/*******************************************************************************
 * Copyright (c) 2000, 2004 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.ui.views.navigator;

import java.util.Vector;

/**
 * A string pattern matcher, suppporting ?*? and ??? wildcards.
 */
/* package */class StringMatcher {
    protected String fPattern;

    protected int fLength; // pattern length

    protected boolean fIgnoreWildCards;

    protected boolean fIgnoreCase;

    protected boolean fHasLeadingStar;

    protected boolean fHasTrailingStar;

    protected String fSegments[]; //the given pattern is split into * separated segments

    /* boundary value beyond which we don't need to search in the text */
    protected int fBound = 0;

    protected static final char fSingleWildCard = '\u0000';

    public static class Position {
        int start; //inclusive

        int end; //exclusive

        public Position(int start, int end) {
            this.start = start;
            this.end = end;
        }

        public int getStart() {
            return start;
        }

        public int getEnd() {
            return end;
        }
    }

    /**
     * StringMatcher constructor takes in a String object that is a simple 
     * pattern which may contain '*' for 0 and many characters and
     * '?' for exactly one character.  
     *
     * Literal '*' and '?' characters must be escaped in the pattern 
     * e.g., "\*" means literal "*", etc.
     *
     * Escaping any other character (including the escape character itself), 
     * just results in that character in the pattern.
     * e.g., "\a" means "a" and "\\" means "\"
     *
     * If invoking the StringMatcher with string literals in Java, don't forget
     * escape characters are represented by "\\".
     *
     * @param pattern the pattern to match text against
     * @param ignoreCase if true, case is ignored
     * @param ignoreWildCards if true, wild cards and their escape sequences are ignored
     * 		  (everything is taken literally).
     */
    public StringMatcher(String pattern, boolean ignoreCase,
            boolean ignoreWildCards) {
        if (pattern == null)
            throw new IllegalArgumentException();
        fIgnoreCase = ignoreCase;
        fIgnoreWildCards = ignoreWildCards;
        fPattern = pattern;
        fLength = pattern.length();

        if (fIgnoreWildCards) {
            parseNoWildCards();
        } else {
            parseWildCards();
        }
    }

    /**
     * Find the first occurrence of the pattern between <code>start</code)(inclusive) 
     * and <code>end</code>(exclusive).  
     * @param <code>text</code>, the String object to search in 
     * @param <code>start</code>, the starting index of the search range, inclusive
     * @param <code>end</code>, the ending index of the search range, exclusive
     * @return an <code>StringMatcher.Position</code> object that keeps the starting 
     * (inclusive) and ending positions (exclusive) of the first occurrence of the 
     * pattern in the specified range of the text; return null if not found or subtext
     * is empty (start==end). A pair of zeros is returned if pattern is empty string
     * Note that for pattern like "*abc*" with leading and trailing stars, position of "abc"
     * is returned. For a pattern like"*??*" in text "abcdf", (1,3) is returned
     */
    public StringMatcher.Position find(String text, int start, int end) {
        if (text == null)
            throw new IllegalArgumentException();

        int tlen = text.length();
        if (start < 0)
            start = 0;
        if (end > tlen)
            end = tlen;
        if (end < 0 || start >= end)
            return null;
        if (fLength == 0)
            return new Position(start, start);
        if (fIgnoreWildCards) {
            int x = posIn(text, start, end);
            if (x < 0)
                return null;
            return new Position(x, x + fLength);
        }

        int segCount = fSegments.length;
        if (segCount == 0)//pattern contains only '*'(s)
            return new Position(start, end);

        int curPos = start;
        int matchStart = -1;
        int i;
        for (i = 0; i < segCount && curPos < end; ++i) {
            String current = fSegments[i];
            int nextMatch = regExpPosIn(text, curPos, end, current);
            if (nextMatch < 0)
                return null;
            if (i == 0)
                matchStart = nextMatch;
            curPos = nextMatch + current.length();
        }
        if (i < segCount) // Ensure all segments match
            return null;
        return new Position(matchStart, curPos);
    }

