload.
* <p>
* DynamicSets are always mapped as singletons in Guice. Sets store Providers
* internally, and resolve the provider to an instance on demand. This enables
* registrations to decide between singleton and non-singleton members.
*/
public class DynamicSet<T> implements Iterable<T> {
/**
* Declare a singleton {@code DynamicSet<T>} with a binder.
* <p>
* Sets must be defined in a Guice module before they can be bound:
* <pre>
* DynamicSet.setOf(binder(), Interface.class);
* DynamicSet.bind(binder(), Interface.class).to(Impl.class);
* </pre>
*
* @param binder a new binder created in the module.
* @param member type of entry in the set.
*/
public static <T> void setOf(Binder binder, Class<T> member) {
setOf(binder, TypeLiteral.get(member));
}
/**
* Declare a singleton {@code DynamicSet<T>} with a binder.
* <p>
* Sets must be defined in a Guice module before they can be bound:
* <pre>
* DynamicSet.setOf(binder(), new TypeLiteral<Thing<Foo>>() {});
* </pre>
*
* @param binder a new binder created in the module.
* @param member type of entry in the set.
*/
public static <T> void setOf(Binder binder, TypeLiteral<T> member) {
@SuppressWarnings("unchecked")
Key<DynamicSet<T>> key = (Key<DynamicSet<T>>) Key.get(
Types.newParameterizedType(DynamicSet.class, member.getType()));
binder.bind(key)
.toProvider(new DynamicSetProvider<>(member))
.in(Scopes.SINGLETON);
}
/**
* Bind one implementation into the set using a unique annotation.
*
* @param binder a new binder created in the module.
* @param type type of entries in the set.
* @return a binder to continue configuring the new set member.
*/
public static <T> LinkedBindingBuilder<T> bind(Binder binder, Class<T> type) {
return bind(binder, TypeLiteral.get(type));
}
/**
* Bind one implementation into the set using a unique annotation.
*
* @param binder a new binder created in the module.
* @param type type of entries in the set.
* @return a binder to continue configuring the new set member.
*/
public static <T> LinkedBindingBuilder<T> bind(Binder binder, TypeLiteral<T> type) {
return binder.bind(type).annotatedWith(UniqueAnnotations.create());
}
/**
* Bind a named implementation into the set.
*
* @param binder a new binder created in the module.
* @param type type of entries in the set.
* @param name {@code @Named} annotation to apply instead of a unique
* annotation.
* @return a binder to continue configuring the new set member.
*/
public static <T> LinkedBindingBuilder<T> bind(Binder binder,
Class<T> type,
Named name) {
return bind(binder, TypeLiteral.get(type));
}
/**
* Bind a named implementation into the set.
*
* @param binder a new binder created in the module.
* @param type type of entries in the set.
* @param name {@code @Named} annotation to apply instead of a unique
* annotation.
* @return a binder to continue configuring the new set member.
*/
public static <T> LinkedBindingBuilder<T> bind(Binder binder,
TypeLiteral<T> type,
Named name) {
return binder.bind(type).annotatedWith(name);
}
public static <T> DynamicSet<T> emptySet() {
return new DynamicSet<T>(
Collections.<AtomicReference<Provider<T>>> emptySet());
}
private final CopyOnWriteArrayList<AtomicReference<Provider<T>>> items;
DynamicSet(Collection<AtomicReference<Provider<T>>> base) {
items = new CopyOnWriteArrayList<>(base);
}
@Override
public Iterator<T> iterator() {
final Iterator<AtomicReference<Provider<T>>> itr = items.iterator();
return new Iterator<T>() {
private T next;
@Override
public boolean hasNext() {
while (next == null && itr.hasNext()) {
Provider<T> p = itr.next().get();
if (p != null) {
try {
next = p.get();
} catch (RuntimeException e) {
// TODO Log failed member of DynamicSet.
}
}
}
return next != null;
}
@Override
public T next() {
if (hasNext()) {
T result = next;
next = null;
return result;
}
throw new NoSuchElementException();
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
};
}
/**
* Add one new element to the set.
*
* @param item the item to add to the collection. Must not be null.
* @return handle to remove the item at a later point in time.
*/
public RegistrationHandle add(final T item) {
return add(Providers.of(item));
}
/**
* Add one new element to the set.
*
* @param item the item to add to the collection. Must not be null.
* @return handle to remove the item at a later point in time.
*/
public RegistrationHandle add(final Provider<T> item) {
final AtomicReference<Provider<T>> ref = new AtomicReference<>(item);
items.add(ref);
return new RegistrationHandle() {
@Override
public void remove() {
if (ref.compareAndSet(item, null)) {
items.remove(ref);
}
}
};
}
/**
* Add one new element that may be hot-replaceable in the future.
*
* @param key unique description from the item's Guice binding. This can be
* later obtained from the registration handle to facilitate matching
* with the new equivalent instance during a hot reload.
* @param item the item to add to the collection right now. Must not be null.
* @return a handle that can remove this item later, or hot-swap the item
* without it ever leaving the collection.
*/
public ReloadableRegistrationHandle<T> add(Key<T> key, Provider<T> item) {
AtomicReference<Provider<T>> ref = new AtomicReference<>(item);
items.add(ref);
return new ReloadableHandle(ref, key, item);
}
private class ReloadableHandle implements ReloadableRegistrationHandle<T> {
private final AtomicReference<Provider<T>> ref;
private final Key<T> key;
private final Provider<T> item;
ReloadableHandle(AtomicReference<Provider<T>> ref,
Key<T> key,
Provider<T> item) {
this.ref = ref;
this.key = key;
this.item = item;
}
@Override
public void remove() {
if (ref.compareAndSet(item, null)) {
items.remove(ref);
}
}
@Override
public Key<T> getKey() {
return key;
}
@Override
public ReloadableHandle replace(Key<T> newKey, Provider<T> newItem) {
if (ref.compareAndSet(item, newItem)) {
return new ReloadableHandle(ref, newKey, newItem);
}
return null;
}
}
}