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

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

// Config is the Telegram connector's runtime configuration, read from the
// environment. The bot token lives only in this process (ARCHITECTURE.md §12).
type Config struct {
	// BotToken is the Telegram Bot API token (TELEGRAM_BOT_TOKEN, required). It
	// both authenticates the Bot API client and is the HMAC secret for Mini App
	// initData validation.
	BotToken string
	// 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).
	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.
	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
	// GameChannelID is the chat id of the bot's game channel for SendToGameChannel
	// (TELEGRAM_GAME_CHANNEL_ID, optional; 0 disables channel posts).
	GameChannelID int64
	// LogLevel is the zap log level (TELEGRAM_LOG_LEVEL, default info).
	LogLevel string
}

// Load reads the connector configuration from the environment, applying defaults
// and validating the required fields.
func Load() (Config, error) {
	cfg := Config{
		BotToken:   os.Getenv("TELEGRAM_BOT_TOKEN"),
		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"),
	}
	if cfg.BotToken == "" {
		return Config{}, fmt.Errorf("config: TELEGRAM_BOT_TOKEN is required")
	}
	if cfg.MiniAppURL == "" {
		return Config{}, fmt.Errorf("config: TELEGRAM_MINIAPP_URL is required")
	}
	if v := strings.TrimSpace(os.Getenv("TELEGRAM_GAME_CHANNEL_ID")); v != "" {
		id, err := strconv.ParseInt(v, 10, 64)
		if err != nil {
			return Config{}, fmt.Errorf("config: TELEGRAM_GAME_CHANNEL_ID %q: %w", v, err)
		}
		cfg.GameChannelID = id
	}
	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
}