/*
  Mediazentrale - Personal Media Center
  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.mediaz.api;

import com.google.gson.Gson;
import com.sun.net.httpserver.HttpExchange;
import com.sun.net.httpserver.HttpHandler;
import de.uhilger.mediaz.App;
import de.uhilger.mediaz.Server;
import static de.uhilger.mediaz.Server.RB_SLASH;
import de.uhilger.mediaz.store.FileStorage;
import de.uhilger.mediaz.entity.Entity;
import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * HttpHandler fuer die Ablage von Entitaeten der Mediazentrale
 * 
 * @author Ulrich Hilger
 * @version 1, 5.4.2021
 */
public class StorageHandler implements HttpHandler  {
  
  private static final Logger logger = Logger.getLogger(StorageHandler.class.getName());

  
  /*
    Das REST-Muster sieht je Entitaet fuenf Faelle vor (Beispiel Ablageort):
    
    1. HTTP GET Ablageort/[Name]: Liefere den Ablageort als JSON
    2. HTTP GET Ablageort/: Liefere einer Liste von Ablageorten als JSON
    3. HTTP PUT: schreibe einen neuen Ablageort auf die Platte
    4. HTTP POST: schreibe Aenderungen auf die Platte
    5. HTTP DELETE: loesche den Ablageort
  
    Beispiele:
  
    HTTP GET an /mz/api/store/Ablageort/
    liefert eine Liste der Namen vorhandener Ablageorte
  
    HTTP GET an /mz/api/store/Ablageort/Katalog
    liest den Ablageort namens "Katalog"
  
    HTTP POST an /mz/api/store/Ablageort
    schreibt den neuen Ablageort im Body der Anfrage (Neu)
  
    HTTP PUT an /mz/api/store/Ablageort
    sucht den Ablageort mit dem Namen laut Body der Anfrage 
    und schreibt den Inhalt aus der Anfrage in die Datei (Aenderung)
  
    HTTP DELETE an /mz/api/store/Ablageort/Katalog
    löscht den Ablageort namens "Katalog"
  
  */
  
  /** Name der HTTP Methode GET */
  public static final String HTTP_GET = "GET";
  
  /** Name der HTTP Methode PUT */
  public static final String HTTP_PUT = "PUT";
  
  /** Name der HTTP Methode POST */
  public static final String HTTP_POST = "POST";
  
  /** Name der HTTP Methode DELETE */
  public static final String HTTP_DELETE = "DELETE";

  @Override
  public void handle(HttpExchange e) throws IOException {
    String method = e.getRequestMethod();
    String response = "";
    int code = 200;
    switch(method) {
      case HTTP_GET:
        String json = lesen(e);
        if(json != null) {
          response = json;
        } else {
          response = "nicht gefunden";
          code = 404;
        }
        break;
        
      case HTTP_PUT:
        response = aendern(e);
        break;
        
      case HTTP_POST:
        response = neu(e);
        break;
        
      case HTTP_DELETE:
        boolean geloescht = loeschen(e);
        if(geloescht) {
          response = "geloescht";
        } else {
          response = "nicht geloescht";
        }
        break;
    }
    logger.info(response);
    e.sendResponseHeaders(code, response.length());
    OutputStream os = e.getResponseBody();
    os.write(response.getBytes());
    os.close();        
  }
  
  private String neu(HttpExchange e) throws IOException {
    String path = e.getRequestURI().toString();
    String[] elems = path.split(App.getRs(Server.RB_SLASH));
    String type = elems[elems.length - 1];
    String body = bodyLesen(e);
    String filename = ""; 
    FileStorage fs = new FileStorage(App.getInitParameter(App.getRs(App.RB_AP_CONF)));
    Gson gson = new Gson();
    logger.log(Level.INFO, "type: {0}", type);
    Object o = gson.fromJson(body, fs.typeFromName(type).getType());
    if(o instanceof Entity) {
      Object antwortObjekt = fs.write((Entity) o);
      if(antwortObjekt instanceof File) {
        File file = (File) antwortObjekt;
        logger.log(Level.INFO, "Datei {0} geschrieben.", file.getAbsolutePath());
        filename = file.getName();
      }
    }
    return type + FileHandler.STR_BLANK + filename;
  }
  
  private String aendern(HttpExchange e) throws IOException {
    return neu(e); // einstweilen wird einfach ueberschrieben
  }
  
  private boolean loeschen(HttpExchange e) {
    String path = e.getRequestURI().toString();
    String[] elems = path.split(App.getRs(Server.RB_SLASH));
    String type = elems[elems.length - 2];
    String elemName = elems[elems.length - 1];
    FileStorage fs = new FileStorage(App.getInitParameter(App.getRs(App.RB_AP_CONF)));
    return fs.delete(type, elemName);
  }
  
  private String lesen(HttpExchange e) {
    String path = e.getRequestURI().toString();
    String[] elems = path.split(App.getRs(Server.RB_SLASH));
    FileStorage fs = new FileStorage(App.getInitParameter(App.getRs(App.RB_AP_CONF)));
    if(path.endsWith(App.getRs(RB_SLASH))) {
      String type = elems[elems.length - 1];
      logger.info(type);
      List list = fs.list(type);
      Gson gson = new Gson();
      return gson.toJson(list);
    } else {
      String type = elems[elems.length - 2];
      String elemName = elems[elems.length - 1];
      return fs.readJson(type, elemName);
    }
  }
  
  
  private String bodyLesen(HttpExchange e) throws IOException {
    InputStream is = e.getRequestBody();
    BufferedReader r = new BufferedReader(new InputStreamReader(is));
    StringBuilder sb = new StringBuilder();
    String line = r.readLine();
    while(line != null) {
      sb.append(line);
      line = r.readLine();
    }
    r.close();
    String json = sb.toString();
    logger.log(Level.INFO, "json: {0}", json);
    return json;
  }
}