//
// ========================================================================
// Copyright (c) 1995-2020 Mort Bay Consulting Pty Ltd and others.
//
// This program and the accompanying materials are made available under
// the terms of the Eclipse Public License 2.0 which is available at
// https://www.eclipse.org/legal/epl-2.0
//
// This Source Code may also be made available under the following
// Secondary Licenses when the conditions for such availability set
// forth in the Eclipse Public License, v. 2.0 are satisfied:
// the Apache License v2.0 which is available at
// https://www.apache.org/licenses/LICENSE-2.0
//
// SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
// ========================================================================
//

package org.eclipse.jetty.util.ssl;

import java.io.File;
import java.io.IOException;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.TimeUnit;
import java.util.function.Consumer;

import org.eclipse.jetty.util.Callback;
import org.eclipse.jetty.util.Scanner;
import org.eclipse.jetty.util.annotation.ManagedAttribute;
import org.eclipse.jetty.util.annotation.ManagedOperation;
import org.eclipse.jetty.util.component.ContainerLifeCycle;
import org.eclipse.jetty.util.resource.Resource;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

The KeyStoreScanner is used to monitor the KeyStore file used by the SslContextFactory. It will reload the SslContextFactory if it detects that the KeyStore file has been modified.
If the TrustStore file needs to be changed, then this should be done before touching the KeyStore file, the SslContextFactory.reload(Consumer<SslContextFactory>) will only occur after the KeyStore file has been modified.
/**
 * <p>The {@link KeyStoreScanner} is used to monitor the KeyStore file used by the {@link SslContextFactory}.
 * It will reload the {@link SslContextFactory} if it detects that the KeyStore file has been modified.</p>
 * <p>If the TrustStore file needs to be changed, then this should be done before touching the KeyStore file,
 * the {@link SslContextFactory#reload(Consumer)} will only occur after the KeyStore file has been modified.</p>
 */
public class KeyStoreScanner extends ContainerLifeCycle implements Scanner.DiscreteListener
{
    private static final Logger LOG = LoggerFactory.getLogger(KeyStoreScanner.class);

    private final SslContextFactory sslContextFactory;
    private final File keystoreFile;
    private final Scanner _scanner;

    public KeyStoreScanner(SslContextFactory sslContextFactory)
    {
        this.sslContextFactory = sslContextFactory;
        try
        {
            Resource keystoreResource = sslContextFactory.getKeyStoreResource();
            File monitoredFile = keystoreResource.getFile();
            if (monitoredFile == null || !monitoredFile.exists())
                throw new IllegalArgumentException("keystore file does not exist");
            if (monitoredFile.isDirectory())
                throw new IllegalArgumentException("expected keystore file not directory");

            if (keystoreResource.getAlias() != null)
            {
                // this resource has an alias, use the alias, as that's what's returned in the Scanner
                monitoredFile = new File(keystoreResource.getAlias());
            }

            keystoreFile = monitoredFile;
            if (LOG.isDebugEnabled())
                LOG.debug("Monitored Keystore File: {}", monitoredFile);
        }
        catch (IOException e)
        {
            throw new IllegalArgumentException("could not obtain keystore file", e);
        }

        File parentFile = keystoreFile.getParentFile();
        if (!parentFile.exists() || !parentFile.isDirectory())
            throw new IllegalArgumentException("error obtaining keystore dir");

        _scanner = new Scanner();
        _scanner.addDirectory(parentFile.toPath());
        _scanner.setScanInterval(1);
        _scanner.setReportDirs(false);
        _scanner.setReportExistingFilesOnStartup(false);
        _scanner.setScanDepth(1);
        _scanner.addListener(this);
        addBean(_scanner);
    }

    @Override
    public void fileAdded(String filename)
    {
        if (LOG.isDebugEnabled())
            LOG.debug("added {}", filename);

        if (keystoreFile.toPath().toString().equals(filename))
            reload();
    }

    @Override
    public void fileChanged(String filename)
    {
        if (LOG.isDebugEnabled())
            LOG.debug("changed {}", filename);

        if (keystoreFile.toPath().toString().equals(filename))
            reload();
    }

    @Override
    public void fileRemoved(String filename)
    {
        if (LOG.isDebugEnabled())
            LOG.debug("removed {}", filename);

        if (keystoreFile.toPath().toString().equals(filename))
            reload();
    }

    @ManagedOperation(value = "Scan for changes in the SSL Keystore", impact = "ACTION")
    public boolean scan(long waitMillis)
    {
        if (LOG.isDebugEnabled())
            LOG.debug("scanning");

        CompletableFuture<Boolean> cf = new CompletableFuture<>();
        try
        {
            // Perform 2 scans to be sure that the scan is stable.
            _scanner.scan(Callback.from(() ->
                _scanner.scan(Callback.from(() -> cf.complete(true), cf::completeExceptionally)), cf::completeExceptionally));
            return cf.get(waitMillis, TimeUnit.MILLISECONDS);
        }
        catch (Exception e)
        {
            throw new RuntimeException(e);
        }
    }

    @ManagedOperation(value = "Reload the SSL Keystore", impact = "ACTION")
    public void reload()
    {
        if (LOG.isDebugEnabled())
            LOG.debug("reloading keystore file {}", keystoreFile);

        try
        {
            sslContextFactory.reload(scf ->
            {
            });
        }
        catch (Throwable t)
        {
            LOG.warn("Keystore Reload Failed", t);
        }
    }

    @ManagedAttribute("scanning interval to detect changes which need reloaded")
    public int getScanInterval()
    {
        return _scanner.getScanInterval();
    }

    public void setScanInterval(int scanInterval)
    {
        _scanner.setScanInterval(scanInterval);
    }
}