    /**
     * match the given <code>text</code> with the pattern 
     * @return true if matched eitherwise false
     * @param <code>text</code>, a String object 
     */
    public boolean match(String text) {
        return match(text, 0, text.length());
    }

    /**
     * Given the starting (inclusive) and the ending (exclusive) poisitions in the   
     * <code>text</code>, determine if the given substring matches with aPattern  
     * @return true if the specified portion of the text matches the pattern
     * @param String <code>text</code>, a String object that contains the substring to match 
     * @param int <code>start<code> marks the starting position (inclusive) of the substring
     * @param int <code>end<code> marks the ending index (exclusive) of the substring 
     */
    public boolean match(String text, int start, int end) {
        if (null == text)
            throw new IllegalArgumentException();

        if (start > end)
            return false;

        if (fIgnoreWildCards)
            return (end - start == fLength)
                    && fPattern.regionMatches(fIgnoreCase, 0, text, start,
                            fLength);
        int segCount = fSegments.length;
        if (segCount == 0 && (fHasLeadingStar || fHasTrailingStar)) // pattern contains only '*'(s)
            return true;
        if (start == end)
            return fLength == 0;
        if (fLength == 0)
            return start == end;

        int tlen = text.length();
        if (start < 0)
            start = 0;
        if (end > tlen)
            end = tlen;

        int tCurPos = start;
        int bound = end - fBound;
        if (bound < 0)
            return false;
        int i = 0;
        String current = fSegments[i];
        int segLength = current.length();

        /* process first segment */
        if (!fHasLeadingStar) {
            if (!regExpRegionMatches(text, start, current, 0, segLength)) {
                return false;
            } else {
                ++i;
                tCurPos = tCurPos + segLength;
            }
        }
        if ((fSegments.length == 1) && (!fHasLeadingStar)
                && (!fHasTrailingStar)) {
            // only one segment to match, no wildcards specified
            return tCurPos == end;
        }
        /* process middle segments */
        for (; i < segCount && tCurPos <= bound; ++i) {
            current = fSegments[i];
            int currentMatch;
            int k = current.indexOf(fSingleWildCard);
            if (k < 0) {
                currentMatch = textPosIn(text, tCurPos, end, current);
                if (currentMatch < 0)
                    return false;
            } else {
                currentMatch = regExpPosIn(text, tCurPos, end, current);
                if (currentMatch < 0)
                    return false;
            }
            tCurPos = currentMatch + current.length();
        }

        /* process final segment */
        if (!fHasTrailingStar && tCurPos != end) {
            int clen = current.length();
            return regExpRegionMatches(text, end - clen, current, 0, clen);
        }
        return i == segCount;
    }

    /**
     * This method parses the given pattern into segments seperated by wildcard '*' characters.
     * Since wildcards are not being used in this case, the pattern consists of a single segment.
     */
    private void parseNoWildCards() {
        fSegments = new String[1];
        fSegments[0] = fPattern;
        fBound = fLength;
    }

    /**
     * Parses the given pattern into segments seperated by wildcard '*' characters.
     * @param p, a String object that is a simple regular expression with '*' and/or '?'
     */
    private void parseWildCards() {
        if (fPattern.startsWith("*"))//$NON-NLS-1$
            fHasLeadingStar = true;
        if (fPattern.endsWith("*")) {//$NON-NLS-1$
            /* make sure it's not an escaped wildcard */
            if (fLength > 1 && fPattern.charAt(fLength - 2) != '\\') {
                fHasTrailingStar = true;
            }
        }

        Vector temp = new Vector();

        int pos = 0;
        StringBuffer buf = new StringBuffer();
        while (pos < fLength) {
            char c = fPattern.charAt(pos++);
            switch (c) {
            case '\\':
                if (pos >= fLength) {
                    buf.append(c);
                } else {
                    char next = fPattern.charAt(pos++);
                    /* if it's an escape sequence */
                    if (next == '*' || next == '?' || next == '\\') {
                        buf.append(next);
                    } else {
                        /* not an escape sequence, just insert literally */
                        buf.append(c);
                        buf.append(next);
                    }
                }
                break;
            case '*':
                if (buf.length() > 0) {
                    /* new segment */
                    temp.addElement(buf.toString());
                    fBound += buf.length();
                    buf.setLength(0);
                }
                break;
            case '?':
                /* append special character representing single match wildcard */
                buf.append(fSingleWildCard);
                break;
            default:
                buf.append(c);
            }
        }

