/*-
 * ============LICENSE_START=======================================================
 * ONAP - SO
 * ================================================================================
 * Copyright (C) 2017 AT&T Intellectual Property. All rights reserved.
 * Copyright (C) 2017 Huawei Technologies Co., Ltd. All rights reserved.
 * ================================================================================
 * Modifications Copyright (C) 2018 IBM.
 * Modifications Copyright (c) 2019 Samsung
 * ================================================================================
 * 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.onap.so.adapters.sdnc.sdncrest;

import java.io.StringReader;
import java.net.HttpURLConnection;
import java.net.SocketTimeoutException;
import java.util.Arrays;
import java.util.List;
import javax.xml.XMLConstants;
import javax.xml.bind.DatatypeConverter;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;
import org.onap.so.logger.LoggingAnchor;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.methods.HttpDelete;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.methods.HttpPut;
import org.apache.http.client.methods.HttpRequestBase;
import org.apache.http.conn.ConnectTimeoutException;
import org.apache.http.entity.ContentType;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.util.EntityUtils;
import org.onap.so.adapters.sdnc.impl.Constants;
import org.onap.so.adapters.sdncrest.SDNCErrorCommon;
import org.onap.so.adapters.sdncrest.SDNCResponseCommon;
import org.onap.logging.filter.base.ErrorCode;
import org.onap.so.logger.MessageEnum;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;
import org.xml.sax.InputSource;
import org.onap.so.utils.CryptoUtils;
import org.springframework.core.env.Environment;

/**
 * Sends requests to SDNC and processes the responses.
 */
@Component
public abstract class SDNCConnector {
    private static final Logger logger = LoggerFactory.getLogger(SDNCConnector.class);

    private static final String XPATH_EXCEPTION = "XPath Exception";
    @Autowired
    private Environment env;

    public SDNCResponseCommon send(String content, TypedRequestTunables rt) {
        logger.debug("SDNC URL: {}", rt.getSdncUrl());
        logger.debug("SDNC Request Body:\n {}", content);

        HttpRequestBase method = null;
        HttpResponse httpResponse = null;

        try {

            HttpClient client = HttpClientBuilder.create().build();

            method = getHttpRequestMethod(content, rt);


            String userCredentials = CryptoUtils.decrypt(env.getProperty(Constants.SDNC_AUTH_PROP),
                    env.getProperty(Constants.ENCRYPTION_KEY_PROP));
            String authorization = "Basic " + DatatypeConverter.printBase64Binary(userCredentials.getBytes());
            if (null != method) {
                method.setHeader("Authorization", authorization);
                method.setHeader("Accept", "application/yang.data+xml");
            } else {
                logger.debug("method is NULL:");
            }

            httpResponse = client.execute(method);

            String responseContent = null;
            if (httpResponse.getEntity() != null) {
                responseContent = EntityUtils.toString(httpResponse.getEntity(), "UTF-8");
            }

            int statusCode = httpResponse.getStatusLine().getStatusCode();
            String statusMessage = httpResponse.getStatusLine().getReasonPhrase();

            logger.debug("SDNC Response: {} {}", statusCode,
                    statusMessage + (responseContent == null ? "" : System.lineSeparator() + responseContent));

            if (httpResponse.getStatusLine().getStatusCode() >= 300) {
                String errMsg = "SDNC returned " + statusCode + " " + statusMessage;

                String errors = analyzeErrors(responseContent);
                if (errors != null && !errors.isEmpty()) {
                    errMsg += " " + errors;
                }

                logError(errMsg);

                return createErrorResponse(statusCode, errMsg, rt);
            }

            httpResponse = null;

            if (null != method) {
                method.reset();
            } else {
                logger.debug("method is NULL:");
            }

            method = null;

            logger.info(LoggingAnchor.THREE, MessageEnum.RA_RESPONSE_FROM_SDNC.toString(), responseContent, "SDNC");
            return createResponseFromContent(statusCode, statusMessage, responseContent, rt);

        } catch (SocketTimeoutException | ConnectTimeoutException e) {
            String errMsg = "Request to SDNC timed out";
            logError(errMsg, e);
            return createErrorResponse(HttpURLConnection.HTTP_CLIENT_TIMEOUT, errMsg, rt);

        } catch (Exception e) {
            String errMsg = "Error processing request to SDNC";
            logError(errMsg, e);
            return createErrorResponse(HttpURLConnection.HTTP_INTERNAL_ERROR, errMsg, rt);

        } finally {
            if (httpResponse != null) {
                try {
                    EntityUtils.consume(httpResponse.getEntity());
                } catch (Exception e) {
                    logger.debug("Exception:", e);
                }
            }

            if (method != null) {
                try {
                    method.reset();
                } catch (Exception e) {
                    logger.debug("Exception:", e);
                }
            }
        }
    }

    private HttpRequestBase getHttpRequestMethod(String content, TypedRequestTunables rt) {

        int timeout = Integer.parseInt(rt.getTimeout());
        HttpRequestBase method = null;

