// Package config loads the Telegram connector's environment configuration.
package config

import (
	"fmt"
	"os"
	"strconv"
	"strings"

	pkgtel "scrabble/pkg/telemetry"
)

// Languages is the set of service languages a bot may be tagged with. Each is a
// separate bot (own token + game channel) serving that audience; the same Telegram
// user id spans them all (ARCHITECTURE.md §12).
var Languages = []string{"en", "ru"}

// BotConfig is one language-tagged bot's settings.
type BotConfig struct {
	// Token is the Telegram Bot API token (TELEGRAM_BOT_TOKEN_<LANG>). It both
	// authenticates the Bot API client and is the HMAC secret for Mini App initData
	// validation against this bot.
	Token string
	// GameChannelID is the chat id of this bot's game channel for SendToGameChannel
	// (TELEGRAM_GAME_CHANNEL_ID_<LANG>, optional; 0 disables channel posts).
	GameChannelID int64
}

// Config is the Telegram connector's runtime configuration, read from the
// environment. The bot tokens live only in this process (ARCHITECTURE.md §12).
type Config struct {
	// Bots maps a service language (one of Languages) to that language's bot
	// settings. A language is present when its TELEGRAM_BOT_TOKEN_<LANG> is set; at
	// least one bot is required.
	Bots map[string]BotConfig
	// GRPCAddr is the listen address of the connector gRPC server that gateway and
	// backend call (TELEGRAM_GRPC_ADDR, default :9091).
	GRPCAddr string
	// MiniAppURL is the HTTPS origin of the Mini App registered with BotFather; it
	// is the base of every launch button, to which a deep-link adds a startapp
	// query parameter (TELEGRAM_MINIAPP_URL, required). It is shared by all bots
	// (one gateway origin); initData is signed per bot token.
	MiniAppURL string
	// APIBaseURL overrides the Bot API host (TELEGRAM_API_BASE_URL, optional;
	// default https://api.telegram.org) — used for a local mock or a self-hosted
	// Bot API server. Shared by all bots.
	APIBaseURL string
	// TestEnv routes the Bot API client to Telegram's test environment
	// (.../bot<token>/test/METHOD) (TELEGRAM_TEST_ENV=true, default false).
	TestEnv bool
	// LogLevel is the zap log level (TELEGRAM_LOG_LEVEL, default info).
	LogLevel string
	// Telemetry configures the OpenTelemetry providers (shared bootstrap).
	Telemetry pkgtel.Config
}

// Load reads the connector configuration from the environment, applying defaults
// and validating the required fields.
func Load() (Config, error) {
	cfg := Config{
		Bots:       map[string]BotConfig{},
		GRPCAddr:   envOr("TELEGRAM_GRPC_ADDR", ":9091"),
		MiniAppURL: os.Getenv("TELEGRAM_MINIAPP_URL"),
		APIBaseURL: os.Getenv("TELEGRAM_API_BASE_URL"),
		TestEnv:    os.Getenv("TELEGRAM_TEST_ENV") == "true",
		LogLevel:   envOr("TELEGRAM_LOG_LEVEL", "info"),
	}
	for _, lang := range Languages {
		suffix := strings.ToUpper(lang)
		token := os.Getenv("TELEGRAM_BOT_TOKEN_" + suffix)
		if token == "" {
			continue
		}
		bot := BotConfig{Token: token}
		if v := strings.TrimSpace(os.Getenv("TELEGRAM_GAME_CHANNEL_ID_" + suffix)); v != "" {
			id, err := strconv.ParseInt(v, 10, 64)
			if err != nil {
				return Config{}, fmt.Errorf("config: TELEGRAM_GAME_CHANNEL_ID_%s %q: %w", suffix, v, err)
			}
			bot.GameChannelID = id
		}
		cfg.Bots[lang] = bot
	}
	tel := pkgtel.DefaultConfig("scrabble-telegram")
	tel.ServiceName = envOr("TELEGRAM_SERVICE_NAME", tel.ServiceName)
	tel.TracesExporter = envOr("TELEGRAM_OTEL_TRACES_EXPORTER", tel.TracesExporter)
	tel.MetricsExporter = envOr("TELEGRAM_OTEL_METRICS_EXPORTER", tel.MetricsExporter)
	cfg.Telemetry = tel
	if len(cfg.Bots) == 0 {
		return Config{}, fmt.Errorf("config: at least one TELEGRAM_BOT_TOKEN_<LANG> (LANG in %v) is required", Languages)
	}
	if cfg.MiniAppURL == "" {
		return Config{}, fmt.Errorf("config: TELEGRAM_MINIAPP_URL is required")
	}
	if err := cfg.Telemetry.Validate(); err != nil {
		return Config{}, fmt.Errorf("config: %w", err)
	}
	return cfg, nil
}

// envOr returns the environment value for key, or def when it is unset or empty.
func envOr(key, def string) string {
	if v := os.Getenv(key); v != "" {
		return v
	}
	return def
}