// Package connector implements the Telegram gRPC service (pkg/proto/telegram/v1):
// the gateway calls ValidateInitData (Mini App auth) and Notify (out-of-app push);
// the admin surface (Stage 10) calls SendToUser and SendToGameChannel. The generic
// methods address a recipient by the identity external_id, so a future platform
// connector can implement the same service.
//
// The connector hosts one bot per configured service language (en/ru); the same
// Telegram user id spans them all. ValidateInitData tries each bot's token in turn
// and reports which bot validated (its service language); the push and admin
// methods route to the bot the request selects by language.
package connector

import (
	"context"
	"errors"
	"fmt"
	"strconv"

	"go.uber.org/zap"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/status"

	telegramv1 "scrabble/pkg/proto/telegram/v1"
	"scrabble/platform/telegram/internal/initdata"
	"scrabble/platform/telegram/internal/loginwidget"
	"scrabble/platform/telegram/internal/render"
)

// Sender delivers Telegram messages to a chat. *bot.Bot implements it.
type Sender interface {
	// Notify sends a notification with a Mini App launch button to chatID.
	Notify(ctx context.Context, chatID int64, text, buttonText, startParam string) error
	// SendText sends a plain text message to chatID.
	SendText(ctx context.Context, chatID int64, text string) error
}

// BotRuntime is one configured language-tagged bot: its sender, game channel id,
// and the two HMAC validators bound to its token.
type BotRuntime struct {
	// Language is the bot's service language (en/ru).
	Language string
	// Sender delivers messages through this bot.
	Sender Sender
	// ChannelID is this bot's game channel (0 disables channel posts).
	ChannelID int64
	// InitValidator verifies Mini App initData signed by this bot's token.
	InitValidator initdata.Validator
	// WidgetValidator verifies Login Widget data signed by this bot's token.
	WidgetValidator loginwidget.Validator
}

// Server implements telegramv1.TelegramServer over one or more language-tagged bots.
type Server struct {
	telegramv1.UnimplementedTelegramServer
	bots  map[string]BotRuntime // keyed by service language
	order []string              // stable iteration order for validation
	log   *zap.Logger
}

// NewServer builds the gRPC service from the configured bots (at least one).
func NewServer(bots []BotRuntime, log *zap.Logger) *Server {
	if log == nil {
		log = zap.NewNop()
	}
	m := make(map[string]BotRuntime, len(bots))
	order := make([]string, 0, len(bots))
	for _, b := range bots {
		m[b.Language] = b
		order = append(order, b.Language)
	}
	return &Server{bots: m, order: order, log: log}
}

// ValidateInitData verifies Mini App launch data against each bot's token in turn
// and returns the user identity plus the validating bot's service language (which
// routes the user's later push) and its set of offered game languages.
func (s *Server) ValidateInitData(ctx context.Context, req *telegramv1.ValidateInitDataRequest) (*telegramv1.ValidateInitDataResponse, error) {
	var lastErr error
	for _, lang := range s.order {
		u, err := s.bots[lang].InitValidator.Validate(req.GetInitData())
		if err != nil {
			lastErr = err
			continue
		}
		return &telegramv1.ValidateInitDataResponse{
			ExternalId:         u.ExternalID,
			Username:           u.Username,
			FirstName:          u.FirstName,
			LanguageCode:       u.LanguageCode,
			ServiceLanguage:    lang,
			SupportedLanguages: []string{lang},
		}, nil
	}
	if lastErr == nil {
		lastErr = errors.New("no bot configured")
	}
	return nil, status.Error(codes.InvalidArgument, lastErr.Error())
}

// ValidateLoginWidget verifies Login Widget authorization data against each bot's
// token in turn and returns the user identity, for attaching a Telegram identity to
// an existing account (Stage 11).
func (s *Server) ValidateLoginWidget(ctx context.Context, req *telegramv1.ValidateLoginWidgetRequest) (*telegramv1.ValidateLoginWidgetResponse, error) {
	var lastErr error
	for _, lang := range s.order {
		u, err := s.bots[lang].WidgetValidator.Validate(req.GetData())
		if err != nil {
			lastErr = err
			continue
		}
		return &telegramv1.ValidateLoginWidgetResponse{
			ExternalId: u.ExternalID,
			Username:   u.Username,
			FirstName:  u.FirstName,
		}, nil
	}
	if lastErr == nil {
		lastErr = errors.New("no bot configured")
	}
	return nil, status.Error(codes.InvalidArgument, lastErr.Error())
}

