/*
 * $Id$
 *
 * This file is part of the Cloud Services Integration Platform (CSIP),
 * a Model-as-a-Service framework, API and application suite.
 *
 * 2012-2017, Olaf David and others, OMSLab, Colorado State University.
 *
 * OMSLab licenses this file to you under the MIT license.
 * See the LICENSE file in the project root for more information.
 */
package csip.sdm;

import static csip.sdm.SDMDriver.*;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.sql.SQLException;
import java.util.Arrays;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.net.ssl.HttpsURLConnection;
import org.apache.commons.io.IOUtils;
import org.apache.http.HeaderElement;
import org.apache.http.HeaderElementIterator;
import org.apache.http.HttpEntity;
import org.apache.http.HttpException;
import org.apache.http.HttpHost;
import org.apache.http.HttpRequest;
import org.apache.http.HttpRequestInterceptor;
import org.apache.http.HttpResponse;

import org.apache.http.auth.AuthScope;
import org.apache.http.client.CredentialsProvider;
import org.apache.http.client.config.AuthSchemes;
import org.apache.http.client.config.CookieSpecs;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.entity.EntityBuilder;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.protocol.HttpClientContext;
import org.apache.http.config.RegistryBuilder;
import org.apache.http.conn.ConnectionKeepAliveStrategy;

import org.apache.http.conn.routing.HttpRoute;
import org.apache.http.conn.socket.ConnectionSocketFactory;
import org.apache.http.conn.socket.PlainConnectionSocketFactory;
import org.apache.http.conn.ssl.SSLConnectionSocketFactory;
import org.apache.http.entity.ContentType;
import org.apache.http.impl.auth.BasicScheme;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.impl.conn.PoolingHttpClientConnectionManager;
import org.apache.http.message.BasicHeaderElementIterator;
import org.apache.http.pool.PoolStats;
import org.apache.http.protocol.HTTP;
import org.apache.http.protocol.HttpContext;
import org.apache.http.ssl.SSLContexts;
import org.codehaus.jettison.json.JSONException;
import org.codehaus.jettison.json.JSONObject;

/**
 *
 * @author <a href="mailto:shaun.case@colostate.edu">Shaun Case</a>
 */
public class SDMClient {

    private static int MAX_RETRIES = 10;
    private static int THREAD_SLEEP_ON_RETRY = 500;  // 1/2 second, wait between retries.
    private String url;

    private static final PoolingHttpClientConnectionManager CM;

    static ConnectionKeepAliveStrategy myStrategy = (HttpResponse response, HttpContext context) -> {
        // Honor 'keep-alive' header
        HeaderElementIterator it = new BasicHeaderElementIterator(
                response.headerIterator(HTTP.CONN_KEEP_ALIVE));
        while (it.hasNext()) {
            HeaderElement he = it.nextElement();
            String param = he.getName();
            String value = he.getValue();
            if (value != null && param.equalsIgnoreCase("timeout")) {
                try {
                    return Long.parseLong(value) * 1000;
                } catch (NumberFormatException ignore) {
                }
            }
        }
        HttpHost target = (HttpHost) context.getAttribute(
                HttpClientContext.HTTP_TARGET_HOST);

        return 30 * 1000;
    };

    static {

        CM = new PoolingHttpClientConnectionManager(
                RegistryBuilder.<ConnectionSocketFactory>create()
                        .register("http", PlainConnectionSocketFactory.getSocketFactory())
                        .register("https", new SSLConnectionSocketFactory(SSLContexts.createSystemDefault()))
                        .build()
        );

        CM.setMaxTotal(3000);
        // Increase default max connection per route to 75
        CM.setDefaultMaxPerRoute(2500);
        // Increase max connections for localhost:80 to 125
        //HttpHost localhost = new HttpHost("locahost", 80);
        //CM.setMaxPerRoute(new HttpRoute(localhost), 150);   
    }

