/*
 * 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.sshd.common.util;

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.StringTokenizer;

/**
 * <p>This is a utility class used by selectors and DirectoryScanner. The
 * functionality more properly belongs just to selectors, but unfortunately
 * DirectoryScanner exposed these as protected methods. Thus we have to
 * support any subclasses of DirectoryScanner that may access these methods.
 * </p>
 * <p>This is a Singleton.</p>
 *
 * @author Arnout J. Kuiper
 *         <a href="mailto:ajkuiper@wxs.nl">ajkuiper@wxs.nl</a>
 * @author Magesh Umasankar
 * @author <a href="mailto:bruce@callenish.com">Bruce Atherton</a>
 * @version $Id$
 * @since 1.5
 */
public final class SelectorUtils {

    public static final String PATTERN_HANDLER_PREFIX = "[";

    public static final String PATTERN_HANDLER_SUFFIX = "]";

    public static final String REGEX_HANDLER_PREFIX = "%regex" + PATTERN_HANDLER_PREFIX;

    public static final String ANT_HANDLER_PREFIX = "%ant" + PATTERN_HANDLER_PREFIX;

    /**
     * Private Constructor
     */
    private SelectorUtils() {
    }

    /**
     * <p>Tests whether or not a given path matches the start of a given
     * pattern up to the first "**".</p>
     *
     * <p>This is not a general purpose test and should only be used if you
     * can live with false positives. For example, <code>pattern=**\a</code>
     * and <code>str=b</code> will yield <code>true</code>.</p>
     *
     * @param pattern The pattern to match against. Must not be
     *                <code>null</code>.
     * @param str     The path to match, as a String. Must not be
     *                <code>null</code>.
     * @return whether or not a given path matches the start of a given
     *         pattern up to the first "**".
     */
    public static boolean matchPatternStart(String pattern, String str) {
        return matchPatternStart(pattern, str, true);
    }

    /**
     * <p>Tests whether or not a given path matches the start of a given
     * pattern up to the first "**".</p>
     *
     * <p>This is not a general purpose test and should only be used if you
     * can live with false positives. For example, <code>pattern=**\a</code>
     * and <code>str=b</code> will yield <code>true</code>.</p>
     *
     * @param pattern         The pattern to match against. Must not be
     *                        <code>null</code>.
     * @param str             The path to match, as a String. Must not be
     *                        <code>null</code>.
     * @param isCaseSensitive Whether or not matching should be performed
     *                        case sensitively.
     * @return whether or not a given path matches the start of a given
     *         pattern up to the first "**".
     */
    public static boolean matchPatternStart(String pattern, String str,
                                            boolean isCaseSensitive) {
        if (pattern.length() > (REGEX_HANDLER_PREFIX.length() + PATTERN_HANDLER_SUFFIX.length() + 1)
                && pattern.startsWith(REGEX_HANDLER_PREFIX) && pattern.endsWith(PATTERN_HANDLER_SUFFIX)) {
            // FIXME: ICK! But we can't do partial matches for regex, so we have to reserve judgement until we have
            // a file to deal with, or we can definitely say this is an exclusion...
            return true;
        } else {
            if (pattern.length() > (ANT_HANDLER_PREFIX.length() + PATTERN_HANDLER_SUFFIX.length() + 1)
                    && pattern.startsWith(ANT_HANDLER_PREFIX) && pattern.endsWith(PATTERN_HANDLER_SUFFIX)) {
                pattern =
                        pattern.substring(ANT_HANDLER_PREFIX.length(), pattern.length() - PATTERN_HANDLER_SUFFIX.length());
            }

            String altStr = str.replace('\\', '/');

            return matchAntPathPatternStart(pattern, str, File.separator, isCaseSensitive)
                    || matchAntPathPatternStart(pattern, altStr, "/", isCaseSensitive);
        }
    }

    private static boolean matchAntPathPatternStart(String pattern, String str, String separator, boolean isCaseSensitive) {
        // When str starts with a File.separator, pattern has to start with a
        // File.separator.
        // When pattern starts with a File.separator, str has to start with a
        // File.separator.
        if (str.startsWith(separator) !=
                pattern.startsWith(separator)) {
            return false;
        }

