Bifrost: Implement player advancement notifications. Oh my god this was hard and it still is ugly.

foundation-core/src/main/kotlin/cloud/kubelet/foundation/core/util/AdvancementTitleCache.kt

@@ -0,0 +1,74 @@
+package cloud.kubelet.foundation.core.util
+
+import net.kyori.adventure.text.serializer.gson.GsonComponentSerializer
+import net.kyori.adventure.text.serializer.legacy.LegacyComponentSerializer
+import org.bukkit.advancement.Advancement
+import java.lang.reflect.Field
+import java.util.concurrent.ConcurrentHashMap
+
+private fun Advancement.getInternalHandle(): Any =
+  javaClass.getMethod("getHandle").invoke(this)
+
+private fun Class<*>.getDeclaredFieldAccessible(name: String): Field {
+  val field = getDeclaredField(name)
+  if (!field.trySetAccessible()) {
+    throw RuntimeException("Failed to set reflection permissions to accessible.")
+  }
+  return field
+}
+
+private fun Advancement.getInternalAdvancementDisplay(handle: Any = getInternalHandle()): Any? =
+  handle.javaClass.methods.firstOrNull {
+    it.returnType.simpleName == "AdvancementDisplay" &&
+        it.parameterCount == 0
+  }?.invoke(handle) ?: handle.javaClass.getDeclaredFieldAccessible("c").get(handle)
+
+private fun Advancement.displayTitleText(): String? {
+  val handle = getInternalHandle()
+  val advancementDisplay = getInternalAdvancementDisplay(handle) ?: return null
+  try {
+    val field = advancementDisplay.javaClass.getDeclaredField("a")
+    field.trySetAccessible()
+    val message = field.get(advancementDisplay)
+    val title = message.javaClass.getMethod("getString").invoke(message)
+    return title.toString()
+  } catch (_: Exception) {
+  }
+
+  val titleComponentField = advancementDisplay.javaClass.declaredFields.firstOrNull {
+    it.type.simpleName == "IChatBaseComponent"
+  }
+
+  if (titleComponentField != null) {
+    titleComponentField.trySetAccessible()
+    val titleChatBaseComponent = titleComponentField.get(advancementDisplay)
+    val title = titleChatBaseComponent.javaClass.getMethod("getText").invoke(titleChatBaseComponent).toString()
+    if (title.isNotBlank()) {
+      return title
+    }
+
+    val chatSerializerClass = titleChatBaseComponent.javaClass.declaredClasses.firstOrNull {
+      it.simpleName == "ChatSerializer"
+    }
+
+    if (chatSerializerClass != null) {
+      val componentJson = chatSerializerClass
+          .getMethod("a", titleChatBaseComponent.javaClass)
+          .invoke(null, titleChatBaseComponent).toString()
+      val gson = GsonComponentSerializer.gson().deserialize(componentJson)
+      return LegacyComponentSerializer.legacySection().serialize(gson)
+    }
+  }
+
+  val rawAdvancementName = key.key
+  return rawAdvancementName.substring(rawAdvancementName.lastIndexOf("/") + 1)
+    .lowercase().split("_")
+    .joinToString(" ") { it.substring(0, 1).uppercase() + it.substring(1) }
+}
+
+object AdvancementTitleCache {
+  private val cache = ConcurrentHashMap<Advancement, String?>()
+
+  fun of(advancement: Advancement): String? =
+    cache.computeIfAbsent(advancement) { it.displayTitleText() }
+}