/*
 * $Id: MessageResources.java 471754 2006-11-06 14:55:09Z husted $
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.struts.util;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import java.io.Serializable;
import java.text.MessageFormat;
import java.util.HashMap;
import java.util.Locale;

/**
 * General purpose abstract class that describes an API for retrieving
 * Locale-sensitive messages from underlying resource locations of an
 * unspecified design, and optionally utilizing the <code>MessageFormat</code>
 * class to produce internationalized messages with parametric replacement.
 * <p> Calls to <code>getMessage()</code> variants without a
 * <code>Locale</code> argument are presumed to be requesting a message string
 * in the default <code>Locale</code> for this JVM. <p> Calls to
 * <code>getMessage()</code> with an unknown key, or an unknown
 * <code>Locale</code> will return <code>null</code> if the
 * <code>returnNull</code> property is set to <code>true</code>.  Otherwise, a
 * suitable error message will be returned instead. <p> <strong>IMPLEMENTATION
 * NOTE</strong> - Classes that extend this class must be Serializable so that
 * instances may be used in distributable application server environments.
 *
 * @version $Rev: 471754 $ $Date: 2005-08-29 23:57:50 -0400 (Mon, 29 Aug 2005)
 *          $
 */
public abstract class MessageResources implements Serializable {
  // ------------------------------------------------------------- Properties

  /**
   * Commons Logging instance.
   */
  protected static Log log = LogFactory.getLog(MessageResources.class);

  // --------------------------------------------------------- Static Methods

  /**
   * The default MessageResourcesFactory used to create MessageResources
   * instances.
   */
  protected static MessageResourcesFactory defaultFactory = null;

  /**
   * The configuration parameter used to initialize this MessageResources.
   */
  protected String config = null;

  /**
   * The default Locale for our environment.
   */
  protected Locale defaultLocale = Locale.getDefault();

  /**
   * The <code>MessageResourcesFactory</code> that created this instance.
   */
  protected MessageResourcesFactory factory = null;

  /**
   * The set of previously created MessageFormat objects, keyed by the key
   * computed in <code>messageKey()</code>.
   */
  protected HashMap formats = new HashMap();

  /**
   * Indicate is a <code>null</code> is returned instead of an error message
   * string when an unknown Locale or key is requested.
   */
  protected boolean returnNull = false;

  /**
   * Indicates whether 'escape processing' should be performed on the error
   * message string.
   */
  private boolean escape = true;

  // ----------------------------------------------------------- Constructors

  /**
   * Construct a new MessageResources according to the specified
   * parameters.
   *
   * @param factory The MessageResourcesFactory that created us
   * @param config  The configuration parameter for this MessageResources
   */
  public MessageResources(MessageResourcesFactory factory, String config) {
    this(factory, config, false);
  }

  /**
   * Construct a new MessageResources according to the specified
   * parameters.
   *
   * @param factory    The MessageResourcesFactory that created us
   * @param config     The configuration parameter for this
   *                   MessageResources
   * @param returnNull The returnNull property we should initialize with
   */
  public MessageResources(MessageResourcesFactory factory, String config,
                          boolean returnNull) {
    super();
    this.factory = factory;
    this.config = config;
    this.returnNull = returnNull;
  }

  /**
   * The configuration parameter used to initialize this MessageResources.
   *
   * @return parameter used to initialize this MessageResources
   */
  public String getConfig() {
    return (this.config);
  }

  /**
   * The <code>MessageResourcesFactory</code> that created this instance.
   *
   * @return <code>MessageResourcesFactory</code> that created instance
   */
  public MessageResourcesFactory getFactory() {
    return (this.factory);
  }

  /**
   * Indicates that a <code>null</code> is returned instead of an error
   * message string if an unknown Locale or key is requested.
   *
   * @return true if null is returned if unknown key or locale is requested
   */
  public boolean getReturnNull() {
    return (this.returnNull);
  }

  /**
   * Indicates that a <code>null</code> is returned instead of an error
   * message string if an unknown Locale or key is requested.
   *
   * @param returnNull true Indicates that a <code>null</code> is returned
   *                   if an unknown Locale or key is requested.
   */
  public void setReturnNull(boolean returnNull) {
    this.returnNull = returnNull;
  }

  /**
   * Indicates whether 'escape processing' should be performed on the error
   * message string.
   *
   * @since Struts 1.2.8
   */
  public boolean isEscape() {
    return escape;
  }

  /**
   * Set whether 'escape processing' should be performed on the error
   * message string.
   *
   * @since Struts 1.2.8
   */
  public void setEscape(boolean escape) {
    this.escape = escape;
  }

