package app

import (
	"fmt"
	"strings"
	"time"
)

func restoreAppMarksFromState() error {
	appMarksMu.Lock()
	defer appMarksMu.Unlock()

	if err := ensureAppMarksNft(); err != nil {
		return err
	}

	st := loadAppMarksState()
	now := time.Now().UTC()
	changed := pruneExpiredAppMarksLocked(&st, now)

	clearManagedAppMarkRules(appMarksChain)
	clearManagedAppMarkRules(appMarksGuardChain)

	traffic := loadTrafficModeState()
	vpnIface, _ := resolveTrafficIface(traffic.PreferredIface)
	vpnIface = strings.TrimSpace(vpnIface)

	kept := make([]appMarkItem, 0, len(st.Items))
	for _, it := range st.Items {
		target := strings.ToLower(strings.TrimSpace(it.Target))
		if target != "vpn" && target != "direct" {
			changed = true
			continue
		}

		rel := normalizeCgroupRelOnly(it.CgroupRel)
		if rel == "" {
			rel = normalizeCgroupRelOnly(it.Cgroup)
		}
		if rel == "" {
			changed = true
			continue
		}

		id := it.ID
		if id == 0 {
			inode, err := cgroupDirInode(rel)
			if err != nil {
				changed = true
				continue
			}
			id = inode
			it.ID = inode
			changed = true
		}

		level := it.Level
		if level <= 0 {
			level = strings.Count(strings.Trim(rel, "/"), "/") + 1
			it.Level = level
			changed = true
		}

		abs := "/" + strings.TrimPrefix(rel, "/")
		it.CgroupRel = rel
		it.Cgroup = abs

		if _, err := cgroupDirInode(rel); err != nil {
			changed = true
			continue
		}

		iface := ""
		if target == "vpn" {
			if vpnIface == "" {
				// Keep state for later retry when VPN interface appears.
				kept = append(kept, it)
				continue
			}
			iface = vpnIface
		}

		if err := nftInsertAppMarkRule(target, rel, level, id, iface); err != nil {
			appendTraceLine("traffic", fmt.Sprintf("appmarks restore failed target=%s id=%d err=%v", target, id, err))
			kept = append(kept, it)
			continue
		}
		if !nftHasAppMarkRule(target, id) {
			appendTraceLine("traffic", fmt.Sprintf("appmarks restore post-check failed target=%s id=%d", target, id))
			kept = append(kept, it)
			continue
		}
		kept = append(kept, it)
	}
	st.Items = kept

	if changed {
		return saveAppMarksState(st)
	}
	return nil
}