/*
 * 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.linear;

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

import org.apache.commons.math.MathRuntimeException;
import org.apache.commons.math.util.CompositeFormat;

/**
 * Formats a vector in components list format "{v0; v1; ...; vk-1}".
 * <p>
 * The prefix and suffix "{" and "}" and the separator "; " can be replaced by
 * any user-defined strings. The number format for components can be configured.
 * </p>
 * <p>
 * White space is ignored at parse time, even if it is in the prefix, suffix or
 * separator specifications. So even if the default separator does include a
 * space character that is used at format time, both input string "{1;1;1}" and
 * " { 1 ; 1 ; 1 } " will be parsed without error and the same vector will be
 * returned. In the second case, however, the parse position after parsing will
 * be just after the closing curly brace, i.e. just before the trailing space.
 * </p>
 *
 * @version $Revision$ $Date$
 * @since 2.0
 */
public class RealVectorFormat extends CompositeFormat {

	/** Serializable version identifier */
	private static final long serialVersionUID = -708767813036157690L;

	/** The default prefix: "{". */
	private static final String DEFAULT_PREFIX = "{";

	/** The default suffix: "}". */
	private static final String DEFAULT_SUFFIX = "}";

	/** The default separator: ", ". */
	private static final String DEFAULT_SEPARATOR = "; ";

	/** Prefix. */
	private final String prefix;

	/** Suffix. */
	private final String suffix;

	/** Separator. */
	private final String separator;

	/** Trimmed prefix. */
	private final String trimmedPrefix;

	/** Trimmed suffix. */
	private final String trimmedSuffix;

	/** Trimmed separator. */
	private final String trimmedSeparator;

	/** The format used for components. */
	private NumberFormat format;

	/**
	 * Create an instance with default settings.
	 * <p>
	 * The instance uses the default prefix, suffix and separator: "{", "}", and
	 * "; " and the default number format for components.
	 * </p>
	 */
	public RealVectorFormat() {
		this(DEFAULT_PREFIX, DEFAULT_SUFFIX, DEFAULT_SEPARATOR, getDefaultNumberFormat());
	}

	/**
	 * Create an instance with a custom number format for components.
	 * 
	 * @param format
	 *            the custom format for components.
	 */
	public RealVectorFormat(final NumberFormat format) {
		this(DEFAULT_PREFIX, DEFAULT_SUFFIX, DEFAULT_SEPARATOR, format);
	}

	/**
	 * Create an instance with custom prefix, suffix and separator.
	 * 
	 * @param prefix
	 *            prefix to use instead of the default "{"
	 * @param suffix
	 *            suffix to use instead of the default "}"
	 * @param separator
	 *            separator to use instead of the default "; "
	 */
	public RealVectorFormat(final String prefix, final String suffix, final String separator) {
		this(prefix, suffix, separator, getDefaultNumberFormat());
	}

	/**
	 * Create an instance with custom prefix, suffix, separator and format for
	 * components.
	 * 
	 * @param prefix
	 *            prefix to use instead of the default "{"
	 * @param suffix
	 *            suffix to use instead of the default "}"
	 * @param separator
	 *            separator to use instead of the default "; "
	 * @param format
	 *            the custom format for components.
	 */
	public RealVectorFormat(final String prefix, final String suffix, final String separator,
			final NumberFormat format) {
		this.prefix = prefix;
		this.suffix = suffix;
		this.separator = separator;
		trimmedPrefix = prefix.trim();
		trimmedSuffix = suffix.trim();
		trimmedSeparator = separator.trim();
		this.format = format;
	}

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

	/**
	 * Get the format prefix.
	 * 
	 * @return format prefix.
	 */
	public String getPrefix() {
		return prefix;
	}

	/**
	 * Get the format suffix.
	 * 
	 * @return format suffix.
	 */
	public String getSuffix() {
		return suffix;
	}

	/**
	 * Get the format separator between components.
	 * 
	 * @return format separator.
	 */
	public String getSeparator() {
		return separator;
	}

	/**
	 * Get the components format.
	 * 
	 * @return components format.
	 */
	public NumberFormat getFormat() {
		return format;
	}

	/**
	 * Returns the default real vector format for the current locale.
	 * 
	 * @return the default real vector format.
	 */
	public static RealVectorFormat getInstance() {
		return getInstance(Locale.getDefault());
	}

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

	/**
	 * This static method calls {@link #format(Object)} on a default instance of
	 * RealVectorFormat.
	 *
	 * @param v
	 *            RealVector object to format
	 * @return A formatted vector
	 */
	public static String formatRealVector(RealVector v) {
		return getInstance().format(v);
	}

	/**
	 * Formats a {@link RealVector} object to produce a string.
	 * 
	 * @param vector
	 *            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(RealVector vector, StringBuffer toAppendTo, FieldPosition pos) {

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

		// format prefix
		toAppendTo.append(prefix);

		// format components
		for (int i = 0; i < vector.getDimension(); ++i) {
			if (i > 0) {
				toAppendTo.append(separator);
			}
			formatDouble(vector.getEntry(i), format, toAppendTo, pos);
		}

		// format suffix
		toAppendTo.append(suffix);

		return toAppendTo;

	}

	/**
	 * Formats a object to produce a string.
	 * <p>
	 * <code>obj</code> must be a {@link RealVector} object. Any other type of
	 * object will result in an {@link IllegalArgumentException} being thrown.
	 * </p>
	 * 
	 * @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(Object obj, StringBuffer toAppendTo, FieldPosition pos) {

		if (obj instanceof RealVector) {
			return format((RealVector) obj, toAppendTo, pos);
		}

		throw MathRuntimeException.createIllegalArgumentException("cannot format a {0} instance as a real vector",
				obj.getClass().getName());

	}

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

	/**
	 * Parses a string to produce a {@link RealVector} object.
	 * 
	 * @param source
	 *            the string to parse
	 * @param pos
	 *            input/ouput parsing parameter.
	 * @return the parsed {@link RealVector} object.
	 */
	public ArrayRealVector parse(String source, ParsePosition pos) {
		int initialIndex = pos.getIndex();

		// parse prefix
		parseAndIgnoreWhitespace(source, pos);
		if (!parseFixedstring(source, trimmedPrefix, pos)) {
			return null;
		}

		// parse components
		List<Number> components = new ArrayList<Number>();
		for (boolean loop = true; loop;) {

			if (!components.isEmpty()) {
				parseAndIgnoreWhitespace(source, pos);
				if (!parseFixedstring(source, trimmedSeparator, pos)) {
					loop = false;
				}
			}

			if (loop) {
				parseAndIgnoreWhitespace(source, pos);
				Number component = parseNumber(source, format, pos);
				if (component != null) {
					components.add(component);
				} else {
					// invalid component
					// set index back to initial, error index should already be
					// set
					pos.setIndex(initialIndex);
					return null;
				}
			}

		}

		// parse suffix
		parseAndIgnoreWhitespace(source, pos);
		if (!parseFixedstring(source, trimmedSuffix, pos)) {
			return null;
		}

		// build vector
		double[] data = new double[components.size()];
		for (int i = 0; i < data.length; ++i) {
			data[i] = components.get(i).doubleValue();
		}
		return new ArrayRealVector(data, false);

	}

	/**
	 * Parses a string to produce a object.
	 * 
	 * @param source
	 *            the string to parse
	 * @param pos
	 *            input/ouput parsing parameter.
	 * @return the parsed object.
	 * @see java.text.Format#parseObject(java.lang.String,
	 *      java.text.ParsePosition)
	 */
	@Override
	public Object parseObject(String source, ParsePosition pos) {
		return parse(source, pos);
	}

}
