package firewall

import (
	"crypto/sha256"
	"fmt"
	"net"
	"os/exec"
	"sync"
)

var setApplyMu sync.Mutex

func replaceSet(name, family string, addresses []string) error {
	setApplyMu.Lock()
	defer setApplyMu.Unlock()
	if len(name) > 31 {
		return fmt.Errorf("address list name too long: %s", name)
	}
	for _, address := range addresses {
		ip := net.ParseIP(address)
		if ip == nil {
			ip, _, _ = net.ParseCIDR(address)
		}
		if ip == nil || (ip.To4() != nil) != (family == "inet") {
			return fmt.Errorf("invalid %s address: %s", family, address)
		}
	}
	hash := sha256.Sum256([]byte(name))
	temp := fmt.Sprintf("dt_tmp_%x", hash[:8])
	run := func(args ...string) error {
		out, err := exec.Command("ipset", args...).CombinedOutput()
		if err != nil {
			return fmt.Errorf("ipset %v: %s: %w", args, out, err)
		}
		return nil
	}
	if err := run("create", temp, "hash:net", "family", family, "maxelem", "262144", "-exist"); err != nil {
		return err
	}
	defer exec.Command("ipset", "destroy", temp).Run()
	if err := run("flush", temp); err != nil {
		return err
	}
	for _, address := range addresses {
		if err := run("add", temp, address, "-exist"); err != nil {
			return err
		}
	}
	if err := run("create", name, "hash:net", "family", family, "maxelem", "262144", "-exist"); err != nil {
		return err
	}
	return run("swap", temp, name)
}