From 304867c1f835b9dd0f5aad103b5914891fb5b096 Mon Sep 17 00:00:00 2001
From: tastybento <tastybento@wasteofplastic.com>
Date: Sat, 2 May 2020 18:49:58 -0700
Subject: [PATCH] Prevents duplicate addon loading.

https://github.com/BentoBoxWorld/BentoBox/issues/1339
---
 .../bentobox/api/addons/AddonDescription.java |  9 ++++++++
 .../bentobox/managers/AddonsManager.java      | 23 ++++++++++++++++++-
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/src/main/java/world/bentobox/bentobox/api/addons/AddonDescription.java b/src/main/java/world/bentobox/bentobox/api/addons/AddonDescription.java
index efa00fa85..1ad76c777 100644
--- a/src/main/java/world/bentobox/bentobox/api/addons/AddonDescription.java
+++ b/src/main/java/world/bentobox/bentobox/api/addons/AddonDescription.java
@@ -269,4 +269,13 @@ public final class AddonDescription {
             return this;
         }
     }
+
+    /* (non-Javadoc)
+     * @see java.lang.Object#toString()
+     */
+    @Override
+    public String toString() {
+        return "AddonDescription [" + (name != null ? "name=" + name + ", " : "")
+                + (version != null ? "version=" + version : "") + "]";
+    }
 }
diff --git a/src/main/java/world/bentobox/bentobox/managers/AddonsManager.java b/src/main/java/world/bentobox/bentobox/managers/AddonsManager.java
index 3584dbcfd..23a9bc701 100644
--- a/src/main/java/world/bentobox/bentobox/managers/AddonsManager.java
+++ b/src/main/java/world/bentobox/bentobox/managers/AddonsManager.java
@@ -98,7 +98,17 @@ public class AddonsManager {
             // try loading the addon
             // Get description in the addon.yml file
             YamlConfiguration data = addonDescription(jar);
-
+            // Check if the addon is already loaded (duplicate version?)
+            String main = data.getString("main");
+            if (main != null) {
+                if (this.getAddonByMainClassName(main).isPresent()) {
+                    getAddonByMainClassName(main).ifPresent(a -> {
+                        plugin.logError("Duplicate addon! Addon " + a.getDescription().getName() + " " + a.getDescription().getVersion() + " has already been loaded!");
+                        plugin.logError("Remove the duplicate and restart!");
+                    });
+                    return;
+                }
+            }
             // Load the addon
             addonClassLoader = new AddonClassLoader(this, data, f, this.getClass().getClassLoader());
 
@@ -341,6 +351,17 @@ public class AddonsManager {
         return addons.stream().filter(a -> a.getDescription().getName().equalsIgnoreCase(name)).map(a -> (T) a).findFirst();
     }
 
+    /**
+     * Gets the addon by main class name
+     * @param name - main class name
+     * @return Optional addon object
+     */
+    @NonNull
+    @SuppressWarnings("unchecked")
+    public <T extends Addon> Optional<T> getAddonByMainClassName(@NonNull String name){
+        return addons.stream().filter(a -> a.getDescription().getMain().equalsIgnoreCase(name)).map(a -> (T) a).findFirst();
+    }
+
     @NonNull
     private YamlConfiguration addonDescription(@NonNull JarFile jar) throws InvalidAddonFormatException, IOException, InvalidConfigurationException {
         // Obtain the addon.yml file