AppleScript: Bulk-rename export EML messages

bulk-rename-eml.jxa.js

#!/usr/bin/env osascript -l JavaScript

const App = Application.currentApplication();
App.includeStandardAdditions = true;

function run(_) {
  // Prompt for folder selection.
  const dir = `${App.chooseFolder({
    withPrompt: 'Select the folder containing your exported messages...',
  })}`;

  // Read content of directory into list.
  const messages = App.doShellScript(`ls '${dir}'`).split('\r');

  messages.forEach((path) => {
    path = `${dir}/${path}`;

    // Skip if path does not end in `.eml`.
    if ([...path].slice(-4).join('') != '.eml') {
      return;
    }

    // Read message content to string.
    const content = $.NSString.stringWithContentsOfFileEncodingError(
      path,
      $.NSUTF8StringEncoding,
      $(),
    ).js;
    
    // Skip if file was unreadable.
    if (typeof content == 'undefined') {
      return;
    }

    // Extract parts for renaming...
    const { subject } = content.match(/(^Subject:\s?(?<subject>.+))/im).groups;
    let { sender } = content.match(/(^From:\s?(?<sender>.+))/im).groups;
    if ((senderAddress = sender.match(/\<[^@]+@[^\>]+\>/))) {
      sender = senderAddress[0].replace(/(\<|\>)/g, '');
    }
    let { timestamp } = content.match(/(^Date:\s?(?<timestamp>.+))/im).groups;

    // Skip if unable to extract all parts...
    if (!subject || !sender || !timestamp) {
      return;
    }

    // Reformat date to desired format...
    timestamp = new Date(timestamp);
    const year = timestamp.getFullYear().toString();
    const month = (timestamp.getMonth() + 1).toString().padStart(2, '0');
    const day = timestamp.getDate().toString().padStart(2, '0');
    const hours = timestamp.getHours().toString().padStart(2, '0');
    const minutes = timestamp.getMinutes().toString().padStart(2, '0');
    const seconds = timestamp.getSeconds().toString().padStart(2, '0');
    timestamp = year + month + day + '_' + hours + minutes + seconds;

    // Perform rename operation.
    const basename = `[${timestamp}][${sender}] ${subject}`.trim().replace(/[\/\?<>\\:\*\'|"]/g, '_');
    App.doShellScript(
      `mv '${path}' '${dir}/${basename}.eml'`,
    );
  });
}