Code improvements, move back from shared repo

src/util.go

@@ -1,14 +1,109 @@
 package main
 
 import (
+	"crypto/sha1"
 	_ "embed"
+	"encoding/hex"
 	"fmt"
-	"log"
-	"os"
+	"io"
+	"net/http"
+	"regexp"
 	"strconv"
 	"strings"
+	"sync"
 )
 
+var (
+	//go:embed icon.png
+	defaultIconBytes []byte
+	blockedServers   *MutexArray[string] = nil
+	ipAddressRegExp  *regexp.Regexp      = regexp.MustCompile(`^\d{1,3}(\.\d{1,3}){3}$`)
+)
+
+type MutexArray[K comparable] struct {
+	List  []K
+	Mutex *sync.Mutex
+}
+
+func (m *MutexArray[K]) Has(value K) bool {
+	m.Mutex.Lock()
+
+	defer m.Mutex.Unlock()
+
+	for _, v := range m.List {
+		if v == value {
+			return true
+		}
+	}
+
+	return false
+}
+
+func GetBlockedServerList() error {
+	resp, err := http.Get("https://sessionserver.mojang.com/blockedservers")
+
+	if err != nil {
+		return err
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("unexpected status code: %d", resp.StatusCode)
+	}
+
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+
+	if err != nil {
+		return err
+	}
+
+	blockedServers = &MutexArray[string]{
+		List:  strings.Split(string(body), "\n"),
+		Mutex: &sync.Mutex{},
+	}
+
+	return nil
+}
+
+func IsBlockedAddress(address string) bool {
+	split := strings.Split(strings.ToLower(address), ".")
+
+	isIPAddress := ipAddressRegExp.MatchString(address)
+
+	for k := range split {
+		newAddress := ""
+
+		switch k {
+		case 0:
+			{
+				newAddress = strings.Join(split, ".")
+
+				break
+			}
+		default:
+			{
+				if isIPAddress {
+					newAddress = fmt.Sprintf("%s.*", strings.Join(split[0:len(split)-k], "."))
+				} else {
+					newAddress = fmt.Sprintf("*.%s", strings.Join(split[k:], "."))
+				}
+
+				break
+			}
+		}
+
+		newAddressBytes := sha1.Sum([]byte(newAddress))
+		newAddressHash := hex.EncodeToString(newAddressBytes[:])
+
+		if blockedServers.Has(newAddressHash) {
+			return true
+		}
+	}
+
+	return false
+}
+
 func ParseAddress(address string, defaultPort uint16) (string, uint16, error) {
 	result := strings.SplitN(address, ":", 2)
 
@@ -28,17 +123,3 @@ func ParseAddress(address string, defaultPort uint16) (string, uint16, error) {
 
 	return result[0], uint16(port), nil
 }
-
-func GetInstanceID() (uint16, error) {
-	if instanceID := os.Getenv("INSTANCE_ID"); len(instanceID) > 0 {
-		value, err := strconv.ParseUint(instanceID, 10, 16)
-
-		if err != nil {
-			log.Fatal(err)
-		}
-
-		return uint16(value), nil
-	}
-
-	return 0, nil
-}