        RequestConfig requestConfig = RequestConfig.custom().setSocketTimeout(timeout).setConnectTimeout(timeout)
                .setConnectionRequestTimeout(timeout).build();

        if ("POST".equals(rt.getReqMethod())) {
            HttpPost httpPost = new HttpPost(rt.getSdncUrl());
            httpPost.setConfig(requestConfig);
            httpPost.setEntity(new StringEntity(content, ContentType.APPLICATION_XML));
            method = httpPost;
        } else if ("PUT".equals(rt.getReqMethod())) {
            HttpPut httpPut = new HttpPut(rt.getSdncUrl());
            httpPut.setConfig(requestConfig);
            httpPut.setEntity(new StringEntity(content, ContentType.APPLICATION_XML));
            method = httpPut;
        } else if ("GET".equals(rt.getReqMethod())) {
            HttpGet httpGet = new HttpGet(rt.getSdncUrl());
            httpGet.setConfig(requestConfig);
            method = httpGet;
        } else if ("DELETE".equals(rt.getReqMethod())) {
            HttpDelete httpDelete = new HttpDelete(rt.getSdncUrl());
            httpDelete.setConfig(requestConfig);
            method = httpDelete;
        }
        return method;
    }

    protected void logError(String errMsg) {
        logger.error(LoggingAnchor.FOUR, MessageEnum.RA_EXCEPTION_COMMUNICATE_SDNC.toString(), "SDNC",
                ErrorCode.AvailabilityError.getValue(), errMsg);
    }

    protected void logError(String errMsg, Throwable t) {
        logger.error(LoggingAnchor.FOUR, MessageEnum.RA_EXCEPTION_COMMUNICATE_SDNC.toString(), "SDNC",
                ErrorCode.AvailabilityError.getValue(), errMsg, t);
    }

    /**
     * Generates a response object from content received from SDNC. The response object may be a success response object
     * or an error response object. This method must be overridden by the subclass to return the correct object type.
     *
     * @param statusCode the response status code from SDNC (e.g. 200)
     * @param statusMessage the response status message from SDNC (e.g. "OK")
     * @param responseContent the body of the response from SDNC (possibly null)
     * @param rt request tunables
     * @return a response object
     */
    protected abstract SDNCResponseCommon createResponseFromContent(int statusCode, String statusMessage,
            String responseContent, TypedRequestTunables rt);

    /**
     * Generates an error response object. This method must be overridden by the subclass to return the correct object
     * type.
     *
     * @param statusCode the response status code (from SDNC, or internally generated)
     * @param errMsg the error message (normally a verbose explanation of the error)
     * @param rt request tunables
     * @return an error response object
     */
    protected abstract SDNCErrorCommon createErrorResponse(int statusCode, String errMsg, TypedRequestTunables rt);

    /**
     * Called by the send() method to analyze errors that may be encoded in the content of non-2XX responses. By
     * default, this method tries to parse the content as a restconf error.
     *
     * <pre>
     * xmlns = "urn:ietf:params:xml:ns:yang:ietf-restconf"
     * </pre>
     *
     * If an error (or errors) can be obtained from the content, then the result is a string in this format:
     *
     * <pre>
     * [error-type:TYPE, error-tag:TAG, error-message:MESSAGE] ...
     * </pre>
     *
     * If no error could be obtained from the content, then the result is null.
     * <p>
     * The subclass can override this method to provide another implementation.
     */
    protected String analyzeErrors(String content) {
        if (content == null || content.isEmpty()) {
            return null;
        }

        // Confirmed with Andrew Shen on 11/1/16 that SDNC will send content like
        // this in error responses (non-2XX response codes) to "agnostic" service
        // requests.
        //
        // <errors xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf">
        // <error>
        // <error-type>protocol</error-type>
        // <error-tag>malformed-message</error-tag>
        // <error-message>Error parsing input: The element type "input" must be terminated by the matching end-tag
        // "&lt;/input&gt;".</error-message>
        // </error>
        // </errors>

        String output = null;

        try {
            XPathFactory xpathFactory = XPathFactory.newInstance();
            XPath xpath = xpathFactory.newXPath();
            DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();
            documentBuilderFactory.setFeature(XMLConstants.FEATURE_SECURE_PROCESSING, true);
            documentBuilderFactory.setFeature("http://xml.org/sax/features/external-general-entities", false);
            documentBuilderFactory.setFeature("http://xml.org/sax/features/external-parameter-entities", false);
            InputSource source = new InputSource(new StringReader(content));
            Document doc = documentBuilderFactory.newDocumentBuilder().parse(source);
            NodeList errors = (NodeList) xpath.evaluate("errors/error", doc, XPathConstants.NODESET);
            StringBuilder errorDetails = getErrorDetails(xpath, errors);
            if (errorDetails != null) {
                output = errorDetails.toString();
            }
        } catch (Exception e) {
            logger.error(LoggingAnchor.FOUR, MessageEnum.RA_ANALYZE_ERROR_EXC.toString(), "SDNC",
                    ErrorCode.DataError.getValue(), "Exception while analyzing errors", e);
        }

        return output;
    }

    private StringBuilder getErrorDetails(XPath xpath, NodeList errors) {

        StringBuilder output = null;

        for (int i = 0; i < errors.getLength(); i++) {
            Element error = (Element) errors.item(i);

            StringBuilder info = new StringBuilder();

            List<String> errorAttributesList = Arrays.asList("error-type", "error-tag", "error-message");

            for (String errorAttrib : errorAttributesList) {
                try {
                    String errorAttribValue = xpath.evaluate(errorAttrib, error);
                    info.append(errorAttrib).append(":").append(errorAttribValue);
                } catch (XPathExpressionException e) {
                    logger.error(LoggingAnchor.SIX, MessageEnum.RA_EVALUATE_XPATH_ERROR.toString(), errorAttrib,
                            error.toString(), "SDNC", ErrorCode.DataError.getValue(), XPATH_EXCEPTION, e);
                }
            }

            if (!info.toString().isEmpty()) {
                if (output == null) {
                    output = new StringBuilder("[" + info + "]");
                } else {
                    output.append(" [").append(info).append("]");
                }
            }
        }
        return output;
    }
}