Add option for scale-up allow/deny lists for servers (#397)

server/allow_deny_list.go

@@ -0,0 +1,84 @@
+package server
+
+import (
+	"encoding/json"
+	"github.com/google/uuid"
+	"os"
+)
+
+type AllowDenyLists struct {
+	Allowlist []PlayerInfo
+	Denylist []PlayerInfo
+}
+
+type AllowDenyConfig struct {
+	Global AllowDenyLists
+	Servers map[string]AllowDenyLists
+}
+
+func ParseAllowDenyConfig(allowDenyListPath string) (*AllowDenyConfig, error) {
+	allowDenyConfig := AllowDenyConfig{}
+	data, err := os.ReadFile(allowDenyListPath)
+	if err != nil {
+		return nil, err
+	}
+	err = json.Unmarshal(data, &allowDenyConfig)
+	if err != nil {
+		return nil, err
+	}
+	return &allowDenyConfig, nil
+}
+
+func entryMatchesPlayer(entry *PlayerInfo, userInfo *PlayerInfo) bool {
+	// User has added an "empty" entry
+	// This should never match player info
+	if entry.Name == "" && entry.Uuid == uuid.Nil {
+		return false
+	}
+	
+	if entry.Name != "" && entry.Uuid != uuid.Nil {
+		return *entry == *userInfo
+	}
+
+	if entry.Uuid != uuid.Nil {
+		return entry.Uuid == userInfo.Uuid
+	}
+
+	return entry.Name == userInfo.Name
+}
+
+func (allowDenyConfig *AllowDenyConfig) ServerAllowsPlayer(serverAddress string, userInfo *PlayerInfo) bool {
+	if allowDenyConfig == nil {
+		return true
+	}
+
+	allowlist := allowDenyConfig.Global.Allowlist
+	denylist := allowDenyConfig.Global.Denylist
+	serverAllowDenyConfig, ok := allowDenyConfig.Servers[serverAddress]
+	// Merges global allow/deny lists with server-specific allow/deny lists if provided
+	if ok {
+		allowlist = append(allowlist, serverAllowDenyConfig.Allowlist...)
+		denylist = append(denylist, serverAllowDenyConfig.Denylist...)
+	}
+
+	// If the allowlist is not empty, the player must have an entry or they will be denied
+	// If the allowlist is empty, then the denylist is checked
+	// If the allowlist is empty and the player was not in the denylist, then they are allowed
+	for _, allowedPlayer := range allowlist {
+		if entryMatchesPlayer(&allowedPlayer, userInfo) {
+			return true
+		}
+	}
+
+	if len(allowlist) > 0 {
+		return false
+	}
+
+	for _, deniedPlayer := range denylist {
+		if entryMatchesPlayer(&deniedPlayer, userInfo) {
+			return false
+		}
+	}
+
+	return true
+}