package com.juick.config;

import java.util.concurrent.TimeUnit;
 
import org.apache.http.HeaderElement;
import org.apache.http.HeaderElementIterator;
import org.apache.http.HttpResponse;
import org.apache.http.client.config.CookieSpecs;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.conn.ConnectionKeepAliveStrategy;
 
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.impl.conn.PoolingHttpClientConnectionManager;
import org.apache.http.message.BasicHeaderElementIterator;
import org.apache.http.protocol.HTTP;
import org.apache.http.protocol.HttpContext;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.scheduling.annotation.Scheduled;
 
/**
 * - Uses a connection pool to re-use connections and save overhead of creating connections.
 * - Has a custom connection keep-alive strategy (to apply a default keep-alive if one isn't specified)
 * - Starts an idle connection monitor to continuously clean up stale connections.
 */
@Configuration
public class HttpClientConfig {
 
    private static final Logger LOGGER = LoggerFactory.getLogger(HttpClientConfig.class);
 
    // Determines the timeout in milliseconds until a connection is established.
    private static final int CONNECT_TIMEOUT = 30000;
     
    // The timeout when requesting a connection from the connection manager.
    private static final int REQUEST_TIMEOUT = 30000;
     
    // The timeout for waiting for data
    private static final int SOCKET_TIMEOUT = 60000;
 
    private static final int MAX_TOTAL_CONNECTIONS = 50;
    private static final int DEFAULT_KEEP_ALIVE_TIME_MILLIS = 20 * 1000;
    private static final int CLOSE_IDLE_CONNECTION_WAIT_TIME_SECS = 30;
 
    @Bean
    public PoolingHttpClientConnectionManager poolingConnectionManager() {
        PoolingHttpClientConnectionManager poolingConnectionManager = new PoolingHttpClientConnectionManager();
        poolingConnectionManager.setMaxTotal(MAX_TOTAL_CONNECTIONS);
        return poolingConnectionManager;
    }
 
    @Bean
    public ConnectionKeepAliveStrategy connectionKeepAliveStrategy() {
        return new ConnectionKeepAliveStrategy() {
            @Override
            public long getKeepAliveDuration(HttpResponse response, HttpContext context) {
                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")) {
                        return Long.parseLong(value) * 1000;
                    }
                }
                return DEFAULT_KEEP_ALIVE_TIME_MILLIS;
            }
        };
    }
 
    @Bean
    public CloseableHttpClient httpClient() {
        RequestConfig requestConfig = RequestConfig.custom()
                .setCookieSpec(CookieSpecs.IGNORE_COOKIES)
                .setConnectionRequestTimeout(REQUEST_TIMEOUT)
                .setConnectTimeout(CONNECT_TIMEOUT)
                .setSocketTimeout(SOCKET_TIMEOUT).build();
 
        return HttpClients.custom()
                .setDefaultRequestConfig(requestConfig)
                .setConnectionManager(poolingConnectionManager())
                .setKeepAliveStrategy(connectionKeepAliveStrategy())
                .build();
    }
     
    @Bean
    public Runnable idleConnectionMonitor(final PoolingHttpClientConnectionManager connectionManager) {
        return new Runnable() {
            @Override
            @Scheduled(fixedDelay = 10000)
            public void run() {
                try {
                    if (connectionManager != null) {
                        LOGGER.trace("run IdleConnectionMonitor - Closing expired and idle connections...");
                        connectionManager.closeExpiredConnections();
                        connectionManager.closeIdleConnections(CLOSE_IDLE_CONNECTION_WAIT_TIME_SECS, TimeUnit.SECONDS);
                    } else {
                        LOGGER.trace("run IdleConnectionMonitor - Http Client Connection manager is not initialised");
                    }
                } catch (Exception e) {
                    LOGGER.error("run IdleConnectionMonitor - Exception occurred. msg={}, e={}", e.getMessage(), e);
                }
            }
        };
    }
}