        List<String> patDirs = tokenizePath(pattern, separator);
        List<String> strDirs = tokenizePath(str, separator);

        int patIdxStart = 0;
        int patIdxEnd = patDirs.size() - 1;
        int strIdxStart = 0;
        int strIdxEnd = strDirs.size() - 1;

        // up to first '**'
        while (patIdxStart <= patIdxEnd && strIdxStart <= strIdxEnd) {
            String patDir = patDirs.get(patIdxStart);
            if (patDir.equals("**")) {
                break;
            }
            if (!match(patDir, strDirs.get(strIdxStart),
                    isCaseSensitive)) {
                return false;
            }
            patIdxStart++;
            strIdxStart++;
        }

        if (strIdxStart > strIdxEnd) {
            // String is exhausted
            return true;
        } else if (patIdxStart > patIdxEnd) {
            // String not exhausted, but pattern is. Failure.
            return false;
        } else {
            // pattern now holds ** while string is not exhausted
            // this will generate false positives but we can live with that.
            return true;
        }
    }

    /**
     * Tests whether or not a given path matches a given pattern.
     *
     * @param pattern The pattern to match against. Must not be
     *                <code>null</code>.
     * @param str     The path to match, as a String. Must not be
     *                <code>null</code>.
     * @return <code>true</code> if the pattern matches against the string,
     *         or <code>false</code> otherwise.
     */
    public static boolean matchPath(String pattern, String str) {
        return matchPath(pattern, str, true);
    }

    /**
     * Tests whether or not a given path matches a given pattern.
     *
     * @param pattern         The pattern to match against. Must not be
     *                        <code>null</code>.
     * @param str             The path to match, as a String. Must not be
     *                        <code>null</code>.
     * @param isCaseSensitive Whether or not matching should be performed
     *                        case sensitively.
     * @return <code>true</code> if the pattern matches against the string,
     *         or <code>false</code> otherwise.
     */
    public static boolean matchPath(String pattern, String str,
                                    boolean isCaseSensitive) {
        if (pattern.length() > (REGEX_HANDLER_PREFIX.length() + PATTERN_HANDLER_SUFFIX.length() + 1)
                && pattern.startsWith(REGEX_HANDLER_PREFIX) && pattern.endsWith(PATTERN_HANDLER_SUFFIX)) {
            pattern = pattern.substring(REGEX_HANDLER_PREFIX.length(), pattern.length()
                    - PATTERN_HANDLER_SUFFIX.length());

            return str.matches(pattern);
        } else {
            if (pattern.length() > (ANT_HANDLER_PREFIX.length() + PATTERN_HANDLER_SUFFIX.length() + 1)
                    && pattern.startsWith(ANT_HANDLER_PREFIX) && pattern.endsWith(PATTERN_HANDLER_SUFFIX)) {
                pattern =
                        pattern.substring(ANT_HANDLER_PREFIX.length(), pattern.length() - PATTERN_HANDLER_SUFFIX.length());
            }

            return matchAntPathPattern(pattern, str, isCaseSensitive);
        }
    }

    private static boolean matchAntPathPattern(String pattern, String str, boolean isCaseSensitive) {
        // When str starts with a File.separator, pattern has to start with a
        // File.separator.
        // When pattern starts with a File.separator, str has to start with a
        // File.separator.
        if (str.startsWith(File.separator) !=
                pattern.startsWith(File.separator)) {
            return false;
        }

        List<String> patDirs = tokenizePath(pattern, File.separator);
        List<String> strDirs = tokenizePath(str, File.separator);

        int patIdxStart = 0;
        int patIdxEnd = patDirs.size() - 1;
        int strIdxStart = 0;
        int strIdxEnd = strDirs.size() - 1;

