package main

import (
	"bufio"
	"math"
	"os"
	"strconv"
	"strings"
)

// round 将浮点数四舍五入到指定小数位
func round(v float64, places int) float64 {
	factor := math.Pow(10, float64(places))
	return math.Round(v*factor) / factor
}

// readFirstLine 读取文件的第一行
func readFirstLine(path string) string {
	f, err := os.Open(path)
	if err != nil {
		return ""
	}
	defer f.Close()
	scanner := bufio.NewScanner(f)
	if scanner.Scan() {
		return scanner.Text()
	}
	return ""
}

// firstMatchInFile 在文件中查找第一个匹配指定前缀的行，并返回冒号后的内容
func firstMatchInFile(path, prefix string) string {
	f, err := os.Open(path)
	if err != nil {
		return ""
	}
	defer f.Close()
	scanner := bufio.NewScanner(f)
	for scanner.Scan() {
		line := scanner.Text()
		if strings.HasPrefix(strings.TrimSpace(line), prefix) {
			parts := strings.SplitN(line, ":", 2)
			if len(parts) == 2 {
				return strings.TrimSpace(parts[1])
			}
		}
	}
	return ""
}

// readTempFromFile 从文件读取温度值
func readTempFromFile(path string) float64 {
	content := readFirstLine(path)
	if content == "" {
		return 0
	}
	val, err := strconv.ParseFloat(strings.TrimSpace(content), 64)
	if err != nil {
		return 0
	}
	// 温度通常以毫度为单位
	if val > 1000 {
		return round(val/1000, 1)
	}
	return round(val, 1)
}