package env

import (
	"errors"
	"fmt"
	"os"
	"strings"

	"github.com/qdm12/gluetun/internal/configuration/settings"
	"github.com/qdm12/gluetun/internal/constants"
	"github.com/qdm12/govalid/port"
)

func (r *Reader) readOpenVPNSelection() (
	selection settings.OpenVPNSelection, err error) {
	selection.TCP, err = r.readOpenVPNProtocol()
	if err != nil {
		return selection, err
	}

	selection.CustomPort, err = r.readOpenVPNCustomPort()
	if err != nil {
		return selection, err
	}

	selection.PIAEncPreset = r.readPIAEncryptionPreset()

	return selection, nil
}

var ErrOpenVPNProtocolNotValid = errors.New("OpenVPN protocol is not valid")

func (r *Reader) readOpenVPNProtocol() (tcp *bool, err error) {
	envKey := "OPENVPN_PROTOCOL"
	protocol := strings.ToLower(os.Getenv("OPENVPN_PROTOCOL"))
	if protocol == "" {
		// Retro-compatibility
		protocol = strings.ToLower(os.Getenv("PROTOCOL"))
		if protocol != "" {
			envKey = "PROTOCOL"
			r.onRetroActive("PROTOCOL", "OPENVPN_PROTOCOL")
		}
	}

	switch protocol {
	case "":
		return nil, nil //nolint:nilnil
	case constants.UDP:
		return boolPtr(false), nil
	case constants.TCP:
		return boolPtr(true), nil
	default:
		return nil, fmt.Errorf("environment variable %s: %w: %s",
			envKey, ErrOpenVPNProtocolNotValid, protocol)
	}
}

func (r *Reader) readOpenVPNCustomPort() (customPort *uint16, err error) {
	key := "OPENVPN_PORT"
	s := os.Getenv(key)
	if s == "" {
		// Retro-compatibility
		key = "PORT"
		s = os.Getenv(key)
		if s == "" {
			return nil, nil //nolint:nilnil
		}
		r.onRetroActive("PORT", "OPENVPN_PORT")
	}

	customPort = new(uint16)
	*customPort, err = port.Validate(s)
	if err != nil {
		return nil, fmt.Errorf("environment variable %s: %w", key, err)
	}

	return customPort, nil
}