backend/src/services/trainService.services.js

const log     = require('../utils/log.utils');
const db      = require('./dbAccess.services');
const clean   = require('../utils/sanitizer.utils');
const pis     = require('../services/pis.services');

async function findByHeadcodeToday(headcode) {
  const sanitizedHeadcode = clean.removeNonAlphanumeric(headcode);
  log.out(`trainServiceServices.findByHeadcode: Searching for headcode ${sanitizedHeadcode}`, 'dbug');
  const now = new Date();
  const dayMap = ['su', 'm', 't', 'w', 'th', 'f', 's'];
  const shortDay = dayMap[now.getDay()]; // Fetch short day from map
  const query = {
    headcode: sanitizedHeadcode,
    scheduleStartDate: {$lte: now},
    scheduleEndDate: {$gte: now},
    daysRun: {$in: [shortDay]}
  };
  const queryData = await db.query('timetable', query);
  let trainData = await parseTrains(queryData, now);
  let preparedData = [];
  for (const trainService in trainData) {
    // Search for PIS Code for each service
    let tiplocList = await getPublicStops(trainData[trainService]['stops']);
    const pisDetail = await pis.findByTiplocArray(tiplocList);
    trainData[trainService]['pis'] = pisDetail?.[0]?.['code'] ?? 'None';
    preparedData.push(trainData[trainService]);
  }
  return preparedData;
}

module.exports = {
  findByHeadcodeToday,
};

/* Internal Functions, not to be exported */

async function getPublicStops(data) {
  let tiplocList = [];
  for (const publicStop in data) {
    if (data[publicStop]['isPublic']) {
      tiplocList.push(data[publicStop]['tiploc']);
    }
  }
  return tiplocList;
}

async function parseTrains(data, date = new Date() {
  // Parses an array returned from a db-query and removes any service entries that don't apply to {date}
  // {date} shoule be a datetime object and defaults to now if not provided - as a general rule it should always be provided for clarity
  
    // At this point, the returned objects need sorting to ensure the correct object is returned.
  // C, N, O, P is the order - C being the preferred, then N, then O and finally P.
  // If stpindicator == "C" && trainUid (isSame as N, O or P entry) => DO NOT DISPLAY SERVICE ("C" records do not contain the headcode (signalling_id)) so an additional lookup needs to be performed for the trainUid.
  // If stpIndicator == "N" && trainUid (isSame as O or P entry) => Display this instead of "O", or "P"
  // If stpIndicaor == "O" && trainUid (isSame as P entry) => Display this instead of "P"
  // Obviously, remember that several trains can share a headcode, but the trainUid is unique for each service.
  // Probably best to loop through each return here and add to a new [], then if another entry supersedes it, overwrite it in the [].  Then pass to the below part of the function to process the data for sending.
  // Maybe break in to a new function parseTrains() which can take in any dbquery array and remove any services that are not meant to be displayed based on the data provided.  Maybe have a date as an input so it can be used in the future to fetch trains for a given date in the future - due to database cleaning in db-manager, past dates would need adjustments to how the database is cleaned leaving outdated services available.
  const parsedDate = data;
  return parsedData;
};