package jdk.jfr.internal.consumer;

import java.io.IOException;

import java.nio.file.DirectoryStream;

import java.nio.file.Files;

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.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;

public final class RepositoryFiles {

    private final Path repostory;

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

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

    private volatile boolean closed;

    public RepositoryFiles(Path repostory) {

        this.repostory = repostory;

    }

    public long getTimestamp(Path p) {

        return pathLookup.get(p);

    }

    public Path nextPath(long startTimeNanos) {

        while (!closed) {

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

            if (!after.isEmpty()) {

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

                Logger.log(LogTag.JFR_SYSTEM_STREAMING, LogLevel.TRACE, "Return path " + path + " for start time nanos " + startTimeNanos);

                return path;

            }

            try {

                if (updatePaths(repostory)) {

                    continue;

                }

            } 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

                // of an EventSet was constructed. Just ignore,

                // and retry later.

            }

            try {

                synchronized (pathSet) {

                    pathSet.wait(1000);

                }

            } catch (InterruptedException e) {

                // ignore

            }

        }

        return null;

    }

    private boolean updatePaths(Path repo) throws IOException {

        if (repo == null) {

            repo = Repository.getRepository().getRepositoryPath().toPath();

        }

        boolean foundNew = false;

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

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

        if (!Files.exists(repo)) {

            // Repository removed, probably due to shutdown

            return true;

        }

        try (DirectoryStream<Path> dirStream = Files.newDirectoryStream(repo, "*.jfr")) {

            for (Path p : dirStream) {

                if (!pathLookup.containsKey(p)) {

                    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 = Files.size(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(), 100)) {

            ChunkHeader c = new ChunkHeader(in);

            return c.getStartNanos();

        }

    }

    public void close() {

        synchronized (pathSet) {

            this.closed = true;

            pathSet.notify();

        }

    }

}