Mailspring/app/internal_packages/link-tracking/lib/link-tracking-button.jsx

import {React, APIError, NylasAPIRequest} from 'nylas-exports'
import {MetadataComposerToggleButton} from 'nylas-component-kit'
import {PLUGIN_ID, PLUGIN_NAME} from './link-tracking-constants'

export default class LinkTrackingButton extends React.Component {
  static displayName = 'LinkTrackingButton';

  static propTypes = {
    draft: React.PropTypes.object.isRequired,
    session: React.PropTypes.object.isRequired,
  };

  shouldComponentUpdate(nextProps) {
    return (nextProps.draft.metadataForPluginId(PLUGIN_ID) !== this.props.draft.metadataForPluginId(PLUGIN_ID));
  }

  _title(enabled) {
    const dir = enabled ? "Disable" : "Enable";
    return `${dir} link tracking`
  }

  _errorMessage(error) {
    if (error instanceof APIError && NylasAPIRequest.TimeoutErrorCodes.includes(error.statusCode)) {
      return `Link tracking does not work offline. Please re-enable when you come back online.`
    }
    return `Unfortunately, link tracking servers are currently not available. Please try again later. Error: ${error.message}`
  }

  render() {
    return (
      <MetadataComposerToggleButton
        title={this._title}
        iconName="icon-composer-linktracking.png"
        pluginId={PLUGIN_ID}
        pluginName={PLUGIN_NAME}
        metadataEnabledValue={{tracked: true}}
        stickyToggle
        errorMessage={this._errorMessage}
        draft={this.props.draft}
        session={this.props.session}
      />
    )
  }
}

LinkTrackingButton.containerRequired = false;