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/*
 * Copyright 2016 Google Inc.
 *
 * 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 emujava.util.concurrent.impl;

import java.util.ArrayList;
import java.util.List;
import java.util.function.BiConsumer;
import org.teavm.jso.JSBody;
import org.teavm.jso.JSFunctor;
import org.teavm.jso.JSObject;

/**
 *
 */
final class PromiseImpl implements Promise {
    private V value;
    private Throwable reason;
    private boolean done;
    private final List callbacks = new ArrayList<>();

    @Override
    public void resolve(V value) {
        complete(value, null);
    }

    @Override
    public void reject(Throwable reason) {
        assert reason != null;
        complete(null, reason);
    }

    @Override
    public void then(BiConsumer callback) {
        assert callback != null;
        Runnable run = new Runnable() {
            @Override
            public void run() {
                callback.accept(value, reason);
            }
        };
        then(run);
    }

    @Override
    public void then(Runnable callback) {
        assert callback != null;
        callbacks.add(callback);
        if(done) {
            runCallbacks();
        }
    }

    private void complete(V value, Throwable reason) {
        if(!done) {
            this.value = value;
            this.reason = reason;
            done = true;
            runCallbacks();
        }
    }

    private void runCallbacks() {
        if(!callbacks.isEmpty()) {
            TimerCallback callbackk = new TimerCallback() {
                @Override
                public void onTick() {
                    for(Runnable callback : callbacks) {
                        callback.run();
                    }
                    callbacks.clear();
                }
            };
            setTimeout(callbackk, 0);
        }
    }

    // TODO: use $entry?
    @JSBody(params = {"callback", "time"}, script = "setTimeout(callback, time);")
    private static native int setTimeout(TimerCallback callback, int time);

    @JSFunctor
    private interface TimerCallback extends JSObject {
        void onTick();
    }
}