/*
    * This file is part of ***  M y C o R e  ***
    * See http://www.mycore.de/ for details.
    *
    * MyCoRe is free software: you can redistribute it and/or modify
    * it under the terms of the GNU General Public License as published by
    * the Free Software Foundation, either version 3 of the License, or
    * (at your option) any later version.
    *
   * MyCoRe is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with MyCoRe.  If not, see <http://www.gnu.org/licenses/>.
   */
  
  package org.mycore.pi.purl;
  
  import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.io.OutputStreamWriter;
  import java.net.HttpURLConnection;
  import java.net.URL;
  import java.net.URLEncoder;
  import java.nio.charset.StandardCharsets;
  import java.util.List;
  
  import javax.xml.parsers.DocumentBuilder;
  import javax.xml.parsers.DocumentBuilderFactory;
  
  import org.apache.logging.log4j.LogManager;
  import org.apache.logging.log4j.Logger;
  import org.w3c.dom.Document;
  import org.w3c.dom.Element;
  
  /**
   * PURL Manager to register Persistent URLs on a PURL server
   * <p>
   * for further documentation see PURLZ Wiki:
   * https://code.google.com/archive/p/persistenturls/wikis
   * <p>
   * Hint:
   * -----
   * Please check in your code that you do not register / override regular PURLs in test / development
   * by checking:
   * if (resolvingURL.contains("localhost")) {
   * purl = "/test" + purl;
   * }
   *
   * @author Robert Stephan
   */
  public class MCRPURLManager {
      private static final Logger LOGGER = LogManager.getLogger();
  
      private static final String ADMIN_PATH = "/admin";
  
      private static final String PURL_PATH = ADMIN_PATH + "/purl";
  
      private static final String COOKIE_HEADER_PARAM = "Cookie";
  
      private String purlServerBaseURL;
  
      private String cookie = null;
  
      /**
       * sets the session cookie, if the login was successful
       *
       * @param purlServerURL - the base URL of the PURL server
       * @param user          - the PURL server user
       * @param password      - the user's password
       */
      public void login(String purlServerURL, String user, String password) {
          HttpURLConnection conn = null;
          try {
              purlServerBaseURL = purlServerURL;
              // Get Cookie
              URL url = new URL(purlServerBaseURL + ADMIN_PATH + "/login/login.bsh?referrer=/docs/index.html");
              conn = (HttpURLConnection) url.openConnection();
              conn.connect();
  
              conn.getHeaderFields()
                  .getOrDefault("Set-Cookie", List.of())
                  .forEach(cookie -> {
                      this.cookie = cookie;
                      LOGGER.debug("Cookie: " + cookie);
                  });
              conn.disconnect();
  
              // Login
              String data = "id=" + URLEncoder.encode(user, StandardCharsets.UTF_8);
              data += "&passwd=" + URLEncoder.encode(password, StandardCharsets.UTF_8);
  
              url = new URL(purlServerBaseURL + ADMIN_PATH + "/login/login-submit.bsh");
              conn = (HttpURLConnection) url.openConnection();
              conn.setRequestMethod("POST");
              conn.setRequestProperty(COOKIE_HEADER_PARAM, cookie);
 
             conn.setDoOutput(true);
             try (OutputStreamWriter wr = new OutputStreamWriter(conn.getOutputStream(), StandardCharsets.UTF_8)) {
                 wr.write(data);
                 wr.flush();
                 if (conn.getResponseCode() == 200) {
                     LOGGER.info(conn.getRequestMethod() + " " + conn.getURL() + " -> " + conn.getResponseCode());
                 } else {
                     LOGGER.error(conn.getRequestMethod() + " " + conn.getURL() + " -> " + conn.getResponseCode());
                 }
 
                 // Get the response
                 try (BufferedReader rd = new BufferedReader(new InputStreamReader(conn.getInputStream(),
                     StandardCharsets.UTF_8))) {
 
                     String line;
                     while ((line = rd.readLine()) != null) {
                         if ("PURL User Login Failure".equals(line.trim())) {
                             cookie = null;
                             break;
                         }
 
                     }
                 }
             }
             conn.disconnect();
 
         } catch (IOException e) {
             if (!e.getMessage().contains(
                 "Server returned HTTP response code: 403 for URL: ")) {
                 LOGGER.error(e);
             }
         } finally {
             if (conn != null) {
                 conn.disconnect();
             }
         }
     }
 
