HelpContentLoaderImpl.java

/*
 * Copyright (c) 2009-present the original author or authors.
 *
 * 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.planet57.gshell.help;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
import java.util.Locale;
import java.util.MissingResourceException;

import org.sonatype.goodies.common.ComponentSupport;
import com.planet57.gshell.util.io.PrintBuffer;

import javax.inject.Named;
import javax.inject.Singleton;

/**
 * {@link HelpContentLoader} component.
 *
 * @author <a href="mailto:jason@planet57.com">Jason Dillon</a>
 * @since 2.5
 */
@Named
@Singleton
public class HelpContentLoaderImpl
  extends ComponentSupport
  implements HelpContentLoader
{
  private final String DEFAULT_CONTENT = getClass().getPackage().getName() + ".DefaultHelpContent";

  @Override
  public String load(final String name, final ClassLoader loader) throws MissingContentException, IOException {
    return load(name, Locale.getDefault(), loader);
  }

  private String load(final String name, final Locale locale, final ClassLoader loader)
    throws MissingContentException, IOException
  {
    log.debug("Loading help content for {} ({})", name, locale);

    URL resource = findResource(name, locale, loader);
    if (resource == null) {
      // use default help content if missing
      resource = findResource(DEFAULT_CONTENT, locale, getClass().getClassLoader());
      if (resource == null) {
        throw new MissingContentException(name);
      }
    }

    log.debug("Using resource: {}", resource);

    PrintBuffer buff = new PrintBuffer();
    try (BufferedReader input = new BufferedReader(new InputStreamReader(resource.openStream()))) {
      String line;
      while ((line = input.readLine()) != null) {
        // Ignore lines starting with #, these are comments
        if (!line.startsWith("#")) {
          buff.println(line);
        }
      }
    }

    return buff.toString().trim();
  }

  private URL findResource(final String name, final Locale locale, final ClassLoader loader) {
    assert name != null;
    assert loader != null;

    URL resource = null;

    for (Locale candidate : getCandidateLocales(locale)) {
      String bundle = name;

      if (candidate != null) {
        bundle = toBundleName(name, candidate);
      }

      try {
        resource = loader.getResource(toResourceName(bundle, "help"));
      }
      catch (MissingResourceException e) {
        // ignore
      }
    }
    return resource;
  }

  private List<Locale> getCandidateLocales(final Locale locale) {
    assert locale != null;

    String language = locale.getLanguage();
    String country = locale.getCountry();
    String variant = locale.getVariant();

    List<Locale> locales = new ArrayList<>(4);

    if (variant.length() > 0) {
      locales.add(locale);
    }
    if (country.length() > 0) {
      locales.add((locales.size() == 0) ? locale : new Locale(language, country, ""));
    }
    if (language.length() > 0) {
      locales.add((locales.size() == 0) ? locale : new Locale(language, "", ""));
    }
    locales.add(null);

    return locales;
  }

  private String toBundleName(final String baseName, final Locale locale) {
    assert baseName != null;
    assert locale != null;

    String language = locale.getLanguage();
    String country = locale.getCountry();
    String variant = locale.getVariant();

    if ("".equals(language) && "".equals(country) && "".equals(variant)) {
      return baseName;
    }

    StringBuilder buff = new StringBuilder(baseName);
    buff.append('_');
    if (!"".equals(variant)) {
      buff.append(language).append('_').append(country).append('_').append(variant);
    }
    else if (!"".equals(country)) {
      buff.append(language).append('_').append(country);
    }
    else {
      buff.append(language);
    }

    return buff.toString();
  }

  private String toResourceName(final String bundleName, final String suffix) {
    assert bundleName != null;
    assert suffix != null;
    return bundleName.replace('.', '/') + '.' + suffix;
  }
}