// Package config loads ingest-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 {
	MQTTBrokerURL string
	MQTTClientID  string
	MQTTTopic     string

	ClickHouseAddr     string
	ClickHouseDatabase string
	ClickHouseUsername string
	ClickHousePassword string

	RabbitMQURL string

	BatchMaxSize       int
	BatchFlushInterval time.Duration
	BatchFlushTimeout  time.Duration
}

func Load() (Config, error) {
	cfg := Config{
		MQTTBrokerURL: fmt.Sprintf("tcp://%s:%s", getEnv("MQTT_HOST", "localhost"), getEnv("MQTT_PORT", "1883")),
		MQTTClientID:  getEnv("INGEST_MQTT_CLIENT_ID", "ingest-service"),
		MQTTTopic:     getEnv("INGEST_MQTT_TOPIC", "devices/+/telemetry"),

		ClickHouseAddr:     fmt.Sprintf("%s:%s", getEnv("CLICKHOUSE_HOST", "localhost"), getEnv("CLICKHOUSE_NATIVE_PORT", "9000")),
		ClickHouseDatabase: getEnv("CLICKHOUSE_DB", "telemetry"),
		ClickHouseUsername: getEnv("CLICKHOUSE_USER", "default"),
		ClickHousePassword: getEnv("CLICKHOUSE_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.BatchMaxSize, err = getEnvInt("INGEST_BATCH_MAX_SIZE", 500); err != nil {
		return Config{}, err
	}
	if cfg.BatchFlushInterval, err = getEnvDuration("INGEST_BATCH_FLUSH_INTERVAL", 5*time.Second); err != nil {
		return Config{}, err
	}
	if cfg.BatchFlushTimeout, err = getEnvDuration("INGEST_BATCH_FLUSH_TIMEOUT", 10*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
}