/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.sshd.sftp.client.impl;

import java.io.IOException;
import java.io.Writer;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.StandardOpenOption;
import java.util.Date;
import java.util.EnumSet;
import java.util.concurrent.TimeUnit;

import org.apache.sshd.common.Factory;
import org.apache.sshd.common.io.IoSession;
import org.apache.sshd.common.random.Random;
import org.apache.sshd.common.session.Session;
import org.apache.sshd.common.util.buffer.Buffer;
import org.apache.sshd.common.util.buffer.ByteArrayBuffer;
import org.apache.sshd.sftp.SftpModuleProperties;
import org.apache.sshd.sftp.client.AbstractSftpClientTestSupport;
import org.apache.sshd.sftp.client.RawSftpClient;
import org.apache.sshd.sftp.client.SftpClient;
import org.apache.sshd.sftp.client.SftpClient.CloseableHandle;
import org.apache.sshd.sftp.client.SftpClient.OpenMode;
import org.apache.sshd.sftp.common.SftpConstants;
import org.apache.sshd.util.test.CommonTestSupportUtils;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Disabled;
import org.junit.jupiter.api.MethodOrderer.MethodName;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.TestMethodOrder;
import org.junit.jupiter.api.Timeout;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * @author <a href="mailto:dev@mina.apache.org">Apache MINA SSHD Project</a>
 */
@TestMethodOrder(MethodName.class)
class SftpRemotePathChannelTest extends AbstractSftpClientTestSupport {

    SftpRemotePathChannelTest() throws IOException {
        super();
    }

    @BeforeEach
    void setUp() throws Exception {
        setupServer();
    }

    // see SSHD-697
    @Test
    void fileChannel() throws IOException {
        Path targetPath = detectTargetFolder();
        Path lclSftp = CommonTestSupportUtils.resolve(
                targetPath, SftpConstants.SFTP_SUBSYSTEM_NAME, getClass().getSimpleName());
        Path lclFile = assertHierarchyTargetFolderExists(lclSftp).resolve(getCurrentTestName() + ".txt");
        Files.deleteIfExists(lclFile);
        byte[] expected
                = (getClass().getName() + "#" + getCurrentTestName() + "(" + new Date() + ")").getBytes(StandardCharsets.UTF_8);

        Path parentPath = targetPath.getParent();
        String remFilePath = CommonTestSupportUtils.resolveRelativeRemotePath(parentPath, lclFile);

        try (SftpClient sftp = createSingleSessionClient();
             FileChannel fc = sftp.openRemotePathChannel(
                     remFilePath, EnumSet.of(
                             StandardOpenOption.CREATE, StandardOpenOption.READ, StandardOpenOption.WRITE))) {
            int writeLen = fc.write(ByteBuffer.wrap(expected));
            assertEquals(expected.length, writeLen, "Mismatched written length");

            FileChannel fcPos = fc.position(0L);
            assertSame(fc, fcPos, "Mismatched positioned file channel");

            byte[] actual = new byte[expected.length];
            int readLen = fc.read(ByteBuffer.wrap(actual));
            assertEquals(writeLen, readLen, "Mismatched read len");
            assertArrayEquals(expected, actual, "Mismatched read data");
        }

        byte[] actual = Files.readAllBytes(lclFile);
        assertArrayEquals(expected, actual, "Mismatched persisted data");
    }

    // see SSHD-967
    @Test
    void transferToFileChannel() throws IOException {
        Path targetPath = detectTargetFolder();
        Path lclSftp = CommonTestSupportUtils.resolve(
                targetPath, SftpConstants.SFTP_SUBSYSTEM_NAME, getClass().getSimpleName());
        Path srcFile = assertHierarchyTargetFolderExists(lclSftp).resolve(getCurrentTestName() + "-src.txt");
        Path parentPath = targetPath.getParent();

        Files.deleteIfExists(srcFile);
        try (Writer output = Files.newBufferedWriter(srcFile, StandardCharsets.UTF_8)) {
            String seed = getClass().getName() + "#" + getCurrentTestName() + "(" + new Date() + ")";
            for (long totalWritten = 0L;
                 totalWritten <= SftpModuleProperties.COPY_BUF_SIZE.getRequiredDefault();
                 totalWritten += seed.length()) {
                output.append(seed).append(System.lineSeparator());
            }
        }

        byte[] expected = Files.readAllBytes(srcFile);
        Path dstFile = srcFile.getParent().resolve(getCurrentTestName() + "-dst.txt");
        Files.deleteIfExists(dstFile);

