WIP

app/services/bill-runs/tpt-supplementary/fetch-previous-transactions.service.js

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+'use strict'
+
+/**
+ * Fetches the previously billed transactions that match, removing any debits cancelled out by previous credits
+ * @module FetchPreviousTransactionsService
+ */
+
+const { db } = require('../../../../db/db.js')
+const { transactionsMatch } = require('../../../lib/general.lib.js')
+const TransactionModel = require('../../../models/transaction.model.js')
+
+/**
+ * Fetches the previously billed transactions that match, removing any debits cancelled out by previous credits
+ *
+ * @param {string} billingAccountId - The UUID that identifies the billing account we need to fetch transactions for
+ * @param {string} licenceId - The UUID that identifies the licence we need to fetch transactions for
+ * @param {number} financialYearEnding - The year the financial billing period ends that we need to fetch transactions
+ * for
+ *
+ * @returns {Promise<object[]>} The resulting matched transactions
+ */
+async function go(billingAccountId, licenceId, financialYearEnding) {
+  const transactions = await _fetch(billingAccountId, licenceId, financialYearEnding)
+
+  return _cleanse(transactions)
+}
+
+/**
+ * Cleanse the transactions by cancelling out matching pairs of debits and credits, and return the remaining debits.
+ *
+ * If a credit matches to a debit then its something that was dealt with in a previous supplementary bill run. We need
+ * to know only about debits that have not been credited.
+ *
+ * @private
+ */
+function _cleanse(transactions) {
+  const credits = transactions.filter((transaction) => {
+    return transaction.credit
+  })
+  const debits = transactions.filter((transaction) => {
+    return !transaction.credit
+  })
+
+  credits.forEach((credit) => {
+    const debitIndex = debits.findIndex((debit) => {
+      return transactionsMatch(debit, credit)
+    })
+
+    if (debitIndex > -1) {
+      debits.splice(debitIndex, 1)
+    }
+  })
+
+  return debits
+}
+
+async function _fetch(billingAccountId, licenceId, financialYearEnding) {
+  return TransactionModel.query()
+    .select([
+      'transactions.authorisedDays',
+      'transactions.billableDays',
+      'transactions.waterUndertaker',
+      'transactions.chargeReferenceId',
+      'transactions.startDate',
+      'transactions.endDate',
+      'transactions.source',
+      'transactions.season',
+      'transactions.loss',
+      'transactions.credit',
+      'transactions.chargeType',
+      'transactions.authorisedQuantity',
+      'transactions.billableQuantity',
+      'transactions.description',
+      'transactions.volume',
+      'transactions.section126Factor',
+      'transactions.section127Agreement',
+      'transactions.secondPartCharge',
+      'transactions.scheme',
+      'transactions.aggregateFactor',
+      'transactions.adjustmentFactor',
+      'transactions.chargeCategoryCode',
+      'transactions.chargeCategoryDescription',
+      'transactions.supportedSource',
+      'transactions.supportedSourceName',
+      'transactions.newLicence',
+      'transactions.waterCompanyCharge',
+      'transactions.winterOnly',
+      'transactions.purposes',
+      // NOTE: The section130Agreement field is a varchar in the DB for historic reasons. It seems some early PRESROC
+      // transactions recorded values other than 'true' or 'false'. For SROC though, it will only ever be true/false. We
+      // generate our calculated billing transaction lines based on the Section130 flag against charge_elements which is
+      // always a boolean. So, to avoid issues when we need to compare the values we cast this to a boolean when
+      // fetching the data.
+      db.raw('transactions.section_130_agreement::boolean')
+    ])
+    .innerJoin('billLicences', 'transactions.billLicenceId', 'billLicences.id')
+    .innerJoin('bills', 'billLicences.billId', 'bills.id')
+    .innerJoin('billRuns', 'bills.billRunId', 'billRuns.id')
+    .where({
+      'billLicences.licenceId': licenceId,
+      'bills.billingAccountId': billingAccountId,
+      'bills.financialYearEnding': financialYearEnding,
+      'billRuns.status': 'sent',
+      'billRuns.scheme': 'sroc'
+    })
+}
+
+module.exports = {
+  go
+}

