package edns

import (
	"errors"
	"fmt"
	"strings"
)

type UnsupportedError struct {
	Message string
}

func (err *UnsupportedError) Error() string { return err.Message }

func IsUnsupported(err error) bool {
	var unsupported *UnsupportedError
	return errors.As(err, &unsupported)
}

type Provider struct {
	ID            string
	Profile       string
	SourceURL     string
	VerifiedDate  string
	DoHURL        string
	DoTAddr       string
	DoTName       string
	DoQAddr       string
	DoQName       string
	DoH3URL       string
	DNSCryptStamp string
}

var providers = map[string]Provider{
	"cloudflare": {
		ID:           "cloudflare",
		Profile:      "unfiltered",
		SourceURL:    "https://developers.cloudflare.com/1.1.1.1/encryption/",
		VerifiedDate: "2026-08-13",
		DoHURL:       "https://cloudflare-dns.com/dns-query",
		DoTAddr:      "one.one.one.one:853",
		DoTName:      "one.one.one.one",
		DoH3URL:      "https://cloudflare-dns.com/dns-query",
	},
	"google": {
		ID:           "google",
		Profile:      "unfiltered",
		SourceURL:    "https://developers.google.com/speed/public-dns/docs/secure-transports",
		VerifiedDate: "2026-08-13",
		DoHURL:       "https://dns.google/dns-query",
		DoTAddr:      "dns.google:853",
		DoTName:      "dns.google",
		DoH3URL:      "https://dns.google/dns-query",
	},
	"quad9": {
		ID:           "quad9",
		Profile:      "security-filtered",
		SourceURL:    "https://docs.quad9.net/services/",
		VerifiedDate: "2026-08-13",
		DoHURL:       "https://dns.quad9.net/dns-query",
		DoTAddr:      "dns.quad9.net:853",
		DoTName:      "dns.quad9.net",
	},
	"adguard": {
		ID:            "adguard",
		Profile:       "ad-and-security-filtered",
		SourceURL:     "https://adguard-dns.io/kb/en/public-dns/overview/",
		VerifiedDate:  "2026-08-13",
		DoHURL:        "https://dns.adguard-dns.com/dns-query",
		DoTAddr:       "dns.adguard-dns.com:853",
		DoTName:       "dns.adguard-dns.com",
		DoQAddr:       "dns.adguard-dns.com:853",
		DoQName:       "dns.adguard-dns.com",
		DNSCryptStamp: "sdns://AQMAAAAAAAAAETk0LjE0MC4xNC4xNDo1NDQzINErR_JS3PLCu_iZEIbq95zkSV2LFsigxDIuUso_OQhzIjIuZG5zY3J5cHQuZGVmYXVsdC5uczEuYWRndWFyZC5jb20",
	},
}

func (provider Provider) Endpoint(protocol string) (string, error) {
	var endpoint string
	switch strings.ToLower(protocol) {
	case "doh":
		endpoint = provider.DoHURL
	case "dot":
		endpoint = provider.DoTAddr
	case "doq":
		endpoint = provider.DoQAddr
	case "doh3":
		endpoint = provider.DoH3URL
	case "dnscrypt":
		endpoint = provider.DNSCryptStamp
	default:
		return "", &UnsupportedError{Message: fmt.Sprintf("protocol %q is not available", protocol)}
	}
	if endpoint == "" {
		return "", &UnsupportedError{Message: fmt.Sprintf("provider %q does not support protocol %q", provider.ID, protocol)}
	}
	return endpoint, nil
}

func FindProvider(name string) (Provider, error) {
	provider, ok := providers[strings.ToLower(name)]
	if !ok {
		return Provider{}, fmt.Errorf("unknown provider %q", name)
	}
	return provider, nil
}