/*

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * particular file as subject to the "Classpath" exception as provided

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 */

package java.nio.file.attribute;

import static java.nio.file.attribute.PosixFilePermission.*;

import java.util.*;

/**

 * This class consists exclusively of static methods that operate on sets of

 * {@link PosixFilePermission} objects.

 *

 * @since 1.7

 */

public final class PosixFilePermissions {

    private PosixFilePermissions() { }

    // Write string representation of permission bits to {@code sb}.

    private static void writeBits(StringBuilder sb, boolean r, boolean w, boolean x) {

        if (r) {

            sb.append('r');

        } else {

            sb.append('-');

        }

        if (w) {

            sb.append('w');

        } else {

            sb.append('-');

        }

        if (x) {

            sb.append('x');

        } else {

            sb.append('-');

        }

    }

    /**

     * Returns the {@code String} representation of a set of permissions. It

     * is guaranteed that the returned {@code String} can be parsed by the

     * {@link #fromString} method.

     *

     * <p> If the set contains {@code null} or elements that are not of type

     * {@code PosixFilePermission} then these elements are ignored.

     *

     * @param   perms

     *          the set of permissions

     *

     * @return  the string representation of the permission set

     */

    public static String toString(Set<PosixFilePermission> perms) {

        StringBuilder sb = new StringBuilder(9);

        writeBits(sb, perms.contains(OWNER_READ), perms.contains(OWNER_WRITE),

          perms.contains(OWNER_EXECUTE));

        writeBits(sb, perms.contains(GROUP_READ), perms.contains(GROUP_WRITE),

          perms.contains(GROUP_EXECUTE));

        writeBits(sb, perms.contains(OTHERS_READ), perms.contains(OTHERS_WRITE),

          perms.contains(OTHERS_EXECUTE));

        return sb.toString();

    }

    private static boolean isSet(char c, char setValue) {

        if (c == setValue)

            return true;

        if (c == '-')

            return false;

        throw new IllegalArgumentException("Invalid mode");

    }

    private static boolean isR(char c) { return isSet(c, 'r'); }

    private static boolean isW(char c) { return isSet(c, 'w'); }

    private static boolean isX(char c) { return isSet(c, 'x'); }

    /**

     * Returns the set of permissions corresponding to a given {@code String}

     * representation.

     *

     * <p> The {@code perms} parameter is a {@code String} representing the

     * permissions. It has 9 characters that are interpreted as three sets of

     * three. The first set refers to the owner's permissions; the next to the

     * group permissions and the last to others. Within each set, the first

     * character is {@code 'r'} to indicate permission to read, the second

     * character is {@code 'w'} to indicate permission to write, and the third

     * character is {@code 'x'} for execute permission. Where a permission is

     * not set then the corresponding character is set to {@code '-'}.

     *

     * <p> <b>Usage Example:</b>

     * Suppose we require the set of permissions that indicate the owner has read,

     * write, and execute permissions, the group has read and execute permissions

     * and others have none.

     * <pre>

     *   Set<PosixFilePermission> perms = PosixFilePermissions.fromString("rwxr-x---");

     * </pre>

     *

     * @param   perms

     *          string representing a set of permissions

     *

     * @return  the resulting set of permissions

     *

     * @throws  IllegalArgumentException

     *          if the string cannot be converted to a set of permissions

     *

     * @see #toString(Set)

     */

    public static Set<PosixFilePermission> fromString(String perms) {

        if (perms.length() != 9)

            throw new IllegalArgumentException("Invalid mode");

        Set<PosixFilePermission> result = new HashSet<PosixFilePermission>();

        if (isR(perms.charAt(0))) result.add(OWNER_READ);

        if (isW(perms.charAt(1))) result.add(OWNER_WRITE);

        if (isX(perms.charAt(2))) result.add(OWNER_EXECUTE);

        if (isR(perms.charAt(3))) result.add(GROUP_READ);

        if (isW(perms.charAt(4))) result.add(GROUP_WRITE);

        if (isX(perms.charAt(5))) result.add(GROUP_EXECUTE);

        if (isR(perms.charAt(6))) result.add(OTHERS_READ);

        if (isW(perms.charAt(7))) result.add(OTHERS_WRITE);

        if (isX(perms.charAt(8))) result.add(OTHERS_EXECUTE);

        return result;

    }

    /**

     * Creates a {@link FileAttribute}, encapsulating a copy of the given file

     * permissions, suitable for passing to the {@link java.nio.file.Path#createFile

     * createFile} or {@link java.nio.file.Path#createDirectory createDirectory}

     * methods.

     *

     * @param   perms

     *          the set of permissions

     *

     * @return  an attribute encapsulating the given file permissions with

     *          {@link FileAttribute#name name} {@code "posix:permissions"}

     *

     * @throws  ClassCastException

     *          if the set contains elements that are not of type {@code

     *          PosixFilePermission}

     */

    public static FileAttribute<Set<PosixFilePermission>>

        asFileAttribute(Set<PosixFilePermission> perms)

    {

        // copy set and check for nulls (CCE will be thrown if an element is not

        // a PosixFilePermission)

        perms = new HashSet<PosixFilePermission>(perms);

        for (PosixFilePermission p: perms) {

            if (p == null)

                throw new NullPointerException();

        }

        final Set<PosixFilePermission> value = perms;

        return new FileAttribute<Set<PosixFilePermission>>() {

            @Override

            public String name() {

                return "posix:permissions";

            }

            @Override

            public Set<PosixFilePermission> value() {

                return Collections.unmodifiableSet(value);

            }

        };

    }

}