/*
    * Copyright (C) 2009, Google Inc.
    * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org> and others
    *
    * This program and the accompanying materials are made available under the
    * terms of the Eclipse Distribution License v. 1.0 which is available at
    * https://www.eclipse.org/org/documents/edl-v10.php.
    *
    * SPDX-License-Identifier: BSD-3-Clause
   */
  
  package org.eclipse.jgit.util;
  
  import org.eclipse.jgit.internal.JGitText;
  import org.eclipse.jgit.lib.Constants;
  
  /**
   * Searches text using only substring search.
   * <p>
   * Instances are thread-safe. Multiple concurrent threads may perform matches on
   * different character sequences at the same time.
   */
  public class RawSubStringPattern {
  	private final String needleString;
  
  	private final byte[] needle;
  
  	/**
  	 * Construct a new substring pattern.
  	 *
  	 * @param patternText
  	 *            text to locate. This should be a literal string, as no
  	 *            meta-characters are supported by this implementation. The
  	 *            string may not be the empty string.
  	 */
  	public RawSubStringPattern(String patternText) {
  		if (patternText.length() == 0)
  			throw new IllegalArgumentException(JGitText.get().cannotMatchOnEmptyString);
  		needleString = patternText;
  
  		final byte[] b = Constants.encode(patternText);
  		needle = new byte[b.length];
  		for (int i = 0; i < b.length; i++)
  			needle[i] = lc(b[i]);
  	}
  
  	/**
  	 * Match a character sequence against this pattern.
  	 *
  	 * @param rcs
  	 *            the sequence to match. Must not be null but the length of the
  	 *            sequence is permitted to be 0.
  	 * @return offset within <code>rcs</code> of the first occurrence of this
  	 *         pattern; -1 if this pattern does not appear at any position of
  	 *         <code>rcs</code>.
  	 */
  	public int match(RawCharSequence rcs) {
  		final int needleLen = needle.length;
  		final byte first = needle[0];
  
  		final byte[] text = rcs.buffer;
  		int matchPos = rcs.startPtr;
  		final int maxPos = rcs.endPtr - needleLen;
  
  		OUTER: for (; matchPos <= maxPos; matchPos++) {
  			if (neq(first, text[matchPos])) {
  				while (++matchPos <= maxPos && neq(first, text[matchPos])) {
  					/* skip */
  				}
  				if (matchPos > maxPos)
  					return -1;
  			}
  
  			int si = matchPos + 1;
  			for (int j = 1; j < needleLen; j++, si++) {
  				if (neq(needle[j], text[si]))
  					continue OUTER;
  			}
  			return matchPos;
  		}
  		return -1;
  	}
  
  	private static final boolean neq(byte a, byte b) {
  		return a != b && a != lc(b);
  	}
  
  	private static final byte lc(byte q) {
  		return (byte) StringUtils.toLowerCase((char) (q & 0xff));
  	}
  
  	/**
  	 * Get the literal pattern string this instance searches for.
  	 *
  	 * @return the pattern string given to our constructor.
  	 */
  	public String pattern() {
  		return needleString;
  	}
 
 	/** {@inheritDoc} */
 	@Override
 	public String toString() {
 		return pattern();
 	}
 }