read.go

//go:build !darwin && !windows && !openbsd && !netbsd && !freebsd

package systemd

import (
	"bytes"
	"fmt"
	"path"
	"strconv"
	"strings"

	"github.com/creativeprojects/resticprofile/constants"
	"github.com/spf13/afero"
)

// Read parses systemd service and timer unit files and returns their configuration.
// The unit parameter should be in the format "resticprofile-backup@profile-name.service".
// The unitType parameter determines whether to read from system or user unit directories.
func (u Unit) Read(unit string, unitType UnitType) (*Config, error) {
	var err error
	if !strings.HasSuffix(unit, ".service") {
		return nil, fmt.Errorf("invalid unit name format: %s (must end with .service)", unit)
	}
	unitsDir := systemdSystemDir
	if unitType == UserUnit {
		unitsDir, err = u.GetUserDir()
		if err != nil {
			return nil, err
		}
	}
	filename := path.Join(unitsDir, unit)
	serviceSections, err := u.readSystemdUnit(filename)
	if err != nil {
		return nil, err
	}
	filename = strings.Replace(filename, ".service", ".timer", 1)
	timerSections, err := u.readSystemdUnit(filename)
	if err != nil {
		return nil, err
	}

	profileName, commandName := parseServiceFileName(unit)
	cfg := &Config{
		Title:                profileName,
		SubTitle:             commandName,
		JobDescription:       getSingleValue(serviceSections, "Unit", "Description"),
		WorkingDirectory:     getSingleValue(serviceSections, "Service", "WorkingDirectory"),
		CommandLine:          getSingleValue(serviceSections, "Service", "ExecStart"),
		UnitType:             unitType,
		Environment:          getValues(serviceSections, "Service", "Environment"),
		Nice:                 getIntegerValue(serviceSections, "Service", "Nice"),
		IOSchedulingClass:    getIntegerValue(serviceSections, "Service", "IOSchedulingClass"),
		IOSchedulingPriority: getIntegerValue(serviceSections, "Service", "IOSchedulingPriority"),
		Schedules:            getValues(timerSections, "Timer", "OnCalendar"),
		Priority:             getPriority(getSingleValue(serviceSections, "Service", "CPUSchedulingPolicy")),
		User:                 getSingleValue(serviceSections, "Service", "User"),
	}
	return cfg, nil
}

// readSystemdUnit returns a map of sections with key/values pair.
// This implementation doesn't support multiline values (since these are not generated by resticprofile)
func (u Unit) readSystemdUnit(filename string) (map[string]map[string][]string, error) {
	content, err := afero.ReadFile(u.fs, filename)
	if err != nil {
		return nil, err
	}
	currentSection := ""
	sections := make(map[string]map[string][]string, 3)
	lines := bytes.Split(content, []byte("\n"))
	for _, line := range lines {
		line = bytes.TrimSpace(line)
		if len(line) == 0 {
			continue
		}
		// Skip comments
		if bytes.HasPrefix(line, []byte("#")) {
			continue
		}
		if bytes.HasPrefix(line, []byte("[")) && bytes.HasSuffix(line, []byte("]")) {
			// start of a section
			currentSection = string(bytes.TrimSpace(line[1 : len(line)-1]))
			continue
		}
		if key, value, found := strings.Cut(string(line), "="); found {
			value = strings.Trim(value, `"`)
			if sections[currentSection] == nil {
				sections[currentSection] = map[string][]string{
					key: {value},
				}
			} else if sections[currentSection][key] == nil {
				sections[currentSection][key] = []string{value}
			} else {
				sections[currentSection][key] = append(sections[currentSection][key], value)
			}
		}
	}
	return sections, nil
}

func getIntegerValue(from map[string]map[string][]string, section, key string) int {
	str := getSingleValue(from, section, key)
	value, _ := strconv.Atoi(str)
	return value
}

func getSingleValue(from map[string]map[string][]string, section, key string) string {
	if section, found := from[section]; found {
		if values, found := section[key]; found {
			if len(values) > 0 {
				return values[0]
			}
		}
	}
	return ""
}

func getValues(from map[string]map[string][]string, section, key string) []string {
	if section, found := from[section]; found {
		if values, found := section[key]; found {
			return values
		}
	}
	return nil
}

// parseServiceFileName to detect profile and command names from the file name.
// format is: `resticprofile-backup@profile-name.service`
func parseServiceFileName(filename string) (profileName, commandName string) {
	filename = strings.TrimPrefix(filename, "resticprofile-")
	filename = strings.TrimSuffix(filename, ".service")
	commandName, profileName, _ = strings.Cut(filename, "@")
	profileName = strings.TrimPrefix(profileName, "profile-")
	return
}

// getPriority maps systemd CPU scheduling policy to schedule priority constants.
//   - "idle" maps to background priority
//   - all other values map to standard priority
func getPriority(input string) string {
	switch input {
	case "idle":
		return constants.SchedulePriorityBackground
	default:
		return constants.SchedulePriorityStandard
	}
}