/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You 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.apache.coyote.http2;

import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;
import org.apache.tomcat.util.res.StringManager;

/**
 * Base class for all streams including the connection (referred to as Stream 0) and is used primarily when managing
 * prioritization.
 */
abstract class AbstractStream {

    private static final Log log = LogFactory.getLog(AbstractStream.class);
    private static final StringManager sm = StringManager.getManager(AbstractStream.class);

    private final Integer identifier;
    private final String idAsString;

    private long windowSize = ConnectionSettingsBase.DEFAULT_INITIAL_WINDOW_SIZE;
    protected final Lock windowAllocationLock = new ReentrantLock();
    protected final Condition windowAllocationAvailable = windowAllocationLock.newCondition();

    private volatile int connectionAllocationRequested = 0;
    private volatile int connectionAllocationMade = 0;


    AbstractStream(Integer identifier) {
        this.identifier = identifier;
        this.idAsString = identifier.toString();
    }


    /**
     * @return the stream identifier
     */
    final Integer getIdentifier() {
        return identifier;
    }


    /**
     * @return the stream identifier as a String
     */
    final String getIdAsString() {
        return idAsString;
    }


    /**
     * @return the stream identifier
     */
    final int getIdAsInt() {
        return identifier.intValue();
    }


    /**
     * Set the window size for this stream.
     * @param windowSize the value
     */
    final void setWindowSize(long windowSize) {
        windowAllocationLock.lock();
        try {
            this.windowSize = windowSize;
        } finally {
            windowAllocationLock.unlock();
        }
    }


    /**
     * @return the window size
     */
    final long getWindowSize() {
        windowAllocationLock.lock();
        try {
            return windowSize;
        } finally {
            windowAllocationLock.unlock();
        }
    }


    /**
     * Increment window size.
     *
     * @param increment The amount by which the window size should be increased
     *
     * @throws Http2Exception If the window size is now higher than the maximum allowed
     */
    void incrementWindowSize(int increment) throws Http2Exception {
        windowAllocationLock.lock();
        try {
            // No need for overflow protection here.
            // Increment can't be more than Integer.MAX_VALUE and once windowSize
            // goes beyond 2^31-1 an error is triggered.
            windowSize += increment;

            if (log.isTraceEnabled()) {
                log.trace(sm.getString("abstractStream.windowSizeInc", getConnectionId(), getIdAsString(),
                        Integer.toString(increment), Long.toString(windowSize)));
            }

            if (windowSize > ConnectionSettingsBase.MAX_WINDOW_SIZE) {
                String msg = sm.getString("abstractStream.windowSizeTooBig", getConnectionId(), identifier,
                        Integer.toString(increment), Long.toString(windowSize));
                if (identifier.intValue() == 0) {
                    throw new ConnectionException(msg, Http2Error.FLOW_CONTROL_ERROR);
                } else {
                    throw new StreamException(msg, Http2Error.FLOW_CONTROL_ERROR, identifier.intValue());
                }
            }
        } finally {
            windowAllocationLock.unlock();
        }
    }


    /**
     * Decrement window size.
     *
     * @param decrement The amount by which the window size should be decreased
     */
    final void decrementWindowSize(int decrement) {
        windowAllocationLock.lock();
        try {
            // No need for overflow protection here. Decrement can never be larger
            // the Integer.MAX_VALUE and once windowSize goes negative no further
            // decrements are permitted
            windowSize -= decrement;
            if (log.isTraceEnabled()) {
                log.trace(sm.getString("abstractStream.windowSizeDec", getConnectionId(), getIdAsString(),
                        Integer.toString(decrement), Long.toString(windowSize)));
            }
        } finally {
            windowAllocationLock.unlock();
        }
    }


    /**
     * @return the requested amount of resources requested
     */
    final int getConnectionAllocationRequested() {
        return connectionAllocationRequested;
    }


    /**
     * Set the amount of requested resources.
     * @param connectionAllocationRequested the value
     */
    final void setConnectionAllocationRequested(int connectionAllocationRequested) {
        log.trace(sm.getString("abstractStream.setConnectionAllocationRequested", getConnectionId(), getIdAsString(),
                Integer.toString(this.connectionAllocationRequested), Integer.toString(connectionAllocationRequested)));
        this.connectionAllocationRequested = connectionAllocationRequested;
    }


    /**
     * @return the allocation that was made at the connection level
     */
    final int getConnectionAllocationMade() {
        return connectionAllocationMade;
    }


    /**
     * Set the allocation made at the connection level.
     * @param connectionAllocationMade the value
     */
    final void setConnectionAllocationMade(int connectionAllocationMade) {
        log.trace(sm.getString("abstractStream.setConnectionAllocationMade", getConnectionId(), getIdAsString(),
                Integer.toString(this.connectionAllocationMade), Integer.toString(connectionAllocationMade)));
        this.connectionAllocationMade = connectionAllocationMade;
    }


    /**
     * @return the connection id
     */
    abstract String getConnectionId();
}
