atom/src/protocol-handler-installer.js

const { ipcRenderer } = require('electron');

const SETTING = 'core.uriHandlerRegistration';
const PROMPT = 'prompt';
const ALWAYS = 'always';
const NEVER = 'never';

module.exports = class ProtocolHandlerInstaller {
  isSupported() {
    return ['win32', 'darwin'].includes(process.platform);
  }

  async isDefaultProtocolClient() {
    return ipcRenderer.invoke('isDefaultProtocolClient', {
      protocol: 'atom',
      path: process.execPath,
      args: ['--uri-handler', '--']
    });
  }

  async setAsDefaultProtocolClient() {
    // This Electron API is only available on Windows and macOS. There might be some
    // hacks to make it work on Linux; see https://github.com/electron/electron/issues/6440
    return (
      this.isSupported() &&
      ipcRenderer.invoke('setAsDefaultProtocolClient', {
        protocol: 'atom',
        path: process.execPath,
        args: ['--uri-handler', '--']
      })
    );
  }

  async initialize(config, notifications) {
    if (!this.isSupported()) {
      return;
    }

    const behaviorWhenNotProtocolClient = config.get(SETTING);
    switch (behaviorWhenNotProtocolClient) {
      case PROMPT:
        if (await !this.isDefaultProtocolClient()) {
          this.promptToBecomeProtocolClient(config, notifications);
        }
        break;
      case ALWAYS:
        if (await !this.isDefaultProtocolClient()) {
          this.setAsDefaultProtocolClient();
        }
        break;
      case NEVER:
        if (process.platform === 'win32') {
          // Only win32 supports deregistration
          const Registry = require('winreg');
          const commandKey = new Registry({ hive: 'HKCR', key: `\\atom` });
          commandKey.destroy((_err, _val) => {
            /* no op */
          });
        }
        break;
      default:
      // Do nothing
    }
  }

  promptToBecomeProtocolClient(config, notifications) {
    let notification;

    const withSetting = (value, fn) => {
      return function() {
        config.set(SETTING, value);
        fn();
      };
    };

    const accept = () => {
      notification.dismiss();
      this.setAsDefaultProtocolClient();
    };
    const decline = () => {
      notification.dismiss();
    };

    notification = notifications.addInfo(
      'Register as default atom:// URI handler?',
      {
        dismissable: true,
        icon: 'link',
        description:
          'Atom is not currently set as the default handler for atom:// URIs. Would you like Atom to handle ' +
          'atom:// URIs?',
        buttons: [
          {
            text: 'Yes',
            className: 'btn btn-info btn-primary',
            onDidClick: accept
          },
          {
            text: 'Yes, Always',
            className: 'btn btn-info',
            onDidClick: withSetting(ALWAYS, accept)
          },
          {
            text: 'No',
            className: 'btn btn-info',
            onDidClick: decline
          },
          {
            text: 'No, Never',
            className: 'btn btn-info',
            onDidClick: withSetting(NEVER, decline)
          }
        ]
      }
    );
  }
};