extension.js

// The module 'vscode' contains the VS Code extensibility API
// Import the module and reference it with the alias vscode in your code below
const fs = require('fs');
const path = require('path');
const vscode = require('vscode');
const getWebviewContent = require('./lib/content');

// this method is called when your extension is activated
// your extension is activated the very first time the command is executed
function activate(context) {
  let panel;
  const _disposables = [];

  context.subscriptions.push(
    vscode.commands.registerCommand('fsmViewer.view', () => {
      panel = vscode.window.createWebviewPanel(
        'fsmViewer',
        'FSM Viewer',
        vscode.ViewColumn.Two,
        {
          // Enable scripts in the webview
          enableScripts: true
        }
      );

      vscode.workspace.onDidChangeTextDocument(
        e => {
          if (e.document === vscode.window.activeTextEditor.document) {
            panel.webview.html = getWebviewContent(context);
          }
        },
        null,
        _disposables
      );

      vscode.window.onDidChangeTextEditorSelection(
        e => {
          if (e.textEditor === vscode.window.activeTextEditor) {
            panel.webview.html = getWebviewContent(context);
          }
        },
        null,
        _disposables
      );

      vscode.window.onDidChangeActiveTextEditor(
        e => {
          // panel.webview.html = getWebviewContent(context);
        },
        null,
        _disposables
      );

      panel.webview.onDidReceiveMessage(
        async message => {
          switch (message.command) {
            case 'svg':
              const filename = await vscode.window.showInputBox({
                prompt: 'Relative to project root',
                placeHolder: 'Type the ouput filename'
              });

              filename &&
                fs.writeFileSync(
                  path.join(vscode.workspace.rootPath, filename),
                  message.content
                );
              break;
            default:
          }
        },
        null,
        _disposables
      );

      panel.onDidDispose(
        () => {
          console.log('panel closed');

          while (_disposables.length) {
            const item = _disposables.pop();
            if (item) {
              item.dispose();
            }
          }

          vscode.commands.executeCommand(
            'setContext',
            'fsmViewer:canExport',
            false
          );
        },
        null,
        context.subscriptions
      );

      panel.webview.html = getWebviewContent(context);
    })
  );

  context.subscriptions.push(
    vscode.commands.registerCommand('fsmViewer.save', () => {
      panel.webview.postMessage({
        command: 'save'
      });
    })
  );
}

exports.activate = activate;

// this method is called when your extension is deactivated
function deactivate() {
  console.log('deactivate');
}
exports.deactivate = deactivate;