/*

 * 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

 * published by the Free Software Foundation.  Oracle designates this

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

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * 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.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

package sun.nio.fs;

import java.nio.file.Path;

import java.nio.file.spi.FileTypeDetector;

import java.util.Locale;

import java.io.IOException;

/**

 * Base implementation of FileTypeDetector

 */

public abstract class AbstractFileTypeDetector

    extends FileTypeDetector

{

    protected AbstractFileTypeDetector() {

        super();

    }

    /**

     * Invokes the appropriate probe method to guess a file's content type,

     * and checks that the content type's syntax is valid.

     */

    @Override

    public final String probeContentType(Path file) throws IOException {

        if (file == null)

            throw new NullPointerException("'file' is null");

        String result = implProbeContentType(file);

        return (result == null) ? null : parse(result);

    }

    /**

     * Probes the given file to guess its content type.

     */

    protected abstract String implProbeContentType(Path file)

        throws IOException;

    /**

     * Parses a candidate content type into its type and subtype, returning

     * null if either token is invalid.

     */

    private static String parse(String s) {

        int slash = s.indexOf('/');

        int semicolon = s.indexOf(';');

        if (slash < 0)

            return null;  // no subtype

        String type = s.substring(0, slash).trim().toLowerCase(Locale.ENGLISH);

        if (!isValidToken(type))

            return null;  // invalid type

        String subtype = (semicolon < 0) ? s.substring(slash + 1) :

            s.substring(slash + 1, semicolon);

        subtype = subtype.trim().toLowerCase(Locale.ENGLISH);

        if (!isValidToken(subtype))

            return null;  // invalid subtype

        StringBuilder sb = new StringBuilder(type.length() + subtype.length() + 1);

        sb.append(type);

        sb.append('/');

        sb.append(subtype);

        return sb.toString();

    }

    /**

     * Special characters

     */

    private static final String TSPECIALS = "()<>@,;:/[]?=\\\"";

    /**

     * Returns true if the character is a valid token character.

     */

    private static boolean isTokenChar(char c) {

        return (c > 040) && (c < 0177) && (TSPECIALS.indexOf(c) < 0);

    }

    /**

     * Returns true if the given string is a legal type or subtype.

     */

    private static boolean isValidToken(String s) {

        int len = s.length();

        if (len == 0)

            return false;

        for (int i = 0; i < len; i++) {

            if (!isTokenChar(s.charAt(i)))

                return false;

        }

        return true;

    }

}