/*
  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.google.gson.Gson;
import com.sun.net.httpserver.Authenticator;
import com.sun.net.httpserver.HttpContext;
import com.sun.net.httpserver.HttpHandler;
import com.sun.net.httpserver.HttpServer;
import de.uhilger.neon.entity.ContextDescriptor;
import de.uhilger.neon.entity.NeonDescriptor;
import de.uhilger.neon.entity.ServerDescriptor;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.InetSocketAddress;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.concurrent.Executors;

/**
 * Einen Neon-Server aus einer Beschreibungsdatei herstellen
 *
 * Die Werte aus der Beschreibungsdatei werden in die Attribute der HttpContext-Objekte geschrieben,
 * die zu jedem Server eroeffnet werden.
 *
 * Die Entitaeten stehen wie folgt in Beziehung: HttpServer -1:n-> HttpContext -1:1-> HttpHandler
 *
 * Die Factory legt die Kontexte, Handler sowie die Verbindung zu den Actors selbsttaetig an. Alle
 * Parameter aus 'attributes'-Elementen der Beschreibungsdatei werden als Attribute in den
 * HttpContext uebertragen. Deshalb ist es wichtig, dass die Attributnamen eindeutig gewaehlt
 * werden, damit sie sich nicht gegenseitig ueberschreiben.
 *
 * @author Ulrich Hilger
 * @version 1, 6.2.2024
 */
public class Factory {

  public Factory() {
    listeners = new ArrayList<>();
  }

  /**
   * Beschreibungsdatei lesen
   *
   * @param file die Datei, die den Server beschreibt
   * @return ein Objekt, das den Server beschreibt
   * @throws IOException wenn die Datei nicht gelesen werden konnte
   */
  public NeonDescriptor readDescriptor(File file) throws IOException {
    //Logger logger = Logger.getLogger(Factory.class.getName());
    //logger.log(Level.INFO, "reading NeonDescriptor from {0}", file.getAbsolutePath());

    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();

    Gson gson = new Gson();
    return gson.fromJson(sb.toString(), NeonDescriptor.class);
  }
  
  public void runInstance(NeonDescriptor d) 
          throws ClassNotFoundException, NoSuchMethodException, InstantiationException, 
          IllegalAccessException, IllegalArgumentException, InvocationTargetException, IOException {
    this.runInstance(d, null, new ArrayList<>());
  }

  public void runInstance(NeonDescriptor d, List<String> packageNames) 
          throws ClassNotFoundException, NoSuchMethodException, InstantiationException, 
          IllegalAccessException, IllegalArgumentException, InvocationTargetException, IOException {
    this.runInstance(d, packageNames, new ArrayList<>());
  }
  /**
   * Einen Neon-Server gemaess einem Serverbeschreibungsobjekt herstellen und starten
   *
   * @param d das Object mit der Serverbeschreibung
   * @param packageNames Namen der Packages, aus der rekursiv vorgefundene Actors eingebaut werden
   * sollen
   * @param sdp die DataProvider fuer diese Neon-Instanz
   * @throws ClassNotFoundException
   * @throws NoSuchMethodException
   * @throws InstantiationException
   * @throws IllegalAccessException
   * @throws IllegalArgumentException
   * @throws InvocationTargetException
   * @throws IOException
   */
  public void runInstance(NeonDescriptor d, List<String> packageNames, List<DataProvider> sdp) 
          throws ClassNotFoundException, NoSuchMethodException, InstantiationException, 
          IllegalAccessException, IllegalArgumentException, InvocationTargetException, IOException {
    List serverList = d.server;
    Iterator<ServerDescriptor> serverIterator = serverList.iterator();
    while (serverIterator.hasNext()) {
      ServerDescriptor sd = serverIterator.next();
      HttpServer server = HttpServer.create(new InetSocketAddress(sd.port), 0);
      fireServerCreated(server);

      if(packageNames == null) {
        packageNames = d.actorPackages;
      }
      addContexts(d, server, sd.contexts, packageNames, sdp);

      server.setExecutor(Executors.newFixedThreadPool(10));
      server.start();
    }
    fireInstanceStarted();
  }
  
  private Authenticator createAuthenticator(NeonDescriptor d) {
    Authenticator auth = null;
    if(d.authenticator != null) {
      try {
        Object authObj = Class.forName(d.authenticator.className)
                .getDeclaredConstructor().newInstance();
        if(authObj instanceof Authenticator) {
          auth = (Authenticator) authObj;
          return auth;
        }
      } catch (ClassNotFoundException | NoSuchMethodException | SecurityException | 
              InstantiationException | IllegalAccessException | IllegalArgumentException | 
              InvocationTargetException ex) {
        // Klasse nicht gefunden. Muss das geloggt oder sonstwie behandel werden?
        return null;
      }      
    }    
    return auth;
  }

