/*
 * Copyright (c) 2018, 2019, 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.internal.platform.cgroupv1;

import java.io.BufferedReader;
import java.io.IOException;
import java.math.BigInteger;
import java.io.UncheckedIOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.security.AccessController;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import java.util.ArrayList;
import java.util.List;
import java.util.Optional;
import java.util.function.Function;
import java.util.stream.Stream;

public class SubSystem {
    String root;
    String mountPoint;
    String path;

    public SubSystem(String root, String mountPoint) {
        this.root = root;
        this.mountPoint = mountPoint;
    }

    public void setPath(String cgroupPath) {
        if (root != null && cgroupPath != null) {
            if (root.equals("/")) {
                if (!cgroupPath.equals("/")) {
                    path = mountPoint + cgroupPath;
                }
                else {
                    path = mountPoint;
                }
            }
            else {
                if (root.equals(cgroupPath)) {
                    path = mountPoint;
                }
                else {
                    if (cgroupPath.startsWith(root)) {
                        if (cgroupPath.length() > root.length()) {
                            String cgroupSubstr = cgroupPath.substring(root.length());
                            path = mountPoint + cgroupSubstr;
                        }
                    }
                }
            }
        }
    }

    public String path() {
        return path;
    }

    /**
     * getSubSystemStringValue
     *
     * Return the first line of the file "parm" argument from the subsystem.
     *
     * TODO:  Consider using weak references for caching BufferedReader object.
     *
     * @param subsystem
     * @param parm
     * @return Returns the contents of the file specified by param.
     */
    public static String getStringValue(SubSystem subsystem, String parm) {
        if (subsystem == null) return null;

        try {
            return subsystem.readStringValue(parm);
        } catch (IOException e) {
            return null;
        }
    }

    private String readStringValue(String param) throws IOException {
        PrivilegedExceptionAction<BufferedReader> pea = () ->
                Files.newBufferedReader(Paths.get(path(), param));
        try (BufferedReader bufferedReader =
                     AccessController.doPrivileged(pea)) {
            String line = bufferedReader.readLine();
            return line;
        } catch (PrivilegedActionException e) {
            Metrics.unwrapIOExceptionAndRethrow(e);
            throw new InternalError(e.getCause());
        } catch (UncheckedIOException e) {
            throw e.getCause();
        }
    }

    public static long getLongValueMatchingLine(SubSystem subsystem,
                                                     String param,
                                                     String match,
                                                     Function<String, Long> conversion) {
        long retval = Metrics.unlimited_minimum + 1; // default unlimited
        try {
            List<String> lines = subsystem.readMatchingLines(param);
            for (String line: lines) {
                if (line.contains(match)) {
                    retval = conversion.apply(line);
                    break;
                }
            }
        } catch (IOException e) {
            // Ignore. Default is unlimited.
        }
        return retval;
    }

    private List<String> readMatchingLines(String param) throws IOException {
        try {
            PrivilegedExceptionAction<List<String>> pea = () ->
                    Files.readAllLines(Paths.get(path(), param));
            return AccessController.doPrivileged(pea);
        } catch (PrivilegedActionException e) {
            Metrics.unwrapIOExceptionAndRethrow(e);
            throw new InternalError(e.getCause());
        } catch (UncheckedIOException e) {
            throw e.getCause();
        }
    }

    public static long getLongValue(SubSystem subsystem, String parm) {
        String strval = getStringValue(subsystem, parm);
        return convertStringToLong(strval);
    }

    public static long convertStringToLong(String strval) {
        if (strval == null) return 0L;

        long retval = 0;

        try {
            retval = Long.parseLong(strval);
        } catch (NumberFormatException e) {
            // For some properties (e.g. memory.limit_in_bytes) we may overflow the range of signed long.
            // In this case, return Long.max
            BigInteger b = new BigInteger(strval);
            if (b.compareTo(BigInteger.valueOf(Long.MAX_VALUE)) > 0) {
                return Long.MAX_VALUE;
            }
        }

        return retval;
    }

    public static double getDoubleValue(SubSystem subsystem, String parm) {
        String strval = getStringValue(subsystem, parm);

        if (strval == null) return 0L;

        double retval = Double.parseDouble(strval);

        return retval;
    }

    /**
     * getSubSystemlongEntry
     *
     * Return the long value from the line containing the string "entryname"
     * within file "parm" in the "subsystem".
     *
     * TODO:  Consider using weak references for caching BufferedReader object.
     *
     * @param subsystem
     * @param parm
     * @param entryname
     * @return long value
     */
    public static long getLongEntry(SubSystem subsystem, String parm, String entryname) {
        String val = null;

        if (subsystem == null) return 0L;

        try (Stream<String> lines = Metrics.readFilePrivileged(Paths.get(subsystem.path(), parm))) {

            Optional<String> result = lines.map(line -> line.split(" "))
                                           .filter(line -> (line.length == 2 &&
                                                   line[0].equals(entryname)))
                                           .map(line -> line[1])
                                           .findFirst();

            return result.isPresent() ? Long.parseLong(result.get()) : 0L;
        } catch (IOException e) {
            return 0L;
        } catch (UncheckedIOException e) {
            return 0L;
        }
    }

    public static int getIntValue(SubSystem subsystem, String parm) {
        String val = getStringValue(subsystem, parm);

        if (val == null) return 0;

        return Integer.parseInt(val);
    }

    /**
     * StringRangeToIntArray
     *
     * Convert a string in the form of  1,3-4,6 to an array of
     * integers containing all the numbers in the range.
     *
     * @param range
     * @return int[] containing a sorted list of processors or memory nodes
     */
    public static int[] StringRangeToIntArray(String range) {
        int[] ints = new int[0];

        if (range == null) return ints;

        ArrayList<Integer> results = new ArrayList<>();
        String strs[] = range.split(",");
        for (String str : strs) {
            if (str.contains("-")) {
                String lohi[] = str.split("-");
                // validate format
                if (lohi.length != 2) {
                    continue;
                }
                int lo = Integer.parseInt(lohi[0]);
                int hi = Integer.parseInt(lohi[1]);
                for (int i = lo; i <= hi; i++) {
                    results.add(i);
                }
            }
            else {
                results.add(Integer.parseInt(str));
            }
        }

        // sort results
        results.sort(null);

        // convert ArrayList to primitive int array
        ints = new int[results.size()];
        int i = 0;
        for (Integer n : results) {
            ints[i++] = n;
        }

        return ints;
    }

    public static class MemorySubSystem extends SubSystem {

        private boolean hierarchical;
        private boolean swapenabled;

        public MemorySubSystem(String root, String mountPoint) {
            super(root, mountPoint);
        }

        boolean isHierarchical() {
            return hierarchical;
        }

        void setHierarchical(boolean hierarchical) {
            this.hierarchical = hierarchical;
        }

        boolean isSwapEnabled() {
            return swapenabled;
        }

        void setSwapEnabled(boolean swapenabled) {
            this.swapenabled = swapenabled;
        }

    }
}