/*
  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.store;

import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;
import de.uhilger.mediaz.App;
import de.uhilger.mediaz.Server;
import de.uhilger.mediaz.entity.Ablageort;
import de.uhilger.mediaz.entity.Abspieler;
import de.uhilger.mediaz.entity.Abspielliste;
import de.uhilger.mediaz.entity.Einstellung;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.logging.Logger;
import de.uhilger.mediaz.entity.Entity;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.logging.Level;

/**
 * Ablage fuer Dateien der Mediazentrale
 * 
 * [Basispfad]/[Typ]/[Name]
 * 
 * Typ ist eine der Klassen der Package entity
 * Name muss identisch mit dem Element laut Entity.getName() sein
 * 
 * @author ulrich
 * @version 1, 5.4.2021
 */
public class FileStorage implements Storage {
  
  private static final Logger logger = Logger.getLogger(FileStorage.class.getName());
  
  /** StorageType Ablageort */
  public static final String ST_ABLAGEORT = "Ablageort";
  public static final String ST_EINSTELLUNG = "Einstellung";
  public static final String ST_ABSPIELER = "Abspieler";
  
  private final String fileBase;
  
  private final Map<String, TypeToken> types;
  
  public FileStorage(String base) {
    this.fileBase = base;
    
    // Beispiel: TypeToken<List<String>> list = new TypeToken<List<String>>() {};
    TypeToken<Ablageort> ttAblageort = new TypeToken<Ablageort>() {};
    TypeToken<Einstellung> ttEinstellung = new TypeToken<Einstellung>() {};
    TypeToken<Abspieler> ttAbspieler = new TypeToken<Abspieler>() {};
    TypeToken<Abspielliste> ttAbspielliste = new TypeToken<Abspielliste>() {};
    types = new HashMap();
    types.put(Ablageort.class.getSimpleName(), ttAblageort);
    types.put(Einstellung.class.getSimpleName(), ttEinstellung);
    types.put(Abspieler.class.getSimpleName(), ttAbspieler);
    types.put(Abspielliste.class.getSimpleName(), ttAbspielliste);
  }
  
  /**
   * Ein Objekt als JSON in eine Datei schreiben
   * 
   * Es wird in den Ordner geschrieben, der von conf angegeben ist
   * 
   * Wenn es z.B.ein Ablage-Objekt ist, wird das Objekt in die Datei
 [conf]/Ablage/[name der Ablage].json geschrieben
 
 Der Name der Ablage muss eindeutig sein
   * 
   * 
   * @param entity  das Objekt, das geschrieben werden soll
   * @param overwrite true, wenn Aenderung, false fuer neue Elemente
   * @return  die Datei oder null, wenn die Datei existiert und ein 
   * neues Element (overwrite=false) uebergeben wurde
   * @throws java.io.IOException 
   */
  public File writeToFile(Entity entity, boolean overwrite) throws IOException {
    String className = entity.getClass().getSimpleName();
    logger.finer(className); 
    File dir = new File(fileBase, className);
    dir.mkdirs();
    File file = new File(dir, entity.getName());
    if(file.exists() && !overwrite) {      
      return null;
    } else {
      FileWriter fw = new FileWriter(file);
      Gson gson = new Gson();
      fw.write(gson.toJson(entity));
      fw.flush();
      fw.close();
      return file;
    }
  }
  
  public String readFromFile(File file) throws IOException {
    StringBuilder sb = new StringBuilder();
    BufferedReader r = new BufferedReader(new FileReader(file));
    String line = r.readLine();
    while(line != null) {
      sb.append(line);
      line = r.readLine();
    }
    r.close();
    return sb.toString();
  }
  
  public Entity entityFromFile(File file) throws ClassNotFoundException, FileNotFoundException, IOException {
    String json = readFromFile(file);
    Gson gson = new Gson();
    return gson.fromJson(json, typeFromName(typeNameFromPath(file)).getType());
  }
  
  private String typeNameFromPath(File file) {
    String[] parts = file.getPath().split(App.getRs(Server.RB_SLASH));
    return parts[parts.length-2];
  }

  @Override
  public Object write(Entity e, boolean overwrite) {
    try {
      return writeToFile(e, overwrite);
    } catch (IOException ex) {
      logger.log(Level.SEVERE, null, ex);
      return null;
    }
  }

  @Override
  public Entity read(String typ, String name) {
    try {
      return entityFromFile(getFile(typ, name));
    } catch (ClassNotFoundException | IOException ex) {
      logger.log(Level.SEVERE, null, ex);
      return null;
    }
  }

  @Override
  public List<String> list(String typ) {
    File base = new File(fileBase);
    File dir = new File(base, typ);
    List<String> list = new ArrayList();
    File[] files = dir.listFiles();
    if(files != null) {
      for(File file : files) {
        //NamedItem n = new NamedItem();
        //n.setLabel(file.getName());
        list.add(file.getName());
      }
    }
    return list;
  }
  
  @Override
  public TypeToken typeFromName(String name) {
    return types.get(name);
  }

  @Override
  public String readJson(String typ, String name) {
    try {
      return readFromFile(getFile(typ, name));
    } catch (IOException ex) {
      logger.log(Level.SEVERE, null, ex);
      return null;
    }
  }
  
  private File getFile(String typ, String name) {
    File base = new File(fileBase);
    File dir = new File(base, typ);
    return new File(dir, name);    
  }

  @Override
  public boolean delete(String typ, String name) {
    File file = getFile(typ, name);
    if(file.exists()) {
      return file.delete();
    } else {
      return false;
    }
  }

  @Override
  public List<Entity> listObjects(String typ) {
    File base = new File(fileBase);
    File dir = new File(base, typ);
    List<Entity> list = new ArrayList();
    File[] files = dir.listFiles();
    if(files != null) {
      for(File file : files) {
        try {
          list.add(entityFromFile(file));
        } catch (ClassNotFoundException | IOException ex) {
          logger.log(Level.SEVERE, null, ex);
        }
      }
    }
    return list;
  }
  
  public boolean exists(String typ, String name) {
    return getFile(typ, name).exists();
  }
  
}