/*

 * Copyright (c) 2006, 2012, Oracle and/or its affiliates. All rights reserved.

 * 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

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package com.sun.tools.javac.processing;

import java.io.BufferedReader;

import java.io.FileNotFoundException;

import java.io.IOException;

import java.io.InputStream;

import java.io.InputStreamReader;

import java.net.MalformedURLException;

import java.net.URL;

/**

 * Utility class to determine if a service can be found on the

 * path that might be used to create a class loader.

 *

 * <p><b>This is NOT part of any supported API.

 * If you write code that depends on this, you do so at your own risk.

 * This code and its internal interfaces are subject to change or

 * deletion without notice.</b>

 *

 */

// based on sun.misc.Service

class ServiceProxy {

    static class ServiceConfigurationError extends Error {

        static final long serialVersionUID = 7732091036771098303L;

        ServiceConfigurationError(String msg) {

            super(msg);

        }

    }

    private static final String prefix = "META-INF/services/";

    private static void fail(Class<?> service, String msg)

            throws ServiceConfigurationError {

        throw new ServiceConfigurationError(service.getName() + ": " + msg);

    }

    private static void fail(Class<?> service, URL u, int line, String msg)

            throws ServiceConfigurationError {

        fail(service, u + ":" + line + ": " + msg);

    }

    /**

     * Parse the content of the given URL as a provider-configuration file.

     *

     * @param  service

     *         The service class for which providers are being sought;

     *         used to construct error detail strings

     *

     * @param  u

     *         The URL naming the configuration file to be parsed

     *

     * @return true if the name of a service is found

     *

     * @throws ServiceConfigurationError

     *         If an I/O error occurs while reading from the given URL, or

     *         if a configuration-file format error is detected

     */

    private static boolean parse(Class<?> service, URL u) throws ServiceConfigurationError {

        InputStream in = null;

        BufferedReader r = null;

        try {

            in = u.openStream();

            r = new BufferedReader(new InputStreamReader(in, "utf-8"));

            int lc = 1;

            String ln;

            while ((ln = r.readLine()) != null) {

                int ci = ln.indexOf('#');

                if (ci >= 0) ln = ln.substring(0, ci);

                ln = ln.trim();

                int n = ln.length();

                if (n != 0) {

                    if ((ln.indexOf(' ') >= 0) || (ln.indexOf('\t') >= 0))

                        fail(service, u, lc, "Illegal configuration-file syntax");

                    int cp = ln.codePointAt(0);

                    if (!Character.isJavaIdentifierStart(cp))

                        fail(service, u, lc, "Illegal provider-class name: " + ln);

                    for (int i = Character.charCount(cp); i < n; i += Character.charCount(cp)) {

                        cp = ln.codePointAt(i);

                        if (!Character.isJavaIdentifierPart(cp) && (cp != '.'))

                            fail(service, u, lc, "Illegal provider-class name: " + ln);

                    }

                    return true;

                }

            }

        } catch (FileNotFoundException x) {

            return false;

        } catch (IOException x) {

            fail(service, ": " + x);

        } finally {

            try {

                if (r != null) r.close();

            } catch (IOException y) {

                fail(service, ": " + y);

            }

            try {

                if (in != null) in.close();

            } catch (IOException y) {

                fail(service, ": " + y);

            }

        }

        return false;

    }

    /**

     * Return true if a description for at least one service is found in the

     * service configuration files in the given URLs.

     */

    public static boolean hasService(Class<?> service, URL[] urls)

            throws ServiceConfigurationError {

        for (URL url: urls) {

            try {

                String fullName = prefix + service.getName();

                URL u = new URL(url, fullName);

                boolean found = parse(service, u);

                if (found)

                    return true;

            } catch (MalformedURLException e) {

                // should not happen; ignore it if it does

            }

        }

        return false;

    }

}