//go:build standalone

package checker

import (
	"context"
	"fmt"
	"net"
	"strings"

	sdk "git.happydns.org/checker-sdk-go/checker"
)

// collectFallback queries DNS for SRV records directly when no upstream
// service payload is available (standalone CLI/HTTP mode).
func (p *srvProvider) collectFallback(ctx context.Context, opts sdk.CheckerOptions) (any, error) {
	subdomain, _ := sdk.GetOption[string](opts, "subdomain")
	domain, _ := sdk.GetOption[string](opts, "domain")

	serviceDomain := strings.TrimSuffix(subdomain, ".")
	if domain != "" {
		if serviceDomain != "" {
			serviceDomain += "." + strings.TrimSuffix(domain, ".")
		} else {
			serviceDomain = strings.TrimSuffix(domain, ".")
		}
	}
	if serviceDomain == "" {
		return nil, fmt.Errorf("missing 'domain' option")
	}

	// Empty service/proto tells the resolver to query the literal name as-is,
	// preserving _svc._proto labels already encoded in serviceDomain.
	_, srvs, err := net.DefaultResolver.LookupSRV(ctx, "", "", serviceDomain)
	if err != nil {
		return nil, fmt.Errorf("SRV lookup for %s: %w", serviceDomain, err)
	}
	if len(srvs) == 0 {
		return nil, fmt.Errorf("no SRV records at %s", serviceDomain)
	}

	tcpTimeout := durationOpt(opts, "tcpTimeout", 3000)
	udpTimeout := durationOpt(opts, "udpTimeout", 2000)

	svc, proto := parseOwner(serviceDomain, serviceDomain)
	data := &SRVData{
		ServiceDomain: serviceDomain,
		Records:       make([]SRVRecord, 0, len(srvs)),
	}
	for _, s := range srvs {
		rec := SRVRecord{
			Service:  svc,
			Proto:    proto,
			Owner:    serviceDomain,
			Target:   strings.TrimSuffix(s.Target, "."),
			Port:     s.Port,
			Priority: s.Priority,
			Weight:   s.Weight,
		}
		resolveAndProbe(ctx, &rec, tcpTimeout, udpTimeout)
		data.Records = append(data.Records, rec)
	}
	return data, nil
}