Implement folding

package.json

@@ -46,7 +46,16 @@
             "plugin:@typescript-eslint/recommended"
         ],
         "rules": {
-            "comma-dangle": ["warn", "always-multiline"],
+            "comma-dangle": [
+                "warn",
+                "always-multiline"
+            ],
+            "max-len": [
+                "warn",
+                {
+                    "code": 120
+                }
+            ],
             "@typescript-eslint/explicit-module-boundary-types": "off",
             "@typescript-eslint/semi": "warn"
         }

src/extension.ts

@@ -9,17 +9,25 @@ import * as vscode from 'vscode';
 import { Options } from './options';
 import { Preview } from './preview';
 import { CompletionItemProvider } from './completion';
+import { FoldingRangeProvider, FoldingRangeContext } from './folding';
 
 export function activate(context: vscode.ExtensionContext) {
     context.subscriptions.push(
         vscode.workspace.onDidSaveTextDocument(Preview.update),
-        vscode.workspace.onDidCloseTextDocument(Preview.close),
+        vscode.workspace.onDidCloseTextDocument((document) => {
+            Preview.close(document);
+            FoldingRangeContext.close(document);
+        }),
+        vscode.workspace.onDidOpenTextDocument(FoldingRangeContext.open),
+        vscode.workspace.onDidChangeTextDocument(FoldingRangeContext.update),
         vscode.commands.registerTextEditorCommand('texinfo.showPreview', Preview.show),
         vscode.languages.registerCompletionItemProvider('texinfo', new CompletionItemProvider(), '@'),
+        vscode.languages.registerFoldingRangeProvider('texinfo', new FoldingRangeProvider()),
     );
 }
 
 export function deactivate() {
     Preview.destroyAll();
     Options.clear();
+    FoldingRangeContext.clear();
 }

src/folding.ts

@@ -0,0 +1,144 @@
+/**
+ * folding.ts
+ * 
+ * @author CismonX <admin@cismon.net>
+ * @license MIT
+ */
+
+import * as vscode from 'vscode';
+
+/**
+ * Provide folding range info for Texinfo source code.
+ */
+export class FoldingRangeProvider implements vscode.FoldingRangeProvider {
+
+    provideFoldingRanges(document: vscode.TextDocument) {
+        return FoldingRangeContext.get(document).foldingRanges;
+    }
+}
+
+export class FoldingRangeContext {
+
+    private static readonly map = new Map<vscode.TextDocument, FoldingRangeContext>();
+
+    static open(document: vscode.TextDocument) {
+        if (document.languageId === 'texinfo') {
+            new FoldingRangeContext(document);
+        }
+    }
+
+    static get(document: vscode.TextDocument) {
+        return FoldingRangeContext.map.get(document) ?? new FoldingRangeContext(document);
+    }
+
+    static update(event: vscode.TextDocumentChangeEvent) {
+        if (event.document.languageId !== 'texinfo') {
+            return;
+        }
+        FoldingRangeContext.get(event.document)?.update(event.contentChanges);
+    }
+
+    static close(document: vscode.TextDocument) {
+        FoldingRangeContext.map.delete(document);
+    }
+
+    static clear() {
+        FoldingRangeContext.map.clear();
+    }
+
+    foldingRanges = <vscode.FoldingRange[]>[];
+
+    private commentRange?: vscode.FoldingRange;
+
+    private headerStart?: number;
+
+    private closingBlocks = <ClosingBlock[]>[];
+
+    private constructor(private readonly document: vscode.TextDocument) {
+        FoldingRangeContext.map.set(document, this);
+        this.calculateFoldingRanges();
+    }
+
+    private calculateFoldingRanges() {
+        for (let idx = this.document.lineCount - 1; idx >= 0; --idx) {
+            const line = this.document.lineAt(idx);
+            const lineText = line.text;
+            const lineNum = line.lineNumber;
+            if (!lineText.startsWith('@')) {
+                continue;
+            }
+            if (this.processComment(lineText, lineNum)) {
+                continue;
+            }
+            this.processBlock(lineText, lineNum);
+        }
+        if (this.commentRange !== undefined) {
+            if (this.commentRange.end - this.commentRange.start > 1) {
+                this.foldingRanges.push(this.commentRange);
+            }
+        }
+    }
+
+    private processComment(lineText: string, lineNum: number) {
+        if (lineText.startsWith('c', 1)) {
+            if (!lineText.startsWith(' ', 2) && !lineText.startsWith('omment ', 2)) {
+                return false;
+            }
+            // Check for opening/closing header.
+            if (lineText.startsWith('%**', lineText[2] === ' ' ? 3 : 9)) {
+                if (this.headerStart === undefined) {
+                    this.headerStart = lineNum;
+                } else {
+                    this.foldingRanges.push(new vscode.FoldingRange(lineNum, this.headerStart));
+                    this.headerStart = undefined;
+                }
+            }
+            if (this.commentRange === undefined) {
+                this.commentRange = new vscode.FoldingRange(lineNum, lineNum, vscode.FoldingRangeKind.Comment);
+            } else if (this.commentRange.start - 1 === lineNum) {
+                this.commentRange.start = lineNum;
+            } else {
+                this.foldingRanges.push(this.commentRange);
+                this.commentRange = new vscode.FoldingRange(lineNum, lineNum, vscode.FoldingRangeKind.Comment);
+            }
+            return true;
+        }
+        return false;
+    }
+
+    private processBlock(lineText: string, lineNum: number) {
+        if (lineText.startsWith('end ', 1)) {
+            this.closingBlocks.push({ name: lineText.substring(5), line: lineNum });
+        } else {
+            const closingBlock = this.closingBlocks.pop();
+            if (closingBlock === undefined) {
+                return;
+            }
+            if (lineText.substring(1, closingBlock.name.length + 2).trim() === closingBlock.name) {
+                this.foldingRanges.push(new vscode.FoldingRange(lineNum, closingBlock.line));
+            } else {
+                this.closingBlocks.push(closingBlock);
+            }
+        }
+    }
+
+    private update(events: readonly vscode.TextDocumentContentChangeEvent[]) {
+        // console.log(events);
+    }
+}
+
+/**
+ * Represents a Texinfo block marked "closing" by `@end` command.
+ */
+interface ClosingBlock {
+
+    /**
+     * The name of the block.
+     */
+    name: string;
+
+    /**
+     * The terminating line number of the block.
+     */
+    line: number;
+}