/*
 * ====================================================================
 * 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.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */

package ch.boye.httpclientandroidlib.impl;

import java.io.IOException;

import ch.boye.httpclientandroidlib.HttpConnectionMetrics;
import ch.boye.httpclientandroidlib.HttpEntity;
import ch.boye.httpclientandroidlib.HttpEntityEnclosingRequest;
import ch.boye.httpclientandroidlib.HttpException;
import ch.boye.httpclientandroidlib.HttpRequest;
import ch.boye.httpclientandroidlib.HttpRequestFactory;
import ch.boye.httpclientandroidlib.HttpResponse;
import ch.boye.httpclientandroidlib.HttpServerConnection;
import ch.boye.httpclientandroidlib.entity.ContentLengthStrategy;
import ch.boye.httpclientandroidlib.impl.entity.EntityDeserializer;
import ch.boye.httpclientandroidlib.impl.entity.EntitySerializer;
import ch.boye.httpclientandroidlib.impl.entity.LaxContentLengthStrategy;
import ch.boye.httpclientandroidlib.impl.entity.StrictContentLengthStrategy;
import ch.boye.httpclientandroidlib.impl.io.HttpRequestParser;
import ch.boye.httpclientandroidlib.impl.io.HttpResponseWriter;
import ch.boye.httpclientandroidlib.io.EofSensor;
import ch.boye.httpclientandroidlib.io.HttpMessageParser;
import ch.boye.httpclientandroidlib.io.HttpMessageWriter;
import ch.boye.httpclientandroidlib.io.HttpTransportMetrics;
import ch.boye.httpclientandroidlib.io.SessionInputBuffer;
import ch.boye.httpclientandroidlib.io.SessionOutputBuffer;
import ch.boye.httpclientandroidlib.message.LineFormatter;
import ch.boye.httpclientandroidlib.message.LineParser;
import ch.boye.httpclientandroidlib.params.HttpParams;

/**
 * Abstract server-side HTTP connection capable of transmitting and receiving
 * data using arbitrary {@link SessionInputBuffer} and
 * {@link SessionOutputBuffer} implementations.
 * <p>
 * The following parameters can be used to customize the behavior of this
 * class:
 * <ul>
 *  <li>{@link ch.boye.httpclientandroidlib.params.CoreProtocolPNames#STRICT_TRANSFER_ENCODING}</li>
 *  <li>{@link ch.boye.httpclientandroidlib.params.CoreConnectionPNames#MAX_HEADER_COUNT}</li>
 * </ul>
 *
 * @since 4.0
 */
public abstract class AbstractHttpServerConnection implements HttpServerConnection {

    private final EntitySerializer entityserializer;
    private final EntityDeserializer entitydeserializer;

    private SessionInputBuffer inbuffer = null;
    private SessionOutputBuffer outbuffer = null;
    private EofSensor eofSensor = null;
    private HttpMessageParser requestParser = null;
    private HttpMessageWriter responseWriter = null;
    private HttpConnectionMetricsImpl metrics = null;

    /**
     * Creates an instance of this class.
     * <p>
     * This constructor will invoke {@link #createEntityDeserializer()}
     * and {@link #createEntitySerializer()} methods in order to initialize
     * HTTP entity serializer and deserializer implementations for this
     * connection.
     */
    public AbstractHttpServerConnection() {
        super();
        this.entityserializer = createEntitySerializer();
        this.entitydeserializer = createEntityDeserializer();
    }

    /**
     * Asserts if the connection is open.
     *
     * @throws IllegalStateException if the connection is not open.
     */
    protected abstract void assertOpen() throws IllegalStateException;

    /**
     * Creates an instance of {@link EntityDeserializer} with the
     * {@link LaxContentLengthStrategy} implementation to be used for
     * de-serializing entities received over this connection.
     * <p>
     * This method can be overridden in a super class in order to create
     * instances of {@link EntityDeserializer} using a custom
     * {@link ContentLengthStrategy}.
     *
     * @return HTTP entity deserializer
     */
    protected EntityDeserializer createEntityDeserializer() {
        return new EntityDeserializer(new LaxContentLengthStrategy());
    }

    /**
     * Creates an instance of {@link EntitySerializer} with the
     * {@link StrictContentLengthStrategy} implementation to be used for
     * serializing HTTP entities sent over this connection.
     * <p>
     * This method can be overridden in a super class in order to create
     * instances of {@link EntitySerializer} using a custom
     * {@link ContentLengthStrategy}.
     *
     * @return HTTP entity serialzier.
     */
    protected EntitySerializer createEntitySerializer() {
        return new EntitySerializer(new StrictContentLengthStrategy());
    }

    /**
     * Creates an instance of {@link DefaultHttpRequestFactory} to be used
     * for creating {@link HttpRequest} objects received by over this
     * connection.
     * <p>
     * This method can be overridden in a super class in order to provide
     * a different implementation of the {@link HttpRequestFactory} interface.
     *
     * @return HTTP request factory.
     */
    protected HttpRequestFactory createHttpRequestFactory() {
        return new DefaultHttpRequestFactory();
    }

