/*
 * 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.commons.math.fraction;

import java.text.FieldPosition;
import java.text.NumberFormat;
import java.text.ParseException;
import java.text.ParsePosition;
import java.util.Locale;

import org.apache.commons.math.ConvergenceException;
import org.apache.commons.math.MathRuntimeException;

/**
 * Formats a Fraction number in proper format or improper format. The number
 * format for each of the whole number, numerator and, denominator can be
 * configured.
 *
 * @since 1.1
 * @version $Revision$ $Date$
 */
public class FractionFormat extends AbstractFormat {

	/** Serializable version identifier */
	private static final long serialVersionUID = 3008655719530972611L;

	/**
	 * Create an improper formatting instance with the default number format for
	 * the numerator and denominator.
	 */
	public FractionFormat() {
	}

	/**
	 * Create an improper formatting instance with a custom number format for
	 * both the numerator and denominator.
	 * 
	 * @param format
	 *            the custom format for both the numerator and denominator.
	 */
	public FractionFormat(final NumberFormat format) {
		super(format);
	}

	/**
	 * Create an improper formatting instance with a custom number format for
	 * the numerator and a custom number format for the denominator.
	 * 
	 * @param numeratorFormat
	 *            the custom format for the numerator.
	 * @param denominatorFormat
	 *            the custom format for the denominator.
	 */
	public FractionFormat(final NumberFormat numeratorFormat, final NumberFormat denominatorFormat) {
		super(numeratorFormat, denominatorFormat);
	}

	/**
	 * Get the set of locales for which complex formats are available. This is
	 * the same set as the {@link NumberFormat} set.
	 * 
	 * @return available complex format locales.
	 */
	public static Locale[] getAvailableLocales() {
		return NumberFormat.getAvailableLocales();
	}

	/**
	 * This static method calls formatFraction() on a default instance of
	 * FractionFormat.
	 *
	 * @param f
	 *            Fraction object to format
	 * @return A formatted fraction in proper form.
	 */
	public static String formatFraction(Fraction f) {
		return getImproperInstance().format(f);
	}

	/**
	 * Returns the default complex format for the current locale.
	 * 
	 * @return the default complex format.
	 */
	public static FractionFormat getImproperInstance() {
		return getImproperInstance(Locale.getDefault());
	}

	/**
	 * Returns the default complex format for the given locale.
	 * 
	 * @param locale
	 *            the specific locale used by the format.
	 * @return the complex format specific to the given locale.
	 */
	public static FractionFormat getImproperInstance(final Locale locale) {
		return new FractionFormat(getDefaultNumberFormat(locale));
	}

	/**
	 * Returns the default complex format for the current locale.
	 * 
	 * @return the default complex format.
	 */
	public static FractionFormat getProperInstance() {
		return getProperInstance(Locale.getDefault());
	}

	/**
	 * Returns the default complex format for the given locale.
	 * 
	 * @param locale
	 *            the specific locale used by the format.
	 * @return the complex format specific to the given locale.
	 */
	public static FractionFormat getProperInstance(final Locale locale) {
		return new ProperFractionFormat(getDefaultNumberFormat(locale));
	}

	/**
	 * Create a default number format. The default number format is based on
	 * {@link NumberFormat#getNumberInstance(java.util.Locale)} with the only
	 * customizing is the maximum number of fraction digits, which is set to 0.
	 * 
	 * @return the default number format.
	 */
	protected static NumberFormat getDefaultNumberFormat() {
		return getDefaultNumberFormat(Locale.getDefault());
	}

