/*

 * Copyright (c) 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.jfr.internal.consumer;

import java.io.IOException;

import java.nio.file.DirectoryStream;

import java.nio.file.Path;

import java.util.ArrayList;

import java.util.Collections;

import java.util.HashMap;

import java.util.HashSet;

import java.util.List;

import java.util.Map;

import java.util.NavigableMap;

import java.util.Set;

import java.util.SortedMap;

import java.util.TreeMap;

import jdk.jfr.internal.LogLevel;

import jdk.jfr.internal.LogTag;

import jdk.jfr.internal.Logger;

import jdk.jfr.internal.Repository;

import jdk.jfr.internal.SecuritySupport.SafePath;

public final class RepositoryFiles {

    private final FileAccess fileAccess;

    private final NavigableMap<Long, Path> pathSet = new TreeMap<>();

    private final Map<Path, Long> pathLookup = new HashMap<>();

    private final Path repository;

    private volatile boolean closed;

    public RepositoryFiles(FileAccess fileAccess, Path repository) {

        this.repository = repository;

        this.fileAccess = fileAccess;

    }

    public long getTimestamp(Path p) {

        return pathLookup.get(p);

    }

    public Path lastPath() {

        if (waitForPaths()) {

            return pathSet.lastEntry().getValue();

        }

        return null; // closed

    }

    public Path firstPath(long startTimeNanos) {

        if (waitForPaths()) {

            // Pick closest chunk before timestamp

            Long time = pathSet.floorKey(startTimeNanos);

            if (time != null) {

                startTimeNanos = time;

            }

            return path(startTimeNanos);

        }

        return null; // closed

    }

    private boolean waitForPaths() {

        while (!closed) {

            try {

                if (updatePaths()) {

                    break;

                }

            } catch (IOException e) {

                Logger.log(LogTag.JFR_SYSTEM_STREAMING, LogLevel.DEBUG, "IOException during repository file scan " + e.getMessage());

                // This can happen if a chunk is being removed

                // between the file was discovered and an instance

                // was accessed, or if new file has been written yet

                // Just ignore, and retry later.

            }

            nap();

        }

        return !closed;

    }

    public Path nextPath(long startTimeNanos) {

        return path(startTimeNanos);

    }

    private Path path(long timestamp) {

        if (closed) {

            return null;

        }

        while (true) {

            SortedMap<Long, Path> after = pathSet.tailMap(timestamp);

            if (!after.isEmpty()) {

                Path path = after.get(after.firstKey());

                return path;

            }

            if (!waitForPaths()) {

                return null; // closed

            }

        }

    }

    private void nap() {

        try {

            synchronized (pathSet) {

                pathSet.wait(1000);

            }

        } catch (InterruptedException e) {

            // ignore

        }

    }

    private boolean updatePaths() throws IOException {

        boolean foundNew = false;

        Path repoPath = repository;

        if (repoPath == null) {

            // Always get the latest repository if 'jcmd JFR.configure

            // repositorypath=...' has been executed

            SafePath sf = Repository.getRepository().getRepositoryPath();

            if (sf == null) {

                return false; // not initialized

            }

            repoPath = sf.toPath();

        }

        try (DirectoryStream<Path> dirStream = fileAccess.newDirectoryStream(repoPath)) {

            List<Path> added = new ArrayList<>();

            Set<Path> current = new HashSet<>();

            for (Path p : dirStream) {

                if (!pathLookup.containsKey(p)) {

                    String s = p.toString();

                    if (s.endsWith(".jfr")) {

                        added.add(p);

                        Logger.log(LogTag.JFR_SYSTEM_STREAMING, LogLevel.DEBUG, "New file found: " + p.toAbsolutePath());

                    }

                    current.add(p);

                }

            }

            List<Path> removed = new ArrayList<>();

            for (Path p : pathLookup.keySet()) {

                if (!current.contains(p)) {

                    removed.add(p);

                }

            }

            for (Path remove : removed) {

                Long time = pathLookup.get(remove);

                pathSet.remove(time);

                pathLookup.remove(remove);

            }

            Collections.sort(added, (p1, p2) -> p1.compareTo(p2));

            for (Path p : added) {

                // Only add files that have a complete header

                // as the JVM may be in progress writing the file

                long size = fileAccess.fileSize(p);

                if (size >= ChunkHeader.HEADER_SIZE) {

                    long startNanos = readStartTime(p);

                    pathSet.put(startNanos, p);

                    pathLookup.put(p, startNanos);

                    foundNew = true;

                }

            }

            return foundNew;

        }

    }

    private long readStartTime(Path p) throws IOException {

        try (RecordingInput in = new RecordingInput(p.toFile(), fileAccess, 100)) {

            ChunkHeader c = new ChunkHeader(in);

            return c.getStartNanos();

        }

    }

    public void close() {

        synchronized (pathSet) {

            this.closed = true;

            pathSet.notify();

        }

    }

}