package service

import (
	"errors"
	"fmt"
	"slices"

	"github.com/qdm12/gluetun/internal/constants/providers"
	"github.com/qdm12/gosettings"
)

type Settings struct {
	Enabled        *bool
	PortForwarder  PortForwarder
	Filepath       string
	UpCommand      string
	DownCommand    string
	Interface      string // needed for PIA, PrivateVPN and ProtonVPN, tun0 for example
	ServerName     string // needed for PIA
	CanPortForward bool   // needed for PIA
	ListeningPorts []uint16
	PortsCount     uint16
	Username       string // needed for PIA
	Password       string // needed for PIA
}

func (s Settings) Copy() (copied Settings) {
	copied.Enabled = gosettings.CopyPointer(s.Enabled)
	copied.PortForwarder = s.PortForwarder
	copied.Filepath = s.Filepath
	copied.UpCommand = s.UpCommand
	copied.DownCommand = s.DownCommand
	copied.Interface = s.Interface
	copied.ServerName = s.ServerName
	copied.CanPortForward = s.CanPortForward
	copied.ListeningPorts = gosettings.CopySlice(s.ListeningPorts)
	copied.PortsCount = s.PortsCount
	copied.Username = s.Username
	copied.Password = s.Password
	return copied
}

func (s *Settings) OverrideWith(update Settings) {
	s.Enabled = gosettings.OverrideWithPointer(s.Enabled, update.Enabled)
	s.PortForwarder = gosettings.OverrideWithComparable(s.PortForwarder, update.PortForwarder)
	s.Filepath = gosettings.OverrideWithComparable(s.Filepath, update.Filepath)
	s.UpCommand = gosettings.OverrideWithComparable(s.UpCommand, update.UpCommand)
	s.DownCommand = gosettings.OverrideWithComparable(s.DownCommand, update.DownCommand)
	s.Interface = gosettings.OverrideWithComparable(s.Interface, update.Interface)
	s.ServerName = gosettings.OverrideWithComparable(s.ServerName, update.ServerName)
	s.CanPortForward = gosettings.OverrideWithComparable(s.CanPortForward, update.CanPortForward)
	s.ListeningPorts = gosettings.OverrideWithSlice(s.ListeningPorts, update.ListeningPorts)
	s.PortsCount = gosettings.OverrideWithComparable(s.PortsCount, update.PortsCount)
	s.Username = gosettings.OverrideWithComparable(s.Username, update.Username)
	s.Password = gosettings.OverrideWithComparable(s.Password, update.Password)
}

func (s *Settings) Validate(forStartup bool) (err error) {
	// Minimal validation
	if s.Filepath == "" {
		return errors.New("file path not set")
	}

	if !forStartup {
		// No additional validation needed if the service
		// is not to be started with the given settings.
		return nil
	}

	// Startup validation requires additional fields set.
	switch {
	case s.PortForwarder == nil:
		return errors.New("port forwarder not set")
	case s.Interface == "":
		return errors.New("interface not set")
	case s.PortsCount == 0:
		return errors.New("ports count cannot be zero")
	}

	switch s.PortForwarder.Name() {
	case providers.PrivateInternetAccess:
		switch {
		case s.ServerName == "":
			return errors.New("server name not set")
		case s.Username == "":
			return errors.New("username not set")
		case s.Password == "":
			return errors.New("password not set")
		}
	case providers.Protonvpn:
		const maxPortsCount = 4
		if s.PortsCount > maxPortsCount {
			return fmt.Errorf("ports count too high: %d > %d", s.PortsCount, maxPortsCount)
		}
	default:
		const maxPortsCount = 1
		if s.PortsCount > maxPortsCount {
			return fmt.Errorf("ports count too high: %d > %d", s.PortsCount, maxPortsCount)
		}
	}

	if !slices.Equal(s.ListeningPorts, []uint16{0}) {
		switch {
		case len(s.ListeningPorts) != int(s.PortsCount):
			return fmt.Errorf("listening ports length must be equal to ports count: %d != %d",
				len(s.ListeningPorts), s.PortsCount)
		case slices.Contains(s.ListeningPorts, 0):
			return fmt.Errorf("listening port cannot be 0: in %v", s.ListeningPorts)
		}
	}

	return nil
}