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RESTHeart Commons - Common classes for core components and plugins.
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/*-
 * ========================LICENSE_START=================================
 * restheart-commons
 * %%
 * Copyright (C) 2019 - 2024 SoftInstigate
 * %%
 * 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.
 * =========================LICENSE_END==================================
 */
package org.restheart.exchange;

import java.io.IOException;
import java.lang.reflect.Field;

import io.undertow.connector.PooledByteBuffer;
import io.undertow.server.HttpServerExchange;
import io.undertow.util.AttachmentKey;

/**
 *
 * Base class for Request implementation that can be used in proxied requests.
 *
 * It stores the response content in the BUFFERED_REQUEST_DATA attachment
 * of the HttpServerExchange.
 *
 * @author Andrea Di Cesare {@literal }
 * @param  generic type
 */
public abstract class ProxyRequest extends Request implements BufferedExchange, AutoCloseable {
    public ProxyRequest(HttpServerExchange exchange) {
        super(exchange);
    }

    @Override
    public abstract T readContent() throws IOException;

    @Override
    public abstract void writeContent(T content) throws IOException;

    @SuppressWarnings("unchecked")
    protected AttachmentKey getRawContentKey() {
        Field f;

        try {
            f = HttpServerExchange.class.getDeclaredField("BUFFERED_REQUEST_DATA");
            f.setAccessible(true);
        } catch (NoSuchFieldException | SecurityException ex) {
            throw new RuntimeException("could not find BUFFERED_REQUEST_DATA field", ex);
        }

        try {
            return (AttachmentKey) f.get(getWrappedExchange());
        } catch (IllegalArgumentException | IllegalAccessException ex) {
            throw new RuntimeException("could not access BUFFERED_REQUEST_DATA field", ex);
        }
    }

    @Override
    public void setBuffer(PooledByteBuffer[] raw) {
        // close the current buffer pool
        var oldBuffers = getWrappedExchange().getAttachment(getRawContentKey());
        if (oldBuffers != null) {
            for (var oldBuffer: oldBuffers) {
                if (oldBuffer != null) {
                    oldBuffer.close();
                }
            }
        }

        getWrappedExchange().putAttachment(getRawContentKey(), raw);
    }

    @Override
    public PooledByteBuffer[] getBuffer() {
        if (!isContentAvailable()) {
            throw new IllegalStateException("Request content is not available. "
                    + "Add a Request Inteceptor with "
                    + "@RegisterPlugin(requiresContent = true) to make "
                    + "the content available.");
        }

        return getWrappedExchange().getAttachment(getRawContentKey());
    }

    @Override
    public boolean isContentAvailable() {
        return null != getWrappedExchange().getAttachment(getRawContentKey());
    }

    /**
     * Closes this resource, relinquishing any underlying resources.
     */
    @Override
    public void close() {
        if (isContentAvailable()) {
            for (var b: this.getBuffer()) {
                if (b != null) {
                    b.close();
                }
            }

            this.setBuffer(null);
        }
    }
}