/*
 * Copyright 2012-2020 the original author or authors.
 *
 * Licensed 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
 *
 *      https://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 com.github.dockerjava.transport;

import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.util.Arrays;
import java.util.List;

import com.sun.jna.LastErrorException;
import com.sun.jna.Native;
import com.sun.jna.Platform;
import com.sun.jna.Structure;

/**
 * {@link DomainSocket} implementation for Linux based platforms.
 *
 * @author Phillip Webb
 */
class LinuxDomainSocket extends DomainSocket {

    static {
        Native.register(Platform.C_LIBRARY_NAME);
    }

    LinuxDomainSocket(String path) throws IOException {
        super(path);
    }

    private static final int MAX_PATH_LENGTH = 108;

    @Override
    protected void connect(String path, int handle) {
        SockaddrUn address = new SockaddrUn(AF_LOCAL, path.getBytes(StandardCharsets.UTF_8));
        connect(handle, address, address.size());
    }

    private native int connect(int fd, SockaddrUn address, int addressLen) throws LastErrorException;

    /**
     * Native {@code sockaddr_un} structure as defined in {@code sys/un.h}.
     */
    public static class SockaddrUn extends Structure implements Structure.ByReference {

        public short sunFamily;

        public byte[] sunPath = new byte[MAX_PATH_LENGTH];

        private SockaddrUn(byte sunFamily, byte[] path) {
            if (path.length > MAX_PATH_LENGTH) {
                throw new IllegalArgumentException("Path cannot exceed " + MAX_PATH_LENGTH + " bytes");
            }
            System.arraycopy(path, 0, this.sunPath, 0, path.length);
            this.sunPath[path.length] = 0;
            this.sunFamily = sunFamily;
            allocateMemory();
        }

        @Override
        protected List<String> getFieldOrder() {
            return Arrays.asList("sunFamily", "sunPath");
        }

    }

}
