/*
 * 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.lang.text;

import java.text.Format;
import java.text.MessageFormat;
import java.text.ParsePosition;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.Locale;
import java.util.Map;

import org.apache.commons.lang.Validate;

/**
 * Extends <code>java.text.MessageFormat</code> to allow pluggable/additional formatting
 * options for embedded format elements.  Client code should specify a registry
 * of <code>FormatFactory</code> instances associated with <code>String</code>
 * format names.  This registry will be consulted when the format elements are 
 * parsed from the message pattern.  In this way custom patterns can be specified,
 * and the formats supported by <code>java.text.MessageFormat</code> can be overridden
 * at the format and/or format style level (see MessageFormat).  A "format element"
 * embedded in the message pattern is specified (<b>()?</b> signifies optionality):<br />
 * <code>{</code><i>argument-number</i><b>(</b><code>,</code><i>format-name</i><b>(</b><code>,</code><i>format-style</i><b>)?)?</b><code>}</code>
 *
 * <p>
 * <i>format-name</i> and <i>format-style</i> values are trimmed of surrounding whitespace
 * in the manner of <code>java.text.MessageFormat</code>.  If <i>format-name</i> denotes
 * <code>FormatFactory formatFactoryInstance</code> in <code>registry</code>, a <code>Format</code>
 * matching <i>format-name</i> and <i>format-style</i> is requested from
 * <code>formatFactoryInstance</code>.  If this is successful, the <code>Format</code>
 * found is used for this format element.
 * </p>
 *
 * <p>NOTICE: The various subformat mutator methods are considered unnecessary; they exist on the parent
 * class to allow the type of customization which it is the job of this class to provide in
 * a configurable fashion.  These methods have thus been disabled and will throw
 * <code>UnsupportedOperationException</code> if called.
 * </p>
 * 
 * <p>Limitations inherited from <code>java.text.MessageFormat</code>:
 * <ul>
 * <li>When using "choice" subformats, support for nested formatting instructions is limited
 *     to that provided by the base class.</li>
 * <li>Thread-safety of <code>Format</code>s, including <code>MessageFormat</code> and thus
 *     <code>ExtendedMessageFormat</code>, is not guaranteed.</li>
 * </ul>
 * </p>
 * 
 * @author Matt Benson
 * @author Niall Pemberton
 * @since 2.4
 * @version $Id$
 */
public class ExtendedMessageFormat extends MessageFormat {
    private static final long serialVersionUID = -2362048321261811743L;

    private static final String DUMMY_PATTERN = "";
    private static final String ESCAPED_QUOTE = "''";
    private static final char START_FMT = ',';
    private static final char END_FE = '}';
    private static final char START_FE = '{';
    private static final char QUOTE = '\'';

    private String toPattern;
    private Map registry;

    /**
     * Create a new ExtendedMessageFormat for the default locale.
     * 
     * @param pattern String
     * @throws IllegalArgumentException in case of a bad pattern.
     */
    public ExtendedMessageFormat(String pattern) {
        this(pattern, Locale.getDefault());
    }

    /**
     * Create a new ExtendedMessageFormat.
     * 
     * @param pattern String
     * @param locale Locale
     * @throws IllegalArgumentException in case of a bad pattern.
     */
    public ExtendedMessageFormat(String pattern, Locale locale) {
        this(pattern, locale, null);
    }

    /**
     * Create a new ExtendedMessageFormat for the default locale.
     * 
     * @param pattern String
     * @param registry Registry of format factories:  Map<String, FormatFactory>
     * @throws IllegalArgumentException in case of a bad pattern.
     */
    public ExtendedMessageFormat(String pattern, Map registry) {
        this(pattern, Locale.getDefault(), registry);
    }

    /**
     * Create a new ExtendedMessageFormat.
     * 
     * @param pattern String
     * @param locale Locale
     * @param registry Registry of format factories:  Map<String, FormatFactory>
     * @throws IllegalArgumentException in case of a bad pattern.
     */
    public ExtendedMessageFormat(String pattern, Locale locale, Map registry) {
        super(DUMMY_PATTERN);
        setLocale(locale);
        this.registry = registry;
        applyPattern(pattern);
    }

    /**
     * {@inheritDoc}
     */
    public String toPattern() {
        return toPattern;
    }

    /**
     * Apply the specified pattern.
     * 
     * @param pattern String
     */
    public final void applyPattern(String pattern) {
        if (registry == null) {
            super.applyPattern(pattern);
            toPattern = super.toPattern();
            return;
        }
        ArrayList foundFormats = new ArrayList();
        ArrayList foundDescriptions = new ArrayList();
        StringBuffer stripCustom = new StringBuffer(pattern.length());

