Use fallback NMS version if not supported

Author: Rothes

bukkit/nms/src/main/kotlin/io/github/rothes/protocolstringreplacer/nms/NmsManager.kt

@@ -4,12 +4,14 @@ import io.github.rothes.protocolstringreplacer.nms.packetreader.IBlockEntityType
 import io.github.rothes.protocolstringreplacer.nms.packetreader.IDisguisedPacketHandler
 import io.github.rothes.protocolstringreplacer.nms.packetreader.IMenuTypeGetter
 import io.github.rothes.protocolstringreplacer.nms.packetreader.IPacketReader
+import java.util.function.Consumer
 
 object NmsManager {
 
     private const val PACKAGE_PREFIX = "io.github.rothes.protocolstringreplacer.nms"
 
     private lateinit var minecraftVersion: String
+    lateinit var warningFunction: Consumer<String>
 
     fun setVersion(major: Int, minor: Int) {
         var m = minor
@@ -22,6 +24,20 @@ object NmsManager {
                 m++
             }
         }
+        // On older versions we are not using NMS.
+        if (major >= 19) {
+            warningFunction.accept("Minecraft version 1.$major.$minor is not supported by the plugin version you are running on.")
+            m = minor
+            while (--m >= 0) {
+                setVersionProp(major, m)
+                try {
+                    create<IPacketReader>()
+                    warningFunction.accept("Fallback to 1.$major.$m support and luckily it could be compatible.")
+                    return
+                } catch (ignored: ClassNotFoundException) {
+                }
+            }
+        }
         setVersionProp(major, minor)
     }
 

bukkit/src/main/java/io/github/rothes/protocolstringreplacer/ProtocolStringReplacer.java

@@ -18,6 +18,8 @@
 import io.github.rothes.protocolstringreplacer.upgrade.AbstractUpgradeHandler;
 import io.github.rothes.protocolstringreplacer.upgrade.UpgradeEnum;
 import io.github.rothes.protocolstringreplacer.util.FileUtils;
+import kotlin.Unit;
+import kotlin.jvm.functions.Function1;
 import org.apache.commons.lang.Validate;
 import org.bukkit.Bukkit;
 import org.bukkit.configuration.ConfigurationSection;
@@ -102,6 +104,7 @@ public ProtocolStringReplacer() {
         String[] split = Bukkit.getServer().getBukkitVersion().split("-")[0].split("\\.");
         serverMajorVersion = Byte.parseByte(split[1]);
         serverMinorVersion = split.length > 2 ? Byte.parseByte(split[2]) : 0;
+        NmsManager.INSTANCE.setWarningFunction(ProtocolStringReplacer::warn);
         NmsManager.INSTANCE.setVersion(serverMajorVersion, serverMinorVersion);
 
         // Start Console Replacer first to remove the Ansi in log files.