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  /*
   * (C) Copyright Taligent, Inc. 1996, 1997 - All Rights Reserved
   * (C) Copyright IBM Corp. 1996 - 1998 - All Rights Reserved
   *
   *   The original version of this source code and documentation is copyrighted
   * and owned by Taligent, Inc., a wholly-owned subsidiary of IBM. These
   * materials are provided under terms of a License Agreement between Taligent
   * and Sun. This technology is protected by multiple US and International
   * patents. This notice and attribution to Taligent may not be removed.
   *   Taligent is a registered trademark of Taligent, Inc.
   *
   */
  
  package java.text;
  
  import java.io.Serializable;
  
  /**
   * <code>Format</code> is an abstract base class for formatting locale-sensitive
   * information such as dates, messages, and numbers.
   *
   * <p>
   * <code>Format</code> defines the programming interface for formatting
   * locale-sensitive objects into <code>String</code>s (the
   * <code>format</code> method) and for parsing <code>String</code>s back
   * into objects (the <code>parseObject</code> method).
   *
   * <p>
   * Generally, a format's <code>parseObject</code> method must be able to parse
   * any string formatted by its <code>format</code> method. However, there may
   * be exceptional cases where this is not possible. For example, a
   * <code>format</code> method might create two adjacent integer numbers with
   * no separator in between, and in this case the <code>parseObject</code> could
   * not tell which digits belong to which number.
   *
   * <h3>Subclassing</h3>
   *
   * <p>
   * The Java Platform provides three specialized subclasses of <code>Format</code>--
   * <code>DateFormat</code>, <code>MessageFormat</code>, and
   * <code>NumberFormat</code>--for formatting dates, messages, and numbers,
   * respectively.
   * <p>
   * Concrete subclasses must implement three methods:
   * <ol>
   * <li> <code>format(Object obj, StringBuffer toAppendTo, FieldPosition pos)</code>
   * <li> <code>formatToCharacterIterator(Object obj)</code>
   * <li> <code>parseObject(String source, ParsePosition pos)</code>
   * </ol>
   * These general methods allow polymorphic parsing and formatting of objects
   * and are used, for example, by <code>MessageFormat</code>.
   * Subclasses often also provide additional <code>format</code> methods for
   * specific input types as well as <code>parse</code> methods for specific
   * result types. Any <code>parse</code> method that does not take a
   * <code>ParsePosition</code> argument should throw <code>ParseException</code>
   * when no text in the required format is at the beginning of the input text.
   *
   * <p>
   * Most subclasses will also implement the following factory methods:
   * <ol>
   * <li>
   * <code>getInstance</code> for getting a useful format object appropriate
   * for the current locale
   * <li>
   * <code>getInstance(Locale)</code> for getting a useful format
   * object appropriate for the specified locale
   * </ol>
   * In addition, some subclasses may also implement other
   * <code>getXxxxInstance</code> methods for more specialized control. For
   * example, the <code>NumberFormat</code> class provides
   * <code>getPercentInstance</code> and <code>getCurrencyInstance</code>
   * methods for getting specialized number formatters.
   *
   * <p>
   * Subclasses of <code>Format</code> that allow programmers to create objects
   * for locales (with <code>getInstance(Locale)</code> for example)
   * must also implement the following class method:
   * <blockquote>
   * <pre>
   * public static Locale[] getAvailableLocales()
   * </pre>
   * </blockquote>
   *
   * <p>
   * And finally subclasses may define a set of constants to identify the various
   * fields in the formatted output. These constants are used to create a FieldPosition
   * object which identifies what information is contained in the field and its
   * position in the formatted result. These constants should be named
   * <code><em>item</em>_FIELD</code> where <code><em>item</em></code> identifies
   * the field. For examples of these constants, see <code>ERA_FIELD</code> and its
   * friends in {@link DateFormat}.
   *
   * <h4><a name="synchronization">Synchronization</a></h4>
   *
   * <p>
   * Formats are generally not synchronized.
   * It is recommended to create separate format instances for each thread.
   * If multiple threads access a format concurrently, it must be synchronized
   * externally.
   *
   * @see          ParsePosition
   * @see          FieldPosition
   * @see          NumberFormat
   * @see          DateFormat
   * @see          MessageFormat
   * @author       Mark Davis
   */
  public abstract class Format implements Serializable, Cloneable {
  
      private static final long serialVersionUID = -299282585814624189L;
  
      /**
       * Sole constructor.  (For invocation by subclass constructors, typically
       * implicit.)
       */
      protected Format() {
      }
  