  // --------------------------------------------------------- Public Methods

  /**
   * Returns a text message for the specified key, for the default Locale.
   *
   * @param key The message key to look up
   */
  public String getMessage(String key) {
    return this.getMessage((Locale) null, key, null);
  }

  /**
   * Returns a text message after parametric replacement of the specified
   * parameter placeholders.
   *
   * @param key  The message key to look up
   * @param args An array of replacement parameters for placeholders
   */
  public String getMessage(String key, Object[] args) {
    return this.getMessage((Locale) null, key, args);
  }

  /**
   * Returns a text message after parametric replacement of the specified
   * parameter placeholders.
   *
   * @param key  The message key to look up
   * @param arg0 The replacement for placeholder {0} in the message
   */
  public String getMessage(String key, Object arg0) {
    return this.getMessage((Locale) null, key, arg0);
  }

  /**
   * Returns a text message after parametric replacement of the specified
   * parameter placeholders.
   *
   * @param key  The message key to look up
   * @param arg0 The replacement for placeholder {0} in the message
   * @param arg1 The replacement for placeholder {1} in the message
   */
  public String getMessage(String key, Object arg0, Object arg1) {
    return this.getMessage((Locale) null, key, arg0, arg1);
  }

  /**
   * Returns a text message after parametric replacement of the specified
   * parameter placeholders.
   *
   * @param key  The message key to look up
   * @param arg0 The replacement for placeholder {0} in the message
   * @param arg1 The replacement for placeholder {1} in the message
   * @param arg2 The replacement for placeholder {2} in the message
   */
  public String getMessage(String key, Object arg0, Object arg1, Object arg2) {
    return this.getMessage((Locale) null, key, arg0, arg1, arg2);
  }

  /**
   * Returns a text message after parametric replacement of the specified
   * parameter placeholders.
   *
   * @param key  The message key to look up
   * @param arg0 The replacement for placeholder {0} in the message
   * @param arg1 The replacement for placeholder {1} in the message
   * @param arg2 The replacement for placeholder {2} in the message
   * @param arg3 The replacement for placeholder {3} in the message
   */
  public String getMessage(String key, Object arg0, Object arg1, Object arg2,
                           Object arg3) {
    return this.getMessage((Locale) null, key, arg0, arg1, arg2, arg3);
  }

  /**
   * Returns a text message for the specified key, for the default Locale. A
   * null string result will be returned by this method if no relevant
   * message resource is found for this key or Locale, if the
   * <code>returnNull</code> property is set.  Otherwise, an appropriate
   * error message will be returned. <p> This method must be implemented by
   * a concrete subclass.
   *
   * @param locale The requested message Locale, or <code>null</code> for
   *               the system default Locale
   * @param key    The message key to look up
   */
  public abstract String getMessage(Locale locale, String key);

  /**
   * Returns a text message after parametric replacement of the specified
   * parameter placeholders.  A null string result will be returned by this
   * method if no resource bundle has been configured.
   *
   * @param locale The requested message Locale, or <code>null</code> for
   *               the system default Locale
   * @param key    The message key to look up
   * @param args   An array of replacement parameters for placeholders
   */
  public String getMessage(Locale locale, String key, Object[] args) {
    // Cache MessageFormat instances as they are accessed
    if (locale == null) {
      locale = defaultLocale;
    }

    MessageFormat format = null;
    String formatKey = messageKey(locale, key);

    synchronized (formats) {
      format = (MessageFormat) formats.get(formatKey);

      if (format == null) {
        String formatString = getMessage(locale, key);

        if (formatString == null) {
          return returnNull ? null : ("???" + formatKey + "???");
        }

        format = new MessageFormat(escape(formatString));
        format.setLocale(locale);
        formats.put(formatKey, format);
      }
    }

    return format.format(args);
  }

  /**
   * Returns a text message after parametric replacement of the specified
   * parameter placeholders.  A null string result will never be returned by
   * this method.
   *
   * @param locale The requested message Locale, or <code>null</code> for
   *               the system default Locale
   * @param key    The message key to look up
   * @param arg0   The replacement for placeholder {0} in the message
   */
  public String getMessage(Locale locale, String key, Object arg0) {
    return this.getMessage(locale, key, new Object[]{arg0});
  }

  /**
   * Returns a text message after parametric replacement of the specified
   * parameter placeholders.  A null string result will never be returned by
   * this method.
   *
   * @param locale The requested message Locale, or <code>null</code> for
   *               the system default Locale
   * @param key    The message key to look up
   * @param arg0   The replacement for placeholder {0} in the message
   * @param arg1   The replacement for placeholder {1} in the message
   */
  public String getMessage(Locale locale, String key, Object arg0, Object arg1) {
    return this.getMessage(locale, key, new Object[]{arg0, arg1});
  }