    /**
     * Pings a HTTP URL. This effectively sends a HEAD request and returns
     * <code>true</code> if the response code is in the 200-399 range.
     *
     * @param url The HTTP URL to be pinged.
     * @param timeout The timeout in millis for both the connection timeout and
     * the response read timeout. Note that the total timeout is effectively two
     * times the given timeout.
     * @return the time to respond if the given HTTP URL has returned response
     * code 200-399 on a HEAD request within the given timeout, otherwise
     * <code>-1</code>.
     */
    public static long ping(String url, int timeout) {
        try {
            HttpsURLConnection connection = (HttpsURLConnection) new URL(url).openConnection();
            connection.setConnectTimeout(timeout);
            connection.setReadTimeout(timeout);
            connection.setRequestMethod("HEAD");
            long start = System.currentTimeMillis();
            int responseCode = connection.getResponseCode();
            long end = System.currentTimeMillis();
            return (200 <= responseCode && responseCode <= 399) ? (end - start) : -1;
        } catch (IOException E) {
            return -1;
        }
    }

    private CredentialsProvider creds;
    private CloseableHttpClient httpClient;

    private Logger log;

    /**
     * Create a Client
     */
    SDMClient(DBProperties props, String url) {
        this.url = url;
        if (!props.isLoggingDefault()) {
            String level = props.getLogging();
            log = Logger.getAnonymousLogger();
            log.setLevel(Level.parse(level));
        }

        int timeout = props.getTimeout();

        RequestConfig reqConfig = init(timeout);
        httpClient = HttpClientBuilder.create()
                .setDefaultRequestConfig(reqConfig)
                .setConnectionManager(CM)
                .setKeepAliveStrategy(myStrategy)
                .build();
    }

    private RequestConfig init(int timeout) {
        RequestConfig reqConfig = RequestConfig.custom()
                .setConnectTimeout(timeout * 1000)
                .setConnectionRequestTimeout(timeout * 1000)
                .setSocketTimeout(timeout * 1000) // 10 minute max per run
                .setCookieSpec(CookieSpecs.BEST_MATCH)
                .setExpectContinueEnabled(true)
                .setStaleConnectionCheckEnabled(true)
                .setTargetPreferredAuthSchemes(Arrays.asList(AuthSchemes.NTLM, AuthSchemes.DIGEST))
                .setProxyPreferredAuthSchemes(Arrays.asList(AuthSchemes.BASIC))
                .build();
        return reqConfig;
    }

    /**
     * HTTP Post with the request JSON.
     *
     * @param uri the endpoint
     * @param req the request JSON
     * @return the response JSON
     * @throws java.sql.SQLException
     */
    JSONObject doPOST(JSONObject req) throws SQLException {
        int retryCount = 0;

        EntityBuilder builder = EntityBuilder.create();
        builder.setText(req.toString());
        builder.setContentType(ContentType.APPLICATION_JSON);

        HttpPost post = new HttpPost(url);
        post.setEntity(builder.build());

        if (log != null && log.isLoggable(Level.INFO)) {
            log.info("POST: " + url);
            log.info("REQUEST JSON: " + req);
        }

        while (retryCount < MAX_RETRIES) {
            try (CloseableHttpResponse httpResponse = httpClient.execute(post)) {
                InputStream responseStream = httpResponse.getEntity().getContent();
                String response = IOUtils.toString(responseStream);
                if (log != null && log.isLoggable(Level.INFO)) {
                    log.info("RESPONSE JSON: " + response);
                    PoolStats ps = CM.getTotalStats();
                    log.info("http-client-connections pool [avail=" + ps.getAvailable() + " leased=" + ps.getLeased() + " pending=" + ps.getPending() + "] ");
                }
                return new JSONObject(response);
            } catch (JSONException ex) {
                throw new SQLException("Invalid SDM return data: " + ex.getMessage(), ex);
            } catch (IOException ex) {
                String exMessage = ex.getMessage();
                if (exMessage.toLowerCase().contains("socket is closed") || exMessage.toLowerCase().contains("connection refused")) {
                    retryCount++;
                    log.warning("Retrying: " + retryCount + ", for" + url + ":  " + exMessage);
                    try{
                        Thread.sleep(THREAD_SLEEP_ON_RETRY);
                    } catch (InterruptedException ex1) {
                        log.info("Thread sleep in retry of doPost interrupted.");
                    }
                } else {
                    throw new SQLException("Communication error with SDM host: " + exMessage, ex);
                }
            } finally {
                //post.releaseConnection();    
                post.completed();
            }
        }

        return null;
    }

    private class PreemptiveAuthInterceptor implements HttpRequestInterceptor {

        @Override
        @SuppressWarnings("deprecation")
        public void process(final HttpRequest request, final HttpContext context) throws HttpException, IOException {
            request.addHeader(BasicScheme.authenticate(creds.getCredentials(AuthScope.ANY), "US-ASCII", false));
        }
    }
}