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// 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 static com.google.common.collect.ImmutableSet.toImmutableSet;
import static com.google.common.collect.ImmutableSortedSet.toImmutableSortedSet;
import static java.util.Comparator.naturalOrder;

import com.google.common.collect.ImmutableSet;
import com.google.common.collect.ImmutableSortedSet;
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;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;

/**
 * A set of members that can be modified as plugins reload.
 *
 * 

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 implements Iterable { /** * Declare a singleton {@code DynamicSet} with a binder. * *

Sets must be defined in a Guice module before they can be bound: * *

   *   DynamicSet.setOf(binder(), Interface.class);
   *   DynamicSet.bind(binder(), Interface.class).to(Impl.class);
   * 
* * @param binder a new binder created in the module. * @param member type of entry in the set. */ public static void setOf(Binder binder, Class member) { binder.disableCircularProxies(); setOf(binder, TypeLiteral.get(member)); } /** * Declare a singleton {@code DynamicSet} with a binder. * *

Sets must be defined in a Guice module before they can be bound: * *

   *   DynamicSet.setOf(binder(), new TypeLiteral<Thing<Foo>>() {});
   * 
* * @param binder a new binder created in the module. * @param member type of entry in the set. */ public static void setOf(Binder binder, TypeLiteral member) { @SuppressWarnings("unchecked") Key> key = (Key>) Key.get(Types.newParameterizedType(DynamicSet.class, member.getType())); binder.disableCircularProxies(); 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 LinkedBindingBuilder bind(Binder binder, Class type) { binder.disableCircularProxies(); 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 LinkedBindingBuilder bind(Binder binder, TypeLiteral type) { binder.disableCircularProxies(); 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 LinkedBindingBuilder bind(Binder binder, Class type, Named name) { binder.disableCircularProxies(); 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 LinkedBindingBuilder bind(Binder binder, TypeLiteral type, Named name) { binder.disableCircularProxies(); return binder.bind(type).annotatedWith(name); } public static DynamicSet emptySet() { return new DynamicSet<>(Collections.emptySet()); } private final CopyOnWriteArrayList>> items; DynamicSet(Collection>> base) { items = new CopyOnWriteArrayList<>(base); } public DynamicSet() { this(Collections.emptySet()); } @Override public Iterator iterator() { Iterator> entryIterator = entries().iterator(); return new Iterator() { @Override public boolean hasNext() { return entryIterator.hasNext(); } @Override public T next() { Extension next = entryIterator.next(); return next != null ? next.getProvider().get() : null; } }; } public Iterable> entries() { final Iterator>> itr = items.iterator(); return () -> new Iterator>() { private Extension next; @Override public boolean hasNext() { while (next == null && itr.hasNext()) { Extension p = itr.next().get(); if (p != null) { next = p; } } return next != null; } @Override public Extension next() { if (hasNext()) { Extension result = next; next = null; return result; } throw new NoSuchElementException(); } @Override public void remove() { throw new UnsupportedOperationException(); } }; } /** * Returns {@code true} if this set contains the given item. * * @param item item to check whether or not it is contained. * @return {@code true} if this set contains the given item. */ public boolean contains(T item) { Iterator iterator = iterator(); while (iterator.hasNext()) { T candidate = iterator.next(); if (candidate == item) { return true; } } return false; } /** * Get the names of all running plugins supplying this type. * * @return sorted set of active plugins that supply at least one item. */ public ImmutableSortedSet plugins() { return items.stream() .map(i -> i.get().getPluginName()) .collect(toImmutableSortedSet(naturalOrder())); } /** * Get the items exported by a single plugin. * * @param pluginName name of the plugin. * @return items exported by a plugin. */ public ImmutableSet> byPlugin(String pluginName) { return items.stream() .filter(i -> i.get().getPluginName().equals(pluginName)) .map(i -> i.get().getProvider()) .collect(toImmutableSet()); } /** * 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(String pluginName, T item) { return add(pluginName, 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(String pluginName, Provider item) { final AtomicReference> ref = new AtomicReference<>(new Extension<>(pluginName, item)); items.add(ref); return () -> { if (ref.compareAndSet(ref.get(), null)) { items.remove(ref); } }; } /** * Add one new element that may be hot-replaceable in the future. * * @param pluginName unique name of the plugin providing the item. * @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 add(String pluginName, Key key, Provider item) { AtomicReference> ref = new AtomicReference<>(new Extension<>(pluginName, item)); items.add(ref); return new ReloadableHandle(ref, key, ref.get()); } public Stream stream() { return StreamSupport.stream(spliterator(), false); } private class ReloadableHandle implements ReloadableRegistrationHandle { private final AtomicReference> ref; private final Key key; private final Extension item; ReloadableHandle(AtomicReference> ref, Key key, Extension 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 getKey() { return key; } @Override public ReloadableHandle replace(Key newKey, Provider newItem) { Extension n = new Extension<>(item.getPluginName(), newItem); if (ref.compareAndSet(item, n)) { return new ReloadableHandle(ref, newKey, n); } return null; } } }




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