/**
# Copyright 2021-2023 NVIDIA CORPORATION
#
# 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
#
#     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 docker

import (
	"fmt"
	"net"
	"syscall"
	"time"

	log "github.com/sirupsen/logrus"
)

const (
	reloadBackoff     = 5 * time.Second
	maxReloadAttempts = 6

	socketMessageToGetPID = "GET /info HTTP/1.0\r\n\r\n"
)

// SignalDocker sends a SIGHUP signal to docker daemon
func SignalDocker(socket string) error {
	log.Infof("Sending SIGHUP signal to docker")

	// Wrap the logic to perform the SIGHUP in a function so we can retry it on failure
	retriable := func() error {
		conn, err := net.Dial("unix", socket)
		if err != nil {
			return fmt.Errorf("unable to dial: %v", err)
		}
		defer conn.Close()

		sconn, err := conn.(*net.UnixConn).SyscallConn()
		if err != nil {
			return fmt.Errorf("unable to get syscall connection: %v", err)
		}

		err1 := sconn.Control(func(fd uintptr) {
			err = syscall.SetsockoptInt(int(fd), syscall.SOL_SOCKET, syscall.SO_PASSCRED, 1)
		})
		if err1 != nil {
			return fmt.Errorf("unable to issue call on socket fd: %v", err1)
		}
		if err != nil {
			return fmt.Errorf("unable to SetsockoptInt on socket fd: %v", err)
		}

		_, _, err = conn.(*net.UnixConn).WriteMsgUnix([]byte(socketMessageToGetPID), nil, nil)
		if err != nil {
			return fmt.Errorf("unable to WriteMsgUnix on socket fd: %v", err)
		}

		oob := make([]byte, 1024)
		_, oobn, _, _, err := conn.(*net.UnixConn).ReadMsgUnix(nil, oob)
		if err != nil {
			return fmt.Errorf("unable to ReadMsgUnix on socket fd: %v", err)
		}

		oob = oob[:oobn]
		scm, err := syscall.ParseSocketControlMessage(oob)
		if err != nil {
			return fmt.Errorf("unable to ParseSocketControlMessage from message received on socket fd: %v", err)
		}

		ucred, err := syscall.ParseUnixCredentials(&scm[0])
		if err != nil {
			return fmt.Errorf("unable to ParseUnixCredentials from message received on socket fd: %v", err)
		}

		err = syscall.Kill(int(ucred.Pid), syscall.SIGHUP)
		if err != nil {
			return fmt.Errorf("unable to send SIGHUP to 'docker' process: %v", err)
		}

		return nil
	}

	// Try to send a SIGHUP up to maxReloadAttempts times
	var err error
	for i := 0; i < maxReloadAttempts; i++ {
		err = retriable()
		if err == nil {
			break
		}
		if i == maxReloadAttempts-1 {
			break
		}
		log.Warningf("Error signaling docker, attempt %v/%v: %v", i+1, maxReloadAttempts, err)
		time.Sleep(reloadBackoff)
	}
	if err != nil {
		log.Warningf("Max retries reached %v/%v, aborting", maxReloadAttempts, maxReloadAttempts)
		return err
	}

	log.Infof("Successfully signaled docker")

	return nil
}