        String remFilePath = CommonTestSupportUtils.resolveRelativeRemotePath(parentPath, srcFile);
        try (SftpClient sftp = createSingleSessionClient();
             FileChannel srcChannel = sftp.openRemotePathChannel(
                     remFilePath, EnumSet.of(StandardOpenOption.READ));
             FileChannel dstChannel = FileChannel.open(dstFile,
                     StandardOpenOption.CREATE, StandardOpenOption.WRITE)) {
            long numXfered = srcChannel.transferTo(0L, expected.length, dstChannel);
            assertEquals(expected.length, numXfered, "Mismatched reported transfer count");
        }

        byte[] actual = Files.readAllBytes(dstFile);
        assertEquals(expected.length, actual.length, "Mismatched transferred size");
        assertArrayEquals(expected, actual, "Mismatched transferred data");
    }

    // see SSHD-1182
    @Test
    void transferToFileChannelWithOffset() throws IOException {
        Path targetPath = detectTargetFolder();
        Path lclSftp = CommonTestSupportUtils.resolve(
                targetPath, SftpConstants.SFTP_SUBSYSTEM_NAME, getClass().getSimpleName());
        Path srcFile = assertHierarchyTargetFolderExists(lclSftp).resolve(getCurrentTestName() + "-src.txt");
        Path parentPath = targetPath.getParent();

        Files.deleteIfExists(srcFile);
        try (Writer output = Files.newBufferedWriter(srcFile, StandardCharsets.UTF_8)) {
            String seed = getClass().getName() + "#" + getCurrentTestName() + "(" + new Date() + ")";
            for (long totalWritten = 0L;
                 totalWritten <= SftpModuleProperties.COPY_BUF_SIZE.getRequiredDefault();
                 totalWritten += seed.length()) {
                output.append(seed).append(System.lineSeparator());
            }
        }

        byte[] data = Files.readAllBytes(srcFile);
        int offset = data.length / 4;
        byte[] expected = new byte[data.length - offset];
        System.arraycopy(data, offset, expected, 0, expected.length);

        Path dstFile = srcFile.getParent().resolve(getCurrentTestName() + "-dst.txt");
        Files.deleteIfExists(dstFile);

        String remFilePath = CommonTestSupportUtils.resolveRelativeRemotePath(parentPath, srcFile);
        try (SftpClient sftp = createSingleSessionClient();
             FileChannel srcChannel = sftp.openRemotePathChannel(
                     remFilePath, EnumSet.of(StandardOpenOption.READ));
             FileChannel dstChannel = FileChannel.open(dstFile,
                     StandardOpenOption.CREATE, StandardOpenOption.WRITE)) {
            long numXfered = srcChannel.transferTo(offset, expected.length, dstChannel);
            assertEquals(expected.length, numXfered, "Mismatched reported transfer count");
        }

        byte[] actual = Files.readAllBytes(dstFile);
        assertEquals(expected.length, actual.length, "Mismatched transferred size");
        assertArrayEquals(expected, actual, "Mismatched transferred data");
    }

    // see SSHD-970
    @Test
    @Timeout(value = 10000, unit = TimeUnit.MILLISECONDS)
    void transferToFileChannelLoopFile() throws IOException {
        Path targetPath = detectTargetFolder();
        Path lclSftp = CommonTestSupportUtils.resolve(
                targetPath, SftpConstants.SFTP_SUBSYSTEM_NAME, getClass().getSimpleName());
        Path srcFile = assertHierarchyTargetFolderExists(lclSftp).resolve(getCurrentTestName() + "-src.txt");
        Path parentPath = targetPath.getParent();

        Files.deleteIfExists(srcFile);
        try (Writer output = Files.newBufferedWriter(srcFile, StandardCharsets.UTF_8)) {
            String seed = getClass().getName() + "#" + getCurrentTestName() + "(" + new Date() + ")";
            output.append(seed).append(System.lineSeparator());
        }

        byte[] expected = Files.readAllBytes(srcFile);
        Path dstFile = srcFile.getParent().resolve(getCurrentTestName() + "-dst.txt");
        Files.deleteIfExists(dstFile);

