package app

import (
	"encoding/json"
	"os"
	"path/filepath"

	dnscfgpkg "selective-vpn-api/app/dnscfg"
)

func loadDNSUpstreamsConfFile() DNSUpstreams {
	data, err := os.ReadFile(dnsUpstreamsConf)
	if err != nil {
		return dnscfgUpstreamsToApp(dnscfgLegacyDefaults())
	}
	pkgCfg := dnscfgpkg.ParseUpstreamsConf(string(data), dnscfgLegacyDefaults(), normalizeDNSUpstream)
	return dnscfgUpstreamsToApp(pkgCfg)
}

func saveDNSUpstreamsConfFile(cfg DNSUpstreams) error {
	pkgCfg := dnscfgpkg.NormalizeUpstreams(dnscfgUpstreamsFromApp(cfg), dnscfgLegacyDefaults(), normalizeDNSUpstream)
	cfg = dnscfgUpstreamsToApp(pkgCfg)
	content := dnscfgpkg.RenderUpstreamsConf(pkgCfg)

	if err := os.MkdirAll(filepath.Dir(dnsUpstreamsConf), 0o755); err != nil {
		return err
	}
	tmp := dnsUpstreamsConf + ".tmp"
	if err := os.WriteFile(tmp, []byte(content), 0o644); err != nil {
		return err
	}
	if err := os.Rename(tmp, dnsUpstreamsConf); err != nil {
		return err
	}

	// Legacy JSON mirror for backward compatibility with older UI/runtime bits.
	_ = os.MkdirAll(stateDir, 0o755)
	if b, err := json.MarshalIndent(cfg, "", "  "); err == nil {
		_ = os.WriteFile(dnsUpstreamsPath, b, 0o644)
	}
	return nil
}