        // up to first '**'
        while (patIdxStart <= patIdxEnd && strIdxStart <= strIdxEnd) {
            String patDir = (String) patDirs.get(patIdxStart);
            if (patDir.equals("**")) {
                break;
            }
            if (!match(patDir, (String) strDirs.get(strIdxStart),
                    isCaseSensitive)) {
                patDirs = null;
                strDirs = null;
                return false;
            }
            patIdxStart++;
            strIdxStart++;
        }
        if (strIdxStart > strIdxEnd) {
            // String is exhausted
            for (int i = patIdxStart; i <= patIdxEnd; i++) {
                if (!patDirs.get(i).equals("**")) {
                    patDirs = null;
                    strDirs = null;
                    return false;
                }
            }
            return true;
        } else {
            if (patIdxStart > patIdxEnd) {
                // String not exhausted, but pattern is. Failure.
                patDirs = null;
                strDirs = null;
                return false;
            }
        }

        // up to last '**'
        while (patIdxStart <= patIdxEnd && strIdxStart <= strIdxEnd) {
            String patDir = (String) patDirs.get(patIdxEnd);
            if (patDir.equals("**")) {
                break;
            }
            if (!match(patDir, (String) strDirs.get(strIdxEnd),
                    isCaseSensitive)) {
                patDirs = null;
                strDirs = null;
                return false;
            }
            patIdxEnd--;
            strIdxEnd--;
        }
        if (strIdxStart > strIdxEnd) {
            // String is exhausted
            for (int i = patIdxStart; i <= patIdxEnd; i++) {
                if (!patDirs.get(i).equals("**")) {
                    patDirs = null;
                    strDirs = null;
                    return false;
                }
            }
            return true;
        }

        while (patIdxStart != patIdxEnd && strIdxStart <= strIdxEnd) {
            int patIdxTmp = -1;
            for (int i = patIdxStart + 1; i <= patIdxEnd; i++) {
                if (patDirs.get(i).equals("**")) {
                    patIdxTmp = i;
                    break;
                }
            }
            if (patIdxTmp == patIdxStart + 1) {
                // '**/**' situation, so skip one
                patIdxStart++;
                continue;
            }
            // Find the pattern between padIdxStart & padIdxTmp in str between
            // strIdxStart & strIdxEnd
            int patLength = (patIdxTmp - patIdxStart - 1);
            int strLength = (strIdxEnd - strIdxStart + 1);
            int foundIdx = -1;
            strLoop:
            for (int i = 0; i <= strLength - patLength; i++) {
                for (int j = 0; j < patLength; j++) {
                    String subPat = (String) patDirs.get(patIdxStart + j + 1);
                    String subStr = (String) strDirs.get(strIdxStart + i + j);
                    if (!match(subPat, subStr, isCaseSensitive)) {
                        continue strLoop;
                    }
                }

                foundIdx = strIdxStart + i;
                break;
            }

            if (foundIdx == -1) {
                patDirs = null;
                strDirs = null;
                return false;
            }

            patIdxStart = patIdxTmp;
            strIdxStart = foundIdx + patLength;
        }

        for (int i = patIdxStart; i <= patIdxEnd; i++) {
            if (!patDirs.get(i).equals("**")) {
                patDirs = null;
                strDirs = null;
                return false;
            }
        }

        return true;
    }

    /**
     * Tests whether or not a string matches against a pattern.
     * The pattern may contain two special characters:<br>
     * '*' means zero or more characters<br>
     * '?' means one and only one character
     *
     * @param pattern The pattern to match against.
     *                Must not be <code>null</code>.
     * @param str     The string which must be matched against the pattern.
     *                Must not be <code>null</code>.
     * @return <code>true</code> if the string matches against the pattern,
     *         or <code>false</code> otherwise.
     */
    public static boolean match(String pattern, String str) {
        return match(pattern, str, true);
    }