        String remFilePath = CommonTestSupportUtils.resolveRelativeRemotePath(parentPath, srcFile);
        try (SftpClient sftp = createSingleSessionClient();
             FileChannel srcChannel = sftp.openRemotePathChannel(
                     remFilePath, EnumSet.of(StandardOpenOption.READ));
             FileChannel dstChannel = FileChannel.open(dstFile,
                     StandardOpenOption.CREATE, StandardOpenOption.WRITE)) {
            // SftpRemotePathChannel.DEFAULT_TRANSFER_BUFFER_SIZE > expected.length => Infinite loop
            long numXfered
                    = srcChannel.transferTo(0L, SftpModuleProperties.COPY_BUF_SIZE.getRequiredDefault(), dstChannel);
            assertEquals(expected.length, numXfered, "Mismatched reported transfer count");
        }

        byte[] actual = Files.readAllBytes(dstFile);
        assertEquals(expected.length, actual.length, "Mismatched transferred size");
        assertArrayEquals(expected, actual, "Mismatched transferred data");
    }

    // see SSHD-967
    @Test
    void transferFromFileChannel() throws IOException {
        Path targetPath = detectTargetFolder();
        Path lclSftp = CommonTestSupportUtils.resolve(
                targetPath, SftpConstants.SFTP_SUBSYSTEM_NAME, getClass().getSimpleName());
        Path srcFile = assertHierarchyTargetFolderExists(lclSftp).resolve(getCurrentTestName() + "-src.txt");
        Path parentPath = targetPath.getParent();

        Files.deleteIfExists(srcFile);
        try (Writer output = Files.newBufferedWriter(srcFile, StandardCharsets.UTF_8)) {
            String seed = getClass().getName() + "#" + getCurrentTestName() + "(" + new Date() + ")";
            for (long totalWritten = 0L;
                 totalWritten <= SftpModuleProperties.COPY_BUF_SIZE.getRequiredDefault();
                 totalWritten += seed.length()) {
                output.append(seed).append(System.lineSeparator());
            }
        }

        byte[] expected = Files.readAllBytes(srcFile);
        Path dstFile = srcFile.getParent().resolve(getCurrentTestName() + "-dst.txt");
        Files.deleteIfExists(dstFile);

        String remFilePath = CommonTestSupportUtils.resolveRelativeRemotePath(parentPath, dstFile);
        try (SftpClient sftp = createSingleSessionClient();
             FileChannel dstChannel = sftp.openRemotePathChannel(
                     remFilePath, EnumSet.of(StandardOpenOption.CREATE, StandardOpenOption.WRITE));
             FileChannel srcChannel = FileChannel.open(srcFile, StandardOpenOption.READ)) {
            long numXfered = dstChannel.transferFrom(srcChannel, 0L, expected.length);
            assertEquals(expected.length, numXfered, "Mismatched reported transfer count");
        }

        byte[] actual = Files.readAllBytes(dstFile);
        assertEquals(expected.length, actual.length, "Mismatched transferred size");
        assertArrayEquals(expected, actual, "Mismatched transferred data");
    }

    @Test
    void transferFromFileChannelWithOffset() throws IOException {
        Path targetPath = detectTargetFolder();
        Path lclSftp = CommonTestSupportUtils.resolve(
                targetPath, SftpConstants.SFTP_SUBSYSTEM_NAME, getClass().getSimpleName());
        Path srcFile = assertHierarchyTargetFolderExists(lclSftp).resolve(getCurrentTestName() + "-src.txt");
        Path parentPath = targetPath.getParent();

        Files.deleteIfExists(srcFile);
        try (Writer output = Files.newBufferedWriter(srcFile, StandardCharsets.UTF_8)) {
            String seed = getClass().getName() + "#" + getCurrentTestName() + "(" + new Date() + ")";
            for (long totalWritten = 0L;
                 totalWritten <= SftpModuleProperties.COPY_BUF_SIZE.getRequiredDefault();
                 totalWritten += seed.length()) {
                output.append(seed).append(System.lineSeparator());
            }
        }

        byte[] data = Files.readAllBytes(srcFile);
        int offset = data.length / 4;
        byte[] expected = new byte[data.length];
        System.arraycopy(data, 0, expected, offset, expected.length - offset);

