/*
  neon - Embeddable HTTP Server based on jdk.httpserver
  Copyright (C) 2024  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.neon;

import com.sun.net.httpserver.Headers;
import com.sun.net.httpserver.HttpExchange;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.file.Files;
import java.text.SimpleDateFormat;
import java.util.Date;

/**
 * Helfer zur Beantwortung von HTTP-Anfragen
 * 
 * @author Ulrich Hilger
 * @version 1, 03.06.2021
 */
public class HttpResponder {
  
  /* Headernamen */
  public static final String ACCEPT_RANGES_HEADER = "Accept-Ranges";
  public static final String CONTENT_LENGTH = "Content-Length";
  public static final String CONTENT_TYPE = "Content-Type";
  public static final String LAST_MODIFIED_DATE_HEADER = "Last-Modified";

  /* Statuscodes */
  public static final int SC_OK = 200;
  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;
  public static final int SC_INTERNAL_SERVER_ERROR = 500;

  /* String Konstanten */
  public static final String STR_BYTES = "bytes";
  public static final String STR_NOT_FOUND = " not found.";
  public static final String LM_PATTERN = "EEE, dd MMM yyyy HH:mm:ss zzz";
  
  /**
   * Den Inhalt einer Datei ausliefern
   *
   * @param e das Objekt mit Methoden zur Untersuchung der Anfrage sowie zum
   * Anfertigen und Senden der Antwort
   * @param file die Datei, deren Inhalt ausgeliefert werden soll
   * @throws IOException falls etwas schief geht entsteht dieser Fehler
   */
  public void serveFile(HttpExchange e, File file) throws IOException {
    if (file.exists()) {
      setHeaders(e, file);
      e.getResponseHeaders().set(CONTENT_LENGTH, Long.toString(file.length()));
      e.sendResponseHeaders(SC_OK, file.length());
      if(HttpHelper.HTTP_GET.equalsIgnoreCase(e.getRequestMethod())) {
        InputStream in = new FileInputStream(file);
        OutputStream os = e.getResponseBody();        
        write(in, os);
        finish(in, os);
      }
    } else {
      sendNotFound(e, file.getName());
    }
  }

  public void write(InputStream in, OutputStream out) throws IOException {
    byte[] b = new byte[4096];
    int bytesRead = in.read(b);
    while (bytesRead > -1) {
      out.write(b, 0, bytesRead);
      bytesRead = in.read(b);
    }
  }
  
  public void finish(InputStream in, OutputStream out) throws IOException {
    in.close();
    finish(out);
  }

  public void finish(OutputStream out) throws IOException {
    out.flush();
    out.close();
  }
  
  /**
   * Die Header erzeugen, die unabh&auml;ngig davon, ob der ganze 
   * Inhalt oder nur Teile davon ausgeliefert werden sollen, in der 
   * Antwort stehen sollen 
   * 
   * @param e das Objekt mit Methoden zur Untersuchung der Anfrage sowie zum
   * Anfertigen und Senden der Antwort
   * @param file  die Datei, f&uuml;r die die Header gelten
   * @throws IOException falls etwas schief geht entsteht dieser Fehler
   */
  public void setHeaders(HttpExchange e, File file) throws IOException {
    Headers resHeaders = e.getResponseHeaders();
    resHeaders.add(ACCEPT_RANGES_HEADER, STR_BYTES);
    String mimeType = Files.probeContentType(file.toPath());
    if (mimeType != null) {
      resHeaders.add(CONTENT_TYPE, mimeType);
    }
    SimpleDateFormat sdf = new SimpleDateFormat(LM_PATTERN);
    Date date = new Date(file.lastModified());
    resHeaders.add(LAST_MODIFIED_DATE_HEADER, sdf.format(date));
  }

  /**
   * Eine nicht gefunden Antwort senden
   *
   * @param e das Objekt mit Methoden zur Untersuchung der Anfrage sowie zum
   * Anfertigen und Senden der Antwort
   * @param fname Name der Datei, die nicht gefunden wurde
   * @throws IOException falls etwas schief geht entsteht dieser Fehler
   */
  public void sendNotFound(HttpExchange e, String fname) throws IOException {
    antwortSenden(e, SC_NOT_FOUND, fname + STR_NOT_FOUND);
  }  

  public void antwortSenden(HttpExchange exchange, int code, String antwort) throws IOException {
    byte[] bytes = antwort.getBytes();
    exchange.sendResponseHeaders(code, bytes.length);
    OutputStream os = exchange.getResponseBody();
    os.write(bytes);
    finish(os);
  }


  
}