        ParsePosition pos = new ParsePosition(0);
        char[] c = pattern.toCharArray();
        int fmtCount = 0;
        while (pos.getIndex() < pattern.length()) {
            switch (c[pos.getIndex()]) {
            case QUOTE:
                appendQuotedString(pattern, pos, stripCustom, true);
                break;
            case START_FE:
                fmtCount++;
                seekNonWs(pattern, pos);
                int start = pos.getIndex();
                int index = readArgumentIndex(pattern, next(pos));
                stripCustom.append(START_FE).append(index);
                seekNonWs(pattern, pos);
                Format format = null;
                String formatDescription = null;
                if (c[pos.getIndex()] == START_FMT) {
                    formatDescription = parseFormatDescription(pattern,
                            next(pos));
                    format = getFormat(formatDescription);
                    if (format == null) {
                        stripCustom.append(START_FMT).append(formatDescription);
                    }
                }
                foundFormats.add(format);
                foundDescriptions.add(format == null ? null : formatDescription);
                Validate.isTrue(foundFormats.size() == fmtCount);
                Validate.isTrue(foundDescriptions.size() == fmtCount);
                if (c[pos.getIndex()] != END_FE) {
                    throw new IllegalArgumentException(
                            "Unreadable format element at position " + start);
                }
                // fall through
            default:
                stripCustom.append(c[pos.getIndex()]);
                next(pos);
            }
        }
        super.applyPattern(stripCustom.toString());
        toPattern = insertFormats(super.toPattern(), foundDescriptions);
        if (containsElements(foundFormats)) {
            Format[] origFormats = getFormats();
            // only loop over what we know we have, as MessageFormat on Java 1.3 
            // seems to provide an extra format element:
            int i = 0;
            for (Iterator it = foundFormats.iterator(); it.hasNext(); i++) {
                Format f = (Format) it.next();
                if (f != null) {
                    origFormats[i] = f;
                }
            }
            super.setFormats(origFormats);
        }
    }

    /**
     * {@inheritDoc}
     * @throws UnsupportedOperationException
     */
    public void setFormat(int formatElementIndex, Format newFormat) {
        throw new UnsupportedOperationException();
    }

    /**
     * {@inheritDoc}
     * @throws UnsupportedOperationException
     */
    public void setFormatByArgumentIndex(int argumentIndex, Format newFormat) {
        throw new UnsupportedOperationException();
    }

    /**
     * {@inheritDoc}
     * @throws UnsupportedOperationException
     */
    public void setFormats(Format[] newFormats) {
        throw new UnsupportedOperationException();
    }

    /**
     * {@inheritDoc}
     * @throws UnsupportedOperationException
     */
    public void setFormatsByArgumentIndex(Format[] newFormats) {
        throw new UnsupportedOperationException();
    }

    /**
     * Get a custom format from a format description.
     * 
     * @param desc String
     * @return Format
     */
    private Format getFormat(String desc) {
        if (registry != null) {
            String name = desc;
            String args = null;
            int i = desc.indexOf(START_FMT);
            if (i > 0) {
                name = desc.substring(0, i).trim();
                args = desc.substring(i + 1).trim();
            }
            FormatFactory factory = (FormatFactory) registry.get(name);
            if (factory != null) {
                return factory.getFormat(name, args, getLocale());
            }
        }
        return null;
    }

    /**
     * Read the argument index from the current format element
     * 
     * @param pattern pattern to parse
     * @param pos current parse position
     * @return argument index
     */
    private int readArgumentIndex(String pattern, ParsePosition pos) {
        int start = pos.getIndex();
        seekNonWs(pattern, pos);
        StringBuffer result = new StringBuffer();
        boolean error = false;
        for (; !error && pos.getIndex() < pattern.length(); next(pos)) {
            char c = pattern.charAt(pos.getIndex());
            if (Character.isWhitespace(c)) {
                seekNonWs(pattern, pos);
                c = pattern.charAt(pos.getIndex());
                if (c != START_FMT && c != END_FE) {
                    error = true;
                    continue;
                }
            }
            if ((c == START_FMT || c == END_FE) && result.length() > 0) {
                try {
                    return Integer.parseInt(result.toString());
                } catch (NumberFormatException e) {
                    // we've already ensured only digits, so unless something
                    // outlandishly large was specified we should be okay.
                }
            }
            error = !Character.isDigit(c);
            result.append(c);
        }
        if (error) {
            throw new IllegalArgumentException(
                    "Invalid format argument index at position " + start + ": "
                            + pattern.substring(start, pos.getIndex()));
        }
        throw new IllegalArgumentException(
                "Unterminated format element at position " + start);
    }

