/*

 * Copyright (c) 2016, 2018, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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package jdk.internal.net.http.common;

import java.util.concurrent.CompletableFuture;

import java.util.concurrent.CompletionStage;

import java.util.concurrent.atomic.AtomicLong;

import static java.util.Objects.requireNonNull;

/*

 * A CompletableFuture which does not allow any obtrusion logic.

 * All methods of CompletionStage return instances of this class.

 */

public final class MinimalFuture<T> extends CompletableFuture<T> {

    @FunctionalInterface

    public interface ExceptionalSupplier<U> {

        U get() throws Throwable;

    }

    private final static AtomicLong TOKENS = new AtomicLong();

    private final long id;

    public static <U> MinimalFuture<U> completedFuture(U value) {

        MinimalFuture<U> f = new MinimalFuture<>();

        f.complete(value);

        return f;

    }

    public static <U> CompletableFuture<U> failedFuture(Throwable ex) {

        requireNonNull(ex);

        MinimalFuture<U> f = new MinimalFuture<>();

        f.completeExceptionally(ex);

        return f;

    }

    public static <U> CompletableFuture<U> supply(ExceptionalSupplier<U> supplier) {

        CompletableFuture<U> cf = new MinimalFuture<>();

        try {

            U value = supplier.get();

            cf.complete(value);

        } catch (Throwable t) {

            cf.completeExceptionally(t);

        }

        return cf;

    }

    public MinimalFuture() {

        super();

        this.id = TOKENS.incrementAndGet();

    }

    @Override

    public <U> MinimalFuture<U> newIncompleteFuture() {

        return new MinimalFuture<>();

    }

    @Override

    public void obtrudeValue(T value) {

        throw new UnsupportedOperationException();

    }

    @Override

    public void obtrudeException(Throwable ex) {

        throw new UnsupportedOperationException();

    }

    @Override

    public String toString() {

        return super.toString() + " (id=" + id +")";

    }

    public static <U> MinimalFuture<U> of(CompletionStage<U> stage) {

        MinimalFuture<U> cf = new MinimalFuture<>();

        stage.whenComplete((r,t) -> complete(cf, r, t));

        return cf;

    }

    private static <U> void complete(CompletableFuture<U> cf, U result, Throwable t) {

        if (t == null) {

            cf.complete(result);

        } else {

            cf.completeExceptionally(t);

        }

    }

}