feat(zon): Code folding

CHANGELOG.md

@@ -26,6 +26,7 @@ Changelog structure reference:
 - Color settings page
 - Brace and quote matching
 - Code completion
+- Code Folding
 - Indentation
 
 ## [0.4.0]

src/main/java/com/falsepattern/zigbrains/zon/folding/ZonFoldingBuilder.java

@@ -0,0 +1,59 @@
+/*
+ * Copyright 2023 FalsePattern
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.falsepattern.zigbrains.zon.folding;
+
+import com.falsepattern.zigbrains.zon.psi.ZonStruct;
+import com.falsepattern.zigbrains.zon.psi.ZonVisitor;
+import com.intellij.lang.ASTNode;
+import com.intellij.lang.folding.CustomFoldingBuilder;
+import com.intellij.lang.folding.FoldingDescriptor;
+import com.intellij.openapi.editor.Document;
+import com.intellij.openapi.project.DumbAware;
+import com.intellij.openapi.util.TextRange;
+import com.intellij.psi.PsiElement;
+import org.jetbrains.annotations.NotNull;
+
+import java.util.List;
+
+public class ZonFoldingBuilder extends CustomFoldingBuilder implements DumbAware {
+    @Override
+    protected void buildLanguageFoldRegions(@NotNull List<FoldingDescriptor> descriptors, @NotNull PsiElement root, @NotNull Document document, boolean quick) {
+        root.accept(new ZonVisitor() {
+            @Override
+            public void visitElement(@NotNull PsiElement element) {
+                super.visitElement(element);
+                element.acceptChildren(this);
+            }
+
+            @Override
+            public void visitStruct(@NotNull ZonStruct o) {
+                super.visitStruct(o);
+                descriptors.add(new FoldingDescriptor(o, o.getTextRange()));
+            }
+        });
+    }
+
+    @Override
+    protected String getLanguagePlaceholderText(@NotNull ASTNode node, @NotNull TextRange range) {
+        return ".{...}";
+    }
+
+    @Override
+    protected boolean isRegionCollapsedByDefault(@NotNull ASTNode node) {
+        return false;
+    }
+}

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

@@ -105,6 +105,10 @@
 
         <lang.quoteHandler language="Zon"
                            implementationClass="com.falsepattern.zigbrains.zon.braces.ZonQuoteHandler"/>
+
+        <lang.foldingBuilder language="Zon"
+                             implementationClass="com.falsepattern.zigbrains.zon.folding.ZonFoldingBuilder"/>
+
         <!-- endregion Zon -->
 
     </extensions>