/*
 * 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.common.cipher;

import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.EnumSet;
import java.util.List;
import java.util.Objects;
import java.util.Random;
import java.util.Set;

import org.apache.sshd.client.SshClient;
import org.apache.sshd.common.FactoryManager;
import org.apache.sshd.common.NamedFactory;
import org.apache.sshd.common.NamedResource;
import org.apache.sshd.common.cipher.BuiltinCiphers.ParseResult;
import org.apache.sshd.common.util.GenericUtils;
import org.apache.sshd.server.SshServer;
import org.apache.sshd.util.test.BaseTestSupport;
import org.junit.FixMethodOrder;
import org.junit.Test;
import org.junit.runners.MethodSorters;
import org.mockito.Mockito;

/**
 * @author <a href="mailto:dev@mina.apache.org">Apache MINA SSHD Project</a>
 */
@FixMethodOrder(MethodSorters.NAME_ASCENDING)
public class BuiltinCiphersTest extends BaseTestSupport {
    public BuiltinCiphersTest() {
        super();
    }

    @Test
    public void testFromEnumName() {
        for (BuiltinCiphers expected : BuiltinCiphers.VALUES) {
            String name = expected.name();

            for (int index = 0; index < name.length(); index++) {
                BuiltinCiphers actual = BuiltinCiphers.fromString(name);
                assertSame(name + " - mismatched enum values", expected, actual);
                name = shuffleCase(name);   // prepare for next time
            }
        }
    }

    @Test
    public void testFromFactoryName() {
        for (BuiltinCiphers expected : BuiltinCiphers.VALUES) {
            String name = expected.getName();

            for (int index = 0; index < name.length(); index++) {
                BuiltinCiphers actual = BuiltinCiphers.fromFactoryName(name);
                assertSame(name + " - mismatched enum values", expected, actual);
                name = shuffleCase(name);   // prepare for next time
            }
        }
    }

    @Test
    public void testFromFactory() {
        for (BuiltinCiphers expected : BuiltinCiphers.VALUES) {
            if (!expected.isSupported()) {
                System.out.append("Skip unsupported cipher: ").println(expected);
                continue;
            }

            NamedFactory<Cipher> factory = expected;
            assertEquals(expected.name() + " - mismatched factory names", expected.getName(), factory.getName());

            BuiltinCiphers actual = BuiltinCiphers.fromFactory(factory);
            assertSame(expected.getName() + " - mismatched enum values", expected, actual);
        }
    }

    @Test
    public void testAllConstantsCovered() throws Exception {
        Set<BuiltinCiphers> avail = EnumSet.noneOf(BuiltinCiphers.class);
        Field[] fields = BuiltinCiphers.Constants.class.getFields();
        for (Field f : fields) {
            int mods = f.getModifiers();
            if (!Modifier.isStatic(mods)) {
                continue;
            }

            Class<?> type = f.getType();
            if (!String.class.isAssignableFrom(type)) {
                continue;
            }

            String name = Objects.toString(f.get(null), null);
            BuiltinCiphers value = BuiltinCiphers.fromFactoryName(name);
            assertNotNull("No match found for " + name, value);
            assertTrue(name + " re-specified", avail.add(value));
        }

        assertEquals("Incomplete coverage", BuiltinCiphers.VALUES, avail);
    }

    @Test   // make sure that if a cipher is reported as supported we can indeed use it
    public void testSupportedCipher() throws Exception {
        Exception err = null;
        Random rnd = new Random(System.nanoTime());
        for (BuiltinCiphers c : BuiltinCiphers.VALUES) {
            if (c.isSupported()) {
                try {
                    testCipherEncryption(rnd, c.create());
                } catch (Exception e) {
                    System.err.println("Failed (" + e.getClass().getSimpleName() + ") to encrypt using " + c + ": " + e.getMessage());
                    err = e;
                }
            } else {
                System.out.append("Skip unsupported cipher: ").println(c);
            }
        }

        if (err != null) {
            throw err;
        }
    }

    @Test   // make sure that the reported support matches reality by trying to encrypt something
    public void testCipherSupportDetection() throws Exception {
        Random rnd = new Random(System.nanoTime());
        for (BuiltinCiphers c : BuiltinCiphers.VALUES) {
            try {
                testCipherEncryption(rnd, c.create());
                assertTrue("Mismatched support report for " + c, c.isSupported());
            } catch (Exception e) {
                assertFalse("Mismatched support report for " + c, c.isSupported());
            }
        }
    }

    @Test
    public void testSshClientSupportedCiphersConfiguration() throws Exception {
        try (SshClient client = setupTestClient()) {
            testSupportedCiphersConfiguration(client);
        }
    }

