Add ProGuard obfuscation build task

Configures a JavaExec ProGuard task that runs after jar, keeping all
plugin entry points and command/listener classes while repackaging
into the mdbd package.

build.gradle.kts

@@ -9,15 +9,49 @@ repositories {
     maven("https://repo.dmulloy2.net/repository/public/")
 }
 
+val proguardConfig by configurations.creating
+
 dependencies {
     compileOnly("io.papermc.paper:paper-api:1.21.1-R0.1-SNAPSHOT")
     compileOnly("com.comphenix.protocol:ProtocolLib:5.3.0")
+    proguardConfig("com.guardsquare:proguard-base:7.4.2")
 }
 
 java {
     toolchain.languageVersion = JavaLanguageVersion.of(21)
 }
 
+val obfuscateTask = tasks.register<JavaExec>("obfuscate") {
+    description = "Obfuscate the plugin jar using ProGuard"
+    mainClass.set("proguard.ProGuard")
+    classpath = proguardConfig
+
+    val inJar = tasks.named<Jar>("jar").get().archiveFile.get().asFile.path
+    val outJar = layout.buildDirectory.file("libs/${project.name}-${version}-obf.jar").get().asFile.path
+
+    args(
+        "-injars", inJar,
+        "-outjars", outJar,
+        "-dontwarn",
+        "-ignorewarnings",
+
+        "-keep", "class dev.loki.mdbd",
+        "-keep", "class dev.loki.mdbdBootstrap",
+        "-keep", "class dev.loki.mdbdLoader",
+        "-keep", "class dev.loki.command.**",
+        "-keep", "class dev.loki.listener.**",
+        "-keepclassmembers", "class * { @org.bukkit.event.EventHandler *; }",
+        "-keepnames", "class dev.loki.**",
+
+        "-dontoptimize",
+        "-allowaccessmodification",
+        "-repackageclasses", "mdbd",
+        "-keepattributes", "Exceptions,InnerClasses,Signature,Deprecated,SourceFile,LineNumberTable,EnclosingMethod"
+    )
+
+    dependsOn(tasks.named("jar"))
+}
+
 tasks {
     runServer {
         minecraftVersion("1.21.1")
@@ -26,11 +60,12 @@ tasks {
 
     processResources {
         val props = mapOf("version" to version)
-        filesMatching("paper-plugin.yml") {
-            expand(props)
-        }
         filesMatching("*.yml") {
             expand(props)
         }
     }
+
+    named("build") {
+        dependsOn(obfuscateTask)
+    }
 }