        Path dstFile = srcFile.getParent().resolve(getCurrentTestName() + "-dst.txt");
        Files.deleteIfExists(dstFile);

        String remFilePath = CommonTestSupportUtils.resolveRelativeRemotePath(parentPath, dstFile);
        try (SftpClient sftp = createSingleSessionClient();
             FileChannel dstChannel = sftp.openRemotePathChannel(
                     remFilePath, EnumSet.of(StandardOpenOption.CREATE, StandardOpenOption.WRITE));
             FileChannel srcChannel = FileChannel.open(srcFile, StandardOpenOption.READ)) {
            long numXfered = dstChannel.transferFrom(srcChannel, offset, expected.length - offset);
            assertEquals(expected.length - offset, numXfered, "Mismatched reported transfer count");
        }

        byte[] actual = Files.readAllBytes(dstFile);
        assertEquals(expected.length, actual.length, "Mismatched transferred size");
        assertArrayEquals(expected, actual, "Mismatched transferred data");
    }

    /*
     * Demonstrates an DoS vulnerability by opening a file and requesting data from it without actually reading
     * any response data, the buffers in {@link org.apache.sshd.common.channel.BufferedIoOutputStream} fill up until
     * an Out Of Memory Error occurs.
     * To test, the available heap memory of the server must be below the value set in requested_data_volume
     * limit the available heap memory of the junit execution by passing "-Xmx256m" to the VM.
     */
    @Test
    @Timeout(value = 5L * 60L * 1000L, unit = TimeUnit.MILLISECONDS)   // see SSHD-1125
    @Disabled("Used only for debugging SSHD-1125")
    void readRequestsOutOfMemory() throws Exception {
        Path targetPath = detectTargetFolder();
        Path parentPath = targetPath.getParent();
        Path lclSftp = CommonTestSupportUtils.resolve(
                targetPath, SftpConstants.SFTP_SUBSYSTEM_NAME,
                getClass().getSimpleName(), getCurrentTestName());

        // Generate some random data file
        Path testFile = assertHierarchyTargetFolderExists(lclSftp).resolve("file.txt");
        byte[] expected = new byte[1024];
        Factory<? extends Random> factory = sshd.getRandomFactory();
        Random rnd = factory.create();
        rnd.fill(expected);
        Files.write(testFile, expected);

        String file = CommonTestSupportUtils.resolveRelativeRemotePath(parentPath, testFile);
        try (SftpClient sftp = createSingleSessionClient();
             CloseableHandle handle = sftp.open(file, OpenMode.Read)) {
            // Prevent the client from reading any packets from the server to provoke serverside buffers to fill up
            Session session = sftp.getSession();
            IoSession ioSession = session.getIoSession();
            ioSession.suspendRead();

            // Always read from the same offset. Thereby one can work with a small file.
            long curPos = 0L;
            byte[] buffer = new byte[32768];
            long readLength = buffer.length;
            // Request about 1 GB of data
            int requestedDataVolume = 1024 * 1024 * 1204;
            byte[] id = handle.getIdentifier();
            Runtime runtime = Runtime.getRuntime();
            Logger logger = LoggerFactory.getLogger(getClass());
            String testName = getCurrentTestName();
            long maxRequests = requestedDataVolume / readLength;
            for (long i = 0L; i < maxRequests; i++) {
                if ((i & 0x03FF) == 0L) {
                    logger.info("{} - free={}, total={}, max={} after {}/{} requests",
                            testName, runtime.freeMemory(), runtime.totalMemory(), runtime.maxMemory(), i, maxRequests);
                }

                // Send a SSH_FXP_READ command to the server without reading the response
                Buffer requestBuffer = new ByteArrayBuffer(id.length + Long.SIZE, false);
                requestBuffer.putBytes(id);
                requestBuffer.putLong(curPos);
                requestBuffer.putUInt(readLength);
                ((RawSftpClient) sftp).send(SftpConstants.SSH_FXP_READ, requestBuffer);

                Thread.sleep(1L);
            }
            Thread.sleep(1000L);
        }
    }
}
