// 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.ProvisionException;
import com.google.inject.Scopes;
import com.google.inject.TypeLiteral;
import com.google.inject.util.Types;
import java.util.Collections;
import java.util.Iterator;
import java.util.Map;
import java.util.SortedMap;
import java.util.SortedSet;
import java.util.TreeMap;
import java.util.TreeSet;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
/**
* A map of members that can be modified as plugins reload.
* <p>
* Maps index their members by plugin name and export name.
* <p>
* DynamicMaps are always mapped as singletons in Guice. Maps store Providers
* internally, and resolve the provider to an instance on demand. This enables
* registrations to decide between singleton and non-singleton members.
*/
public abstract class DynamicMap<T> implements Iterable<DynamicMap.Entry<T>> {
/**
* Declare a singleton {@code DynamicMap<T>} with a binder.
* <p>
* Maps must be defined in a Guice module before they can be bound:
*
* <pre>
* DynamicMap.mapOf(binder(), Interface.class);
* bind(Interface.class)
* .annotatedWith(Exports.named("foo"))
* .to(Impl.class);
* </pre>
*
* @param binder a new binder created in the module.
* @param member type of value in the map.
*/
public static <T> void mapOf(Binder binder, Class<T> member) {
mapOf(binder, TypeLiteral.get(member));
}
/**
* Declare a singleton {@code DynamicMap<T>} with a binder.
* <p>
* Maps must be defined in a Guice module before they can be bound:
*
* <pre>
* DynamicMap.mapOf(binder(), new TypeLiteral<Thing<Bar>>(){});
* bind(new TypeLiteral<Thing<Bar>>() {})
* .annotatedWith(Exports.named("foo"))
* .to(Impl.class);
* </pre>
*
* @param binder a new binder created in the module.
* @param member type of value in the map.
*/
public static <T> void mapOf(Binder binder, TypeLiteral<T> member) {
@SuppressWarnings("unchecked")
Key<DynamicMap<T>> key = (Key<DynamicMap<T>>) Key.get(
Types.newParameterizedType(DynamicMap.class, member.getType()));
binder.bind(key)
.toProvider(new DynamicMapProvider<>(member))
.in(Scopes.SINGLETON);
}
final ConcurrentMap<NamePair, Provider<T>> items;
DynamicMap() {
items = new ConcurrentHashMap<>(
16 /* initial size */,
0.75f /* load factor */,
1 /* concurrency level of 1, load/unload is single threaded */);
}
/**
* Lookup an implementation by name.
*
* @param pluginName local name of the plugin providing the item.
* @param exportName name the plugin exports the item as.
* @return the implementation. Null if the plugin is not running, or if the
* plugin does not export this name.
* @throws ProvisionException if the registered provider is unable to obtain
* an instance of the requested implementation.
*/
public T get(String pluginName, String exportName) throws ProvisionException {
Provider<T> p = items.get(new NamePair(pluginName, exportName));
return p != null ? p.get() : null;
}
/**
* Get the names of all running plugins supplying this type.
*
* @return sorted set of active plugins that supply at least one item.
*/
public SortedSet<String> plugins() {
SortedSet<String> r = new TreeSet<>();
for (NamePair p : items.keySet()) {
r.add(p.pluginName);
}
return Collections.unmodifiableSortedSet(r);
}
/**
* Get the items exported by a single plugin.
*
* @param pluginName name of the plugin.
* @return items exported by a plugin, keyed by the export name.
*/
public SortedMap<String, Provider<T>> byPlugin(String pluginName) {
SortedMap<String, Provider<T>> r = new TreeMap<>();
for (Map.Entry<NamePair, Provider<T>> e : items.entrySet()) {
if (e.getKey().pluginName.equals(pluginName)) {
r.put(e.getKey().exportName, e.getValue());
}
}
return Collections.unmodifiableSortedMap(r);
}
/** Iterate through all entries in an undefined order. */
public Iterator<Entry<T>> iterator() {
final Iterator<Map.Entry<NamePair, Provider<T>>> i =
items.entrySet().iterator();
return new Iterator<Entry<T>>() {
@Override
public boolean hasNext() {
return i.hasNext();
}
@Override
public Entry<T> next() {
final Map.Entry<NamePair, Provider<T>> e = i.next();
return new Entry<T>() {
@Override
public String getPluginName() {
return e.getKey().pluginName;
}
@Override
public String getExportName() {
return e.getKey().exportName;
}
@Override
public Provider<T> getProvider() {
return e.getValue();
}
};
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
};
}
public interface Entry<T> {
String getPluginName();
String getExportName();
Provider<T> getProvider();
}
static class NamePair {
private final String pluginName;
private final String exportName;
NamePair(String pn, String en) {
this.pluginName = pn;
this.exportName = en;
}
@Override
public int hashCode() {
return pluginName.hashCode() * 31 + exportName.hashCode();
}
@Override
public boolean equals(Object other) {
if (other instanceof NamePair) {
NamePair np = (NamePair) other;
return pluginName.equals(np.pluginName)
&& exportName.equals(np.exportName);
}
return false;
}
}
public static <T> DynamicMap<T> emptyMap() {
return new DynamicMap<T>() {};
}
}