@dwp/govuk-casa/middleware/page/gather.js

Framework for creating basic GOVUK Collect-And-Submit-Applications

const commonBodyParser = require('../../lib/commonBodyParser.js');
const createLogger = require('../../lib/Logger.js');
const JourneyContext = require('../../lib/JourneyContext.js');
const { executeHook, extractSessionableData, runGatherModifiers } = require('./utils.js');

module.exports = (pageMeta = {}) => [commonBodyParser, (req, res, next) => {
  const logger = createLogger('page.gather');
  logger.setSessionId(req.session.id);

  req.casa = req.casa || Object.create(null);

  const pageId = pageMeta.id;
  const { journeyOrigin, plan: journey } = req.casa;

  // Take a traversal snapshot of the journey before we mutate the data/error
  // context
  logger.trace('Take pre-gather traversal snapshot');
  req.casa.preGatherTraversalSnapshot = journey.traverse(req.casa.journeyContext, {
    startWaypoint: journeyOrigin.waypoint,
  });

  /**
   * Store data in request, clearing validation flags prior to validation.
   *
   * @param {object} data Data to store.
   * @returns {void}
   */
  function storeSessionData(data) {
    // Store gathered journey data, and clear any cached validation state for
    // the page. Removing the validation state will prevent onward traversal
    // from this page unil its new content has been validated (by the next
    // middleware in the chain).
    logger.trace('Storing session data for %s', pageId);
    req.casa.journeyContext.setDataForPage(pageMeta, data);
    req.casa.journeyContext.removeValidationStateForPage(pageId);
    JourneyContext.putContext(req.session, req.casa.journeyContext);
  }

  // Promise
  return executeHook(logger, req, res, pageMeta, 'pregather')
    .then(() => {
      // Only data that has matching validators defined in the page meta will be
      // gathered and stored in the session
      const preparedData = extractSessionableData(
        logger,
        pageMeta,
        req.body,
        req.casa.journeyContext,
      );

      // Run this page's "gather modifiers" against each prepared data item
      if (Object.prototype.toString.call(pageMeta.fieldGatherModifiers) === '[object Object]') {
        Object.keys(pageMeta.fieldGatherModifiers).forEach((fieldName) => {
          logger.trace('Run gather-modifier for field %s on waypoint %s', fieldName, pageId);
          const modifiedValue = runGatherModifiers(
            preparedData[fieldName],
            pageMeta.fieldGatherModifiers[fieldName],
          );
          preparedData[fieldName] = modifiedValue;
        });
      }

      // Store all modified data back to req.body so downstream handlers have
      // access to the modified data.
      req.body = Object.assign(Object.create(null), req.body, preparedData);
      return preparedData;
    })
    .then((modifiedData) => (storeSessionData(modifiedData)))
    .then(() => {
      next();
    })
    .catch((err) => {
      next(err);
    });
}]