package main

import (
	"encoding/json"
	"fmt"
	"os"
	"strings"
)

// Config represents the blocklist configuration file.
type Config struct {
	// ListName is the name for the RouterOS address list (e.g. "CountryIPBlocks").
	ListName string `json:"list_name"`

	// Provider specifies which GeoIP data source to use.
	// Supported values: "ipverse" (default), "ipdeny"
	Provider string `json:"provider"`

	// Countries is a list of ISO 3166-1 alpha-2 country codes (lowercase).
	Countries []string `json:"countries"`
}

// LoadConfig reads and validates a blocklist configuration file.
func LoadConfig(filename string) (*Config, error) {
	b, err := os.ReadFile(filename)
	if err != nil {
		return nil, fmt.Errorf("failed to read config file %q: %v", filename, err)
	}

	var cfg Config
	if err := json.Unmarshal(b, &cfg); err != nil {
		return nil, fmt.Errorf("failed to parse config file %q: %v", filename, err)
	}

	// Validate
	if cfg.ListName == "" {
		return nil, fmt.Errorf("config: list_name is required")
	}

	if cfg.Provider == "" {
		cfg.Provider = "ipverse" // default provider
	}
	cfg.Provider = strings.ToLower(cfg.Provider)

	if len(cfg.Countries) == 0 {
		return nil, fmt.Errorf("config: at least one country code is required")
	}

	// Normalize country codes to lowercase
	for i := range cfg.Countries {
		cfg.Countries[i] = strings.ToLower(strings.TrimSpace(cfg.Countries[i]))
	}

	return &cfg, nil
}