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/**
 * 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.tomitribe.util;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.net.MalformedURLException;
import java.net.URL;

public class JarLocation {

    private JarLocation() {
        // no-op
    }

    public static File get() {
        return jarLocation(JarLocation.class);
    }

    public static File jarLocation(final Class clazz) {
        try {
            final String classFileName = clazz.getName().replace(".", "/") + ".class";

            final ClassLoader loader = clazz.getClassLoader();
            URL url;
            if (loader != null) {
                url = loader.getResource(classFileName);
            } else {
                url = clazz.getResource(classFileName);
            }

            if (url == null) {
                throw new IllegalStateException("classloader.getResource(classFileName) returned a null URL");
            }

            if ("jar".equals(url.getProtocol())) {
                final String spec = url.getFile();

                int separator = spec.indexOf('!');
                /*
                 * REMIND: we don't handle nested JAR URLs
                 */
                if (separator == -1) {
                    throw new MalformedURLException("no ! found in jar url spec:" + spec);
                }

                url = new URL(spec.substring(0, separator++));

                return new File(decode(url.getFile()));

            } else if ("file".equals(url.getProtocol())) {
                return toFile(classFileName, url);
            } else {
                throw new IllegalArgumentException("Unsupported URL scheme: " + url.toExternalForm());
            }
        } catch (final RuntimeException e) {
            throw e;
        } catch (final Exception e) {
            throw new IllegalStateException(e);
        }
    }

    private static File toFile(final String classFileName, final URL url) {
        String path = url.getFile();
        path = path.substring(0, path.length() - classFileName.length());
        return new File(decode(path));
    }


    public static String decode(final String fileName) {
        if (fileName.indexOf('%') == -1) return fileName;

        final StringBuilder result = new StringBuilder(fileName.length());
        final ByteArrayOutputStream out = new ByteArrayOutputStream();

        for (int i = 0; i < fileName.length(); ) {
            final char c = fileName.charAt(i);

            if (c == '%') {
                out.reset();
                do {
                    if (i + 2 >= fileName.length()) {
                        throw new IllegalArgumentException("Incomplete % sequence at: " + i);
                    }

                    final int d1 = Character.digit(fileName.charAt(i + 1), 16);
                    final int d2 = Character.digit(fileName.charAt(i + 2), 16);

                    if (d1 == -1 || d2 == -1) {
                        throw new IllegalArgumentException("Invalid % sequence (" + fileName.substring(i, i + 3) + ") at: " + String.valueOf(i));
                    }

                    out.write((byte) ((d1 << 4) + d2));

                    i += 3;

                } while (i < fileName.length() && fileName.charAt(i) == '%');


                result.append(out.toString());

                continue;
            } else {
                result.append(c);
            }

            i++;
        }
        return result.toString();
    }

}