package utils

import (
	"errors"
	"fmt"

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

func GetPort(selection settings.ServerSelection,
	defaultOpenVPNTCP, defaultOpenVPNUDP, defaultWireguard uint16) (port uint16) {
	switch selection.VPN {
	case vpn.Wireguard:
		customPort := *selection.Wireguard.EndpointPort
		if customPort > 0 {
			return customPort
		}
		checkDefined("Wireguard", defaultWireguard)
		return defaultWireguard
	default: // OpenVPN
		customPort := *selection.OpenVPN.CustomPort
		if customPort > 0 {
			return customPort
		}
		if *selection.OpenVPN.TCP {
			checkDefined("OpenVPN TCP", defaultOpenVPNTCP)
			return defaultOpenVPNTCP
		}

		checkDefined("OpenVPN UDP", defaultOpenVPNUDP)
		return defaultOpenVPNUDP
	}
}

func checkDefined(portName string, port uint16) {
	if port > 0 {
		return
	}
	message := fmt.Sprintf("no default %s port is defined!", portName)
	panic(message)
}

var ErrInvalidPort = errors.New("invalid port number")

// CheckPortAllowed for custom port used for OpenVPN.
func CheckPortAllowed(port uint16, tcp bool,
	allowedTCP, allowedUDP []uint16) (err error) {
	allowedPorts := allowedUDP
	protocol := constants.UDP
	if tcp {
		allowedPorts = allowedTCP
		protocol = constants.TCP
	}
	for _, allowedPort := range allowedPorts {
		if port == allowedPort {
			return nil
		}
	}

	return fmt.Errorf("%w: %d for protocol %s",
		ErrInvalidPort, port, protocol)
}