/*
 * Copyright 2012-2017 Red Hat, Inc.
 *
 * This file is part of Thermostat.
 *
 * Thermostat is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published
 * by the Free Software Foundation; either version 2, or (at your
 * option) any later version.
 *
 * Thermostat 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 for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Thermostat; see the file COPYING.  If not see
 * <http://www.gnu.org/licenses/>.
 *
 * Linking this code with other modules is making a combined work
 * based on this code.  Thus, the terms and conditions of the GNU
 * General Public License cover the whole combination.
 *
 * As a special exception, the copyright holders of this code give
 * you permission to link this code with independent modules to
 * produce an executable, regardless of the license terms of these
 * independent modules, and to copy and distribute the resulting
 * executable under terms of your choice, provided that you also
 * meet, for each linked independent module, the terms and conditions
 * of the license of that module.  An independent module is a module
 * which is not derived from or based on this code.  If you modify
 * this code, you may extend this exception to your version of the
 * library, but you are not obligated to do so.  If you do not wish
 * to do so, delete this exception statement from your version.
 */

package com.redhat.thermostat.vm.profiler.agent.jvm;

import java.io.BufferedWriter;
import java.io.IOException;
import java.lang.instrument.Instrumentation;
import java.lang.instrument.UnmodifiableClassException;
import java.lang.management.ManagementFactory;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.OpenOption;
import java.nio.file.Path;
import java.nio.file.StandardOpenOption;
import java.nio.file.attribute.FileAttribute;
import java.nio.file.attribute.PosixFilePermission;
import java.nio.file.attribute.PosixFilePermissions;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.atomic.AtomicLong;

public class InstrumentationControl implements InstrumentationControlMXBean {

    private final Instrumentation instrumentation;
    private final ProfilerInstrumentor classInstrumentor;
    private final ProfileRecorder recorder;
    private final ResultsFileCreator resultsFileCreator;

    private boolean profiling = false;

    private boolean resultsWrittenToDisk = true;
    private String lastResults = null;

    public InstrumentationControl(Instrumentation instrumentation) {
        this(instrumentation, new AsmBasedInstrumentor(), ProfileRecorder.getInstance(), new ResultsFileCreator());
    }

    public InstrumentationControl(Instrumentation instrumentation,
            ProfilerInstrumentor instrumentor,
            ProfileRecorder recorder,
            ResultsFileCreator resultsFileCreator) {
        this.instrumentation = instrumentation;
        this.classInstrumentor = instrumentor;
        this.recorder = recorder;
        this.resultsFileCreator = resultsFileCreator;

        addShutdownHookToSaveData();
    }

    private void addShutdownHookToSaveData() {
        Runtime.getRuntime().addShutdownHook(new Thread() {
            @Override
            public void run() {
                onVmShutdown();
            }
        });
    }

    /** package private for testing */
    void onVmShutdown() {
        writeResultsToDiskIfNotWritten();
    }

    @Override
    public void startProfiling() {
        if (profiling) {
            throw new IllegalStateException("Already started");
        }
        profiling = true;
        resultsWrittenToDisk = false;

        instrumentation.addTransformer(classInstrumentor, true);
        retransformAlreadyLoadedClasses(instrumentation, classInstrumentor);
    }

    @Override
    public void stopProfiling() {
        if (!profiling) {
            throw new IllegalStateException("Not profiling");
        }
        profiling = false;

        instrumentation.removeTransformer(classInstrumentor);
        retransformAlreadyLoadedClasses(instrumentation, classInstrumentor);

        writeProfilingResultsToDisk();
        clearProfileData();
    }

    private void retransformAlreadyLoadedClasses(Instrumentation instrumentation, ProfilerInstrumentor profiler) {
        long start = System.nanoTime();