  /**
   * Returns a text message after parametric replacement of the specified
   * parameter placeholders.  A null string result will never be returned by
   * this method.
   *
   * @param locale The requested message Locale, or <code>null</code> for
   *               the system default Locale
   * @param key    The message key to look up
   * @param arg0   The replacement for placeholder {0} in the message
   * @param arg1   The replacement for placeholder {1} in the message
   * @param arg2   The replacement for placeholder {2} in the message
   */
  public String getMessage(Locale locale, String key, Object arg0,
                           Object arg1, Object arg2) {
    return this.getMessage(locale, key, new Object[]{arg0, arg1, arg2});
  }

  /**
   * Returns a text message after parametric replacement of the specified
   * parameter placeholders.  A null string result will never be returned by
   * this method.
   *
   * @param locale The requested message Locale, or <code>null</code> for
   *               the system default Locale
   * @param key    The message key to look up
   * @param arg0   The replacement for placeholder {0} in the message
   * @param arg1   The replacement for placeholder {1} in the message
   * @param arg2   The replacement for placeholder {2} in the message
   * @param arg3   The replacement for placeholder {3} in the message
   */
  public String getMessage(Locale locale, String key, Object arg0,
                           Object arg1, Object arg2, Object arg3) {
    return this.getMessage(locale, key,
        new Object[]{arg0, arg1, arg2, arg3});
  }

  /**
   * Return <code>true</code> if there is a defined message for the
   * specified key in the system default locale.
   *
   * @param key The message key to look up
   */
  public boolean isPresent(String key) {
    return this.isPresent(null, key);
  }

  /**
   * Return <code>true</code> if there is a defined message for the
   * specified key in the specified Locale.
   *
   * @param locale The requested message Locale, or <code>null</code> for
   *               the system default Locale
   * @param key    The message key to look up
   */
  public boolean isPresent(Locale locale, String key) {
    String message = getMessage(locale, key);

    if (message == null) {
      return false;
    } else if (message.startsWith("???") && message.endsWith("???")) {
      return false; // FIXME - Only valid for default implementation
    } else {
      return true;
    }
  }

  // ------------------------------------------------------ Protected Methods

  /**
   * Escape any single quote characters that are included in the specified
   * message string.
   *
   * @param string The string to be escaped
   */
  protected String escape(String string) {
    if (!isEscape()) {
      return string;
    }

    if ((string == null) || (string.indexOf('\'') < 0)) {
      return string;
    }

    int n = string.length();
    StringBuffer sb = new StringBuffer(n);

    for (int i = 0; i < n; i++) {
      char ch = string.charAt(i);

      if (ch == '\'') {
        sb.append('\'');
      }

      sb.append(ch);
    }

    return sb.toString();
  }

  /**
   * Compute and return a key to be used in caching information by a Locale.
   * <strong>NOTE</strong> - The locale key for the default Locale in our
   * environment is a zero length String.
   *
   * @param locale The locale for which a key is desired
   */
  protected String localeKey(Locale locale) {
    return (locale == null) ? "" : locale.toString();
  }

  /**
   * Compute and return a key to be used in caching information by Locale
   * and message key.
   *
   * @param locale The Locale for which this format key is calculated
   * @param key    The message key for which this format key is calculated
   */
  protected String messageKey(Locale locale, String key) {
    return (localeKey(locale) + "." + key);
  }

  /**
   * Compute and return a key to be used in caching information by locale
   * key and message key.
   *
   * @param localeKey The locale key for which this cache key is calculated
   * @param key       The message key for which this cache key is
   *                  calculated
   */
  protected String messageKey(String localeKey, String key) {
    return (localeKey + "." + key);
  }

  /**
   * Create and return an instance of <code>MessageResources</code> for the
   * created by the default <code>MessageResourcesFactory</code>.
   *
   * @param config Configuration parameter for this message bundle.
   */
  public synchronized static MessageResources getMessageResources(
      String config) {
    if (defaultFactory == null) {
      defaultFactory = MessageResourcesFactory.createFactory();
    }

    return defaultFactory.createResources(config);
  }

  /**
   * Log a message to the Writer that has been configured for our use.
   *
   * @param message The message to be logged
   */
  public void log(String message) {
    log.debug(message);
  }

  /**
   * Log a message and exception to the Writer that has been configured for
   * our use.
   *
   * @param message   The message to be logged
   * @param throwable The exception to be logged
   */
  public void log(String message, Throwable throwable) {
    log.debug(message, throwable);
  }
}
