package transcode_test

import (
	"context"
	"encoding/json"
	"net/http"
	"testing"

	flatbuffers "github.com/google/flatbuffers/go"

	"scrabble/gateway/internal/connector"
	"scrabble/gateway/internal/transcode"
	fb "scrabble/pkg/fbs/scrabblefb"
)

// fakeValidator stands in for the connector's ValidateInitData RPC.
type fakeValidator struct {
	user connector.User
	err  error
}

func (f fakeValidator) ValidateInitData(context.Context, string) (connector.User, error) {
	return f.user, f.err
}

func (f fakeValidator) ValidateLoginWidget(context.Context, string) (connector.User, error) {
	return f.user, f.err
}

func telegramLoginPayload(initData string) []byte {
	b := flatbuffers.NewBuilder(0)
	off := b.CreateString(initData)
	fb.TelegramLoginRequestStart(b)
	fb.TelegramLoginRequestAddInitData(b, off)
	b.Finish(fb.TelegramLoginRequestEnd(b))
	return b.FinishedBytes()
}

func TestTelegramAuthForwardsSeedFields(t *testing.T) {
	var gotBody map[string]string
	backend, cleanup := fakeBackend(t, func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path != "/api/v1/internal/sessions/telegram" {
			t.Errorf("unexpected path %q", r.URL.Path)
		}
		_ = json.NewDecoder(r.Body).Decode(&gotBody)
		_, _ = w.Write([]byte(`{"token":"tok-tg","user_id":"u-tg","is_guest":false,"display_name":"Иван"}`))
	})
	defer cleanup()

	v := fakeValidator{user: connector.User{ExternalID: "42", Username: "neo", FirstName: "Иван", LanguageCode: "ru", ServiceLanguage: "ru", SupportedLanguages: []string{"ru"}}}
	reg := transcode.NewRegistry(backend, v)
	op, ok := reg.Lookup(transcode.MsgAuthTelegram)
	if !ok {
		t.Fatal("auth.telegram not registered")
	}

	payload, err := op.Handler(context.Background(), transcode.Request{Payload: telegramLoginPayload("init")})
	if err != nil {
		t.Fatalf("handler: %v", err)
	}
	sess := fb.GetRootAsSession(payload, 0)
	if string(sess.Token()) != "tok-tg" || string(sess.UserId()) != "u-tg" {
		t.Fatalf("session decoded wrong: token=%q user=%q", sess.Token(), sess.UserId())
	}
	// The validating bot's supported languages ride the Session so the UI gates the
	// New Game variant choice (here: ru -> Russian + Эрудит only).
	if got := sessionLanguages(sess); len(got) != 1 || got[0] != "ru" {
		t.Errorf("session supported_languages = %v, want [ru]", got)
	}
	// The validated launch fields are forwarded so the backend can seed a new account;
	// service_language is recorded to route the account's later out-of-app push.
	if gotBody["external_id"] != "42" || gotBody["language_code"] != "ru" || gotBody["first_name"] != "Иван" || gotBody["service_language"] != "ru" {
		t.Errorf("forwarded body = %+v, want external_id=42 language_code=ru first_name=Иван service_language=ru", gotBody)
	}
}

// sessionLanguages reads the supported_languages vector off a decoded Session.
func sessionLanguages(s *fb.Session) []string {
	out := make([]string, s.SupportedLanguagesLength())
	for i := range out {
		out[i] = string(s.SupportedLanguages(i))
	}
	return out
}

// TestGuestAuthSeedsDefaultLanguages confirms a non-platform (guest) session carries
// the gateway's default supported-languages set, so the web client is ungated.
func TestGuestAuthSeedsDefaultLanguages(t *testing.T) {
	backend, cleanup := fakeBackend(t, func(w http.ResponseWriter, _ *http.Request) {
		_, _ = w.Write([]byte(`{"token":"tok-g","user_id":"u-g","is_guest":true,"display_name":"Guest"}`))
	})
	defer cleanup()

	reg := transcode.NewRegistry(backend, nil, "en", "ru")
	op, _ := reg.Lookup(transcode.MsgAuthGuest)
	payload, err := op.Handler(context.Background(), transcode.Request{})
	if err != nil {
		t.Fatalf("handler: %v", err)
	}
	if got := sessionLanguages(fb.GetRootAsSession(payload, 0)); len(got) != 2 || got[0] != "en" || got[1] != "ru" {
		t.Errorf("guest session supported_languages = %v, want [en ru]", got)
	}
}

func TestTelegramAuthInvalidInitData(t *testing.T) {
	backend, cleanup := fakeBackend(t, func(http.ResponseWriter, *http.Request) {
		t.Error("backend must not be called when initData is invalid")
	})
	defer cleanup()

	reg := transcode.NewRegistry(backend, fakeValidator{err: connector.ErrInvalidInitData})
	op, _ := reg.Lookup(transcode.MsgAuthTelegram)

	_, err := op.Handler(context.Background(), transcode.Request{Payload: telegramLoginPayload("bad")})
	if code, ok := transcode.DomainCode(err); !ok || code != "invalid_init_data" {
		t.Errorf("DomainCode = (%q, %v), want (invalid_init_data, true)", code, ok)
	}
}

// TestTelegramAuthDisabledWithoutConnector confirms a nil validator leaves
// auth.telegram unregistered.
func TestTelegramAuthDisabledWithoutConnector(t *testing.T) {
	backend, cleanup := fakeBackend(t, func(http.ResponseWriter, *http.Request) {})
	defer cleanup()
	reg := transcode.NewRegistry(backend, nil)
	if _, ok := reg.Lookup(transcode.MsgAuthTelegram); ok {
		t.Error("auth.telegram should be unregistered without a connector")
	}
}