package app

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

func snapshotNftSetToFile(setName, dst string) (int, error) {
	elems, err := readNftSetElements(setName)
	if err != nil {
		return 0, err
	}
	if err := writeLinesFile(dst, elems); err != nil {
		return 0, err
	}
	return len(elems), nil
}

func readNftSetElements(setName string) ([]string, error) {
	out, stderr, code, err := runCommandTimeout(
		8*time.Second, "nft", "list", "set", "inet", "agvpn", setName,
	)
	if err != nil || code != 0 {
		msg := strings.ToLower(strings.TrimSpace(out + " " + stderr))
		if strings.Contains(msg, "no such file") ||
			strings.Contains(msg, "not found") ||
			strings.Contains(msg, "does not exist") {
			return nil, nil
		}
		if err != nil {
			return nil, fmt.Errorf("nft list set %s failed: %w", setName, err)
		}
		return nil, fmt.Errorf("nft list set %s failed: %s", setName, strings.TrimSpace(stderr))
	}
	return parseNftSetElementsText(out), nil
}

func parseNftSetElementsText(raw string) []string {
	idx := strings.Index(raw, "elements =")
	if idx < 0 {
		return nil
	}
	chunk := raw[idx:]
	open := strings.Index(chunk, "{")
	if open < 0 {
		return nil
	}
	body := chunk[open+1:]
	closeIdx := strings.Index(body, "}")
	if closeIdx >= 0 {
		body = body[:closeIdx]
	}
	body = strings.ReplaceAll(body, "\r", " ")
	body = strings.ReplaceAll(body, "\n", " ")

	seen := map[string]struct{}{}
	out := make([]string, 0, 1024)
	for _, tok := range strings.Split(body, ",") {
		val := strings.TrimSpace(tok)
		if val == "" {
			continue
		}
		if _, ok := seen[val]; ok {
			continue
		}
		seen[val] = struct{}{}
		out = append(out, val)
	}
	sort.Strings(out)
	return out
}