// Notify renders and delivers an out-of-app notification through the bot selected by
// the recipient's service language. It reports delivered=false (without an error)
// when no bot serves that language, the kind is not pushed out-of-app, or the bot
// could not deliver (e.g. the user never started it), so the gateway treats a
// fallback miss as best-effort.
func (s *Server) Notify(ctx context.Context, req *telegramv1.NotifyRequest) (*telegramv1.NotifyResponse, error) {
	bot, ok := s.bots[req.GetLanguage()]
	if !ok {
		s.log.Warn("notify: no bot for language", zap.String("language", req.GetLanguage()), zap.String("kind", req.GetKind()))
		return &telegramv1.NotifyResponse{Delivered: false}, nil
	}
	msg, ok := render.Render(req.GetKind(), req.GetPayload(), req.GetLanguage())
	if !ok {
		return &telegramv1.NotifyResponse{Delivered: false}, nil
	}
	chat, err := parseChatID(req.GetExternalId())
	if err != nil {
		return nil, status.Error(codes.InvalidArgument, err.Error())
	}
	if err := bot.Sender.Notify(ctx, chat, msg.Text, msg.ButtonText, msg.StartParam); err != nil {
		s.log.Warn("notify delivery failed", zap.String("kind", req.GetKind()), zap.Error(err))
		return &telegramv1.NotifyResponse{Delivered: false}, nil
	}
	return &telegramv1.NotifyResponse{Delivered: true}, nil
}

// SendToUser sends an arbitrary admin message to one user through the bot selected
// by language (an operator choice in the admin console).
func (s *Server) SendToUser(ctx context.Context, req *telegramv1.SendToUserRequest) (*telegramv1.SendResponse, error) {
	bot, err := s.botFor(req.GetLanguage())
	if err != nil {
		return nil, err
	}
	chat, err := parseChatID(req.GetExternalId())
	if err != nil {
		return nil, status.Error(codes.InvalidArgument, err.Error())
	}
	if err := bot.Sender.SendText(ctx, chat, req.GetText()); err != nil {
		s.log.Warn("send to user failed", zap.Error(err))
		return &telegramv1.SendResponse{Delivered: false}, nil
	}
	return &telegramv1.SendResponse{Delivered: true}, nil
}

// SendToGameChannel posts an arbitrary admin message to the game channel of the bot
// selected by language (an operator choice in the admin console).
func (s *Server) SendToGameChannel(ctx context.Context, req *telegramv1.SendToGameChannelRequest) (*telegramv1.SendResponse, error) {
	bot, err := s.botFor(req.GetLanguage())
	if err != nil {
		return nil, err
	}
	if bot.ChannelID == 0 {
		return nil, status.Error(codes.FailedPrecondition, fmt.Sprintf("game channel is not configured for language %q", req.GetLanguage()))
	}
	if err := bot.Sender.SendText(ctx, bot.ChannelID, req.GetText()); err != nil {
		s.log.Warn("send to channel failed", zap.Error(err))
		return &telegramv1.SendResponse{Delivered: false}, nil
	}
	return &telegramv1.SendResponse{Delivered: true}, nil
}

// botFor returns the bot tagged with language, or a FailedPrecondition error when no
// bot serves it (admin broadcasts choose the language explicitly).
func (s *Server) botFor(language string) (BotRuntime, error) {
	bot, ok := s.bots[language]
	if !ok {
		return BotRuntime{}, status.Error(codes.FailedPrecondition, fmt.Sprintf("no bot configured for language %q", language))
	}
	return bot, nil
}

// parseChatID converts a Telegram identity external_id into a numeric chat id.
func parseChatID(externalID string) (int64, error) {
	id, err := strconv.ParseInt(externalID, 10, 64)
	if err != nil {
		return 0, fmt.Errorf("invalid external_id %q", externalID)
	}
	return id, nil
}