/*
 * 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.io.Serializable;
import java.math.BigInteger;
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.MathRuntimeException;

/**
 * Formats a BigFraction number in proper format or improper format.
 * <p>
 * The number format for each of the whole number, numerator and, denominator
 * can be configured.
 * </p>
 *
 * @since 2.0
 * @version $Revision$ $Date$
 */
public class BigFractionFormat extends AbstractFormat implements Serializable {

	/** Serializable version identifier */
	private static final long serialVersionUID = -2932167925527338976L;

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

	/**
	 * 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 BigFractionFormat(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 BigFractionFormat(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 formatBigFraction() on a default instance of
	 * BigFractionFormat.
	 *
	 * @param f
	 *            BigFraction object to format
	 * @return A formatted BigFraction in proper form.
	 */
	public static String formatBigFraction(final BigFraction f) {
		return getImproperInstance().format(f);
	}

	/**
	 * Returns the default complex format for the current locale.
	 * 
	 * @return the default complex format.
	 */
	public static BigFractionFormat 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 BigFractionFormat getImproperInstance(final Locale locale) {
		return new BigFractionFormat(getDefaultNumberFormat(locale));
	}

	/**
	 * Returns the default complex format for the current locale.
	 * 
	 * @return the default complex format.
	 */
	public static BigFractionFormat 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 BigFractionFormat getProperInstance(final Locale locale) {
		return new ProperBigFractionFormat(getDefaultNumberFormat(locale));
	}

	/**
	 * Formats a {@link BigFraction} object to produce a string. The BigFraction
	 * is output in improper format.
	 *
	 * @param BigFraction
	 *            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 BigFraction BigFraction, final StringBuffer toAppendTo, final FieldPosition pos) {

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

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

		return toAppendTo;
	}

	/**
	 * Formats an object and appends the result to a StringBuffer.
	 * <code>obj</code> must be either a {@link BigFraction} object or a
	 * {@link BigInteger} 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) {

		final StringBuffer ret;
		if (obj instanceof BigFraction) {
			ret = format((BigFraction) obj, toAppendTo, pos);
		} else if (obj instanceof BigInteger) {
			ret = format(new BigFraction((BigInteger) obj), toAppendTo, pos);
		} else if (obj instanceof Number) {
			ret = format(new BigFraction(((Number) obj).doubleValue()), toAppendTo, pos);
		} else {
			throw MathRuntimeException
					.createIllegalArgumentException("cannot format given object as a fraction number");
		}

		return ret;
	}

	/**
	 * Parses a string to produce a {@link BigFraction} object.
	 * 
	 * @param source
	 *            the string to parse
	 * @return the parsed {@link BigFraction} object.
	 * @exception ParseException
	 *                if the beginning of the specified string cannot be parsed.
	 */
	@Override
	public BigFraction parse(final String source) throws ParseException {
		final ParsePosition parsePosition = new ParsePosition(0);
		final BigFraction 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 BigFraction} object. This method
	 * expects the string to be formatted as an improper BigFraction.
	 * 
	 * @param source
	 *            the string to parse
	 * @param pos
	 *            input/ouput parsing parameter.
	 * @return the parsed {@link BigFraction} object.
	 */
	@Override
	public BigFraction parse(final String source, final ParsePosition pos) {
		final int initialIndex = pos.getIndex();

		// parse whitespace
		parseAndIgnoreWhitespace(source, pos);

		// parse numerator
		final BigInteger num = parseNextBigInteger(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 BigFraction
			return new BigFraction(num);
		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 BigInteger den = parseNextBigInteger(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 BigFraction(num, den);
	}

	/**
	 * Parses a string to produce a <code>BigInteger</code>.
	 * 
	 * @param source
	 *            the string to parse
	 * @param pos
	 *            input/ouput parsing parameter.
	 * @return a parsed <code>BigInteger</code> or null if string does not
	 *         contain a BigInteger at the specified position
	 */
	protected BigInteger parseNextBigInteger(final String source, final ParsePosition pos) {

		final int start = pos.getIndex();
		int end = (source.charAt(start) == '-') ? (start + 1) : start;
		while ((end < source.length()) && Character.isDigit(source.charAt(end))) {
			++end;
		}

		try {
			BigInteger n = new BigInteger(source.substring(start, end));
			pos.setIndex(end);
			return n;
		} catch (NumberFormatException nfe) {
			pos.setErrorIndex(start);
			return null;
		}

	}

}
