\begin \end folding

META-INF/plugin.xml

@@ -86,6 +86,9 @@
         <lang.commenter
                 implementationClass="mobi.hsz.idea.latex.lang.LatexCommenter"
                 language="LaTeX"/>
+        <lang.foldingBuilder
+                implementationClass="mobi.hsz.idea.latex.lang.LatexFoldingBuilder"
+                language="LaTeX"/>
         <lang.parserDefinition
                 implementationClass="mobi.hsz.idea.latex.lang.LatexParserDefinition"
                 language="LaTeX"/>

resources/messages/LatexBundle.properties

@@ -8,4 +8,5 @@ colorSettings.displayName=LaTeX
 highlighter.instruction=Instruction
 highlighter.argument=Argument
 highlighter.bracket=Brackets
-highlighter.comment=Comment
+highlighter.comment=Comment
+folding.placeholder=...

src/mobi/hsz/idea/latex/lang/LatexFoldingBuilder.java

@@ -0,0 +1,95 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2015 hsz Jakub Chrzanowski <[email protected]>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package mobi.hsz.idea.latex.lang;
+
+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.openapi.util.TextRange;
+import com.intellij.psi.PsiElement;
+import com.intellij.psi.search.PsiElementProcessor;
+import com.intellij.psi.tree.IElementType;
+import com.intellij.psi.util.PsiTreeUtil;
+import com.intellij.util.containers.ContainerUtil;
+import mobi.hsz.idea.latex.LatexBundle;
+import mobi.hsz.idea.latex.psi.LatexFile;
+import mobi.hsz.idea.latex.psi.LatexTypes;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.util.List;
+
+/**
+ * LaTeX folding builder
+ *
+ * @author Jakub Chrzanowski <[email protected]>
+ * @since 0.2
+ */
+public class LatexFoldingBuilder extends FoldingBuilderEx {
+    @NotNull
+    @Override
+    public FoldingDescriptor[] buildFoldRegions(@NotNull PsiElement root, @NotNull Document document, boolean quick) {
+        if (!(root instanceof LatexFile)) {
+            return FoldingDescriptor.EMPTY;
+        }
+        LatexFile file = (LatexFile) root;
+
+        final List<FoldingDescriptor> result = ContainerUtil.newArrayList();
+
+        final List<PsiElement> begins = ContainerUtil.newArrayList();
+
+        if (!quick) {
+            PsiTreeUtil.processElements(file, new PsiElementProcessor() {
+                @Override
+                public boolean execute(@NotNull PsiElement element) {
+                    IElementType type = element.getNode().getElementType();
+                    if (type.equals(LatexTypes.INSTRUCTION_BEGIN)) {
+                        begins.add(element);
+                    } else if (type.equals(LatexTypes.INSTRUCTION_END)) {
+                        PsiElement last = begins.get(begins.size() - 1);
+                        TextRange range = new TextRange(last.getTextRange().getStartOffset(), element.getTextRange().getEndOffset());
+                        result.add(new FoldingDescriptor(last, range));
+                        begins.remove(last);
+                    }
+                    return true;
+                }
+            });
+        }
+
+        return result.toArray(new FoldingDescriptor[result.size()]);
+    }
+
+    @Nullable
+    @Override
+    public String getPlaceholderText(@NotNull ASTNode node) {
+        return node.getTreeParent().getText() + LatexBundle.message("folding.placeholder");
+    }
+
+    @Override
+    public boolean isCollapsedByDefault(@NotNull ASTNode node) {
+        return true;
+    }
+}