/*******************************************************************************
 * Copyright (c) 2011-2012 Igor Fedorenko
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *      Igor Fedorenko - initial API and implementation
 *******************************************************************************/
package org.eclipse.m2e.sourcelookup.internal.launch;

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.List;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;

/**
 * Helper to find and extract information from META-INF/maven pom.properties files.
 */
public abstract class MetaInfMavenScanner<T> {

  private static final String META_INF_MAVEN = "META-INF/maven";

  public List<T> scan(File file, String filename) {
    List<T> result = new ArrayList<T>();
    if (file != null) {
      if (file.isDirectory()) {
        scanFilesystem(new File(file, META_INF_MAVEN), filename, result);
      } else if (file.isFile()) {
        try {
          try (JarFile jar = new JarFile(file)) {
            scanJar(jar, filename, result);
          }
        } catch (IOException e) {
          // fall through
        }
      }
    }
    return result;
  }

  private void scanJar(JarFile jar, String filename, List<T> result) throws IOException {
    Enumeration<JarEntry> entries = jar.entries();
    while (entries.hasMoreElements()) {
      JarEntry entry = entries.nextElement();
      if (!entry.isDirectory()) {
        String name = entry.getName();
        if (name.startsWith(META_INF_MAVEN) && name.endsWith(filename)) {
          try {
            T t = visitJarEntry(jar, entry);
            if (t != null) {
              result.add(t);
            }
          } catch (IOException e) {
            // ignore
          }
        }
      }
    }
  }

  private void scanFilesystem(File dir, String filename, List<T> result) {
    File[] files = dir.listFiles();
    if (files == null) {
      return;
    }
    for (File file : files) {
      if (file.isDirectory()) {
        scanFilesystem(file, filename, result);
      } else if (file.isFile() && filename.equals(file.getName())) {
        try {
          T t = visitFile(file);
          if (t != null) {
            result.add(t);
          }
        } catch (IOException e) {
          // ignore
        }
      }
    }
  }

  protected abstract T visitFile(File file) throws IOException;

  protected abstract T visitJarEntry(JarFile jar, JarEntry entry) throws IOException;
}