/*
 * Copyright 2002-2018 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
 *
 *      https://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.springframework.web.socket.sockjs.client;

import java.net.URI;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.util.concurrent.ListenableFuture;
import org.springframework.util.concurrent.SettableListenableFuture;
import org.springframework.web.client.HttpServerErrorException;
import org.springframework.web.socket.TextMessage;
import org.springframework.web.socket.WebSocketHandler;
import org.springframework.web.socket.WebSocketSession;
import org.springframework.web.socket.sockjs.frame.SockJsFrame;
import org.springframework.web.socket.sockjs.transport.TransportType;

/**
 * Abstract base class for XHR transport implementations to extend.
 *
 * @author Rossen Stoyanchev
 * @since 4.1
 */
public abstract class AbstractXhrTransport implements XhrTransport {

        protected static final String PRELUDE;

        static {
                byte[] bytes = new byte[2048];
                for (int i = 0; i < bytes.length; i++) {
                        bytes[i] = 'h';
                }
                PRELUDE = new String(bytes, SockJsFrame.CHARSET);
        }


        protected final Log logger = LogFactory.getLog(getClass());

        private boolean xhrStreamingDisabled;

        private HttpHeaders requestHeaders = new HttpHeaders();


        @Override
        public List<TransportType> getTransportTypes() {
                return (isXhrStreamingDisabled() ? Collections.singletonList(TransportType.XHR) :
                                Arrays.asList(TransportType.XHR_STREAMING, TransportType.XHR));
        }

        /**
         * An {@code XhrTransport} can support both the "xhr_streaming" and "xhr"
         * SockJS server transports. From a client perspective there is no
         * implementation difference.
         * <p>Typically an {@code XhrTransport} is used as "XHR streaming" first and
         * then, if that fails, as "XHR". In some cases however it may be helpful to
         * suppress XHR streaming so that only XHR is attempted.
         * <p>By default this property is set to {@code false} which means both
         * "XHR streaming" and "XHR" apply.
         */
        public void setXhrStreamingDisabled(boolean disabled) {
                this.xhrStreamingDisabled = disabled;
        }

        /**
         * Whether XHR streaming is disabled or not.
         */
        public boolean isXhrStreamingDisabled() {
                return this.xhrStreamingDisabled;
        }

        /**
         * Configure headers to be added to every executed HTTP request.
         * @param requestHeaders the headers to add to requests
         * @deprecated as of 4.2 in favor of {@link SockJsClient#setHttpHeaderNames}.
         */
        @Deprecated
        public void setRequestHeaders(HttpHeaders requestHeaders) {
                this.requestHeaders.clear();
                if (requestHeaders != null) {
                        this.requestHeaders.putAll(requestHeaders);
                }
        }

        @Deprecated
        public HttpHeaders getRequestHeaders() {
                return this.requestHeaders;
        }


        // Transport methods

        @Override
        @SuppressWarnings("deprecation")
        public ListenableFuture<WebSocketSession> connect(TransportRequest request, WebSocketHandler handler) {
                SettableListenableFuture<WebSocketSession> connectFuture = new SettableListenableFuture<WebSocketSession>();
                XhrClientSockJsSession session = new XhrClientSockJsSession(request, handler, this, connectFuture);
                request.addTimeoutTask(session.getTimeoutTask());

                URI receiveUrl = request.getTransportUrl();
                if (logger.isDebugEnabled()) {
                        logger.debug("Starting XHR " +
                                        (isXhrStreamingDisabled() ? "Polling" : "Streaming") + "session url=" + receiveUrl);
                }

                HttpHeaders handshakeHeaders = new HttpHeaders();
                handshakeHeaders.putAll(getRequestHeaders());
                handshakeHeaders.putAll(request.getHandshakeHeaders());

                connectInternal(request, handler, receiveUrl, handshakeHeaders, session, connectFuture);
                return connectFuture;
        }

        protected abstract void connectInternal(TransportRequest request, WebSocketHandler handler,
                        URI receiveUrl, HttpHeaders handshakeHeaders, XhrClientSockJsSession session,
                        SettableListenableFuture<WebSocketSession> connectFuture);


        // InfoReceiver methods

        @Override
        @SuppressWarnings("deprecation")
        public String executeInfoRequest(URI infoUrl, HttpHeaders headers) {
                if (logger.isDebugEnabled()) {
                        logger.debug("Executing SockJS Info request, url=" + infoUrl);
                }
                HttpHeaders infoRequestHeaders = new HttpHeaders();
                infoRequestHeaders.putAll(getRequestHeaders());
                if (headers != null) {
                        infoRequestHeaders.putAll(headers);
                }
                ResponseEntity<String> response = executeInfoRequestInternal(infoUrl, infoRequestHeaders);
                if (response.getStatusCode() != HttpStatus.OK) {
                        if (logger.isErrorEnabled()) {
                                logger.error("SockJS Info request (url=" + infoUrl + ") failed: " + response);
                        }
                        throw new HttpServerErrorException(response.getStatusCode());
                }
                if (logger.isTraceEnabled()) {
                        logger.trace("SockJS Info request (url=" + infoUrl + ") response: " + response);
                }
                return response.getBody();
        }

        protected abstract ResponseEntity<String> executeInfoRequestInternal(URI infoUrl, HttpHeaders headers);


        // XhrTransport methods

        @Override
        public void executeSendRequest(URI url, HttpHeaders headers, TextMessage message) {
                if (logger.isTraceEnabled()) {
                        logger.trace("Starting XHR send, url=" + url);
                }
                ResponseEntity<String> response = executeSendRequestInternal(url, headers, message);
                if (response.getStatusCode() != HttpStatus.NO_CONTENT) {
                        if (logger.isErrorEnabled()) {
                                logger.error("XHR send request (url=" + url + ") failed: " + response);
                        }
                        throw new HttpServerErrorException(response.getStatusCode());
                }
                if (logger.isTraceEnabled()) {
                        logger.trace("XHR send request (url=" + url + ") response: " + response);
                }
        }

        protected abstract ResponseEntity<String> executeSendRequestInternal(
                        URI url, HttpHeaders headers, TextMessage message);


        @Override
        public String toString() {
                return getClass().getSimpleName();
        }

}