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/*
 * Copyright 2012-2024 CodeLibs Project and the Others.
 *
 * 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.codelibs.fess.suggest.concurrent;

import java.util.ArrayList;
import java.util.Queue;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.TimeUnit;
import java.util.function.Consumer;

import org.codelibs.core.exception.InterruptedRuntimeException;
import org.codelibs.fess.suggest.exception.SuggesterException;
import org.codelibs.fess.suggest.request.Response;

public class Deferred {
    private RESPONSE response = null;

    private Throwable error = null;

    private final Promise promise = new Promise();

    private final Queue> doneCallbacks = new LinkedBlockingQueue<>();

    private final Queue> errorCallbacks = new LinkedBlockingQueue<>();

    private final CountDownLatch latch = new CountDownLatch(1);

    public void resolve(final RESPONSE r) {
        final ArrayList> executeCallbacks;
        synchronized (Deferred.this) {
            if (response != null || error != null) {
                return;
            }
            response = r;

            executeCallbacks = new ArrayList<>(doneCallbacks.size());
            Consumer callback;
            while ((callback = doneCallbacks.poll()) != null) {
                executeCallbacks.add(callback);
            }
        }
        if (executeCallbacks.size() > 0) {
            try {
                executeCallbacks.stream().forEach(callback -> callback.accept(response));
            } catch (final Exception ignore) {}
        }
        latch.countDown();
    }

    public void reject(final Throwable t) {
        final ArrayList> executeCallbacks;
        synchronized (Deferred.this) {
            if (response != null || error != null) {
                return;
            }
            error = t;

            executeCallbacks = new ArrayList<>(errorCallbacks.size());
            Consumer callback;
            while ((callback = errorCallbacks.poll()) != null) {
                executeCallbacks.add(callback);
            }
        }
        if (executeCallbacks.size() > 0) {
            try {
                executeCallbacks.stream().forEach(callback -> callback.accept(error));
            } catch (final Exception ignore) {}
        }
        latch.countDown();
    }

    public Promise then(final Consumer consumer) {
        return promise.then(consumer);
    }

    public Promise error(final Consumer consumer) {
        return promise.error(consumer);
    }

    public Promise promise() {
        return promise;
    }

    public class Promise {
        public Promise then(final Consumer consumer) {
            final ArrayList> executeCallbacks;
            synchronized (Deferred.this) {
                doneCallbacks.add(consumer);
                executeCallbacks = new ArrayList<>(doneCallbacks.size());
                if (response != null) {
                    Consumer callback;
                    while ((callback = doneCallbacks.poll()) != null) {
                        executeCallbacks.add(callback);
                    }
                }
            }
            if (executeCallbacks.size() > 0) {
                executeCallbacks.stream().forEach(callback -> callback.accept(response));
            }
            return this;
        }

        public Promise error(final Consumer consumer) {
            final ArrayList> executeCallbacks;
            synchronized (Deferred.this) {
                errorCallbacks.add(consumer);
                executeCallbacks = new ArrayList<>(errorCallbacks.size());
                if (error != null) {
                    Consumer callback;
                    while ((callback = errorCallbacks.poll()) != null) {
                        executeCallbacks.add(callback);
                    }
                }
            }
            if (executeCallbacks.size() > 0) {
                executeCallbacks.stream().forEach(callback -> callback.accept(error));
            }
            return this;
        }

        public RESPONSE getResponse() {
            return getResponse(1, TimeUnit.MINUTES);
        }

        public RESPONSE getResponse(final long time, final TimeUnit unit) {
            try {
                final boolean isTimeout = !latch.await(time, unit);
                if (isTimeout) {
                    throw new SuggesterException("Request timeout. time:" + time + " unit:" + unit.name());
                }
                if (error != null) {
                    throw new SuggesterException(error);
                }
                return response;
            } catch (final InterruptedException e) {
                throw new InterruptedRuntimeException(e);
            }
        }
    }
}