/*
    * This file is part of dependency-check-core.
    *
    * 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.
   *
   * Copyright (c) 2012 Jeremy Long. All Rights Reserved.
   */
  package org.owasp.dependencycheck.utils;
  
  import java.io.BufferedOutputStream;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.io.File;
  import java.io.FileOutputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.net.HttpURLConnection;
  import java.net.URISyntaxException;
  import java.net.URL;
  import java.security.InvalidAlgorithmParameterException;
  import java.util.zip.GZIPInputStream;
  import java.util.zip.InflaterInputStream;
  import static java.lang.String.format;
  
  /**
   * A utility to download files from the Internet.
   *
   * @author Jeremy Long
   */
  public final class Downloader {
  
      /**
       * The logger.
       */
      private static final Logger LOGGER = LoggerFactory.getLogger(Downloader.class);
      /**
       * The maximum number of redirects that will be followed when attempting to
       * download a file.
       */
      private static final int MAX_REDIRECT_ATTEMPTS = 5;
  
      /**
       * The default HTTP request method for query timestamp
       */
      private static final String HEAD = "HEAD";
  
      /**
       * The HTTP request method which can be used by query timestamp
       */
      private static final String GET = "GET";
  
      /**
       * Private constructor for utility class.
       */
      private Downloader() {
      }
  
      /**
       * Retrieves a file from a given URL and saves it to the outputPath.
       *
       * @param url the URL of the file to download
       * @param outputPath the path to the save the file to
       * @throws DownloadFailedException is thrown if there is an error
       * downloading the file
       */
      public static void fetchFile(URL url, File outputPath) throws DownloadFailedException {
          fetchFile(url, outputPath, true);
      }
  
      /**
       * Retrieves a file from a given URL and saves it to the outputPath.
       *
       * @param url the URL of the file to download
       * @param outputPath the path to the save the file to
       * @param useProxy whether to use the configured proxy when downloading
       * files
       * @throws DownloadFailedException is thrown if there is an error
       * downloading the file
       */
      public static void fetchFile(URL url, File outputPath, boolean useProxy) throws DownloadFailedException {
          if ("file".equalsIgnoreCase(url.getProtocol())) {
              File file;
              try {
                  file = new File(url.toURI());
              } catch (URISyntaxException ex) {
                  final String msg = format("Download failed, unable to locate '%s'", url.toString());
                  throw new DownloadFailedException(msg);
              }
             if (file.exists()) {
                 try {
                     org.apache.commons.io.FileUtils.copyFile(file, outputPath);
                 } catch (IOException ex) {
                     final String msg = format("Download failed, unable to copy '%s' to '%s'", url.toString(), outputPath.getAbsolutePath());
                     throw new DownloadFailedException(msg, ex);
                 }
             } else {
                 final String msg = format("Download failed, file ('%s') does not exist", url.toString());
                 throw new DownloadFailedException(msg);
             }
         } else {
             HttpURLConnection conn = null;
             try {
                 LOGGER.debug("Attempting download of {}", url.toString());
                 conn = URLConnectionFactory.createHttpURLConnection(url, useProxy);
                 conn.setRequestProperty("Accept-Encoding", "gzip, deflate");
                 conn.connect();
                 int status = conn.getResponseCode();
                 int redirectCount = 0;
                 while ((status == HttpURLConnection.HTTP_MOVED_TEMP
                         || status == HttpURLConnection.HTTP_MOVED_PERM
                         || status == HttpURLConnection.HTTP_SEE_OTHER)
                         && MAX_REDIRECT_ATTEMPTS > redirectCount++) {
                     final String location = conn.getHeaderField("Location");
                     try {
                         conn.disconnect();
                     } finally {
                         conn = null;
                     }
                     LOGGER.debug("Download is being redirected from {} to {}", url.toString(), location);
                     conn = URLConnectionFactory.createHttpURLConnection(new URL(location), useProxy);
                     conn.setRequestProperty("Accept-Encoding", "gzip, deflate");
                     conn.connect();
                     status = conn.getResponseCode();
                 }
                 if (status != 200) {
                     try {
                         conn.disconnect();
                     } finally {
                         conn = null;
                     }
                     final String msg = format("Error downloading file %s; received response code %s.", url.toString(), status);
                     throw new DownloadFailedException(msg);
 
