package org.rubypeople.rdt.internal.ui.util;

import java.util.Vector;

/**
 * A string pattern matcher, suppporting * and ? wildcards.
 */
public 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)
			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) {
		if (null == text)
			throw new IllegalArgumentException();
		return match(text, 0, text.length());
	}
	/**
	 * Given the starting (inclusive) and the ending (exclusive) positions 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;
			}
			++i;
			tCurPos= tCurPos + segLength;
		}

		/* process middle segments */	
		while (i < segCount) {
			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();
			i++;
		}

		/* 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= start; i <= max; ++i) {
			if (text.regionMatches(true, i, p, 0, plen))
				return i;
		}
		
		return -1;
	}
}