	/**
	 * Formats a {@link Fraction} object to produce a string. The fraction is
	 * output in improper format.
	 *
	 * @param fraction
	 *            the object to format.
	 * @param toAppendTo
	 *            where the text is to be appended
	 * @param pos
	 *            On input: an alignment field, if desired. On output: the
	 *            offsets of the alignment field
	 * @return the value passed in as toAppendTo.
	 */
	public StringBuffer format(final Fraction fraction, final StringBuffer toAppendTo, final FieldPosition pos) {

		pos.setBeginIndex(0);
		pos.setEndIndex(0);

		getNumeratorFormat().format(fraction.getNumerator(), toAppendTo, pos);
		toAppendTo.append(" / ");
		getDenominatorFormat().format(fraction.getDenominator(), toAppendTo, pos);

		return toAppendTo;
	}

	/**
	 * Formats an object and appends the result to a StringBuffer.
	 * <code>obj</code> must be either a {@link Fraction} object or a
	 * {@link Number} object. Any other type of object will result in an
	 * {@link IllegalArgumentException} being thrown.
	 *
	 * @param obj
	 *            the object to format.
	 * @param toAppendTo
	 *            where the text is to be appended
	 * @param pos
	 *            On input: an alignment field, if desired. On output: the
	 *            offsets of the alignment field
	 * @return the value passed in as toAppendTo.
	 * @see java.text.Format#format(java.lang.Object, java.lang.StringBuffer,
	 *      java.text.FieldPosition)
	 * @throws IllegalArgumentException
	 *             is <code>obj</code> is not a valid type.
	 */
	@Override
	public StringBuffer format(final Object obj, final StringBuffer toAppendTo, final FieldPosition pos) {
		StringBuffer ret = null;

		if (obj instanceof Fraction) {
			ret = format((Fraction) obj, toAppendTo, pos);
		} else if (obj instanceof Number) {
			try {
				ret = format(new Fraction(((Number) obj).doubleValue()), toAppendTo, pos);
			} catch (ConvergenceException ex) {
				throw MathRuntimeException.createIllegalArgumentException(
						"cannot convert given object to a fraction number: {0}", ex.getLocalizedMessage());
			}
		} else {
			throw MathRuntimeException
					.createIllegalArgumentException("cannot format given object as a fraction number");
		}

		return ret;
	}

	/**
	 * Parses a string to produce a {@link Fraction} object.
	 * 
	 * @param source
	 *            the string to parse
	 * @return the parsed {@link Fraction} object.
	 * @exception ParseException
	 *                if the beginning of the specified string cannot be parsed.
	 */
	@Override
	public Fraction parse(final String source) throws ParseException {
		final ParsePosition parsePosition = new ParsePosition(0);
		final Fraction result = parse(source, parsePosition);
		if (parsePosition.getIndex() == 0) {
			throw MathRuntimeException.createParseException(parsePosition.getErrorIndex(),
					"unparseable fraction number: \"{0}\"", source);
		}
		return result;
	}

	/**
	 * Parses a string to produce a {@link Fraction} object. This method expects
	 * the string to be formatted as an improper fraction.
	 * 
	 * @param source
	 *            the string to parse
	 * @param pos
	 *            input/ouput parsing parameter.
	 * @return the parsed {@link Fraction} object.
	 */
	@Override
	public Fraction parse(final String source, final ParsePosition pos) {
		final int initialIndex = pos.getIndex();

		// parse whitespace
		parseAndIgnoreWhitespace(source, pos);

		// parse numerator
		final Number num = getNumeratorFormat().parse(source, pos);
		if (num == null) {
			// invalid integer number
			// set index back to initial, error index should already be set
			// character examined.
			pos.setIndex(initialIndex);
			return null;
		}

		// parse '/'
		final int startIndex = pos.getIndex();
		final char c = parseNextCharacter(source, pos);
		switch (c) {
		case 0:
			// no '/'
			// return num as a fraction
			return new Fraction(num.intValue(), 1);
		case '/':
			// found '/', continue parsing denominator
			break;
		default:
			// invalid '/'
			// set index back to initial, error index should be the last
			// character examined.
			pos.setIndex(initialIndex);
			pos.setErrorIndex(startIndex);
			return null;
		}

		// parse whitespace
		parseAndIgnoreWhitespace(source, pos);

		// parse denominator
		final Number den = getDenominatorFormat().parse(source, pos);
		if (den == null) {
			// invalid integer number
			// set index back to initial, error index should already be set
			// character examined.
			pos.setIndex(initialIndex);
			return null;
		}

		return new Fraction(num.intValue(), den.intValue());
	}

}