                 }
             } catch (IOException ex) {
                 try {
                     if (conn != null) {
                         conn.disconnect();
                     }
                 } finally {
                     conn = null;
                 }
                 if ("Connection reset".equalsIgnoreCase(ex.getMessage())) {
                     final String msg = format("TLS Connection Reset%nPlease see "
                             + "http://jeremylong.github.io/DependencyCheck/general/tlsfailures.html "
                             + "for more information regarding how to resolve the issue.");
                     LOGGER.error(msg);
                     throw new DownloadFailedException(msg, ex);
                 }
                 final String msg = format("Error downloading file %s; unable to connect.", url.toString());
                 throw new DownloadFailedException(msg, ex);
             }
 
             final String encoding = conn.getContentEncoding();
             BufferedOutputStream writer = null;
             InputStream reader = null;
             try {
                 if (encoding != null && "gzip".equalsIgnoreCase(encoding)) {
                     reader = new GZIPInputStream(conn.getInputStream());
                 } else if (encoding != null && "deflate".equalsIgnoreCase(encoding)) {
                     reader = new InflaterInputStream(conn.getInputStream());
                 } else {
                     reader = conn.getInputStream();
                 }
 
                 writer = new BufferedOutputStream(new FileOutputStream(outputPath));
                 final byte[] buffer = new byte[4096];
                 int bytesRead;
                 while ((bytesRead = reader.read(buffer)) > 0) {
                     writer.write(buffer, 0, bytesRead);
                 }
                 LOGGER.debug("Download of {} complete", url.toString());
             } catch (IOException ex) {
                 checkForCommonExceptionTypes(ex);
                 final String msg = format("Error saving '%s' to file '%s'%nConnection Timeout: %d%nEncoding: %s%n",
                         url.toString(), outputPath.getAbsolutePath(), conn.getConnectTimeout(), encoding);
                 throw new DownloadFailedException(msg, ex);
             } catch (Exception ex) {
                 final String msg = format("Unexpected exception saving '%s' to file '%s'%nConnection Timeout: %d%nEncoding: %s%n",
                         url.toString(), outputPath.getAbsolutePath(), conn.getConnectTimeout(), encoding);
                 throw new DownloadFailedException(msg, ex);
             } finally {
                 if (writer != null) {
                     try {
                         writer.close();
                     } catch (IOException ex) {
                         LOGGER.trace("Error closing the writer in Downloader.", ex);
                     }
                 }
                 if (reader != null) {
                     try {
                         reader.close();
                     } catch (IOException ex) {
                         LOGGER.trace("Error closing the reader in Downloader.", ex);
                     }
                 }
                 try {
                     conn.disconnect();
                 } finally {
                     conn = null;
                 }
             }
         }
     }
 
     /**
      * Makes an HTTP Head request to retrieve the last modified date of the
      * given URL. If the file:// protocol is specified, then the lastTimestamp
      * of the file is returned.
      *
      * @param url the URL to retrieve the timestamp from
      * @return an epoch timestamp
      * @throws DownloadFailedException is thrown if an exception occurs making
      * the HTTP request
      */
     public static long getLastModified(URL url) throws DownloadFailedException {
         return getLastModified(url, false);
     }
 