    @Test
    public void testSshSercerSupportedCiphersConfiguration() throws Exception {
        try (SshServer server = setupTestServer()) {
            testSupportedCiphersConfiguration(server);
        }
    }

    private static <M extends FactoryManager> M testSupportedCiphersConfiguration(M manager) {
        Collection<? extends NamedResource> factories = manager.getCipherFactories();
        List<String> names = NamedResource.getNameList(factories);
        for (BuiltinCiphers c : BuiltinCiphers.VALUES) {
            if (BuiltinCiphers.none.equals(c)) {
                continue;   // not always included by default + it is a dummy cipher
            }

            // for now, all key sizes below 128 are supported in JVM(s)
            if (c.getKeySize() <= 128) {
                assertTrue("Supported cipher not configured by default: " + c, names.contains(c.getName()));
            }
        }

        return manager;
    }

    private static void testCipherEncryption(Random rnd, Cipher cipher) throws Exception {
        byte[] key = new byte[cipher.getKdfSize()];
        rnd.nextBytes(key);
        byte[] iv = new byte[cipher.getIVSize()];
        rnd.nextBytes(iv);
        cipher.init(Cipher.Mode.Encrypt, key, iv);

        byte[] data = new byte[cipher.getCipherBlockSize()];
        rnd.nextBytes(data);

        cipher.update(data);
    }

    @Test
    public void testParseCiphersList() {
        List<String> builtin = NamedResource.getNameList(BuiltinCiphers.VALUES);
        List<String> unknown = Arrays.asList(
            getClass().getPackage().getName(), getClass().getSimpleName(), getCurrentTestName());
        Random rnd = new Random();
        for (int index = 0; index < (builtin.size() + unknown.size()); index++) {
            Collections.shuffle(builtin, rnd);
            Collections.shuffle(unknown, rnd);

            List<String> weavedList = new ArrayList<>(builtin.size() + unknown.size());
            for (int bIndex = 0, uIndex = 0; (bIndex < builtin.size()) || (uIndex < unknown.size());) {
                boolean useBuiltin = false;
                if (bIndex < builtin.size()) {
                    useBuiltin = uIndex >= unknown.size() || rnd.nextBoolean();
                }

                if (useBuiltin) {
                    weavedList.add(builtin.get(bIndex));
                    bIndex++;
                } else if (uIndex < unknown.size()) {
                    weavedList.add(unknown.get(uIndex));
                    uIndex++;
                }
            }

            String fullList = GenericUtils.join(weavedList, ',');
            ParseResult result = BuiltinCiphers.parseCiphersList(fullList);
            List<String> parsed = NamedResource.getNameList(result.getParsedFactories());
            List<String> missing = result.getUnsupportedFactories();

            // makes sure not only that the contents are the same but also the order
            assertListEquals(fullList + "[parsed]", builtin, parsed);
            assertListEquals(fullList + "[unsupported]", unknown, missing);
        }
    }

    @Test
    public void testResolveFactoryOnBuiltinValues() {
        for (NamedFactory<Cipher> expected : BuiltinCiphers.VALUES) {
            String name = expected.getName();
            NamedFactory<Cipher> actual = BuiltinCiphers.resolveFactory(name);
            assertSame(name, expected, actual);
        }
    }

    @Test
    public void testNotAllowedToRegisterBuiltinFactories() {
        for (CipherFactory expected : BuiltinCiphers.VALUES) {
            try {
                BuiltinCiphers.registerExtension(expected);
                fail("Unexpected success for " + expected.getName());
            } catch (IllegalArgumentException e) {
                // expected - ignored
            }
        }
    }

    @Test(expected = IllegalArgumentException.class)
    public void testNotAllowedToOverrideRegisteredFactories() {
        CipherFactory expected = Mockito.mock(CipherFactory.class);
        Mockito.when(expected.getName()).thenReturn(getCurrentTestName());

        String name = expected.getName();
        try {
            for (int index = 1; index <= Byte.SIZE; index++) {
                BuiltinCiphers.registerExtension(expected);
                assertEquals("Unexpected success at attempt #" + index, 1, index);
            }
        } finally {
            BuiltinCiphers.unregisterExtension(name);
        }
    }

    @Test
    public void testResolveFactoryOnRegisteredExtension() {
        CipherFactory expected = Mockito.mock(CipherFactory.class);
        Mockito.when(expected.getName()).thenReturn(getCurrentTestName());

        String name = expected.getName();
        try {
            assertNull("Extension already registered", BuiltinCiphers.resolveFactory(name));
            BuiltinCiphers.registerExtension(expected);

            NamedFactory<Cipher> actual = BuiltinCiphers.resolveFactory(name);
            assertSame("Mismatched resolved instance", expected, actual);
        } finally {
            NamedFactory<Cipher> actual = BuiltinCiphers.unregisterExtension(name);
            assertSame("Mismatched unregistered instance", expected, actual);
            assertNull("Extension not un-registered", BuiltinCiphers.resolveFactory(name));
        }
    }

}