    /**
     * Tests whether or not a string matches against a pattern.
     * The pattern may contain two special characters:<br>
     * '*' means zero or more characters<br>
     * '?' means one and only one character
     *
     * @param pattern         The pattern to match against.
     *                        Must not be <code>null</code>.
     * @param str             The string which must be matched against the pattern.
     *                        Must not be <code>null</code>.
     * @param isCaseSensitive Whether or not matching should be performed
     *                        case sensitively.
     * @return <code>true</code> if the string matches against the pattern,
     *         or <code>false</code> otherwise.
     */
    public static boolean match(String pattern, String str,
                                boolean isCaseSensitive) {
        char[] patArr = pattern.toCharArray();
        char[] strArr = str.toCharArray();
        int patIdxStart = 0;
        int patIdxEnd = patArr.length - 1;
        int strIdxStart = 0;
        int strIdxEnd = strArr.length - 1;
        char ch;

        boolean containsStar = false;
        for (int i = 0; i < patArr.length; i++) {
            if (patArr[i] == '*') {
                containsStar = true;
                break;
            }
        }

        if (!containsStar) {
            // No '*'s, so we make a shortcut
            if (patIdxEnd != strIdxEnd) {
                return false; // Pattern and string do not have the same size
            }
            for (int i = 0; i <= patIdxEnd; i++) {
                ch = patArr[i];
                if (ch != '?' && !equals(ch, strArr[i], isCaseSensitive)) {
                    return false; // Character mismatch
                }
            }
            return true; // String matches against pattern
        }

        if (patIdxEnd == 0) {
            return true; // Pattern contains only '*', which matches anything
        }

        // Process characters before first star
        while ((ch = patArr[patIdxStart]) != '*' && strIdxStart <= strIdxEnd) {
            if (ch != '?' && !equals(ch, strArr[strIdxStart], isCaseSensitive)) {
                return false; // Character mismatch
            }
            patIdxStart++;
            strIdxStart++;
        }
        if (strIdxStart > strIdxEnd) {
            // All characters in the string are used. Check if only '*'s are
            // left in the pattern. If so, we succeeded. Otherwise failure.
            for (int i = patIdxStart; i <= patIdxEnd; i++) {
                if (patArr[i] != '*') {
                    return false;
                }
            }
            return true;
        }

        // Process characters after last star
        while ((ch = patArr[patIdxEnd]) != '*' && strIdxStart <= strIdxEnd) {
            if (ch != '?' && !equals(ch, strArr[strIdxEnd], isCaseSensitive)) {
                return false; // Character mismatch
            }
            patIdxEnd--;
            strIdxEnd--;
        }
        if (strIdxStart > strIdxEnd) {
            // All characters in the string are used. Check if only '*'s are
            // left in the pattern. If so, we succeeded. Otherwise failure.
            for (int i = patIdxStart; i <= patIdxEnd; i++) {
                if (patArr[i] != '*') {
                    return false;
                }
            }
            return true;
        }

        // process pattern between stars. padIdxStart and patIdxEnd point
        // always to a '*'.
        while (patIdxStart != patIdxEnd && strIdxStart <= strIdxEnd) {
            int patIdxTmp = -1;
            for (int i = patIdxStart + 1; i <= patIdxEnd; i++) {
                if (patArr[i] == '*') {
                    patIdxTmp = i;
                    break;
                }
            }
            if (patIdxTmp == patIdxStart + 1) {
                // Two stars next to each other, skip the first one.
                patIdxStart++;
                continue;
            }
            // Find the pattern between padIdxStart & padIdxTmp in str between
            // strIdxStart & strIdxEnd
            int patLength = (patIdxTmp - patIdxStart - 1);
            int strLength = (strIdxEnd - strIdxStart + 1);
            int foundIdx = -1;
            strLoop:
            for (int i = 0; i <= strLength - patLength; i++) {
                for (int j = 0; j < patLength; j++) {
                    ch = patArr[patIdxStart + j + 1];
                    if (ch != '?' && !equals(ch, strArr[strIdxStart + i + j], isCaseSensitive)) {
                        continue strLoop;
                    }
                }

                foundIdx = strIdxStart + i;
                break;
            }

            if (foundIdx == -1) {
                return false;
            }

            patIdxStart = patIdxTmp;
            strIdxStart = foundIdx + patLength;
        }

