Implement logger.

src/extension.ts

@@ -7,6 +7,7 @@
 
 import * as vscode from 'vscode';
 import Document from './document';
+import Logger from './logger';
 import Options from './options';
 import Preview from './preview';
 import { CompletionItemProvider } from './completion';
@@ -28,5 +29,6 @@ export function activate(context: vscode.ExtensionContext) {
 
 export function deactivate() {
     Document.clear();
+    Logger.destroy();
     Options.clear();
 }

src/logger.ts

@@ -0,0 +1,48 @@
+/**
+ * logger.ts
+ * 
+ * @author CismonX <admin@cismon.net>
+ * @license MIT
+ */
+
+import * as vscode from 'vscode';
+
+/**
+ * Logger which prints message to VSCode output channel.
+ */
+export default class Logger {
+
+    private static singleton?: Logger;
+
+    private static get instance() {
+        return Logger.singleton ??= new Logger();
+    }
+
+    static log(message: string) {
+        Logger.instance.log(message);
+    }
+
+    static show() {
+        Logger.instance.show();
+    }
+
+    static destroy() {
+        Logger.instance.outputChannel.dispose();
+        Logger.singleton = undefined;
+    }
+
+    private outputChannel: vscode.OutputChannel;
+
+    private constructor() {
+        this.outputChannel = vscode.window.createOutputChannel('Texinfo');
+    }
+
+    private log(message: string) {
+        const dateTime = new Date().toLocaleString(undefined, { hour12: false });
+        this.outputChannel.appendLine(`[ ${dateTime} ]:\n${message}`);
+    }
+
+    private show() {
+        this.outputChannel.show(true);
+    }
+}

src/preview.ts

@@ -80,7 +80,8 @@ export default class Preview {
 
         let htmlCode = await Converter.convertToHtml(this.document.fileName);
         if (htmlCode === undefined) {
-            vscode.window.showErrorMessage(`Failed to show preview for ${this.document.fileName}.`);
+            prompt(`Failed to show preview for ${this.document.fileName}.`, 'Show log', true)
+                .then(result => result && Logger.show());
         } else {
             if (Options.displayImage) {
                 const pathName = path.dirname(this.document.fileName);

src/utils.ts

@@ -8,16 +8,19 @@
 import * as child_process from 'child_process';
 import * as htmlparser from 'node-html-parser';
 import * as vscode from 'vscode';
+import Logger from './logger';
 
 /**
  * Open a prompt with two buttons, "Confirm" and "Cancel", and wait for user action.
  * 
  * @param message The message to be displayed on the prompt.
  * @param confirm Text to be displayed on the "Confirm" button.
+ * @param error Whether the prompt is shown as an error message. Default false.
  * @returns Whether the user clicked the "Confirm" button.
  */
-export async function prompt(message: string, confirm: string) {
-    return confirm === await vscode.window.showInformationMessage(message, confirm, 'Cancel');
+export async function prompt(message: string, confirm: string, error = false) {
+    const func = error ? vscode.window.showErrorMessage : vscode.window.showInformationMessage;
+    return confirm === await func(message, confirm, 'Cancel');
 }
 
 /**
@@ -32,10 +35,10 @@ export function exec(path: string, args: string[], maxBuffer: number) {
     return new Promise<string | undefined>(resolve => {
         child_process.execFile(path, args, { maxBuffer: maxBuffer }, (error, stdout, stderr) => {
             if (error) {
-                console.error(stderr ? stderr : error);
+                Logger.log(stderr ? stderr : error.message);
                 resolve(undefined);
             } else {
-                stderr && console.log(stderr);
+                stderr && Logger.log(stderr);
                 resolve(stdout);
             }
         });