/*
 * Copyright (C) 2015 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.preload;

import org.xml.sax.Attributes;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.DefaultHandler;

import java.io.File;
import java.io.FileReader;
import java.text.DateFormat;
import java.util.Collection;
import java.util.Date;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.Map;

import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;

/**
 * Helper class for serialization and deserialization of a collection of DumpData objects to XML.
 */
public class DumpDataIO {

  /**
   * Serialize the given collection to an XML document. Returns the produced string.
   */
  public static String serialize(Collection<DumpData> data) {
      // We'll do this by hand, constructing a DOM or similar is too complicated for our simple
      // use case.

      StringBuilder sb = new StringBuilder();
      sb.append("<preloaded-classes-data>\n");

      for (DumpData d : data) {
          serialize(d, sb);
      }

      sb.append("</preloaded-classes-data>\n");
      return sb.toString();
  }

  private static void serialize(DumpData d, StringBuilder sb) {
      sb.append("<data package=\"" + d.packageName + "\" date=\"" +
              DateFormat.getDateTimeInstance().format(d.date) +"\">\n");

      for (Map.Entry<String, String> e : d.dumpData.entrySet()) {
          sb.append("<class name=\"" + e.getKey() + "\" classloader=\"" + e.getValue() + "\"/>\n");
      }

      sb.append("</data>\n");
  }

  /**
   * Load a collection of DumpData objects from the given file.
   */
  public static Collection<DumpData> deserialize(File f) throws Exception {
      // Use SAX parsing. Our format is very simple. Don't do any schema validation or such.

      SAXParserFactory spf = SAXParserFactory.newInstance();
      spf.setNamespaceAware(false);
      SAXParser saxParser = spf.newSAXParser();

      XMLReader xmlReader = saxParser.getXMLReader();
      DumpDataContentHandler ddch = new DumpDataContentHandler();
      xmlReader.setContentHandler(ddch);
      xmlReader.parse(new InputSource(new FileReader(f)));

      return ddch.data;
  }

  private static class DumpDataContentHandler extends DefaultHandler {
      Collection<DumpData> data = new LinkedList<DumpData>();
      DumpData openData = null;

      @Override
      public void startElement(String uri, String localName, String qName, Attributes attributes)
              throws SAXException {
          if (qName.equals("data")) {
              if (openData != null) {
                  throw new IllegalStateException();
              }
              String pkg = attributes.getValue("package");
              String dateString = attributes.getValue("date");

              if (pkg == null || dateString == null) {
                  throw new IllegalArgumentException();
              }

              try {
                  Date date = DateFormat.getDateTimeInstance().parse(dateString);
                  openData = new DumpData(pkg, new HashMap<String, String>(), date);
              } catch (Exception e) {
                  throw new RuntimeException(e);
              }
          } else if (qName.equals("class")) {
              if (openData == null) {
                  throw new IllegalStateException();
              }
              String className = attributes.getValue("name");
              String classLoader = attributes.getValue("classloader");

              if (className == null || classLoader == null) {
                  throw new IllegalArgumentException();
              }

              openData.dumpData.put(className, classLoader.equals("null") ? null : classLoader);
          }
      }

      @Override
      public void endElement(String uri, String localName, String qName) throws SAXException {
          if (qName.equals("data")) {
              if (openData == null) {
                  throw new IllegalStateException();
              }
              openData.countBootClassPath();

              data.add(openData);
              openData = null;
          }
      }
  }
}