/*
 * $Id: WildcardHelper.java 54929 2004-10-16 16:38:42Z germuska $ 
 *
 * Copyright 2003-2004 The Apache Software Foundation.
 * 
 * Licensed 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.struts.util;

import java.util.Map;

/**
 * This class is an utility class that perform wilcard-patterns matching and
 * isolation taken from Apache Cocoon.
 *
 * @since Struts 1.2
 * @version $Rev: 54929 $ $Date: 2004-10-16 17:38:42 +0100 (Sat, 16 Oct 2004) $
 */
public class WildcardHelper {

    /** The int representing '*' in the pattern <code>int []</code>. */
    protected static final int MATCH_FILE = -1;
    
    /** The int representing '**' in the pattern <code>int []</code>. */
    protected static final int MATCH_PATH = -2;
    
    /** The int representing begin in the pattern <code>int []</code>. */
    protected static final int MATCH_BEGIN = -4;
    
    /** The int representing end in pattern <code>int []</code>. */
    protected static final int MATCH_THEEND = -5;
    
    /** The int value that terminates the pattern <code>int []</code>. */
    protected static final int MATCH_END = -3;


    /**
     * Translate the given <code>String</code> into a <code>int []</code>
     * representing the pattern matchable by this class.
     * <br>
     * This function translates a <code>String</code> into an int array
     * converting the special '*' and '\' characters.
     * <br>
     * Here is how the conversion algorithm works:
     * <ul>
     *   <li>The '*' character is converted to MATCH_FILE, meaning that zero
     *        or more characters (excluding the path separator '/') are to
     *        be matched.</li>
     *   <li>The '**' sequence is converted to MATCH_PATH, meaning that zero
     *       or more characters (including the path separator '/') are to
     *        be matched.</li>
     *   <li>The '\' character is used as an escape sequence ('\*' is
     *       translated in '*', not in MATCH_FILE). If an exact '\' character
     *       is to be matched the source string must contain a '\\'.
     *       sequence.</li>
     * </ul>
     * When more than two '*' characters, not separated by another character,
     * are found their value is considered as '**' (MATCH_PATH).
     * <br>
     * The array is always terminated by a special value (MATCH_END).
     * <br>
     * All MATCH* values are less than zero, while normal characters are equal
     * or greater.
     *
     * @param data The string to translate.
     * @return The encoded string as an int array, terminated by the MATCH_END
     *         value (don't consider the array length).
     * @exception NullPointerException If data is null.
     */
    public int[] compilePattern(String data) {

        // Prepare the arrays
        int expr[] = new int[data.length() + 2];
        char buff[] = data.toCharArray();

        // Prepare variables for the translation loop
        int y = 0;
        boolean slash = false;

        // Must start from beginning
        expr[y++] = MATCH_BEGIN;

        if (buff.length > 0) {
            if (buff[0] == '\\') {
                slash = true;
            } else if (buff[0] == '*') {
                expr[y++] = MATCH_FILE;
            }  else {
                expr[y++] = buff[0];
            }

            // Main translation loop
            for (int x = 1; x < buff.length; x++) {
                // If the previous char was '\' simply copy this char.
                if (slash) {
                    expr[y++] = buff[x];
                    slash = false;
                // If the previous char was not '\' we have to do a bunch of 
                // checks
                } else {
                    // If this char is '\' declare that and continue
                    if (buff[x] == '\\') {
                        slash = true;
                    // If this char is '*' check the previous one
                    } else if (buff[x] == '*') {
                        // If the previous character als was '*' match a path
                        if (expr[y - 1] <= MATCH_FILE) {
                            expr[y - 1] = MATCH_PATH;
                        } else {
                            expr[y++] = MATCH_FILE;
                        }
                    } else {
                        expr[y++] = buff[x];
                    }
                }
            }
        }

        // Must match end at the end
        expr[y] = MATCH_THEEND;
        return expr;
    }

