package config

import (
	"errors"
	"os"
)

// Config holds runtime configuration for the Home Assistant gRPC gateway.
type Config struct {
	GRPCPort     string // GRPC_PORT, default "50051"
	HABaseURL    string // HA_BASE_URL, e.g. "http://ha.home.arpa:8123"
	HAToken      string // HA_TOKEN — long-lived access token (required)
	OTELEndpoint string // OTEL_ENDPOINT, e.g. "otel-collector.monitoring.svc:4317"
	LogLevel     string // LOG_LEVEL, default "info"
	LogFormat    string // LOG_FORMAT, default "json"
	// empty = telemetry disabled (local dev default)
}

// Load reads configuration from environment variables and applies defaults.
func Load() (*Config, error) {
	token := os.Getenv("HA_TOKEN")
	if token == "" {
		return nil, errors.New("HA_TOKEN is required but not set")
	}

	port := os.Getenv("GRPC_PORT")
	if port == "" {
		port = "50051"
	}

	return &Config{
		GRPCPort:     port,
		HABaseURL:    os.Getenv("HA_BASE_URL"),
		HAToken:      token,
		OTELEndpoint: os.Getenv("OTEL_ENDPOINT"),
		LogLevel:     getenvDefault("LOG_LEVEL", "info"),
		LogFormat:    getenvDefault("LOG_FORMAT", "json"),
	}, nil
}

// getenvDefault keeps config loading concise for optional variables with defaults.
func getenvDefault(key, fallback string) string {
	if v := os.Getenv(key); v != "" {
		return v
	}
	return fallback
}