/*

 * Copyright (c) 2016, 2018, 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

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package jdk.jfr.internal.jfc;

import java.io.IOException;

import java.io.InputStream;

import java.io.Reader;

import java.nio.charset.StandardCharsets;

import java.nio.file.Files;

import java.nio.file.NoSuchFileException;

import java.nio.file.Path;

import java.nio.file.Paths;

import java.text.ParseException;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.List;

import jdk.jfr.Configuration;

import jdk.jfr.internal.LogLevel;

import jdk.jfr.internal.LogTag;

import jdk.jfr.internal.Logger;

import jdk.jfr.internal.SecuritySupport;

import jdk.jfr.internal.SecuritySupport.SafePath;

/**

 * {@link Configuration} factory for JFC files. *

 */

public final class JFC {

    private static final int BUFFER_SIZE = 8192;

    private static final int MAXIMUM_FILE_SIZE = 1024 * 1024;

    private static final int MAX_BUFFER_SIZE = Integer.MAX_VALUE - 8;

    private static volatile List<KnownConfiguration> knownConfigurations;

    /**

     * Reads a known configuration file (located into a string, but doesn't

     * parse it until it's being used.

     */

    private static final class KnownConfiguration {

        private final String content;

        private final String filename;

        private final String name;

        private Configuration configuration;

        public KnownConfiguration(SafePath knownPath) throws IOException {

            this.content = readContent(knownPath);

            this.name = nameFromPath(knownPath.toPath());

            this.filename = nullSafeFileName(knownPath.toPath());

        }

        public boolean isNamed(String name) {

            return filename.equals(name) || this.name.equals(name);

        }

        public Configuration getConfigurationFile() throws IOException, ParseException {

            if (configuration == null) {

                configuration = JFCParser.createConfiguration(name, content);

            }

            return configuration;

        }

        public String getName() {

            return name;

        }

        private static String readContent(SafePath knownPath) throws IOException {

            if (SecuritySupport.getFileSize(knownPath) > MAXIMUM_FILE_SIZE) {

                throw new IOException("Configuration with more than "

                        + MAXIMUM_FILE_SIZE + " characters can't be read.");

            }

            try (InputStream r = SecuritySupport.newFileInputStream(knownPath)) {

                return JFC.readContent(r);

            }

        }

    }

    private JFC() {

        // private utility class

    }

    /**

     * Reads a configuration from a file.

     *

     * @param path the file containing the configuration, not {@code null}

     * @return {@link Configuration}, not {@code null}

     * @throws ParseException if the file can't be parsed

     * @throws IOException if the file can't be read

     *

     * @throws SecurityException if a security manager exists and its

     *         <code>checkRead</code> method denies read access to the file.

     * @see java.io.File#getPath()

     * @see java.lang.SecurityManager#checkRead(java.lang.String)

     */

    public static Configuration create(String name, Reader reader) throws IOException, ParseException {

        return JFCParser.createConfiguration(name, reader);

    }

    private static String nullSafeFileName(Path file) throws IOException {

        Path filename = file.getFileName();

        if (filename == null) {

            throw new IOException("Path has no file name");

        }

        return filename.toString();

    }

    public static String nameFromPath(Path file) throws IOException {

        String f = nullSafeFileName(file);

        if (f.endsWith(JFCParser.FILE_EXTENSION)) {

            return f.substring(0, f.length() - JFCParser.FILE_EXTENSION.length());

        } else  {

            return f;

        }

    }

    // Invoked by DCmdStart

    public static Configuration createKnown(String name) throws IOException, ParseException {

        // Known name, no need for permission

        for (KnownConfiguration known : getKnownConfigurations()) {

            if (known.isNamed(name)) {

                return known.getConfigurationFile();

            }

        }

        // Check JFC directory

        SafePath path = SecuritySupport.JFC_DIRECTORY;

        if (path != null && SecuritySupport.exists(path)) {

            for (String extension : Arrays.asList("", JFCParser.FILE_EXTENSION)) {

                SafePath file = new SafePath(path.toPath().resolveSibling(name + extension));

                if (SecuritySupport.exists(file) && !SecuritySupport.isDirectory(file)) {

                    try (Reader r = SecuritySupport.newFileReader(file)) {

                        String jfcName = nameFromPath(file.toPath());

                        return JFCParser.createConfiguration(jfcName, r);

                    }

                }

            }

        }

        // Assume path included in name

        Path localPath = Paths.get(name);

        String jfcName = nameFromPath(localPath);

        try (Reader r = Files.newBufferedReader(localPath)) {

            return JFCParser.createConfiguration(jfcName, r);

        }

    }

    private static String readContent(InputStream source) throws IOException {

        byte[] bytes = read(source, BUFFER_SIZE);

        return new String(bytes, StandardCharsets.UTF_8);

    }

    // copied from java.io.file.Files to avoid dependency on JDK 9 code

    private static byte[] read(InputStream source, int initialSize) throws IOException {

        int capacity = initialSize;

        byte[] buf = new byte[capacity];

        int nread = 0;

        int n;

        for (;;) {

            // read to EOF which may read more or less than initialSize (eg: file

            // is truncated while we are reading)

            while ((n = source.read(buf, nread, capacity - nread)) > 0)

                nread += n;

            // if last call to source.read() returned -1, we are done

            // otherwise, try to read one more byte; if that failed we're done too

            if (n < 0 || (n = source.read()) < 0)

                break;

            // one more byte was read; need to allocate a larger buffer

            if (capacity <= MAX_BUFFER_SIZE - capacity) {

                capacity = Math.max(capacity << 1, BUFFER_SIZE);

            } else {

                if (capacity == MAX_BUFFER_SIZE)

                    throw new OutOfMemoryError("Required array size too large");

                capacity = MAX_BUFFER_SIZE;

            }

            buf = Arrays.copyOf(buf, capacity);

            buf[nread++] = (byte)n;

        }

        return (capacity == nread) ? buf : Arrays.copyOf(buf, nread);

    }

    /**

     * Returns list of predefined configurations available.

     *

     * @return list of configurations, not null

     */

    public static List<Configuration> getConfigurations() {

        List<Configuration> configs = new ArrayList<>();

        for (KnownConfiguration knownConfig : getKnownConfigurations()) {

            try {

                configs.add(knownConfig.getConfigurationFile());

            } catch (IOException e) {

                Logger.log(LogTag.JFR, LogLevel.WARN, "Could not load configuration " + knownConfig.getName() + ". " + e.getMessage());

            } catch (ParseException e) {

                Logger.log(LogTag.JFR, LogLevel.WARN, "Could not parse configuration " + knownConfig.getName() + ". " + e.getMessage());

            }

        }

        return configs;

    }

    private static List<KnownConfiguration> getKnownConfigurations() {

        if (knownConfigurations == null) {

            List<KnownConfiguration> configProxies = new ArrayList<>();

            for (SafePath p : SecuritySupport.getPredefinedJFCFiles()) {

                try {

                    configProxies.add(new KnownConfiguration(p));

                } catch (IOException ioe) {

                    // ignore

                }

            }

            knownConfigurations = configProxies;

        }

        return knownConfigurations;

    }

    public static Configuration getPredefined(String name) throws IOException, ParseException {

        for (KnownConfiguration knownConfig : getKnownConfigurations()) {

            if (knownConfig.getName().equals(name)) {

                return knownConfig.getConfigurationFile();

            }

        }

        throw new NoSuchFileException("Could not locate configuration with name " + name);

    }

}