// Package config loads device-control-service settings from environment
// variables, matching the names used in the repo-root .env.example.
package config

import (
	"fmt"
	"os"
	"strconv"
	"time"
)

type Config struct {
	GRPCPort int

	MQTTBrokerURL string
	MQTTClientID  string

	RedisAddr     string
	RedisPassword string
	RedisDB       int

	RabbitMQURL string

	HealthCheckTimeout  time.Duration
	HealthCheckInterval time.Duration
}

func Load() (Config, error) {
	cfg := Config{
		MQTTBrokerURL: fmt.Sprintf("tcp://%s:%s", getEnv("MQTT_HOST", "localhost"), getEnv("MQTT_PORT", "1883")),
		MQTTClientID:  getEnv("DEVICE_CONTROL_MQTT_CLIENT_ID", "device-control-service"),

		RedisAddr:     fmt.Sprintf("%s:%s", getEnv("REDIS_HOST", "localhost"), getEnv("REDIS_PORT", "6379")),
		RedisPassword: getEnv("REDIS_PASSWORD", ""),

		RabbitMQURL: fmt.Sprintf("amqp://%s:%s@%s:%s/",
			getEnv("RABBITMQ_USER", "guest"),
			getEnv("RABBITMQ_PASSWORD", "guest"),
			getEnv("RABBITMQ_HOST", "localhost"),
			getEnv("RABBITMQ_PORT", "5672"),
		),
	}

	var err error
	if cfg.GRPCPort, err = getEnvInt("DEVICE_CONTROL_GRPC_PORT", 50051); err != nil {
		return Config{}, err
	}
	if cfg.RedisDB, err = getEnvInt("REDIS_DB", 0); err != nil {
		return Config{}, err
	}
	if cfg.HealthCheckTimeout, err = getEnvDuration("DEVICE_CONTROL_HEALTHCHECK_TIMEOUT", 60*time.Second); err != nil {
		return Config{}, err
	}
	if cfg.HealthCheckInterval, err = getEnvDuration("DEVICE_CONTROL_HEALTHCHECK_INTERVAL", 15*time.Second); err != nil {
		return Config{}, err
	}

	return cfg, nil
}

func getEnv(key, fallback string) string {
	if v := os.Getenv(key); v != "" {
		return v
	}
	return fallback
}

func getEnvInt(key string, fallback int) (int, error) {
	v := os.Getenv(key)
	if v == "" {
		return fallback, nil
	}
	n, err := strconv.Atoi(v)
	if err != nil {
		return 0, fmt.Errorf("%s: %w", key, err)
	}
	return n, nil
}

func getEnvDuration(key string, fallback time.Duration) (time.Duration, error) {
	v := os.Getenv(key)
	if v == "" {
		return fallback, nil
	}
	d, err := time.ParseDuration(v)
	if err != nil {
		return 0, fmt.Errorf("%s: %w", key, err)
	}
	return d, nil
}