func sendTTYToCommand(commandUsock *unixsocket.Usock, clientFile *os.File, err error) error {
	if err != nil {
		return err
	}

	return commandUsock.WriteFD(int(clientFile.Fd()))
}

func receiveExitStatus(commandUsock *unixsocket.Usock, err error) (string, error) {
	if err != nil {
		return "", err
	}

	return commandUsock.ReadMessage()
}

func sendExitStatus(usock *unixsocket.Usock, exitStatus string, err error) error {
	if err != nil {
		return err
	}

	_, err = usock.WriteMessage(exitStatus)
	return err
}

func sendClientPidAndArgumentsToCommand(commandUsock *unixsocket.Usock, clientPid int, arguments string, err error) error {
	if err != nil {
		return err
	}

	msg := messages.CreatePidAndArgumentsMessage(clientPid, arguments)
	_, err = commandUsock.WriteMessage(msg)
	return err
}

func sendCommandPidToClient(usock *unixsocket.Usock, pid int, err error) error {
	if err != nil {
		return err
	}

	strPid := strconv.Itoa(pid)
	_, err = usock.WriteMessage(strPid)

	return err
}

func receivePidFromCommand(commandUsock *unixsocket.Usock, err error) (int, error) {
	if err != nil {
		return -1, err
	}

	msg, err := commandUsock.ReadMessage()
	if err != nil {
		return -1, err
	}
	intPid, _, _ := messages.ParsePidMessage(msg)

	return intPid, err
}

func receiveTTY(usock *unixsocket.Usock, err error) (*os.File, error) {
	if err != nil {
		return nil, err
	}

	clientFd, err := usock.ReadFD()
	if err != nil {
		return nil, errors.New("Expected FD, none received!")
	}
	fileName := strconv.Itoa(rand.Int())
	clientFile := unixsocket.FdToFile(clientFd, fileName)

	return clientFile, nil
}

func receiveCommandArgumentsAndPid(usock *unixsocket.Usock, err error) (string, int, string, error) {
	if err != nil {
		return "", -1, "", err
	}

	msg, err := usock.ReadMessage()
	if err != nil {
		return "", -1, "", err
	}
	command, clientPid, arguments, err := messages.ParseClientCommandRequestMessage(msg)
	if err != nil {
		return "", -1, "", err
	}

	return command, clientPid, arguments, err
}

// see docs/client_master_handshake.md
func handleClientConnection(tree *processtree.ProcessTree, usock *unixsocket.Usock) {
	defer usock.Close()
	// we have established first contact to the client.

	command, clientPid, arguments, err := receiveCommandArgumentsAndPid(usock, nil)
	commandNode, slaveNode, err := findCommandAndSlaveNodes(tree, command, err)
	if err != nil {
		// connection was established, no data was sent. Ignore.
		return
	}
	command = commandNode.Name // resolve aliases

	clientFile, err := receiveTTY(usock, err)
	defer clientFile.Close()

	if err == nil && slaveNode.Error != "" {
		// we can skip steps 3-5 as they deal with the command process we're not spawning.
		// Write a fake pid (step 6)
		usock.WriteMessage("0")
		// Write the error message to the terminal
		clientFile.Write([]byte(slaveNode.Error))
		// Skip step 7, and write an exit code to the client (step 8)
		usock.WriteMessage("1")
		return
	}

	commandUsock, err := bootNewCommand(slaveNode, command, err)
	defer commandUsock.Close()

	err = sendClientPidAndArgumentsToCommand(commandUsock, clientPid, arguments, err)

	err = sendTTYToCommand(commandUsock, clientFile, err)

	cmdPid, err := receivePidFromCommand(commandUsock, err)

	err = sendCommandPidToClient(usock, cmdPid, err)

	exitStatus, err := receiveExitStatus(commandUsock, err)

	err = sendExitStatus(usock, exitStatus, err)

	if err != nil {
		slog.Error(err)
	}
	// Done! Hooray!
}