/*
 *  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.tools.ant.util;

import org.apache.tools.ant.BuildException;
import org.apache.tools.ant.taskdefs.condition.Os;

import java.io.File;
import java.util.Random;

/**
 * This class also encapsulates methods which allow Files to be
 * referred to using abstract path names which are translated to native
 * system file paths at runtime as well as copying files or setting
 * their last modification time.
 *
 */
public class FileUtils {
    private static final int DELETE_RETRY_SLEEP_MILLIS = 10;
    private static final int EXPAND_SPACE = 50;
    private static final FileUtils PRIMARY_INSTANCE = new FileUtils();

    //get some non-crypto-grade randomness from various places.
    private static Random rand = new Random(System.currentTimeMillis()
            + Runtime.getRuntime().freeMemory());

    private static final boolean ON_NETWARE = Os.isFamily("netware");
    private static final boolean ON_DOS = Os.isFamily("dos");
    private static final boolean ON_WIN9X = Os.isFamily("win9x");
    private static final boolean ON_WINDOWS = Os.isFamily("windows");

    static final int BUF_SIZE = 8192;


    /**
     * The granularity of timestamps under FAT.
     */
    public static final long FAT_FILE_TIMESTAMP_GRANULARITY = 2000;

    /**
     * The granularity of timestamps under Unix.
     */
    public static final long UNIX_FILE_TIMESTAMP_GRANULARITY = 1000;

    /**
     * The granularity of timestamps under the NT File System.
     * NTFS has a granularity of 100 nanoseconds, which is less
     * than 1 millisecond, so we round this up to 1 millisecond.
     */
    public static final long NTFS_FILE_TIMESTAMP_GRANULARITY = 1;

    /**
     * A one item cache for fromUri.
     * fromUri is called for each element when parseing ant build
     * files. It is a costly operation. This just caches the result
     * of the last call.
     */
    private Object cacheFromUriLock = new Object();
    private String cacheFromUriRequest = null;
    private String cacheFromUriResponse = null;

    /**
     * Factory method.
     *
     * @return a new instance of FileUtils.
     * @deprecated since 1.7.
     *             Use getFileUtils instead,
     * FileUtils do not have state.
     */
    @Deprecated
    public static FileUtils newFileUtils() {
        return new FileUtils();
    }

    /**
     * Method to retrieve The FileUtils, which is shared by all users of this
     * method.
     * @return an instance of FileUtils.
     * @since Ant 1.6.3
     */
    public static FileUtils getFileUtils() {
        return PRIMARY_INSTANCE;
    }

    /**
     * Empty constructor.
     */
    protected FileUtils() {
    }

    /**
     * Verifies that the specified filename represents an absolute path.
     * Differs from new java.io.File("filename").isAbsolute() in that a path
     * beginning with a double file separator--signifying a Windows UNC--must
     * at minimum match "\\a\b" to be considered an absolute path.
     * @param filename the filename to be checked.
     * @return true if the filename represents an absolute path.
     * @throws java.lang.NullPointerException if filename is null.
     * @since Ant 1.6.3
     */
    public static boolean isAbsolutePath(String filename) {
        int len = filename.length();
        if (len == 0) {
            return false;
        }
        char sep = File.separatorChar;
        filename = filename.replace('/', sep).replace('\\', sep);
        char c = filename.charAt(0);
        if (!(ON_DOS || ON_NETWARE)) {
            return (c == sep);
        }
        if (c == sep) {
            // CheckStyle:MagicNumber OFF
            if (!(ON_DOS && len > 4 && filename.charAt(1) == sep)) {
                return false;
            }
            // CheckStyle:MagicNumber ON
            int nextsep = filename.indexOf(sep, 2);
            return nextsep > 2 && nextsep + 1 < len;
        }
        int colon = filename.indexOf(':');
        return (Character.isLetter(c) && colon == 1
                && filename.length() > 2 && filename.charAt(2) == sep)
                || (ON_NETWARE && colon > 0);
    }

    /**
     * Dissect the specified absolute path.
     * @param path the path to dissect.
     * @return String[] {root, remaining path}.
     * @throws java.lang.NullPointerException if path is null.
     * @since Ant 1.7
     */
    public String[] dissect(String path) {
        char sep = File.separatorChar;
        path = path.replace('/', sep).replace('\\', sep);

        // make sure we are dealing with an absolute path
        if (!isAbsolutePath(path)) {
            throw new BuildException(path + " is not an absolute path");
        }
        String root = null;
        int colon = path.indexOf(':');
        if (colon > 0 && (ON_DOS || ON_NETWARE)) {

            int next = colon + 1;
            root = path.substring(0, next);
            char[] ca = path.toCharArray();
            root += sep;
            //remove the initial separator; the root has it.
            next = (ca[next] == sep) ? next + 1 : next;

            StringBuffer sbPath = new StringBuffer();
            // Eliminate consecutive slashes after the drive spec:
            for (int i = next; i < ca.length; i++) {
                if (ca[i] != sep || ca[i - 1] != sep) {
                    sbPath.append(ca[i]);
                }
            }
            path = sbPath.toString();
        } else if (path.length() > 1 && path.charAt(1) == sep) {
            // UNC drive
            int nextsep = path.indexOf(sep, 2);
            nextsep = path.indexOf(sep, nextsep + 1);
            root = (nextsep > 2) ? path.substring(0, nextsep + 1) : path;
            path = path.substring(root.length());
        } else {
            root = File.separator;
            path = path.substring(1);
        }
        return new String[] {root, path};
    }

}