     /**
      * logout from PURL server
      */
     public void logout() {
         HttpURLConnection conn = null;
         int responseCode = -1;
         try {
             URL url = new URL(purlServerBaseURL + ADMIN_PATH + "/logout?referrer=/docs/index.html");
             conn = (HttpURLConnection) url.openConnection();
             conn.setRequestMethod("POST");
             conn.setRequestProperty(COOKIE_HEADER_PARAM, cookie);
 
             conn.setDoOutput(true);
             try (OutputStreamWriter wr = new OutputStreamWriter(conn.getOutputStream(), StandardCharsets.UTF_8)) {
                 wr.flush();
             }
             responseCode = conn.getResponseCode();
             LOGGER.debug(conn.getRequestMethod() + " " + conn.getURL() + " -> " + responseCode);
         } catch (IOException e) {
             if (!e.getMessage().contains(
                 "Server returned HTTP response code: 403 for URL: ")) {
                 LOGGER.error(conn.getRequestMethod() + " " + conn.getURL() + " -> " + responseCode, e);
             }
         } finally {
             if (conn != null) {
                 conn.disconnect();
             }
         }
     }
 
     // returns the response code
 
     /**
      * register a new PURL
      *
      * @param purl        - the PURL
      * @param target      the target URL
      * @param type        - the PURL type
      * @param maintainers - the maintainers
      * @return the HTTP Status Code of the request
      */
     public int registerNewPURL(String purl, String target, String type, String maintainers) {
         int response = 0;
         HttpURLConnection conn = null;
         try {
             // opener.open("http://localhost:8080/admin/purl/net/test2",
             // urllib.urlencode(dict(type="410", maintainers="admin"))).read().close() #
             // Create a 410 purl
 
             URL url = new URL(purlServerBaseURL + PURL_PATH + purl);
             LOGGER.debug(url.toString());
 
             String data = "target=" + URLEncoder.encode(target, StandardCharsets.UTF_8);
             data += "&maintainers=" + maintainers;
             data += "&type=" + type;
 
             LOGGER.debug(data);
 
             // Send data
 
             conn = (HttpURLConnection) url.openConnection();
             conn.setRequestProperty(COOKIE_HEADER_PARAM, cookie);
             conn.setRequestMethod("POST");
 
             conn.setDoOutput(true);
 
             try (OutputStreamWriter wr = new OutputStreamWriter(conn.getOutputStream(), StandardCharsets.UTF_8)) {
                 wr.write(data);
                 wr.flush();
             }
             response = conn.getResponseCode();
 
             if (response != 200 && conn.getErrorStream() != null && LOGGER.isErrorEnabled()) {
                 try (BufferedReader rd = new BufferedReader(new InputStreamReader(conn.getErrorStream(),
                     StandardCharsets.UTF_8))) {
                     String line;
                     LOGGER.error(conn.getRequestMethod() + " " + conn.getURL() + " -> " + conn.getResponseCode());
                     while ((line = rd.readLine()) != null) {
                         LOGGER.error(line);
                     }
                 }
             }
         } catch (Exception e) {
             LOGGER.error(e);
         } finally {
             if (conn != null) {
                 conn.disconnect();
             }
         }
         return response;
     }
 
     /**
      * updates an existing PURL
      *
      * @param purl        - the PURL (relative URL)
      * @param target      - the target URL
      * @param type        - the PURL type
      * @param maintainers list of maintainers (PURL server users or groups)
      * @return the HTTP Status Code of the request
      */
     public int updateExistingPURL(String purl, String target, String type, String maintainers) {
         int response = 0;
         HttpURLConnection conn = null;
         try {
             // opener.open("http://localhost:8080/admin/purl/net/test2",
             // urllib.urlencode(dict(type="410", maintainers="admin"))).read().close() #
             // Create a 410 purl
 
             String strURL = purlServerBaseURL + PURL_PATH + purl;
             strURL += "?target=" + URLEncoder.encode(target, StandardCharsets.UTF_8) + "&maintainers=" + maintainers
                 + "&type=" + type;
 
             URL url = new URL(strURL);
             LOGGER.debug(url.toString());
 
             conn = (HttpURLConnection) url.openConnection();
             conn.setRequestProperty(COOKIE_HEADER_PARAM, cookie);
             conn.setRequestMethod("PUT");
             response = conn.getResponseCode();
 
             if (response != 200 && conn.getErrorStream() != null && LOGGER.isErrorEnabled()) {
                 try (BufferedReader rd = new BufferedReader(new InputStreamReader(conn.getErrorStream(),
                     StandardCharsets.UTF_8))) {
                     String line = null;
                     LOGGER.error(conn.getRequestMethod() + " " + conn.getURL() + " -> " + conn.getResponseCode());
                     while ((line = rd.readLine()) != null) {
                         LOGGER.error(line);
                     }
                 }
             }
         } catch (Exception e) {
             LOGGER.error(e);
         } finally {
             if (conn != null) {
                 conn.disconnect();
             }
         }
         return response;
     }
 
