Update tracker of torrent files

main.go

// iterates over the torrents in ./Torrents
// and updates the tracker of all torrents (top-level, not recursive)

// put this in a directory, do a 
// `go mod init <whatever>` and `go mod tidy` to get dependencies

// update "foo" "bar" "baz" to the desired values &
// go run .

import (
	"fmt"
	"os"
	"path/filepath"

	"github.com/anacrolix/torrent/bencode"
)

type TorrentFile struct {
	Announce string                 `bencode:"announce"`
	Info     map[string]interface{} `bencode:"info"`
}

func main() {

  // iterate on all .torrent files in ./Torrents (symlink as needed)
	pattern := filepath.Join("./Torrents", "*.torrent")

	matches, err := filepath.Glob(pattern)
	if err != nil {
		fmt.Printf("Pattern error: %v\n", err)
		return
	}

	for _, path := range matches {

		// 1. Read the .torrent file
		data, err := os.ReadFile(path)
		if err != nil {
			fmt.Println("Error reading file:", err)
			return
		}

		// 2. Unmarshal contents
		var tf TorrentFile
		err = bencode.Unmarshal(data, &tf)
		if err != nil {
			fmt.Println("Error decoding torrent:", err)
			return
		}

    // Print Announce URL
		fmt.Println("Announce URL:", tf.Announce)
    
    // 3. Conditionally Update (comment this block if you just want to print the Announce URLs)
		if tf.Announce == "foo" || tf.Announce == "bar" {
			tf.Announce = "baz"
			newData, err := bencode.Marshal(tf)
			if err != nil {
				fmt.Println("Error encoding updated torrent:", err)
				return
			}
			err = os.WriteFile(path, newData, 0644)
			if err != nil {
				fmt.Println("Error writing torrent file:", err)
			}
			fmt.Println(">> Updated Announce URL:", tf.Announce)
		}
	}
}