        // All characters in the string are used. Check if only '*'s are left
        // in the pattern. If so, we succeeded. Otherwise failure.
        for (int i = patIdxStart; i <= patIdxEnd; i++) {
            if (patArr[i] != '*') {
                return false;
            }
        }
        return true;
    }

    /**
     * Tests whether two characters are equal.
     */
    private static boolean equals(char c1, char c2, boolean isCaseSensitive) {
        if (c1 == c2) {
            return true;
        }
        if (!isCaseSensitive) {
            // NOTE: Try both upper case and lower case as done by String.equalsIgnoreCase()
            if (Character.toUpperCase(c1) == Character.toUpperCase(c2) ||
                    Character.toLowerCase(c1) == Character.toLowerCase(c2)) {
                return true;
            }
        }
        return false;
    }

    /**
     * Breaks a path up into a Vector of path elements, tokenizing on
     * <code>File.separator</code>.
     *
     * @param path Path to tokenize. Must not be <code>null</code>.
     * @return a List of path elements from the tokenized path
     */
    public static List<String> tokenizePath(String path) {
        return tokenizePath(path, File.separator);
    }

    public static List<String> tokenizePath(String path, String separator) {
        List<String> ret = new ArrayList<String>();
        StringTokenizer st = new StringTokenizer(path, separator);
        while (st.hasMoreTokens()) {
            ret.add(st.nextToken());
        }
        return ret;
    }

    
    /**
     * Normalizes the path by removing '.', '..' and double separators (e.g. '//')
     * @param path
     * @param separator
     * @return normalized path
     * @throws IOException when the path is invalid (e.g. '/first/../..')
     */
    public static String normalizePath(String path, String separator) throws IOException {
        boolean startsWithSeparator = path.startsWith(separator);
        // tokenize
        List<String> tokens = tokenizePath(path, separator);

        // clean up
        for (int i = tokens.size() - 1; i >= 0; i--) {
            String t = tokens.get(i);
            if (t.length() == 0 || t.equals(".")) {
                tokens.remove(i);
            } else if (t.equals("..")) {
                tokens.remove(i);
                if (i >= 1) {
                    tokens.remove(--i);
                }
            }
        }

        // serialize
        StringBuffer buffer = new StringBuffer(path.length());

        for (int i = 0; i < tokens.size(); i++) {
            if (i > 0 || (i == 0 && startsWithSeparator)) buffer.append(separator);
            buffer.append(tokens.get(i));
        }

        return buffer.toString();
    }


    /**
     * Returns dependency information on these two files. If src has been
     * modified later than target, it returns true. If target doesn't exist,
     * it likewise returns true. Otherwise, target is newer than src and
     * is not out of date, thus the method returns false. It also returns
     * false if the src file doesn't even exist, since how could the
     * target then be out of date.
     *
     * @param src         the original file
     * @param target      the file being compared against
     * @param granularity the amount in seconds of slack we will give in
     *                    determining out of dateness
     * @return whether the target is out of date
     */
    public static boolean isOutOfDate(File src, File target, int granularity) {
        if (!src.exists()) {
            return false;
        }
        if (!target.exists()) {
            return true;
        }
        if ((src.lastModified() - granularity) > target.lastModified()) {
            return true;
        }
        return false;
    }

    /**
     * "Flattens" a string by removing all whitespace (space, tab, linefeed,
     * carriage return, and formfeed). This uses StringTokenizer and the
     * default set of tokens as documented in the single arguement constructor.
     *
     * @param input a String to remove all whitespace.
     * @return a String that has had all whitespace removed.
     */
    public static String removeWhitespace(String input) {
        StringBuffer result = new StringBuffer();
        if (input != null) {
            StringTokenizer st = new StringTokenizer(input);
            while (st.hasMoreTokens()) {
                result.append(st.nextToken());
            }
        }
        return result.toString();
    }
}