     /**
      * Makes an HTTP Head request to retrieve the last modified date of the
      * given URL. If the file:// protocol is specified, then the lastTimestamp
      * of the file is returned.
      *
      * @param url the URL to retrieve the timestamp from
      * @param isRetry indicates if this is a retry - to prevent endless loop and
      * stack overflow
      * @return an epoch timestamp
      * @throws DownloadFailedException is thrown if an exception occurs making
      * the HTTP request
      */
     private static long getLastModified(URL url, boolean isRetry) throws DownloadFailedException {
         long timestamp = 0;
         //TODO add the FTP protocol?
         if ("file".equalsIgnoreCase(url.getProtocol())) {
             File lastModifiedFile;
             try {
                 lastModifiedFile = new File(url.toURI());
             } catch (URISyntaxException ex) {
                 final String msg = format("Unable to locate '%s'", url.toString());
                 throw new DownloadFailedException(msg, ex);
             }
             timestamp = lastModifiedFile.lastModified();
         } else {
             final String httpMethod = determineHttpMethod();
             HttpURLConnection conn = null;
             try {
                 conn = URLConnectionFactory.createHttpURLConnection(url);
                 conn.setRequestMethod(httpMethod);
                 conn.connect();
                 final int t = conn.getResponseCode();
                 if (t >= 200 && t < 300) {
                     timestamp = conn.getLastModified();
                 } else {
                     throw new DownloadFailedException(format("%s request returned a non-200 status code", httpMethod));
                 }
             } catch (URLConnectionFailureException ex) {
                 throw new DownloadFailedException(format("Error creating URL Connection for HTTP %s request.", httpMethod), ex);
             } catch (IOException ex) {
                 checkForCommonExceptionTypes(ex);
                 LOGGER.error("IO Exception: " + ex.getMessage());
                 LOGGER.debug("Exception details", ex);
                 if (ex.getCause() != null) {
                     LOGGER.debug("IO Exception cause: " + ex.getCause().getMessage(), ex.getCause());
                 }
                 try {
                     //retry
                     if (!isRetry && Settings.getBoolean(Settings.KEYS.DOWNLOADER_QUICK_QUERY_TIMESTAMP)) {
                         Settings.setBoolean(Settings.KEYS.DOWNLOADER_QUICK_QUERY_TIMESTAMP, false);
                         return getLastModified(url, true);
                     }
                 } catch (InvalidSettingException ex1) {
                     LOGGER.debug("invalid setting?", ex1);
                 }
                 throw new DownloadFailedException(format("Error making HTTP %s request.", httpMethod), ex);
             } finally {
                 if (conn != null) {
                     try {
                         conn.disconnect();
                     } finally {
                         conn = null;
                     }
                 }
             }
         }
         return timestamp;
     }
 
     /**
      * Analyzes the IOException, logs the appropriate information for debugging
      * purposes, and then throws a DownloadFailedException that wraps the IO
      * Exception for common IO Exceptions. This is to provide additional details
      * to assist in resolution of the exception.
      *
      * @param ex the original exception
      * @throws DownloadFailedException a wrapper exception that contains the
      * original exception as the cause
      */
     protected static synchronized void checkForCommonExceptionTypes(IOException ex) throws DownloadFailedException {
         Throwable cause = ex;
         while (cause != null) {
             if (cause instanceof java.net.UnknownHostException) {
                 final String msg = format("Unable to resolve domain '%s'", cause.getMessage());
                 LOGGER.error(msg);
                 throw new DownloadFailedException(msg);
             }
             if (cause instanceof InvalidAlgorithmParameterException) {
                 final String keystore = System.getProperty("javax.net.ssl.keyStore");
                 final String version = System.getProperty("java.version");
                 final String vendor = System.getProperty("java.vendor");
                 LOGGER.info("Error making HTTPS request - InvalidAlgorithmParameterException");
                 LOGGER.info("There appears to be an issue with the installation of Java and the cacerts."
                         + "See closed issue #177 here: https://github.com/jeremylong/DependencyCheck/issues/177");
                 LOGGER.info("Java Info:\njavax.net.ssl.keyStore='{}'\njava.version='{}'\njava.vendor='{}'",
                         keystore, version, vendor);
                 throw new DownloadFailedException("Error making HTTPS request. Please see the log for more details.");
             }
             cause = cause.getCause();
         }
     }
 
     /**
      * Returns the HEAD or GET HTTP method. HEAD is the default.
      *
      * @return the HTTP method to use
      */
     private static String determineHttpMethod() {
         return isQuickQuery() ? HEAD : GET;
     }
 
     /**
      * Determines if the HTTP method GET or HEAD should be used to check the
      * timestamp on external resources.
      *
      * @return true if configured to use HEAD requests
      */
     private static boolean isQuickQuery() {
         boolean quickQuery;
 
         try {
             quickQuery = Settings.getBoolean(Settings.KEYS.DOWNLOADER_QUICK_QUERY_TIMESTAMP, true);
         } catch (InvalidSettingException e) {
             if (LOGGER.isTraceEnabled()) {
                 LOGGER.trace("Invalid settings : {}", e.getMessage(), e);
             }
             quickQuery = true;
         }
         return quickQuery;
     }
 }