    /**
     * Match a pattern agains a string and isolates wildcard replacement into a
     * <code>Stack</code>.
     *
     * @param map  The map to store matched values
     * @param data The string to match
     * @param expr The compiled wildcard expression
     * @return True if a match
     * @throws NullPointerException If any parameters are null
     */
    public boolean match(Map map, String data, int[] expr) {
        if (map == null) {
            throw new NullPointerException ("No map provided");
        }    
        if (data == null) {
            throw new NullPointerException ("No data provided");
        }    
        if (expr == null) {
            throw new NullPointerException ("No pattern expression provided");
        }    


        char buff[] = data.toCharArray();
        // Allocate the result buffer
        char rslt[] = new char[expr.length + buff.length];


        // The previous and current position of the expression character
        // (MATCH_*)
        int charpos = 0;

        // The position in the expression, input, translation and result arrays
        int exprpos = 0;
        int buffpos = 0;
        int rsltpos = 0;
        int offset = -1;

        // The matching count
        int mcount = 0;

        // We want the complete data be in {0}
        map.put(Integer.toString(mcount), data);

        // First check for MATCH_BEGIN
        boolean matchBegin = false;
        if (expr[charpos] == MATCH_BEGIN) {
            matchBegin = true;
            exprpos = ++charpos;
        }

        // Search the fist expression character (except MATCH_BEGIN - already 
        // skipped)
        while (expr[charpos] >= 0) {
            charpos++;
        }    

        // The expression charater (MATCH_*)
        int exprchr = expr[charpos];

        while (true) {
            // Check if the data in the expression array before the current
            // expression character matches the data in the input buffer
            if (matchBegin) {
                if (!matchArray(expr, exprpos, charpos, buff, buffpos)) {
                    return (false);
                }    
                matchBegin = false;
            } else {
                offset = indexOfArray (expr, exprpos, charpos, buff,
                        buffpos);
                if (offset < 0) {
                    return (false);
                }    
            }

            // Check for MATCH_BEGIN
            if (matchBegin) {
                if (offset != 0) {
                    return (false);
                }    
                matchBegin = false;
            }

            // Advance buffpos
            buffpos += (charpos - exprpos);

            // Check for END's
            if (exprchr == MATCH_END) {
                if (rsltpos > 0) {
                    map.put(Integer.toString(++mcount),
                        new String(rslt, 0, rsltpos));
                }    
                // Don't care about rest of input buffer
                return (true);
            } else if (exprchr == MATCH_THEEND) {
                if (rsltpos > 0) {
                    map.put(Integer.toString(++mcount),
                        new String(rslt, 0, rsltpos));
                }    
                // Check that we reach buffer's end
                return (buffpos == buff.length);
            }

            // Search the next expression character
            exprpos = ++charpos;
            while (expr[charpos] >= 0) {
                charpos++;
            }    
            int prevchr = exprchr;
            exprchr = expr[charpos];

            // We have here prevchr == * or **.
            offset = (prevchr == MATCH_FILE)
                    ? indexOfArray (expr, exprpos, charpos, buff, buffpos)
                    : lastIndexOfArray (expr, exprpos, charpos, buff,
                    buffpos);

            if (offset < 0) {
                return (false);
            }    

            // Copy the data from the source buffer into the result buffer
            // to substitute the expression character
            if (prevchr == MATCH_PATH) {
                while (buffpos < offset) {
                    rslt[rsltpos++] = buff[buffpos++];
                }    
            } else {
                // Matching file, don't copy '/'
                while (buffpos < offset) {
                    if (buff[buffpos] == '/') {
                        return (false);
                    }    
                    rslt[rsltpos++] = buff[buffpos++];
                }
            }

            map.put(Integer.toString(++mcount), new String (rslt, 0, rsltpos));
            rsltpos = 0;
        }
    }

     /**
      * Get the offset of a part of an int array within a char array.
      * <br>
      * This method return the index in d of the first occurrence after dpos of
      * that part of array specified by r, starting at rpos and terminating at
      * rend.
      *
      * @param r The array containing the data that need to be matched in d.
      * @param rpos The index of the first character in r to look for.
      * @param rend The index of the last character in r to look for plus 1.
      * @param d The array of char that should contain a part of r.
      * @param dpos The starting offset in d for the matching.
      * @return The offset in d of the part of r matched in d or -1 if that was
      *         not found.
      */
    protected int indexOfArray (int r[], int rpos, int rend,
            char d[], int dpos) {
                