     /**
      * deletes an existing PURL
      *
      * @param purl
      * @return the HTTP Status Code of the request
      */
     public int deletePURL(String purl) {
         int response = 0;
         HttpURLConnection conn = null;
         try {
             URL url = new URL(purlServerBaseURL + PURL_PATH + purl);
             LOGGER.debug(url.toString());
 
             conn = (HttpURLConnection) url.openConnection();
             conn.setRequestProperty(COOKIE_HEADER_PARAM, cookie);
             conn.setRequestMethod("DELETE");
             response = conn.getResponseCode();
 
             if (response != 200 || conn.getErrorStream() != null && LOGGER.isErrorEnabled()) {
                 try (BufferedReader rd = new BufferedReader(new InputStreamReader(conn.getErrorStream(),
                     StandardCharsets.UTF_8))) {
                     String line = null;
                     LOGGER.error(conn.getRequestMethod() + " " + conn.getURL() + " -> " + conn.getResponseCode());
                     while ((line = rd.readLine()) != null) {
                         LOGGER.error(line);
                     }
                 }
             }
         } catch (Exception e) {
             LOGGER.error(e);
         } finally {
             if (conn != null) {
                 conn.disconnect();
             }
         }
         return response;
     }
 
     /**
      * check if a purl has the given target url
      *
      * @param purl      - the purl
      * @param targetURL - the target URL
      * @return true, if the target URL is registered at the given PURL
      */
     public boolean isPURLTargetURLUnchanged(String purl, String targetURL) {
         HttpURLConnection conn = null;
         try {
             URL url = new URL(purlServerBaseURL + PURL_PATH + purl);
             conn = (HttpURLConnection) url.openConnection();
             int response = conn.getResponseCode();
 
             if (response == 200) {
                 DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
                 DocumentBuilder db = dbf.newDocumentBuilder();
                 Document doc = db.parse(conn.getInputStream());
                 /*
                  * <purl status="1"> <id>/test/rosdok/ppn750527188</id> <type>302</type>
                  * <maintainers><uid>rosdok</uid><uid>test</uid></maintainers>
                  * <target><url>http://localhost:8080/rosdok/resolve/id/
                  * rosdok_document_0000000259</url></target> </purl>
                  */
                 Element eTarget = (Element) doc.getDocumentElement().getElementsByTagName("target").item(0);
                 Element eTargetUrl = (Element) eTarget.getElementsByTagName("url").item(0);
                 return targetURL.equals(eTargetUrl.getTextContent().trim());
             }
         } catch (Exception e) {
             LOGGER.error(e);
         } finally {
             if (conn != null) {
                 conn.disconnect();
             }
         }
         return false;
     }
 
     /**
      * return the PURL metadata
      *
      * @param purl      - the purl
      * @return an XML document containing the metadata of the PURL
      *        or null if the PURL does not exist
      */
     public Document retrievePURLMetadata(String purl, String targetURL) {
         HttpURLConnection conn = null;
         try {
             URL url = new URL(purlServerBaseURL + PURL_PATH + purl);
             conn = (HttpURLConnection) url.openConnection();
             int response = conn.getResponseCode();
 
             if (response == 200) {
 
                 DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
                 DocumentBuilder db = dbf.newDocumentBuilder();
 
                 return db.parse(conn.getInputStream());
                 /* <purl status="1">
                  *   <id>/test/rosdok/ppn750527188</id> 
                  *   <type>302</type>
                  *   <maintainers>
                  *     <uid>rosdok</uid>
                  *     <uid>test</uid>
                  *   </maintainers>
                  *   <target>
                  *     <url>http://localhost:8080/rosdok/resolve/id/rosdok_document_0000000259</url>
                  *   </target> 
                  * </purl>
                  */
             }
         } catch (Exception e) {
             LOGGER.error(e);
         } finally {
             if (conn != null) {
                 conn.disconnect();
             }
         }
         return null;
     }
 
     /**
      * check if a PURL exists
      *
      * @param purl      - the purl
      * @return true, if the given PURL is known
      */
     public boolean existsPURL(String purl) {
         HttpURLConnection conn = null;
         try {
             URL url = new URL(purlServerBaseURL + PURL_PATH + purl);
             conn = (HttpURLConnection) url.openConnection();
             int response = conn.getResponseCode();
             return response == 200;
         } catch (Exception e) {
             LOGGER.error(e);
         } finally {
             if (conn != null) {
                 conn.disconnect();
             }
         }
         return false;
     }
 }