      /**
       * Formats an object to produce a string. This is equivalent to
       * <blockquote>
       * {@link #format(Object, StringBuffer, FieldPosition) format}<code>(obj,
       *         new StringBuffer(), new FieldPosition(0)).toString();</code>
       * </blockquote>
       *
       * @param obj    The object to format
       * @return       Formatted string.
       * @exception IllegalArgumentException if the Format cannot format the given
       *            object
       */
      public final String format (Object obj) {
          return format(obj, new StringBuffer(), new FieldPosition(0)).toString();
      }
  
      /**
       * Formats an object and appends the resulting text to a given string
       * buffer.
       * If the <code>pos</code> argument identifies a field used by the format,
       * then its indices are set to the beginning and end of the first such
       * field encountered.
       *
       * @param obj    The object to format
       * @param toAppendTo    where the text is to be appended
       * @param pos    A <code>FieldPosition</code> identifying a field
       *               in the formatted text
       * @return       the string buffer passed in as <code>toAppendTo</code>,
       *               with formatted text appended
       * @exception NullPointerException if <code>toAppendTo</code> or
       *            <code>pos</code> is null
       * @exception IllegalArgumentException if the Format cannot format the given
       *            object
       */
      public abstract StringBuffer format(Object obj,
                      StringBuffer toAppendTo,
                      FieldPosition pos);
  
      /**
       * Formats an Object producing an <code>AttributedCharacterIterator</code>.
       * You can use the returned <code>AttributedCharacterIterator</code>
       * to build the resulting String, as well as to determine information
       * about the resulting String.
       * <p>
       * Each attribute key of the AttributedCharacterIterator will be of type
       * <code>Field</code>. It is up to each <code>Format</code> implementation
       * to define what the legal values are for each attribute in the
       * <code>AttributedCharacterIterator</code>, but typically the attribute
       * key is also used as the attribute value.
       * <p>The default implementation creates an
       * <code>AttributedCharacterIterator</code> with no attributes. Subclasses
       * that support fields should override this and create an
       * <code>AttributedCharacterIterator</code> with meaningful attributes.
       *
       * @exception NullPointerException if obj is null.
       * @exception IllegalArgumentException when the Format cannot format the
       *            given object.
       * @param obj The object to format
       * @return AttributedCharacterIterator describing the formatted value.
       * @since 1.4
       */
      public AttributedCharacterIterator formatToCharacterIterator(Object obj) {
          return createAttributedCharacterIterator(format(obj));
      }
  
      /**
       * Parses text from a string to produce an object.
       * <p>
       * The method attempts to parse text starting at the index given by
       * <code>pos</code>.
       * If parsing succeeds, then the index of <code>pos</code> is updated
       * to the index after the last character used (parsing does not necessarily
       * use all characters up to the end of the string), and the parsed
       * object is returned. The updated <code>pos</code> can be used to
       * indicate the starting point for the next call to this method.
       * If an error occurs, then the index of <code>pos</code> is not
       * changed, the error index of <code>pos</code> is set to the index of
       * the character where the error occurred, and null is returned.
       *
       * @param source A <code>String</code>, part of which should be parsed.
       * @param pos A <code>ParsePosition</code> object with index and error
       *            index information as described above.
       * @return An <code>Object</code> parsed from the string. In case of
       *         error, returns null.
       * @exception NullPointerException if <code>pos</code> is null.
       */
      public abstract Object parseObject (String source, ParsePosition pos);
  
      /**
       * Parses text from the beginning of the given string to produce an object.
       * The method may not use the entire text of the given string.
       *
       * @param source A <code>String</code> whose beginning should be parsed.
       * @return An <code>Object</code> parsed from the string.
       * @exception ParseException if the beginning of the specified string
       *            cannot be parsed.
       */
      public Object parseObject(String source) throws ParseException {
          ParsePosition pos = new ParsePosition(0);
          Object result = parseObject(source, pos);
          if (pos.index == 0) {
              throw new ParseException("Format.parseObject(String) failed",
                  pos.errorIndex);
          }
          return result;
      }
  
      /**
       * Creates and returns a copy of this object.
       *
       * @return a clone of this instance.
       */
      public Object clone() {
          try {
              return super.clone();
          } catch (CloneNotSupportedException e) {
              // will never happen
              throw new InternalError(e);
          }
      }
  
      //
      // Convenience methods for creating AttributedCharacterIterators from
      // different parameters.
      //
  
