package main

import (
	"bufio"
	"encoding/json"
	"fmt"
	"log"
	"net"
	"net/http"
	"os"
)

type Country struct {
	Name        string `json:"name"`
	Url         string `json:"url"`
	v4Addresses []string
}

type JsonListFile struct {
	Countries []Country `json:"countries"`
}

func main() {

	// Validate arguments
	if len(os.Args) < 3 {
		log.Fatalf("usage: %s <blocklistname> <jsonlistfile>", os.Args[0])
	}
	blockListName := os.Args[1]
	jsonListFile := os.Args[2]
	fmt.Printf("generating blocklist %s\n", blockListName)

	// Load blocklist config file
	countries, err := readJsonListFile(jsonListFile)
	if err != nil {
		log.Fatalf("failed to read jsonlistfile '%s': %v", jsonListFile, err)
	}

	// Download up to date geoip CIDR data
	for i := range countries {
		countries[i].v4Addresses, err = downloadAddressList(countries[i].Url)
		if err != nil {
			log.Fatalf("failed to download address list for county'%s': %v", countries[i].Name, err)
		}
	}

	// Generate mikrotik block list
	err = generateOutput(countries, blockListName)
	if err != nil {
		log.Fatalf("failed to generate output file: %v", err)
	}
}

func generateOutput(countries []Country, blockListName string) error {
	output := "/ip firewall address-list\n"
	for _, country := range countries {
		for _, v4Address := range country.v4Addresses {
			output += fmt.Sprintf("add address=%s comment=\"%s\" list=%s\n", v4Address, country.Name, blockListName)
		}
	}

	err := os.WriteFile(fmt.Sprintf("%s.rsc", blockListName), []byte(output), os.ModePerm)
	if err != nil {
		return fmt.Errorf("failed to write file '%s.rsc': %v", blockListName, err)
	}
	return nil
}

func downloadAddressList(url string) ([]string, error) {
	resp, err := http.Get(url)
	if err != nil {
		return nil, fmt.Errorf("http get error on url '%s': %v", url, err)
	}
	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("unexpected http status - expected '%d' but got '%d'", http.StatusOK, resp.StatusCode)
	}
	scanner := bufio.NewScanner(resp.Body)
	scanner.Split(bufio.ScanLines)
	v4Addresses := make([]string, 0)
	for scanner.Scan() {
		line := scanner.Text()
		_, ipnet, err := net.ParseCIDR(line)
		if err != nil {
			log.Printf("skippine line: failed to parse line '%s' to cidr: %v", line, err)
			continue
		}
		v4Addresses = append(v4Addresses, ipnet.String())
	}
	return v4Addresses, nil
}

// reads the json config file containing the lists of countries you want to block
func readJsonListFile(filename string) ([]Country, error) {
	b, err := os.ReadFile(filename)
	if err != nil {
		return nil, fmt.Errorf("failed to open file %s: %v", filename, err)
	}

	jsonListFile := JsonListFile{}

	err = json.Unmarshal(b, &jsonListFile)
	if err != nil {
		return nil, fmt.Errorf("failed to unmarshal json file to jsonListFile struct: %v", err)
	}

	return jsonListFile.Countries, nil
}