package main

import (
	"fmt"
	"os"
	"strings"
	"time"
)

// CountryData holds the resolved CIDR blocks for a single country.
type CountryData struct {
	Code string   // ISO 3166-1 alpha-2 country code
	Name string   // Display name for RouterOS comments
	CIDRs []string // IPv4 CIDR blocks
}

// GenerateRSC produces a RouterOS .rsc script file that populates an address list.
// The filename includes today's date, e.g. "CountryIPBlocks-2026-05-01.rsc".
// Returns the generated filename.
func GenerateRSC(countries []CountryData, listName string) (string, error) {
	now := time.Now()
	datedName := fmt.Sprintf("%s-%s", listName, now.Format("2006-01-02"))
	filename := fmt.Sprintf("%s.rsc", datedName)

	var b strings.Builder

	// Header with metadata
	b.WriteString(fmt.Sprintf("# RouterOS GeoIP Address List: %s\n", datedName))
	b.WriteString(fmt.Sprintf("# Generated: %s\n", now.UTC().Format(time.RFC3339)))
	b.WriteString(fmt.Sprintf("# Countries: %d\n", len(countries)))

	totalCIDRs := 0
	for _, c := range countries {
		totalCIDRs += len(c.CIDRs)
	}
	b.WriteString(fmt.Sprintf("# Total entries: %d\n", totalCIDRs))
	b.WriteString("#\n")

	// Each run creates a uniquely-named list (e.g. CountryIPBlocks-2026-05-01).
	// Workflow: import this file, then atomically swap your firewall rules to
	// reference the new list, then remove the old dated list.
	b.WriteString("/ip firewall address-list\n")

	for _, country := range countries {
		for _, cidr := range country.CIDRs {
			b.WriteString(fmt.Sprintf("add address=%s comment=\"%s\" list=%s\n", cidr, country.Name, datedName))
		}
	}

	if err := os.WriteFile(filename, []byte(b.String()), os.ModePerm); err != nil {
		return "", fmt.Errorf("failed to write file %q: %v", filename, err)
	}

	return filename, nil
}