        /* add last buffer to segment list */
        if (buf.length() > 0) {
            temp.addElement(buf.toString());
            fBound += buf.length();
        }

        fSegments = new String[temp.size()];
        temp.copyInto(fSegments);
    }

    /** 
     * @param <code>text</code>, a string which contains no wildcard
     * @param <code>start</code>, the starting index in the text for search, inclusive
     * @param <code>end</code>, the stopping point of search, exclusive
     * @return the starting index in the text of the pattern , or -1 if not found 
     */
    protected int posIn(String text, int start, int end) {//no wild card in pattern
        int max = end - fLength;

        if (!fIgnoreCase) {
            int i = text.indexOf(fPattern, start);
            if (i == -1 || i > max)
                return -1;
            return i;
        }

        for (int i = start; i <= max; ++i) {
            if (text.regionMatches(true, i, fPattern, 0, fLength))
                return i;
        }

        return -1;
    }

    /** 
     * @param <code>text</code>, a simple regular expression that may only contain '?'(s)
     * @param <code>start</code>, the starting index in the text for search, inclusive
     * @param <code>end</code>, the stopping point of search, exclusive
     * @param <code>p</code>, a simple regular expression that may contains '?'
     * @param <code>caseIgnored</code>, wether the pattern is not casesensitive
     * @return the starting index in the text of the pattern , or -1 if not found 
     */
    protected int regExpPosIn(String text, int start, int end, String p) {
        int plen = p.length();

        int max = end - plen;
        for (int i = start; i <= max; ++i) {
            if (regExpRegionMatches(text, i, p, 0, plen))
                return i;
        }
        return -1;
    }

    /**
     * 
     * @return boolean
     * @param <code>text</code>, a String to match
     * @param <code>start</code>, int that indicates the starting index of match, inclusive
     * @param <code>end</code> int that indicates the ending index of match, exclusive
     * @param <code>p</code>, String,  String, a simple regular expression that may contain '?'
     * @param <code>ignoreCase</code>, boolean indicating wether code>p</code> is case sensitive
     */
    protected boolean regExpRegionMatches(String text, int tStart, String p,
            int pStart, int plen) {
        while (plen-- > 0) {
            char tchar = text.charAt(tStart++);
            char pchar = p.charAt(pStart++);

            /* process wild cards */
            if (!fIgnoreWildCards) {
                /* skip single wild cards */
                if (pchar == fSingleWildCard) {
                    continue;
                }
            }
            if (pchar == tchar)
                continue;
            if (fIgnoreCase) {
                if (Character.toUpperCase(tchar) == Character
                        .toUpperCase(pchar))
                    continue;
                // comparing after converting to upper case doesn't handle all cases;
                // also compare after converting to lower case
                if (Character.toLowerCase(tchar) == Character
                        .toLowerCase(pchar))
                    continue;
            }
            return false;
        }
        return true;
    }

    /** 
     * @param <code>text</code>, the string to match
     * @param <code>start</code>, the starting index in the text for search, inclusive
     * @param <code>end</code>, the stopping point of search, exclusive
     * @param code>p</code>, a string that has no wildcard
     * @param <code>ignoreCase</code>, boolean indicating wether code>p</code> is case sensitive
     * @return the starting index in the text of the pattern , or -1 if not found 
     */
    protected int textPosIn(String text, int start, int end, String p) {

        int plen = p.length();
        int max = end - plen;

        if (!fIgnoreCase) {
            int i = text.indexOf(p, start);
            if (i == -1 || i > max)
                return -1;
            return i;
        }

        for (int i = 0; i <= max; ++i) {
            if (text.regionMatches(true, i, p, 0, plen))
                return i;
        }

        return -1;
    }
}