package main

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

// readMemory 读取内存信息
func readMemory() (MemoryMetrics, error) {
	totals := map[string]uint64{}
	f, err := os.Open("/proc/meminfo")
	if err != nil {
		return MemoryMetrics{}, err
	}
	defer f.Close()
	scanner := bufio.NewScanner(f)
	for scanner.Scan() {
		line := scanner.Text()
		parts := strings.Split(line, ":")
		if len(parts) < 2 {
			continue
		}
		key := strings.TrimSpace(parts[0])
		fields := strings.Fields(strings.TrimSpace(parts[1]))
		if len(fields) == 0 {
			continue
		}
		value, err := strconv.ParseUint(fields[0], 10, 64)
		if err != nil {
			continue
		}
		totals[key] = value * 1024 // kB to bytes
	}
	total := totals["MemTotal"]
	
	// 优先使用 MemAvailable（Linux 3.14+），如果没有则计算
	var free uint64
	if available, ok := totals["MemAvailable"]; ok && available > 0 {
		free = available
	} else {
		// 回退到 MemFree + Buffers + Cached（适用于较老的系统）
		free = totals["MemFree"]
		if buffers, ok := totals["Buffers"]; ok {
			free += buffers
		}
		if cached, ok := totals["Cached"]; ok {
			free += cached
		}
	}
	
	used := total - free
	usedPercent := 0.0
	if total > 0 {
		usedPercent = (float64(used) / float64(total)) * 100
	}
	return MemoryMetrics{
		TotalBytes:  total,
		UsedBytes:   used,
		FreeBytes:   free,
		UsedPercent: round(usedPercent, 2),
	}, nil
}