package dockeragent

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

func readProcUptime() (value float64, retErr error) {
	f, err := openProcUptime()
	if err != nil {
		return 0, err
	}
	defer func() {
		if closeErr := f.Close(); closeErr != nil {
			if retErr != nil {
				retErr = errors.Join(retErr, closeErr)
			} else {
				retErr = closeErr
			}
		}
	}()

	scanner := bufio.NewScanner(f)
	if !scanner.Scan() {
		if err := scanner.Err(); err != nil {
			return 0, err
		}
		return 0, errors.New("empty /proc/uptime")
	}

	fields := strings.Fields(scanner.Text())
	if len(fields) == 0 {
		return 0, errors.New("invalid /proc/uptime contents")
	}

	value, err = strconv.ParseFloat(fields[0], 64)
	if err != nil {
		return 0, err
	}

	return value, nil
}