      /**
       * Creates an <code>AttributedCharacterIterator</code> for the String
       * <code>s</code>.
       *
       * @param s String to create AttributedCharacterIterator from
       * @return AttributedCharacterIterator wrapping s
       */
      AttributedCharacterIterator createAttributedCharacterIterator(String s) {
          AttributedString as = new AttributedString(s);
  
          return as.getIterator();
      }
  
      /**
       * Creates an <code>AttributedCharacterIterator</code> containing the
       * concatenated contents of the passed in
       * <code>AttributedCharacterIterator</code>s.
       *
       * @param iterators AttributedCharacterIterators used to create resulting
       *                  AttributedCharacterIterators
       * @return AttributedCharacterIterator wrapping passed in
       *         AttributedCharacterIterators
       */
      AttributedCharacterIterator createAttributedCharacterIterator(
                         AttributedCharacterIterator[] iterators) {
          AttributedString as = new AttributedString(iterators);
  
          return as.getIterator();
      }
  
      /**
       * Returns an AttributedCharacterIterator with the String
       * <code>string</code> and additional key/value pair <code>key</code>,
       * <code>value</code>.
       *
       * @param string String to create AttributedCharacterIterator from
       * @param key Key for AttributedCharacterIterator
       * @param value Value associated with key in AttributedCharacterIterator
       * @return AttributedCharacterIterator wrapping args
       */
      AttributedCharacterIterator createAttributedCharacterIterator(
                        String string, AttributedCharacterIterator.Attribute key,
                        Object value) {
          AttributedString as = new AttributedString(string);
  
          as.addAttribute(key, value);
          return as.getIterator();
      }
  
      /**
       * Creates an AttributedCharacterIterator with the contents of
       * <code>iterator</code> and the additional attribute <code>key</code>
       * <code>value</code>.
       *
       * @param iterator Initial AttributedCharacterIterator to add arg to
       * @param key Key for AttributedCharacterIterator
       * @param value Value associated with key in AttributedCharacterIterator
       * @return AttributedCharacterIterator wrapping args
       */
      AttributedCharacterIterator createAttributedCharacterIterator(
                AttributedCharacterIterator iterator,
                AttributedCharacterIterator.Attribute key, Object value) {
          AttributedString as = new AttributedString(iterator);
  
          as.addAttribute(key, value);
          return as.getIterator();
      }
  
  
      /**
       * Defines constants that are used as attribute keys in the
       * <code>AttributedCharacterIterator</code> returned
       * from <code>Format.formatToCharacterIterator</code> and as
       * field identifiers in <code>FieldPosition</code>.
       *
       * @since 1.4
       */
      public static class Field extends AttributedCharacterIterator.Attribute {
  
          // Proclaim serial compatibility with 1.4 FCS
          private static final long serialVersionUID = 276966692217360283L;
  
          /**
           * Creates a Field with the specified name.
           *
           * @param name Name of the attribute
           */
          protected Field(String name) {
              super(name);
          }
      }
  
  
      /**
       * FieldDelegate is notified by the various <code>Format</code>
       * implementations as they are formatting the Objects. This allows for
       * storage of the individual sections of the formatted String for
       * later use, such as in a <code>FieldPosition</code> or for an
       * <code>AttributedCharacterIterator</code>.
       * <p>
       * Delegates should NOT assume that the <code>Format</code> will notify
       * the delegate of fields in any particular order.
       *
       * @see FieldPosition#getFieldDelegate
       * @see CharacterIteratorFieldDelegate
       */
      interface FieldDelegate {
          /**
           * Notified when a particular region of the String is formatted. This
           * method will be invoked if there is no corresponding integer field id
           * matching <code>attr</code>.
           *
           * @param attr Identifies the field matched
           * @param value Value associated with the field
           * @param start Beginning location of the field, will be >= 0
           * @param end End of the field, will be >= start and <= buffer.length()
           * @param buffer Contains current formatted value, receiver should
           *        NOT modify it.
           */
          public void formatted(Field attr, Object value, int start,
                                int end, StringBuffer buffer);
  
          /**
           * Notified when a particular region of the String is formatted.
           *
           * @param fieldID Identifies the field by integer
           * @param attr Identifies the field matched
           * @param value Value associated with the field
           * @param start Beginning location of the field, will be >= 0
           * @param end End of the field, will be >= start and <= buffer.length()
           * @param buffer Contains current formatted value, receiver should
           *        NOT modify it.
           */
          public void formatted(int fieldID, Field attr, Object value,
                                int start, int end, StringBuffer buffer);
      }
  }
  