// Command bot is the remote-side Telegram bot. It runs the Bot API long-poll
// (Mini App launch + /start deep-links) and dials the gateway over the reverse mTLS
// bot-link to receive and execute send commands (out-of-app push and admin sends).
// It holds the bot token and is the only component that reaches the Telegram Bot
// API, so it runs on a host with native Telegram access (no VPN) and needs no
// inbound port. See platform/telegram/README.md.
package main

import (
	"context"
	"log"
	"os/signal"
	"sync"
	"syscall"
	"time"

	"go.uber.org/zap"
	"google.golang.org/grpc/credentials"

	"scrabble/pkg/mtls"
	pkgtel "scrabble/pkg/telemetry"
	"scrabble/platform/telegram/internal/bot"
	"scrabble/platform/telegram/internal/botlink"
	"scrabble/platform/telegram/internal/config"
)

// telemetryShutdownTimeout bounds the OpenTelemetry flush during process exit.
const telemetryShutdownTimeout = 5 * time.Second

func main() {
	cfg, err := config.LoadBot()
	if err != nil {
		log.Fatalf("bot: load config: %v", err)
	}
	logger, err := newLogger(cfg.LogLevel)
	if err != nil {
		log.Fatalf("bot: build logger: %v", err)
	}
	defer func() { _ = logger.Sync() }()

	ctx, stop := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
	defer stop()

	if err := run(ctx, cfg, logger); err != nil {
		logger.Fatal("bot: terminated", zap.Error(err))
	}
}

// run wires the bot long-poll and the bot-link client and runs both until the
// context is cancelled.
func run(ctx context.Context, cfg config.BotConfig, logger *zap.Logger) error {
	tel, err := pkgtel.New(ctx, cfg.Telemetry)
	if err != nil {
		return err
	}
	defer func() {
		shutdownCtx, cancel := context.WithTimeout(context.Background(), telemetryShutdownTimeout)
		defer cancel()
		if err := tel.Shutdown(shutdownCtx); err != nil {
			logger.Warn("telemetry shutdown", zap.Error(err))
		}
	}()
	if err := tel.StartRuntimeMetrics(); err != nil {
		logger.Warn("telemetry: start runtime metrics", zap.Error(err))
	}

	b, err := bot.New(bot.Config{
		Token:             cfg.Token,
		APIBaseURL:        cfg.APIBaseURL,
		TestEnv:           cfg.TestEnv,
		MiniAppURL:        cfg.MiniAppURL,
		SendRatePerSecond: cfg.SendRatePerSecond,
	}, logger)
	if err != nil {
		return err
	}

	tlsCfg, err := mtls.ClientConfig(cfg.BotLink.CertFile, cfg.BotLink.KeyFile, cfg.BotLink.CAFile, cfg.BotLink.ServerName)
	if err != nil {
		return err
	}
	exec := botlink.NewExecutor(b, cfg.GameChannelID, logger)
	client := botlink.NewClient(botlink.ClientConfig{
		GatewayAddr:    cfg.BotLink.GatewayAddr,
		InstanceID:     cfg.BotLink.InstanceID,
		OwnsUpdates:    cfg.OwnsUpdates,
		Creds:          credentials.NewTLS(tlsCfg),
		ReconnectDelay: cfg.BotLink.ReconnectDelay,
	}, exec, logger)

	logger.Info("telegram bot starting",
		zap.String("gateway", cfg.BotLink.GatewayAddr),
		zap.String("miniapp_url", cfg.MiniAppURL),
		zap.Bool("owns_updates", cfg.OwnsUpdates),
		zap.Bool("test_env", cfg.TestEnv))

	var wg sync.WaitGroup
	// The long-poll holds the exclusive getUpdates lease (one bot per token); a bot
	// that does not own it only delivers sends over the bot-link.
	if cfg.OwnsUpdates {
		wg.Go(func() { b.Run(ctx) })
	}
	wg.Go(func() {
		if err := client.Run(ctx); err != nil && ctx.Err() == nil {
			logger.Error("bot-link client stopped", zap.Error(err))
		}
	})

	<-ctx.Done()
	wg.Wait()
	return nil
}

// newLogger builds a production JSON logger at the given level.
func newLogger(level string) (*zap.Logger, error) {
	var lvl zap.AtomicLevel
	if err := lvl.UnmarshalText([]byte(level)); err != nil {
		return nil, err
	}
	cfg := zap.NewProductionConfig()
	cfg.Level = lvl
	return cfg.Build()
}