    /**
     * Creates an instance of {@link HttpMessageParser} to be used for parsing
     * HTTP requests received over this connection.
     * <p>
     * This method can be overridden in a super class in order to provide
     * a different implementation of the {@link HttpMessageParser} interface or
     * to pass a different implementation of {@link LineParser} to the
     * the default implementation {@link HttpRequestParser}.
     *
     * @param buffer the session input buffer.
     * @param requestFactory the HTTP request factory.
     * @param params HTTP parameters.
     * @return HTTP message parser.
     */
    protected HttpMessageParser createRequestParser(
            final SessionInputBuffer buffer,
            final HttpRequestFactory requestFactory,
            final HttpParams params) {
        return new HttpRequestParser(buffer, null, requestFactory, params);
    }

    /**
     * Creates an instance of {@link HttpMessageWriter} to be used for
     * writing out HTTP responses sent over this connection.
     * <p>
     * This method can be overridden in a super class in order to provide
     * a different implementation of the {@link HttpMessageWriter} interface or
     * to pass a different implementation of {@link LineFormatter} to the
     * the default implementation {@link HttpResponseWriter}.
     *
     * @param buffer the session output buffer
     * @param params HTTP parameters
     * @return HTTP message writer
     */
    protected HttpMessageWriter createResponseWriter(
            final SessionOutputBuffer buffer,
            final HttpParams params) {
        return new HttpResponseWriter(buffer, null, params);
    }

    /**
     * @since 4.1
     */
    protected HttpConnectionMetricsImpl createConnectionMetrics(
            final HttpTransportMetrics inTransportMetric,
            final HttpTransportMetrics outTransportMetric) {
        return new HttpConnectionMetricsImpl(inTransportMetric, outTransportMetric);
    }

    /**
     * Initializes this connection object with {@link SessionInputBuffer} and
     * {@link SessionOutputBuffer} instances to be used for sending and
     * receiving data. These session buffers can be bound to any arbitrary
     * physical output medium.
     * <p>
     * This method will invoke {@link #createHttpRequestFactory},
     * {@link #createRequestParser(SessionInputBuffer, HttpRequestFactory, HttpParams)}
     * and {@link #createResponseWriter(SessionOutputBuffer, HttpParams)}
     * methods to initialize HTTP request parser and response writer for this
     * connection.
     *
     * @param inbuffer the session input buffer.
     * @param outbuffer the session output buffer.
     * @param params HTTP parameters.
     */
    protected void init(
            final SessionInputBuffer inbuffer,
            final SessionOutputBuffer outbuffer,
            final HttpParams params) {
        if (inbuffer == null) {
            throw new IllegalArgumentException("Input session buffer may not be null");
        }
        if (outbuffer == null) {
            throw new IllegalArgumentException("Output session buffer may not be null");
        }
        this.inbuffer = inbuffer;
        this.outbuffer = outbuffer;
        if (inbuffer instanceof EofSensor) {
            this.eofSensor = (EofSensor) inbuffer;
        }
        this.requestParser = createRequestParser(
                inbuffer,
                createHttpRequestFactory(),
                params);
        this.responseWriter = createResponseWriter(
                outbuffer, params);
        this.metrics = createConnectionMetrics(
                inbuffer.getMetrics(),
                outbuffer.getMetrics());
    }

    public HttpRequest receiveRequestHeader()
            throws HttpException, IOException {
        assertOpen();
        HttpRequest request = (HttpRequest) this.requestParser.parse();
        this.metrics.incrementRequestCount();
        return request;
    }

    public void receiveRequestEntity(final HttpEntityEnclosingRequest request)
            throws HttpException, IOException {
        if (request == null) {
            throw new IllegalArgumentException("HTTP request may not be null");
        }
        assertOpen();
        HttpEntity entity = this.entitydeserializer.deserialize(this.inbuffer, request);
        request.setEntity(entity);
    }

    protected void doFlush() throws IOException  {
        this.outbuffer.flush();
    }

    public void flush() throws IOException {
        assertOpen();
        doFlush();
    }

    public void sendResponseHeader(final HttpResponse response)
            throws HttpException, IOException {
        if (response == null) {
            throw new IllegalArgumentException("HTTP response may not be null");
        }
        assertOpen();
        this.responseWriter.write(response);
        if (response.getStatusLine().getStatusCode() >= 200) {
            this.metrics.incrementResponseCount();
        }
    }

    public void sendResponseEntity(final HttpResponse response)
            throws HttpException, IOException {
        if (response.getEntity() == null) {
            return;
        }
        this.entityserializer.serialize(
                this.outbuffer,
                response,
                response.getEntity());
    }

    protected boolean isEof() {
        return this.eofSensor != null && this.eofSensor.isEof();
    }

    public boolean isStale() {
        if (!isOpen()) {
            return true;
        }
        if (isEof()) {
            return true;
        }
        try {
            this.inbuffer.isDataAvailable(1);
            return isEof();
        } catch (IOException ex) {
            return true;
        }
    }

    public HttpConnectionMetrics getMetrics() {
        return this.metrics;
    }

}