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/*
 * Copyright 2017 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.test.fixtures.server.http;

import com.sun.net.httpserver.HttpExchange;
import org.gradle.internal.time.Time;
import org.gradle.internal.time.Timer;

import javax.annotation.Nullable;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;

class CyclicBarrierRequestHandler implements TrackingHttpHandler, WaitPrecondition {
    private final Timer timer = Time.startTimer();
    private final Lock lock;
    private final Condition condition;
    private final List received = new ArrayList();
    private final List pending = new ArrayList();
    private final int timeoutMs;
    private final WaitPrecondition previous;
    private long mostRecentEvent;
    private boolean cancelled;
    private AssertionError failure;

    CyclicBarrierRequestHandler(Lock lock, int timeoutMs, WaitPrecondition previous, Collection expectations) {
        this.lock = lock;
        condition = lock.newCondition();
        this.timeoutMs = timeoutMs;
        this.previous = previous;
        for (ResourceExpectation expectation : expectations) {
            // Can wait on request if previous handler allows waiting
            ResourceHandler handler = expectation.create(previous);
            pending.add(handler);
        }
    }

    @Override
    public WaitPrecondition getWaitPrecondition() {
        return this;
    }

    @Override
    public void assertCanWait() throws AssertionError {
        lock.lock();
        try {
            // Can wait if this handler has completed or if the previous handler allows waiting
            if (pending.isEmpty()) {
                // Already completed
                return;
            }
            previous.assertCanWait();
        } finally {
            lock.unlock();
        }
    }

    @Override
    public ResponseProducer selectResponseProducer(int id, HttpExchange httpExchange) throws Exception {
        ResourceHandler handler;
        lock.lock();
        try {
            if (pending.isEmpty()) {
                // barrier open, let it travel on
                return null;
            }

            long now = timer.getElapsedMillis();
            if (mostRecentEvent < now) {
                mostRecentEvent = now;
            }

            String path = httpExchange.getRequestURI().getPath().substring(1);
            handler = selectPending(pending, path);
            if (handler == null || !handler.getMethod().equals(httpExchange.getRequestMethod())) {
                failure = new UnexpectedRequestException(String.format("Unexpected request %s /%s received. Waiting for %s, already received %s.", httpExchange.getRequestMethod(), path, format(pending), received));
                condition.signalAll();
                throw failure;
            }

            received.add(httpExchange.getRequestMethod() + " /" + path);
            pending.remove(handler);
            if (pending.isEmpty()) {
                condition.signalAll();
            }

            while (!pending.isEmpty() && failure == null && !cancelled) {
                long waitMs = mostRecentEvent + timeoutMs - timer.getElapsedMillis();
                if (waitMs < 0) {
                    System.out.println(String.format("[%d] timeout waiting for other requests", id));
                    failure = new AssertionError(String.format("Timeout waiting for expected requests to be received. Still waiting for %s, received %s.", format(pending), received));
                    condition.signalAll();
                    throw failure;
                }
                System.out.println(String.format("[%d] waiting for other requests. Still waiting for %s", id, format(pending)));
                condition.await(waitMs, TimeUnit.MILLISECONDS);
            }

            if (failure != null) {
                // Failed in another thread
                System.out.println(String.format("[%d] failure in another thread", id));
                throw failure;
            }
            if (cancelled) {
                return new ResponseProducer() {
                    @Override
                    public void writeTo(int requestId, HttpExchange exchange) {
                        try {
                            exchange.sendResponseHeaders(200, -1);
                        } catch (IOException e) {
                            // Ignore
                        }
                    }
                };
            }
        } finally {
            lock.unlock();
        }

        // All requests completed, write response
        return handler;
    }

    @Override
    public void cancelBlockedRequests() {
        lock.lock();
        try {
            cancelled = true;
            condition.signalAll();
        } finally {
            lock.unlock();
        }
    }

    static String format(List handlers) {
        StringBuilder builder = new StringBuilder();
        builder.append("[");
        for (ResourceHandler handler : handlers) {
            if (builder.length() > 1) {
                builder.append(", ");
            }
            builder.append(handler.getMethod());
            builder.append(" /");
            builder.append(handler.getPath());
        }
        builder.append("]");
        return builder.toString();
    }

    @Nullable
    static  T selectPending(List handlers, String path) {
        for (T handler : handlers) {
            if (handler.getPath().equals(path)) {
                return handler;
            }
        }
        return null;
    }

    @Override
    public void assertComplete(Collection failures) throws AssertionError {
        lock.lock();
        try {
            if (failure != null) {
                // Already reported
                return;
            }
            if (!pending.isEmpty()) {
                failures.add(new AssertionError(String.format("Did not receive expected requests. Waiting for %s, received %s", format(pending), received)));
            }
        } finally {
            lock.unlock();
        }
    }
}