        List<Class<?>> toTransform = new ArrayList<Class<?>>();

        for (Class<?> klass : instrumentation.getAllLoadedClasses()) {
            boolean skipThisClass = false;
            if (!instrumentation.isModifiableClass(klass)) {
                skipThisClass = true;
            }
            if (!profiler.shouldInstrument(klass)) {
                skipThisClass = true;
            }

            if (skipThisClass) {
                continue;
            }

            toTransform.add(klass);
        }

        if (toTransform.size() > 0) {
            Debug.println("AGENT: Retransforming " + toTransform.size() + " classes");
            for (Class<?> klass : toTransform) {
                try {
                    instrumentation.retransformClasses(klass);
                } catch (UnmodifiableClassException e) {
                    throw new AssertionError("Tried to modify an unmodifiable class", e);
                } catch (Error e) {
                    Debug.printlnError("Failed to transform: " + klass.getName());
                    Debug.printlnError("Unable to retransform all classes. Some classes may not have been instrumented correctly!");
                    Debug.printStackTrace(e);
                }
            }
        }
        long end = System.nanoTime();
        Debug.println("AGENT: Retansforming took: " + (end - start) + "ns");
    }

    private void writeResultsToDiskIfNotWritten() {
        if (!resultsWrittenToDisk) {
            writeProfilingResultsToDisk();
        }
    }

    private void writeProfilingResultsToDisk() {
        try {
            ResultsFile resultsFile = resultsFileCreator.get();
            String path = resultsFile.getPath();
            BufferedWriter out = null;
            try {
                out = resultsFile.getWriter();
                Map<String, AtomicLong> data = recorder.getData();
                Debug.println("AGENT: Writing " + data.size() + " results to: " + path);
                for (Map.Entry<String, AtomicLong> entry : data.entrySet()) {
                    out.write(entry.getValue().get() + "\t" + entry.getKey() + "\n");
                }
                resultsWrittenToDisk = true;
                lastResults = path;
            } finally {
                try {
                    if (out != null) {
                        out.close();
                    }
                } catch (IOException e) {
                    // well, we are screwed
                    Debug.printStackTrace(e);
                }
            }
        } catch (IOException e) {
            Debug.printStackTrace(e);
        }
    }

    private void clearProfileData() {
        recorder.clearData();
    }

    @Override
    public boolean isProfiling() {
        return profiling;
    }

    @Override
    public String getProfilingDataFile() {
        return lastResults;
    }

    static class ResultsFileCreator {

        ResultsFile get() throws IOException {
            Path output = createOutput();
            return new ResultsFile(output);
        }

        private boolean isPosixSystem() {
            final String osname = System.getProperty("os.name").toLowerCase();
            final boolean IS_UNIX = !osname.contains("win");
            return IS_UNIX;
        }

        private Path createOutput() throws IOException {
            if (isPosixSystem()) {
                Set<PosixFilePermission> perm = PosixFilePermissions.fromString("rw-------");
                FileAttribute<Set<PosixFilePermission>> attributes = PosixFilePermissions.asFileAttribute(perm);
                // Include the pid so agent can find it. Surround pid with - to
                // avoid false prefix-based matches. Otherwise the agent searching
                // for "-12" may find "-123" as a valid match.
                return Files.createTempFile("thermostat-" + getProcessId() + "-", ".perfdata", attributes);
            }
            else {
                // should check that this is in a secure location
                return Files.createTempFile("thermostat-" + getProcessId() + "-", ".perfdata");
            }
        }

        private String getProcessId() {
            return ManagementFactory.getRuntimeMXBean().getName().split("@")[0];
        }
    }

    static class ResultsFile {

        private final Path path;

        ResultsFile(Path path) { this.path = path; }

        String getPath() { return path.toString(); }

        /** Caller must close the writer when done */
        BufferedWriter getWriter() throws IOException {
            OpenOption[] options = new OpenOption[] {
                    StandardOpenOption.WRITE,
                    StandardOpenOption.TRUNCATE_EXISTING
            };

            return Files.newBufferedWriter(path, StandardCharsets.UTF_8, options);
        }
    }
}