/*
 * $Id: WildcardHelper.java 471754 2006-11-06 14:55:09Z husted $
 *
 * 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.struts.util;

import java.util.Map;

/**
 * This class is an utility class that perform wildcard-patterns matching and
 * isolation taken from Apache Cocoon.
 *
 * @version $Rev: 471754 $ $Date: 2005-05-07 12:11:38 -0400 (Sat, 07 May 2005)
 *          $
 * @since Struts 1.2
 */
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_END = -5;

    /**
     * The int value that terminates the pattern <code>int []</code>.
     */
    protected static final int MATCH_TRM = -3;

    /**
     * <p> 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:</p>
     *
     * <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>
     *
     * <p>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.</p>
     *
     * @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).
     * @throws NullPointerException If data is null.
     */
    public int[] compilePattern(final 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_END;

        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(final Map<String, String> map, final String data, final int[] expr) {

        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)) {
                    break;
                }

                matchBegin = false;
            } else {
                offset = indexOfArray(expr, exprpos, charpos, buff, buffpos);

                if (offset < 0) {
                    break;
                }
            }

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

                matchBegin = false;
            }

            // Advance buffpos
            buffpos += charpos - exprpos;

            // Check for END's
            if (exprchr == MATCH_TRM) {
                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_END) {
                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) {
                break;
            }

            // 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;
        }

        return false;
    }

    /**
     * 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(final int[] r, final int rpos, final int rend,
            final char[] d, final 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) {
            //?? dpos?
            return d.length;
        }
        int pos = 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 = pos; 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 (((pos + rend) - rpos) <= d.length) {
            // Set current startpoint in d
            int y = pos;

            // Check every character in d for equity. If the string is matched
            // return pos
            for (int x = rpos; x <= rend; x++) {
                if (x == rend) {
                    return pos;
                }

                if (r[x] != d[y++]) {
                    break;
                }
            }

            // Increase dpos to search for the same string at next offset
            pos++;
        }

        // 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(final int[] r, final int rpos, final int rend,
            final char[] d, final 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) {
            //?? dpos?
            return d.length;
        }

        // 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(final int[] r, final int rpos, final int rend,
            final char[] d, final int dpos) {
        if ((d.length - dpos) < (rend - rpos)) {
            return false;
        }

        for (int i = rpos, pos = dpos; i < rend; i++) {
            if (r[i] != d[pos++]) {
                return false;
            }
        }

        return true;
    }
}
