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/*
 * Copyright 2010 the original author or authors.
 *
 * 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 org.gradle.internal.event;

import com.google.common.collect.ImmutableSet;
import org.gradle.api.Action;
import org.gradle.internal.dispatch.Dispatch;
import org.gradle.internal.dispatch.MethodInvocation;
import org.gradle.internal.dispatch.ReflectionDispatch;
import org.gradle.util.CollectionUtils;

import java.lang.reflect.Method;
import java.util.Set;

/**
 * An immutable composite {@link org.gradle.internal.dispatch.Dispatch} implementation. Optimized for a small number of elements, and for infrequent modification.
 */
public abstract class BroadcastDispatch extends AbstractBroadcastDispatch {
    private BroadcastDispatch(Class type) {
        super(type);
    }

    public static  BroadcastDispatch empty(Class type) {
        return new EmptyDispatch(type);
    }

    public Class getType() {
        return type;
    }

    public abstract boolean isEmpty();

    public BroadcastDispatch add(Dispatch dispatch) {
        return add(dispatch, dispatch);
    }

    public BroadcastDispatch add(T listener) {
        return add(listener, new ReflectionDispatch(listener));
    }

    public BroadcastDispatch add(String methodName, Action action) {
        assertIsMethod(methodName);
        return add(action, new ActionInvocationHandler(methodName, action));
    }

    abstract BroadcastDispatch add(Object handler, Dispatch dispatch);

    private void assertIsMethod(String methodName) {
        for (Method method : type.getMethods()) {
            if (method.getName().equals(methodName)) {
                return;
            }
        }
        throw new IllegalArgumentException(String.format("Method %s() not found for listener type %s.", methodName,
                type.getSimpleName()));
    }

    public abstract BroadcastDispatch remove(Object listener);

    public abstract BroadcastDispatch addAll(Iterable listeners);

    public abstract BroadcastDispatch removeAll(Iterable listeners);

    private static class ActionInvocationHandler implements Dispatch {
        private final String methodName;
        private final Action action;

        ActionInvocationHandler(String methodName, Action action) {
            this.methodName = methodName;
            this.action = action;
        }

        public void dispatch(MethodInvocation message) {
            if (message.getMethod().getName().equals(methodName)) {
                action.execute(message.getArguments()[0]);
            }
        }
    }

    private static class EmptyDispatch extends BroadcastDispatch {
        EmptyDispatch(Class type) {
            super(type);
        }

        @Override
        public String toString() {
            return "";
        }

        @Override
        public boolean isEmpty() {
            return true;
        }

        @Override
        public BroadcastDispatch remove(Object listener) {
            return this;
        }

        @Override
        public BroadcastDispatch removeAll(Iterable listeners) {
            return this;
        }

        @Override
        BroadcastDispatch add(Object handler, Dispatch dispatch) {
            return new SingletonDispatch(type, handler, dispatch);
        }

        @Override
        public BroadcastDispatch addAll(Iterable listeners) {
            ImmutableSet.Builder> builder = ImmutableSet.builder();
            for (T listener : listeners) {
                builder.add(new SingletonDispatch(type, listener, new ReflectionDispatch(listener)));
            }
            ImmutableSet> result = builder.build();
            if (result.isEmpty()) {
                return this;
            }
            if (result.size() == 1) {
                return result.iterator().next();
            }
            return new CompositeDispatch(type, result);
        }

        @Override
        public void dispatch(MethodInvocation message) {
        }
    }

    private static class SingletonDispatch extends BroadcastDispatch {
        private final Object handler;
        private final Dispatch dispatch;

        SingletonDispatch(Class type, Object handler, Dispatch dispatch) {
            super(type);
            this.handler = handler;
            this.dispatch = dispatch;
        }

        @Override
        public String toString() {
            return handler.toString();
        }

        @Override
        public boolean equals(Object obj) {
            SingletonDispatch other = (SingletonDispatch) obj;
            return handler == other.handler || handler.equals(other.handler);
        }

        @Override
        public int hashCode() {
            return handler.hashCode();
        }

        @Override
        BroadcastDispatch add(Object handler, Dispatch dispatch) {
            if (this.handler == handler || this.handler.equals(handler)) {
                return this;
            }
            return new CompositeDispatch(type, ImmutableSet.of(this, new SingletonDispatch(type, handler, dispatch)));
        }

        @Override
        public BroadcastDispatch addAll(Iterable listeners) {
            ImmutableSet.Builder> builder = ImmutableSet.builder();
            builder.add(this);
            for (T listener : listeners) {
                if (handler == listener || handler.equals(listener)) {
                    continue;
                }
                builder.add(new SingletonDispatch(type, listener, new ReflectionDispatch(listener)));
            }
            ImmutableSet> result = builder.build();
            if (result.size() == 1) {
                return this;
            }
            return new CompositeDispatch(type, result);
        }

        @Override
        public BroadcastDispatch remove(Object listener) {
            if (handler == listener || handler.equals(listener)) {
                return new EmptyDispatch(type);
            }
            return this;
        }

        @Override
        public BroadcastDispatch removeAll(Iterable listeners) {
            for (Object listener : listeners) {
                if (handler == listener || handler.equals(listener)) {
                    return new EmptyDispatch(type);
                }
            }
            return this;
        }

        @Override
        public boolean isEmpty() {
            return false;
        }

        @Override
        public void dispatch(MethodInvocation message) {
            dispatch(message, dispatch);
        }
    }

    private static class CompositeDispatch extends BroadcastDispatch {
        private final ImmutableSet> dispatchers;

        CompositeDispatch(Class type, ImmutableSet> dispatchers) {
            super(type);
            this.dispatchers = dispatchers;
        }

        @Override
        public String toString() {
            return dispatchers.toString();
        }

        @Override
        BroadcastDispatch add(Object handler, Dispatch dispatch) {
            ImmutableSet.Builder> builder = ImmutableSet.builder();
            for (SingletonDispatch listener : dispatchers) {
                if (listener.handler == handler || listener.handler.equals(handler)) {
                    return this;
                }
                builder.add(listener);
            }
            builder.add(new SingletonDispatch(type, handler, dispatch));
            return new CompositeDispatch(type, builder.build());
        }

        @Override
        public BroadcastDispatch addAll(Iterable listeners) {
            ImmutableSet.Builder> builder = ImmutableSet.builder();
            builder.addAll(this.dispatchers);
            for (T listener : listeners) {
                builder.add(new SingletonDispatch(type, listener, new ReflectionDispatch(listener)));
            }
            ImmutableSet> result = builder.build();
            if (result.equals(this.dispatchers)) {
                return this;
            }
            return new CompositeDispatch(type, result);
        }

        @Override
        public BroadcastDispatch remove(Object listener) {
            ImmutableSet.Builder> builder = ImmutableSet.builder();
            boolean found = false;
            for (SingletonDispatch dispatch : dispatchers) {
                if (dispatch.handler == listener || dispatch.handler.equals(listener)) {
                    found = true;
                } else {
                    builder.add(dispatch);
                }
            }
            if (!found) {
                return this;
            }
            ImmutableSet> result = builder.build();
            if (result.size() == 1) {
                return result.iterator().next();
            }
            return new CompositeDispatch(type, result);
        }

        @Override
        public BroadcastDispatch removeAll(Iterable listeners) {
            Set