/*
  http-base - Extensions to jdk.httpserver
  Copyright (C) 2021  Ulrich Hilger

  This program is free software: you can redistribute it and/or modify
  it under the terms of the GNU Affero General Public License as
  published by the Free Software Foundation, either version 3 of the
  License, or (at your option) any later version.

  This program 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 Affero General Public License for more details.

  You should have received a copy of the GNU Affero General Public License
  along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */
package de.uhilger.httpserver.base.handler;

import de.uhilger.httpserver.base.HttpResponder;
import com.sun.net.httpserver.Headers;
import com.sun.net.httpserver.HttpExchange;
import com.sun.net.httpserver.HttpHandler;
import de.uhilger.httpserver.base.HttpHelper;
import de.uhilger.httpserver.base.actor.FileActor;
import java.io.File;
import java.io.IOException;

/**
 * Die Klasse FileHandler dient zur Auslieferung von Dateiinhalten &uuml;ber
 * HTTP.
 *
 * F&uuml;r das Streaming &uuml;ber HTTP wird die Auslieferung von Teilinhalten
 * mit dem Accept-Ranges-Header angeboten und via Range-Header unterst&uuml;tzt.
 * (vgl. https://developer.mozilla.org/en-US/docs/Web/HTTP/Range_requests)
 *
 * @author Ulrich Hilger
 * @version 1, 03.06.2021, (seit 25. M&auml;rz 2021)
 */
public class FileHandler implements HttpHandler {

  /* Headernamen */
  public static final String RANGE_HEADER = "Range";
  public static final String CONTENT_RANGE_HEADER = "Content-Range";
  public static final String CONTENT_TYPE = "Content-Type";
  public static final String CONTENT_LENGTH = "Content-Length";

  /* Statuscodes */
  public static final int SC_OK = 200;
  public static final int SC_PARTIAL_CONTENT = 206;
  public static final int SC_FORBIDDEN = 403;
  public static final int SC_NOT_FOUND = 404;
  public static final int SC_METHOD_NOT_ALLOWED = 405;
  public static final int SC_UNPROCESSABLE_ENTITY = 422;

  /* String Konstanten */
  public static final String STR_SLASH = "/";
  public static final String STR_BLANK = " ";
  public static final String STR_DASH = "-";
  public static final String STR_COMMA = ",";
  public static final String STR_DOT = ".";
  public static final String RANGE_PATTERN = "[^\\d-,]";
  public static final String WELCOME_FILE = "index.html";

  /* Ablageort fuer Webinhalte */
  public static final String ATTR_FILE_BASE = "fileBase";
  
  /* moegliche Dateinamen, wenn kein Name angegeben wurde */
  public static final String ATTR_WELCOME_FILES = "welcomeFiles";

  /**
   * Die Datei ermitteln, die sich aus dem angefragten URL ergibt, pr&uuml;fen,
   * ob die Datei existiert und den Inhalt der Datei abh&auml;ngig davon, ob ein
   * Range-Header vorhanden ist, ganz oder teilweise ausliefern.
   *
   * @param e das Objekt mit Methoden zur Untersuchung der Anfrage sowie zum
   * Anfertigen und Senden der Antwort
   * @throws IOException falls etwas schief geht entsteht dieser Fehler
   */
  @Override
  public void handle(HttpExchange e) throws IOException {
    String fName = new HttpHelper().getFileName(e);
    if (fName.startsWith(STR_DOT)) {
      HttpResponder fs = new HttpResponder();
      fs.sendNotFound(e, fName);
    } else {
      File fileToDeliver = new File(e.getHttpContext().getAttributes().get(ATTR_FILE_BASE).toString(), fName);
      Headers headers = e.getRequestHeaders();
      if (headers.containsKey(RANGE_HEADER)) {
        new FileActor().serveFileParts(e, fileToDeliver);
      } else {
        if (fName.length() < 1 || fName.endsWith(STR_SLASH)) {
          HttpHelper helper = new HttpHelper();
          File welcomeFile = helper.tryWelcomeFiles(e, fName);
          if(welcomeFile != null) {
            fileToDeliver = welcomeFile;
          }
        }
        new HttpResponder().serveFile(e, fileToDeliver);
      }
    }
  }
}