  private void addContexts(NeonDescriptor d, HttpServer server, List contextList, List<String> packageNames, 
          List<DataProvider> sdp) 
          throws ClassNotFoundException, NoSuchMethodException, InstantiationException, 
          IllegalAccessException, IllegalArgumentException, InvocationTargetException, IOException {
    Map<String, HttpHandler> sharedHandlers = new HashMap();
    Iterator<ContextDescriptor> contextIterator = contextList.iterator();
    while (contextIterator.hasNext()) {
      ContextDescriptor cd = contextIterator.next();
      HttpHandler h = buildHandler(cd, sharedHandlers);
      if (h != null) {
        HttpContext ctx = server.createContext(cd.contextPath, h);        
        Map<String, Object> ctxAttrs = ctx.getAttributes();
        /*
          Achtung: Wenn verschiedene Elemente dasselbe Attribut 
          deklarieren, ueberschreiben sie sich die Attribute gegenseitig.
         */
        ctxAttrs.putAll(cd.attributes);        
        if (h instanceof Handler) {         
          for (String packageName : packageNames) {
            wireActors(
                    packageName, Actor.class, (Handler) h, 
                    cd.attributes.get("contextName"));
              ctx.getAttributes().put("serverDataProviderList", sdp);
          }
        }        
        Authenticator auth = createAuthenticator(d);
        if (auth instanceof Authenticator && cd.authenticator instanceof String) {
            ctx.setAuthenticator(auth);      
            ctx.getAttributes().putAll(d.authenticator.attributes);
            fireAuthenticatorCreated(ctx, auth);
        }
        fireHandlerCreated(ctx, h);
        fireContextCreated(ctx);
      } else {
        // Handler konnte nicht erstellt werden
      }
    }
  }
  
  private HttpHandler buildHandler(ContextDescriptor cd, Map<String, HttpHandler> sharedHandlers) throws ClassNotFoundException, NoSuchMethodException, InstantiationException, 
          IllegalAccessException, IllegalArgumentException, InvocationTargetException, IOException {
    HttpHandler h;    
    if (!cd.sharedHandler) {
      h = getHandlerInstance(cd);
    } else {
      HttpHandler sharedHandler = sharedHandlers.get(cd.attributes.get("contextName"));
      if (sharedHandler instanceof HttpHandler) {
        h = sharedHandler;
      } else {
        h = getHandlerInstance(cd);
        sharedHandlers.put(cd.attributes.get("contextName"), h);
      }
    }
    return h;
  }
  
  private HttpHandler getHandlerInstance(ContextDescriptor cd) {
    try {
      Object handlerObj = Class.forName(cd.className)
              .getDeclaredConstructor().newInstance();
      if (handlerObj instanceof HttpHandler) {
        return (HttpHandler) handlerObj;
      } else {
        // kein HttpHandler aus newInstance
        return null;
      }
    } catch (ClassNotFoundException | NoSuchMethodException | SecurityException | 
            InstantiationException | IllegalAccessException | IllegalArgumentException | 
            InvocationTargetException ex) {
      // Klasse nicht gefunden. Muss das geloggt oder sonstwie behandel werden?
      return null;
    }
  }

  private void wireActors(String packageName, Class annotation, Handler h, String contextName) {
    ClassLoader cl = ClassLoader.getSystemClassLoader();
    InputStream stream = cl
            .getResourceAsStream(packageName.replaceAll("[.]", "/"));
    BufferedReader reader = new BufferedReader(new InputStreamReader(stream));
    Iterator i = reader.lines().iterator();
    while (i.hasNext()) {
      String line = i.next().toString();
      if (line.endsWith(".class")) {
        try {
          Class actorClass = Class.forName(packageName + "."
                  + line.substring(0, line.lastIndexOf('.')));
          if (actorClass != null && actorClass.isAnnotationPresent(annotation)) {
            wire(h, actorClass, contextName);
          }
        } catch (ClassNotFoundException ex) {
          // Klasse nicht gefunden. Muss das geloggt oder sonstwie behandel werden?
        }
      } else {
        wireActors(packageName + "." + line, annotation, h, contextName);
      }
    }
  }
  
  /*
    Eine Action-Annotation enthaelt gewoehnlich die Route, 
    die 'unterhalb' des Kontextpfades als 'Ausloeser' zur 
    Ausfuehrung der Action verwendet wird.
  
    Wenn die Action fuer alle Routen 'unterhalb' des 
    Kontextpfades ausgefuehrt werden soll, muss die Action 
    als Route '/' angeben.
  */
  private void wire(Handler h, Class c, String contextName) {
    Method[] methods = c.getMethods();
    for (Method method : methods) {
      Action action = method.getAnnotation(Action.class);
      if (action != null) {
        List actionHandlers = Arrays.asList(action.handler());
        if (actionHandlers.contains(contextName)) {
          h.setActor(action.type(), action.route(), c.getName());
        }
      }
    }
  }

  /* -------------- FactoryListener Implementierung --------------- */
  
  private List<FactoryListener> listeners;

  public void addListener(FactoryListener l) {
    this.listeners.add(l);
  }

  public void removeListener(FactoryListener l) {
    this.listeners.remove(l);
  }

  public void destroy() {
    this.listeners.clear();
    this.listeners = null;
  }

  private void fireServerCreated(HttpServer server) {
    for (FactoryListener l : listeners) {
      l.serverCreated(server);
    }
  }
  
  private void fireHandlerCreated(HttpContext ctx, HttpHandler h) {
    for (FactoryListener l : listeners) {
      l.handlerCreated(ctx, h);
    }
  }

  private void fireContextCreated(HttpContext context) {
    for (FactoryListener l : listeners) {
      l.contextCreated(context);
    }
  }
  
  private void fireAuthenticatorCreated(HttpContext context, Authenticator auth) {
    for (FactoryListener l : listeners) {
      l.authenticatorCreated(context, auth);
    }
  }

  private void fireInstanceStarted() {
    for (FactoryListener l : listeners) {
      l.instanceStarted();
    }
  }
}