package trafficappmarks

import (
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"syscall"
)

func ResolveCgroupV2PathForNft(input string, cgroupRootPath string) (rel string, level int, inodeID uint64, abs string, err error) {
	raw := strings.TrimSpace(input)
	if raw == "" {
		return "", 0, 0, "", fmt.Errorf("empty cgroup")
	}

	rel = NormalizeCgroupRelOnly(raw)
	if rel == "" {
		return "", 0, 0, raw, fmt.Errorf("invalid cgroup path: %s", raw)
	}

	inodeID, err = CgroupDirInode(cgroupRootPath, rel)
	if err != nil {
		return "", 0, 0, raw, err
	}

	level = strings.Count(rel, "/") + 1
	abs = "/" + rel
	return rel, level, inodeID, abs, nil
}

func NormalizeCgroupRelOnly(raw string) string {
	rel := strings.TrimSpace(raw)
	rel = strings.TrimPrefix(rel, "/")
	rel = filepath.Clean(rel)
	if rel == "." || rel == "" {
		return ""
	}
	if strings.HasPrefix(rel, "..") || strings.Contains(rel, "../") {
		return ""
	}
	return rel
}

func CgroupDirInode(cgroupRootPath, rel string) (uint64, error) {
	full := filepath.Join(cgroupRootPath, strings.TrimPrefix(rel, "/"))
	fi, err := os.Stat(full)
	if err != nil || fi == nil || !fi.IsDir() {
		return 0, fmt.Errorf("cgroup not found: %s", "/"+strings.TrimPrefix(rel, "/"))
	}
	st, ok := fi.Sys().(*syscall.Stat_t)
	if !ok || st == nil {
		return 0, fmt.Errorf("cannot stat cgroup: %s", "/"+strings.TrimPrefix(rel, "/"))
	}
	if st.Ino == 0 {
		return 0, fmt.Errorf("invalid cgroup inode id: %s", "/"+strings.TrimPrefix(rel, "/"))
	}
	return st.Ino, nil
}