//go:build linux

package system

import (
	"bufio"
	"os"
	"strings"
	"syscall"
)

// GetInfo reads system memory and disk usage.
// hddPath is the mount path for external HDD; if empty, HDD info is skipped.
func GetInfo(hddPath string) SystemInfo {
	info := SystemInfo{}

	// --- Memory from /proc/meminfo ---
	readMemInfo(&info)

	// --- Root filesystem disk usage ---
	readDiskUsage("/", &info.DiskTotalGB, &info.DiskUsedGB, &info.DiskAvailGB, &info.DiskPercent)

	// --- HDD disk usage (if configured) ---
	if hddPath != "" {
		info.HDDConfigured = true
		readDiskUsage(hddPath, &info.HDDTotalGB, &info.HDDUsedGB, &info.HDDAvailGB, &info.HDDPercent)
	}

	return info
}

func readMemInfo(info *SystemInfo) {
	f, err := os.Open("/proc/meminfo")
	if err != nil {
		return
	}
	defer f.Close()

	var totalKB, availKB uint64
	scanner := bufio.NewScanner(f)
	for scanner.Scan() {
		line := scanner.Text()
		switch {
		case strings.HasPrefix(line, "MemTotal:"):
			totalKB = parseMemLine(line)
		case strings.HasPrefix(line, "MemAvailable:"):
			availKB = parseMemLine(line)
		}
		if totalKB > 0 && availKB > 0 {
			break
		}
	}

	if totalKB > 0 {
		info.TotalMemMB = totalKB / 1024
		info.AvailMemMB = availKB / 1024
		info.UsedMemMB = info.TotalMemMB - info.AvailMemMB
		info.MemPercent = float64(info.UsedMemMB) / float64(info.TotalMemMB) * 100
	}
}

// parseMemLine extracts the kB value from a /proc/meminfo line like "MemTotal:       16384000 kB"
func parseMemLine(line string) uint64 {
	// Remove label prefix up to ':'
	parts := strings.SplitN(line, ":", 2)
	if len(parts) < 2 {
		return 0
	}
	valStr := strings.TrimSpace(parts[1])
	valStr = strings.TrimSuffix(valStr, " kB")
	valStr = strings.TrimSpace(valStr)

	var val uint64
	for _, c := range valStr {
		if c >= '0' && c <= '9' {
			val = val*10 + uint64(c-'0')
		}
	}
	return val
}

func readDiskUsage(path string, totalGB, usedGB, availGB *float64, percent *float64) {
	var stat syscall.Statfs_t
	if err := syscall.Statfs(path, &stat); err != nil {
		return
	}

	bsize := uint64(stat.Bsize)
	total := stat.Blocks * bsize
	avail := stat.Bavail * bsize
	used := total - (stat.Bfree * bsize) // Bfree includes reserved blocks

	const gb = 1024 * 1024 * 1024
	*totalGB = float64(total) / gb
	*usedGB = float64(used) / gb
	*availGB = float64(avail) / gb
	if total > 0 {
		*percent = float64(used) / float64(total) * 100
	}
}