HalifaxStatementQIF.js

// Usage:
//
//   HalifaxAPI.getTransactionHistoryQIF(300).then((qif) => console.log(qif));
//
(function() {
  'use strict';

  const StatementBaseUrl = 'https://secure.halifax-online.co.uk/personal/link/lp_statement_ajax';

  const StatementType = Object.freeze({
    Latest: 'latest',
    Previous: 'previous',
    Next: 'next',
  });

  function getStatementUrl(type) {
    const cacheBuster = Date.now();
    
    let url = StatementBaseUrl;
    url += '?_=' + cacheBuster;
    url += '&viewstatement=' + type;

    return url;
  }

  function fetchStatement(type) {
    return fetch(getStatementUrl(type), {
      credentials: 'include',
    }).then((response) => {
      if (!response.ok) {
        throw new Error('HTTP Error: ' + response.status + ' - ' + response.statusText);
      }

      return response.json();
    });
  }

  function getTransactions(statement) {
    return statement.transactions.items;
  }

  function getTransactionHistoryInternal(limit, resolve, transactionHistory) {
    let statementType = StatementType.Previous;
    if (transactionHistory.length === 0) {
      statementType = StatementType.Latest;
    }
    
    fetchStatement(statementType)
      .then(getTransactions)
      .then((transactions) => {
        Array.prototype.push.apply(transactionHistory, transactions);

        if (transactionHistory.length < limit) {
          getTransactionHistoryInternal(limit, resolve, transactionHistory);
        } else {
          resolve(transactionHistory);
        }
      });
  }

  function getTransactionHistory(limit) {
    return new Promise((resolve, reject) => {
      let transactionHistory = [];
      getTransactionHistoryInternal(limit, resolve, transactionHistory);
    });
  }

  function getTransactionHistoryQIF(limit) {
    return new Promise((resolve, reject) => {
      getTransactionHistory(limit)
        .then((transactions) => {
          resolve('!Type:Bank\n' + transactions.map((transaction) => ({
            date: new Date(transaction.date),
            payee: transaction.completeDescription.join(' ').replace(/\s+/g, ' ').trim(),
            amount: transaction.amount.amount,
          })).map((transaction) => [
            'D' + transaction.date.getDate() + '/' + (transaction.date.getMonth() + 1) + '/' + transaction.date.getFullYear(),
            'P' + transaction.payee,
            'T' + transaction.amount.toFixed(2),
            '^',
          ].join('\n')).join('\n'));
        });
    });
  }

  window.HalifaxAPI = {
    getTransactionHistory: getTransactionHistory,
    getTransactionHistoryQIF: getTransactionHistoryQIF,
  }
})();