package update

import (
	"errors"
	"strconv"
	"strings"
)

var (
	ErrNeedsLinux      = errors.New("Browser updates need Linux with systemd.")
	ErrNeedsSystemd    = errors.New("Browser updates need systemd, which this machine is not running.")
	ErrNeedsRoot       = errors.New("Run this command as root, for example with sudo.")
	ErrServiceNotFound = errors.New("Could not find the RenewCMS service. Pass --service, --binary and --data-dir.")
	ErrDataDirNotFound = errors.New("Could not find the data directory. Pass --data-dir.")
	ErrInvalidPort     = errors.New("The port must be a number between 1 and 65535.")
)

const (
	OSLinux             = "linux"
	pathUnitDescription = "Watch for a RenewCMS restart request"
)

type ServiceDescription struct {
	Name            string
	BinaryPath      string
	DataDir         string
	EnvironmentFile string
}

type InstallOptions struct {
	Service string
	Binary  string
	DataDir string
	Port    string
}

type MachineProbe interface {
	OS() string
	SystemdRunning() bool
	IsRoot() bool
}

type ServiceLocator interface {
	Locate(name string) (ServiceDescription, bool)
	PortFromEnvironmentFile(path string) (string, bool)
}

type UnitWriter interface {
	Write(name string, content string) error
	Remove(name string) (bool, error)
}

type UnitManager interface {
	DaemonReload() error
	EnableNow(unit string) error
	DisableNow(unit string) error
}

type HelperStatusWriter interface {
	Write(dataDir string, status HelperStatus) error
	Remove(dataDir string) (bool, error)
}

func CheckInstallEnvironment(probe MachineProbe) error {
	if probe.OS() != OSLinux {
		return ErrNeedsLinux
	}
	if !probe.SystemdRunning() {
		return ErrNeedsSystemd
	}
	if !probe.IsRoot() {
		return ErrNeedsRoot
	}
	return nil
}

func ValidatePort(port string) error {
	number, err := strconv.Atoi(port)
	if err != nil || number < 1 || number > 65535 {
		return ErrInvalidPort
	}
	return nil
}

func RenderPathUnit(layout HelperLayout) string {
	lines := []string{
		"[Unit]",
		"Description=" + pathUnitDescription,
		"",
		"[Path]",
		"PathExists=" + layout.RestartRequestPath(),
		"Unit=" + ServiceUnitName,
		"",
		"[Install]",
		"WantedBy=multi-user.target",
		"",
	}
	return strings.Join(lines, "\n")
}

func RenderServiceUnit(options InstallOptions) string {
	command := []string{
		quoteUnitArgument(options.Binary),
		"apply-update",
		"--service", quoteUnitArgument(options.Service),
		"--binary", quoteUnitArgument(options.Binary),
		"--data-dir", quoteUnitArgument(options.DataDir),
		"--port", options.Port,
	}
	lines := []string{
		"[Unit]",
		"Description=RenewCMS update helper",
		"",
		"[Service]",
		"Type=oneshot",
		"User=root",
		"ExecStart=" + strings.Join(command, " "),
		"",
	}
	return strings.Join(lines, "\n")
}

var unitArgumentEscaper = strings.NewReplacer(
	`\`, `\\`,
	`"`, `\"`,
	`%`, `%%`,
	`$`, `$$`,
	"\n", `\n`,
	"\r", `\r`,
	"\t", `\t`,
)

func quoteUnitArgument(value string) string {
	if !strings.ContainsAny(value, " \t\r\n\"'\\%$;") {
		return value
	}
	return `"` + unitArgumentEscaper.Replace(value) + `"`
}