        // Check if pos and len are legal
        if (rend < rpos) {
            throw new IllegalArgumentException ("rend < rpos");
        }    
        // If we need to match a zero length string return current dpos
        if (rend == rpos) {
            return (d.length); //?? dpos?
        }    
        // If we need to match a 1 char length string do it simply
        if ((rend - rpos) == 1) {
            // Search for the specified character
            for (int x = dpos; x < d.length; x++) {
                if (r[rpos] == d[x]) {
                    return (x);
                }
            }    
        }
        // Main string matching loop. It gets executed if the characters to
        // match are less then the characters left in the d buffer
        while ((dpos + rend - rpos) <= d.length) {
            // Set current startpoint in d
            int y = dpos;
            // Check every character in d for equity. If the string is matched
            // return dpos
            for (int x = rpos; x <= rend; x++) {
                if (x == rend) {
                    return (dpos);
                }    
                if (r[x] != d[y++]) {
                    break;
                }    
            }
            // Increase dpos to search for the same string at next offset
            dpos++;
        }
        // The remaining chars in d buffer were not enough or the string
        // wasn't matched
        return (-1);
    }

     /**
      * Get the offset of a last occurance of an int array within a char array.
      * <br>
      * This method return the index in d of the last occurrence after dpos of
      * that part of array specified by r, starting at rpos and terminating at
      * rend.
      *
      * @param r The array containing the data that need to be matched in d.
      * @param rpos The index of the first character in r to look for.
      * @param rend The index of the last character in r to look for plus 1.
      * @param d The array of char that should contain a part of r.
      * @param dpos The starting offset in d for the matching.
      * @return The offset in d of the last part of r matched in d or -1 if 
      *         that was not found.
      */
    protected int lastIndexOfArray (int r[], int rpos, int rend,
            char d[], int dpos) {
        // Check if pos and len are legal
        if (rend < rpos) {
            throw new IllegalArgumentException ("rend < rpos");
        }    
        // If we need to match a zero length string return current dpos
        if (rend == rpos) {
            return (d.length); //?? dpos?
        }    

        // If we need to match a 1 char length string do it simply
        if ((rend - rpos) == 1) {
            // Search for the specified character
            for (int x = d.length - 1; x > dpos; x--) {
                if (r[rpos] == d[x]) {
                    return (x);
                }
            }    
        }

        // Main string matching loop. It gets executed if the characters to
        // match are less then the characters left in the d buffer
        int l = d.length - (rend - rpos);
        while (l >= dpos) {
            // Set current startpoint in d
            int y = l;
            // Check every character in d for equity. If the string is matched
            // return dpos
            for (int x = rpos; x <= rend; x++) {
                if (x == rend) {
                    return (l);
                }    
                if (r[x] != d[y++]) {
                    break;
                }    
            }
            // Decrease l to search for the same string at next offset
            l--;
        }
        // The remaining chars in d buffer were not enough or the string
        // wasn't matched
        return (-1);
    }

     /**
      * Matches elements of array r from rpos to rend with array d, starting 
      * from dpos.
      * <br>
      * This method return true if elements of array r from rpos to rend
      * equals elements of array d starting from dpos to dpos+(rend-rpos).
      *
      * @param r The array containing the data that need to be matched in d.
      * @param rpos The index of the first character in r to look for.
      * @param rend The index of the last character in r to look for.
      * @param d The array of char that should start from a part of r.
      * @param dpos The starting offset in d for the matching.
      * @return true if array d starts from portion of array r.
      */
    protected boolean matchArray (int r[], int rpos, int rend,
            char d[], int dpos) {
        if (d.length - dpos < rend - rpos) {
            return (false);
        }    
        for (int i = rpos; i < rend; i++) {
            if (r[i] != d[dpos++]) {
                return (false);
            }
        }    
        return (true);
    }
}