    /**
     * Parse the format component of a format element.
     * 
     * @param pattern string to parse
     * @param pos current parse position
     * @return Format description String
     */
    private String parseFormatDescription(String pattern, ParsePosition pos) {
        int start = pos.getIndex();
        seekNonWs(pattern, pos);
        int text = pos.getIndex();
        int depth = 1;
        for (; pos.getIndex() < pattern.length(); next(pos)) {
            switch (pattern.charAt(pos.getIndex())) {
            case START_FE:
                depth++;
                break;
            case END_FE:
                depth--;
                if (depth == 0) {
                    return pattern.substring(text, pos.getIndex());
                }
                break;
            case QUOTE:
                getQuotedString(pattern, pos, false);
                break;
            }
        }
        throw new IllegalArgumentException(
                "Unterminated format element at position " + start);
    }

    /**
     * Insert formats back into the pattern for toPattern() support.
     *
     * @param pattern source
     * @param customPatterns The custom patterns to re-insert, if any
     * @return full pattern
     */
    private String insertFormats(String pattern, ArrayList customPatterns) {
        if (!containsElements(customPatterns)) {
            return pattern;
        }
        StringBuffer sb = new StringBuffer(pattern.length() * 2);
        ParsePosition pos = new ParsePosition(0);
        int fe = -1;
        int depth = 0;
        while (pos.getIndex() < pattern.length()) {
            char c = pattern.charAt(pos.getIndex());
            switch (c) {
            case QUOTE:
                appendQuotedString(pattern, pos, sb, false);
                break;
            case START_FE:
                depth++;
                if (depth == 1) {
                    fe++;
                    sb.append(START_FE).append(
                            readArgumentIndex(pattern, next(pos)));
                    String customPattern = (String) customPatterns.get(fe);
                    if (customPattern != null) {
                        sb.append(START_FMT).append(customPattern);
                    }
                }
                break;
            case END_FE:
                depth--;
                //fall through:
            default:
                sb.append(c);
                next(pos);
            }
        }
        return sb.toString();
    }

    /**
     * Consume whitespace from the current parse position.
     * 
     * @param pattern String to read
     * @param pos current position
     */
    private void seekNonWs(String pattern, ParsePosition pos) {
        int len = 0;
        char[] buffer = pattern.toCharArray();
        do {
            len = StrMatcher.splitMatcher().isMatch(buffer, pos.getIndex());
            pos.setIndex(pos.getIndex() + len);
        } while (len > 0 && pos.getIndex() < pattern.length());
    }

    /**
     * Convenience method to advance parse position by 1
     * 
     * @param pos ParsePosition
     * @return <code>pos</code>
     */
    private ParsePosition next(ParsePosition pos) {
        pos.setIndex(pos.getIndex() + 1);
        return pos;
    }

    /**
     * Consume a quoted string, adding it to <code>appendTo</code> if
     * specified.
     * 
     * @param pattern pattern to parse
     * @param pos current parse position
     * @param appendTo optional StringBuffer to append
     * @param escapingOn whether to process escaped quotes
     * @return <code>appendTo</code>
     */
    private StringBuffer appendQuotedString(String pattern, ParsePosition pos,
            StringBuffer appendTo, boolean escapingOn) {
        int start = pos.getIndex();
        char[] c = pattern.toCharArray();
        if (escapingOn && c[start] == QUOTE) {
            return appendTo == null ? null : appendTo.append(QUOTE);
        }
        int lastHold = start;
        for (int i = pos.getIndex(); i < pattern.length(); i++) {
            if (escapingOn && pattern.substring(i).startsWith(ESCAPED_QUOTE)) {
                appendTo.append(c, lastHold, pos.getIndex() - lastHold).append(
                        QUOTE);
                pos.setIndex(i + ESCAPED_QUOTE.length());
                lastHold = pos.getIndex();
                continue;
            }
            switch (c[pos.getIndex()]) {
            case QUOTE:
                next(pos);
                return appendTo == null ? null : appendTo.append(c, lastHold,
                        pos.getIndex() - lastHold);
            default:
                next(pos);
            }
        }
        throw new IllegalArgumentException(
                "Unterminated quoted string at position " + start);
    }

    /**
     * Consume quoted string only
     * 
     * @param pattern pattern to parse
     * @param pos current parse position
     * @param escapingOn whether to process escaped quotes
     */
    private void getQuotedString(String pattern, ParsePosition pos,
            boolean escapingOn) {
        appendQuotedString(pattern, pos, null, escapingOn);
    }

    /**
     * Learn whether the specified Collection contains non-null elements.
     * @param coll to check
     * @return <code>true</code> if some Object was found, <code>false</code> otherwise.
     */
    private boolean containsElements(Collection coll) {
        if (coll == null || coll.size() == 0) {
            return false;
        }
        for (Iterator iter = coll.iterator(); iter.hasNext();) {
            if (iter.next() != null) {
                return true;
            }
        }
        return false;
    }
}