Add completion contributor for Bukkit event handlers

src/main/kotlin/platform/bukkit/completion/BukkitEventHandlerCompletionContributor.kt

@@ -0,0 +1,36 @@
+/*
+ * Minecraft Development for IntelliJ
+ *
+ * https://mcdev.io/
+ *
+ * Copyright (C) 2025 minecraft-dev
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation, version 3.0 only.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.demonwav.mcdev.platform.bukkit.completion
+
+import com.intellij.codeInsight.completion.CompletionContributor
+import com.intellij.codeInsight.completion.CompletionType
+import com.intellij.patterns.PlatformPatterns
+import com.intellij.psi.PsiClass
+
+class BukkitEventHandlerCompletionContributor : CompletionContributor() {
+    init {
+        extend(
+            CompletionType.BASIC,
+            PlatformPatterns.psiElement().inside(PsiClass::class.java),
+            BukkitEventHandlerCompletionProvider()
+        )
+    }
+}

src/main/kotlin/platform/bukkit/completion/BukkitEventHandlerCompletionProvider.kt

@@ -0,0 +1,105 @@
+/*
+ * Minecraft Development for IntelliJ
+ *
+ * https://mcdev.io/
+ *
+ * Copyright (C) 2025 minecraft-dev
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation, version 3.0 only.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.demonwav.mcdev.platform.bukkit.completion
+
+import com.demonwav.mcdev.platform.bukkit.util.BukkitConstants
+import com.demonwav.mcdev.util.findContainingClass
+import com.demonwav.mcdev.util.findContainingMethod
+import com.intellij.codeInsight.completion.CompletionParameters
+import com.intellij.codeInsight.completion.CompletionProvider
+import com.intellij.codeInsight.completion.CompletionResultSet
+import com.intellij.codeInsight.completion.PrioritizedLookupElement
+import com.intellij.codeInsight.lookup.LookupElementBuilder
+import com.intellij.icons.AllIcons
+import com.intellij.openapi.project.Project
+import com.intellij.psi.PsiClass
+import com.intellij.psi.PsiMethod
+import com.intellij.psi.PsiModifier
+import com.intellij.psi.impl.JavaPsiFacadeEx
+import com.intellij.psi.search.GlobalSearchScope
+import com.intellij.psi.search.searches.ClassInheritorsSearch
+import com.intellij.psi.util.PsiTreeUtil
+import com.intellij.util.ProcessingContext
+import org.jetbrains.annotations.NotNull
+
+class BukkitEventHandlerCompletionProvider : CompletionProvider<CompletionParameters>() {
+
+    override fun addCompletions(
+        completionParameters: CompletionParameters,
+        processingContext: ProcessingContext,
+        completionResultSet: CompletionResultSet
+    ) {
+        val prefix = completionResultSet.prefixMatcher.prefix
+        if (!prefix.startsWith("on") || prefix.length == 2) {
+            return
+        }
+
+        val position = completionParameters.position
+        val containingClass = position.findContainingClass() ?: return
+        val project = position.project
+        val facade = JavaPsiFacadeEx.getInstance(project)
+
+        val eventListenerClass = facade.findClass(BukkitConstants.LISTENER_CLASS, GlobalSearchScope.allScope(project)) ?: return
+        if (!containingClass.isInheritor(eventListenerClass, true)) {
+            return
+        }
+
+        if (position.findContainingMethod() != null) {
+            return
+        }
+
+        val scope = GlobalSearchScope.allScope(project)
+        val eventBaseClass = facade.findClass(BukkitConstants.EVENT_CLASS, scope) ?: return
+        val eventNameFilter = prefix.substring(2).lowercase()
+
+        ClassInheritorsSearch.search(eventBaseClass, scope, true)
+            .forEach { psiClass ->
+                if (psiClass.isInterface || psiClass.hasModifierProperty(PsiModifier.ABSTRACT)) {
+                    return@forEach
+                }
+
+                val eventSimpleName = psiClass.name ?: return@forEach
+                if (eventNameFilter.isNotEmpty() && !eventSimpleName.lowercase().startsWith(eventNameFilter)) {
+                    return@forEach
+                }
+
+                val lookupString = "on$eventSimpleName"
+                val methodName = lookupString.removeSuffix("Event")
+                val qualifiedName = psiClass.qualifiedName
+
+                val element = LookupElementBuilder
+                    .create(lookupString)
+                    .withPresentableText("$lookupString()")
+                    .withTailText(" - $qualifiedName", true)
+                    .withTypeText("@EventHandler")
+                    .withIcon(AllIcons.Nodes.Method)
+                    .withBaseLookupString(lookupString)
+                    .withBoldness(true)
+                    .withInsertHandler(BukkitEventHandlerInsertHandler(methodName, qualifiedName))
+
+                completionResultSet.addElement(
+                    PrioritizedLookupElement.withPriority(element, 100.0)
+                )
+            }
+
+        completionResultSet.stopHere()
+    }
+}

src/main/kotlin/platform/bukkit/completion/BukkitEventHandlerInsertHandler.kt

@@ -0,0 +1,62 @@
+/*
+ * Minecraft Development for IntelliJ
+ *
+ * https://mcdev.io/
+ *
+ * Copyright (C) 2025 minecraft-dev
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation, version 3.0 only.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.demonwav.mcdev.platform.bukkit.completion
+
+import com.demonwav.mcdev.platform.bukkit.util.BukkitConstants
+import com.intellij.codeInsight.completion.InsertHandler
+import com.intellij.codeInsight.completion.InsertionContext
+import com.intellij.codeInsight.lookup.LookupElement
+import com.intellij.codeInsight.template.TemplateManager
+import com.intellij.codeInsight.template.impl.TextExpression
+import com.intellij.openapi.util.NlsSafe
+import org.jetbrains.annotations.NotNull
+
+class BukkitEventHandlerInsertHandler(
+    private val methodName: String,
+    private val qualifiedName: @NlsSafe String?
+) : InsertHandler<LookupElement> {
+
+    override fun handleInsert(insertionContext: InsertionContext, lookupElement: LookupElement) {
+        val project = insertionContext.project
+        val editor = insertionContext.editor
+
+        val templateManager = TemplateManager.getInstance(project)
+        val template = templateManager.createTemplate("", "")
+        template.isToReformat = true
+
+        template.addTextSegment("@${BukkitConstants.HANDLER_ANNOTATION}\n")
+        template.addTextSegment("public void ")
+        template.addVariable("METHOD_NAME", TextExpression(methodName), true)
+        template.addTextSegment("($qualifiedName ")
+        template.addVariable("EVENT_PARAM", TextExpression("event"), true)
+        template.addTextSegment(") { \n")
+        template.addEndVariable()
+        template.addTextSegment("\n}")
+
+        insertionContext.document.deleteString(
+            insertionContext.startOffset,
+            insertionContext.tailOffset
+        )
+
+        templateManager.startTemplate(editor, template)
+
+    }
+}

src/main/resources/META-INF/plugin.xml

@@ -532,6 +532,13 @@
         <library.presentationProvider
                 implementation="com.demonwav.mcdev.platform.bukkit.framework.ModernPaperPresentationProvider"/>
 
+        <!-- Bukkit Completion Contributor -->
+
+        <completion.contributor
+                language="JAVA"
+                implementationClass="com.demonwav.mcdev.platform.bukkit.completion.BukkitEventHandlerCompletionContributor"
+                order="first"/>
+
         <!--endregion-->
 
         <!--region SPONGE-->