feat(folding): add file reference folding support #101

This commit introduces a new file reference folding builder for the DevIn language, enhancing code folding capabilities within the IDE. The builder, located in `exts/devin-lang/src/main/kotlin/cc/unitmesh/devti/language/folding/DevInFileReferenceFoldingBuilder.kt`, is designed to collapse and expand sections of code that reference files, improving readability and navigation within complex file structures.

The `buildFoldRegions` method is responsible for identifying elements within the PsiElement tree that represent file references and creating corresponding FoldingDescriptors. These descriptors are then used to define the regions that can be folded and unfolded by the IDE.

The existing `exts/devin-lang/src/main/resources/cc.unitmesh.devti.language.xml` file has been modified to register the new folding builder alongside the existing custom variable folding builder. This ensures that both types of code folding are available to users of the DevIn language plugin.

Author: phodal

exts/devin-lang/src/main/kotlin/cc/unitmesh/devti/language/folding/DevInFileReferenceFoldingBuilder.kt

@@ -0,0 +1,40 @@
+package cc.unitmesh.devti.language.folding
+
+import cc.unitmesh.devti.language.psi.DevInTypes
+import com.intellij.lang.ASTNode
+import com.intellij.lang.folding.FoldingBuilderEx
+import com.intellij.lang.folding.FoldingDescriptor
+import com.intellij.openapi.editor.Document
+import com.intellij.psi.PsiElement
+import com.intellij.psi.PsiElementVisitor
+import com.intellij.psi.util.elementType
+
+class DevInFileReferenceFoldingBuilder : FoldingBuilderEx() {
+    override fun isCollapsedByDefault(node: ASTNode): Boolean = true
+    override fun getPlaceholderText(node: ASTNode): String {
+        val parent = node.treeParent ?: return node.text
+        val prop = parent.findChildByType(DevInTypes.PROPERTY_VALUE) ?: return node.text
+
+        return prop.text.split("/").last()
+    }
+
+    override fun buildFoldRegions(root: PsiElement, document: Document, quick: Boolean): Array<FoldingDescriptor> {
+        val descriptors = ArrayList<FoldingDescriptor>()
+        root.accept(object : PsiElementVisitor() {
+            override fun visitElement(element: PsiElement) {
+                if (element.elementType == DevInTypes.AGENT_ID && element.text == "file" && isFileReference(element)) {
+                    descriptors.add(FoldingDescriptor(element.node, element.textRange, null, emptySet(), true))
+                }
+
+                element.acceptChildren(this)
+            }
+
+            private fun isFileReference(element: PsiElement): Boolean {
+                val text = element.text
+                return text.split("/").isNotEmpty()
+            }
+        })
+
+        return descriptors.toTypedArray()
+    }
+}

exts/devin-lang/src/main/resources/cc.unitmesh.devti.language.xml

@@ -22,6 +22,8 @@
 
         <lang.foldingBuilder language="DevIn"
                              implementationClass="cc.unitmesh.devti.language.folding.DevInCustomVariableFoldingBuilder"/>
+        <lang.foldingBuilder language="DevIn"
+                             implementationClass="cc.unitmesh.devti.language.folding.DevInFileReferenceFoldingBuilder"/>
 
         <languageInjector implementation="cc.unitmesh.devti.language.DevInLanguageInjector"/>
     </extensions>