package config

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

type Config struct {
	AppName              string
	Environment          string
	HTTPAddress          string
	DatabaseURL          string
	JWTIssuer            string
	JWTSecret            string
	AccessTokenTTL       time.Duration
	RefreshTokenTTL      time.Duration
	GatewayBootstrapToken string
	DefaultGatewayID     string
	DefaultDNS           []string
	DefaultVPNCIDR       string
	DefaultGatewayHost   string
	DefaultGatewayPubKey string
}

func Load() Config {
	return Config{
		AppName:              getenv("APP_NAME", "NexaVPN"),
		Environment:          getenv("APP_ENV", "development"),
		HTTPAddress:          getenv("HTTP_ADDRESS", ":8080"),
		DatabaseURL:          getenv("DATABASE_URL", "postgres://nexavpn:nexavpn@localhost:5432/nexavpn?sslmode=disable"),
		JWTIssuer:            getenv("JWT_ISSUER", "nexavpn"),
		JWTSecret:            getenv("JWT_SECRET", "change-me-in-production"),
		AccessTokenTTL:       time.Duration(getenvInt("ACCESS_TOKEN_TTL_SECONDS", 900)) * time.Second,
		RefreshTokenTTL:      time.Duration(getenvInt("REFRESH_TOKEN_TTL_SECONDS", 2592000)) * time.Second,
		GatewayBootstrapToken: getenv("GATEWAY_BOOTSTRAP_TOKEN", "nexavpn-gateway-bootstrap"),
		DefaultGatewayID:     getenv("DEFAULT_GATEWAY_ID", ""),
		DefaultDNS:           splitCSV(getenv("DEFAULT_DNS_SERVERS", "10.20.0.53")),
		DefaultVPNCIDR:       getenv("DEFAULT_VPN_CIDR", "100.96.0.0/24"),
		DefaultGatewayHost:   getenv("DEFAULT_GATEWAY_ENDPOINT", "vpn.example.com:51820"),
		DefaultGatewayPubKey: getenv("DEFAULT_GATEWAY_PUBLIC_KEY", "replace-me"),
	}
}

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

	return fallback
}

func getenvInt(key string, fallback int) int {
	if value := os.Getenv(key); value != "" {
		parsed, err := strconv.Atoi(value)
		if err == nil {
			return parsed
		}
	}

	return fallback
}

func splitCSV(value string) []string {
	if value == "" {
		return nil
	}

	var items []string
	start := 0
	for i := range value {
		if value[i] == ',' {
			if start < i {
				items = append(items, value[start:i])
			}
			start = i + 1
		}
	}
	if start < len(value) {
		items = append(items, value[start:])
	}

	return items
}