package update

import (
	domain "RenewCMS/internal/domain/update"
	"os"
	"path/filepath"
	"strconv"
	"strings"
)

const (
	systemUnitDirectory = "/etc/systemd/system"
	unitFilePermissions = 0o644
	unitFileSuffix      = ".service"
)

type SystemdUnits struct {
	directory string
}

var (
	_ domain.UnitWriter     = &SystemdUnits{}
	_ domain.ServiceLocator = &SystemdUnits{}
)

func NewSystemdUnits() *SystemdUnits {
	return NewSystemdUnitsIn(systemUnitDirectory)
}

func NewSystemdUnitsIn(directory string) *SystemdUnits {
	return &SystemdUnits{directory: directory}
}

func (u *SystemdUnits) Write(name string, content string) error {
	return os.WriteFile(filepath.Join(u.directory, name), []byte(content), unitFilePermissions)
}

func (u *SystemdUnits) Remove(name string) (bool, error) {
	return removeFile(filepath.Join(u.directory, name))
}

func (u *SystemdUnits) Locate(name string) (domain.ServiceDescription, bool) {
	content, err := os.ReadFile(filepath.Join(u.directory, name+unitFileSuffix))
	if err != nil {
		return domain.ServiceDescription{}, false
	}
	description := ParseServiceUnit(string(content))
	description.Name = name
	return description, true
}

func (u *SystemdUnits) PortFromEnvironmentFile(path string) (string, bool) {
	if path == "" {
		return "", false
	}
	content, err := os.ReadFile(path)
	if err != nil {
		return "", false
	}
	return portFromEnvironment(string(content))
}

func ParseServiceUnit(content string) domain.ServiceDescription {
	var description domain.ServiceDescription
	for _, line := range strings.Split(content, "\n") {
		key, value, found := strings.Cut(strings.TrimSpace(line), "=")
		if !found {
			continue
		}
		switch key {
		case "ExecStart":
			description.BinaryPath = firstUnitPath(value, "@-:+!")
		case "EnvironmentFile":
			description.EnvironmentFile = firstUnitPath(value, "-")
		case "ReadWritePaths":
			if description.DataDir == "" {
				description.DataDir = firstUnitPath(value, "-+!")
			}
		}
	}
	return description
}

func firstUnitPath(value string, prefixes string) string {
	fields := strings.Fields(value)
	if len(fields) == 0 {
		return ""
	}
	return strings.Trim(strings.TrimLeft(fields[0], prefixes), `"`)
}

func portFromEnvironment(content string) (string, bool) {
	for _, line := range strings.Split(content, "\n") {
		key, value, found := strings.Cut(strings.TrimSpace(line), "=")
		if !found || strings.TrimSpace(key) != "PORT" {
			continue
		}
		port := strings.Trim(strings.TrimSpace(value), `"'`)
		if _, err := strconv.Atoi(port); err == nil {
			return port, true
		}
	}
	return "", false
}