package app

import (
	"fmt"
	"sort"
	"strconv"
	"strings"
)

// parseAppMarkRules extracts "target:id" keys from output_apps chain dump.
func parseAppMarkRules(out string) []string {
	var keys []string
	for _, line := range strings.Split(out, "\n") {
		if key, ok := parseTrafficAppMarkRuleLine(line); ok {
			keys = append(keys, key)
		}
	}
	sort.Strings(keys)
	return dedupeSortedStrings(keys)
}

func parseTrafficAppMarkRuleLine(line string) (string, bool) {
	// comment "svpn_appmark:vpn:123"
	i := strings.Index(line, appMarkCommentPrefix+":")
	if i < 0 {
		return "", false
	}
	rest := line[i:]
	end := len(rest)
	for j := 0; j < len(rest); j++ {
		ch := rest[j]
		if ch == '"' || ch == ' ' || ch == '\t' {
			end = j
			break
		}
	}
	tag := rest[:end]
	parts := strings.Split(tag, ":")
	if len(parts) != 3 {
		return "", false
	}
	tgt := strings.ToLower(strings.TrimSpace(parts[1]))
	idRaw := strings.TrimSpace(parts[2])
	if tgt != "vpn" && tgt != "direct" {
		return "", false
	}
	id, err := strconv.ParseUint(idRaw, 10, 64)
	if err != nil || id == 0 {
		return "", false
	}
	return fmt.Sprintf("%s:%d", tgt, id), true
}

func dedupeSortedStrings(in []string) []string {
	if len(in) == 0 {
		return nil
	}
	out := in[:0]
	last := ""
	for _, it := range in {
		if it == last {
			continue
		}
		out = append(out, it)
		last = it
	}
	return out
}