app/services/bill-runs/tpt-supplementary/generate-bill-run.service.js

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+'use strict'
+
+/**
+ * Generates a tpt supplementary bill run after the users have completed reviewing its match & allocate results
+ * @module GenerateBillRunService
+ */
+
+const BillRunError = require('../../../errors/bill-run.error.js')
+const BillRunModel = require('../../../models/bill-run.model.js')
+const ChargingModuleGenerateBillRunRequest = require('../../../requests/charging-module/generate-bill-run.request.js')
+const ExpandedError = require('../../../errors/expanded.error.js')
+const {
+  calculateAndLogTimeTaken,
+  currentTimeInNanoseconds,
+  timestampForPostgres
+} = require('../../../lib/general.lib.js')
+const FetchBillingAccountsService = require('./fetch-billing-accounts.service.js')
+const HandleErroredBillRunService = require('../handle-errored-bill-run.service.js')
+const LegacyRefreshBillRunRequest = require('../../../requests/legacy/refresh-bill-run.request.js')
+const ProcessBillingPeriodService = require('./process-billing-period.service.js')
+
+/**
+ * Generates a tpt supplementary bill run after the users have completed reviewing its match & allocate results
+ *
+ * In this case, "generate" means that we create the required bills and transactions for them in both this service and
+ * the Charging Module.
+ *
+ * > In the other bill run types this would be the `ProcessBillRunService` but that has already been used to handle the
+ * > match and allocate process in tpt supplementary
+ *
+ * We first fetch all the billing accounts applicable to this bill run and their charge information. We pass these to
+ * `ProcessBillingPeriodService` which will generate the bill for each billing account both in WRLS and the
+ * {@link https://github.com/DEFRA/sroc-charging-module-api | Charging Module API (CHA)}.
+ *
+ * Once `ProcessBillingPeriodService` is complete we tell the CHA to generate the bill run (this calculates final values
+ * for each bill and the bill run overall).
+ *
+ * The final step is to ping the legacy
+ * {@link https://github.com/DEFRA/water-abstraction-service | water-abstraction-service} 'refresh' endpoint. That
+ * service will extract the final values from the CHA and update the records on our side, finally marking the bill run
+ * as **Ready**.
+ *
+ * @param {module:BillRunModel} billRunId - The UUID of the tpt supplementary bill run that has been reviewed and is
+ * ready for generating
+ */
+async function go(billRunId) {
+  const billRun = await _fetchBillRun(billRunId)
+
+  if (billRun.status !== 'review') {
+    throw new ExpandedError('Cannot process a two-part tariff supplementary bill run that is not in review', {
+      billRunId
+    })
+  }
+
+  await _updateStatus(billRunId, 'processing')
+
+  // NOTE: We do not await this call intentionally. We don't want to block the user while we generate the bill run
+  _generateBillRun(billRun)
+}
+
+/**
+ * Unlike other bill runs where the bill run itself and the bills are generated in one process, two-part tariff is
+ * split. The first part which matches and allocates charge information to returns create's the bill run itself. This
+ * service handles the second part where we create the bills using the match and allocate data.
+ *
+ * This means we've already determined the billing period and recorded it against the bill run. So, we retrieve it from
+ * the bill run rather than pass it into the service.
+ *
+ * @private
+ */
+function _billingPeriod(billRun) {
+  const { toFinancialYearEnding } = billRun
+
+  return {
+    startDate: new Date(`${toFinancialYearEnding - 1}-04-01`),
+    endDate: new Date(`${toFinancialYearEnding}-03-31`)
+  }
+}
+
+async function _fetchBillingAccounts(billRunId) {
+  try {
+    return await FetchBillingAccountsService.go(billRunId)
+  } catch (error) {
+    // We know we're saying we failed to process charge versions. But we're stuck with the legacy error codes and this
+    // is the closest one related to what stage we're at in the process
+    throw new BillRunError(error, BillRunModel.errorCodes.failedToProcessChargeVersions)
+  }
+}
+
+async function _fetchBillRun(billRunId) {
+  return BillRunModel.query()
+    .findById(billRunId)
+    .select(['id', 'batchType', 'createdAt', 'externalId', 'regionId', 'scheme', 'status', 'toFinancialYearEnding'])
+}
+
+async function _finaliseBillRun(billRun, billRunPopulated) {
+  // If there are no bill licences then the bill run is considered empty. We just need to set the status to indicate
+  // this in the UI
+  if (!billRunPopulated) {
+    await _updateStatus(billRun.id, 'empty')
+
+    return
+  }
+
+  // We now need to tell the Charging Module to run its generate process. This is where the Charging module finalises
+  // the debit and credit amounts, and adds any additional transactions needed, for example, minimum charge
+  await ChargingModuleGenerateBillRunRequest.send(billRun.externalId)
+
+  await LegacyRefreshBillRunRequest.send(billRun.id)
+}
+
+/**
+ * The go() has to deal with updating the status of the bill run and then passing a response back to the request to
+ * avoid the user seeing a timeout in their browser. So, this is where we actually generate the bills and record the
+ * time taken.
+ *
+ * @private
+ */
+async function _generateBillRun(billRun) {
+  const { id: billRunId } = billRun
+
+  try {
+    const startTime = currentTimeInNanoseconds()
+
+    const billingPeriod = _billingPeriod(billRun)
+
+    await _processBillingPeriod(billingPeriod, billRun)
+
+    calculateAndLogTimeTaken(startTime, 'Process bill run complete', { billRunId })
+  } catch (error) {
+    await HandleErroredBillRunService.go(billRunId, error.code)
+    global.GlobalNotifier.omfg('Bill run process errored', { billRun }, error)
+  }
+}
+
+async function _processBillingPeriod(billingPeriod, billRun) {
+  const { id: billRunId } = billRun
+
+  const billingAccounts = await _fetchBillingAccounts(billRunId)
+
+  const billRunPopulated = await ProcessBillingPeriodService.go(billRun, billingPeriod, billingAccounts)
+
+  await _finaliseBillRun(billRun, billRunPopulated)
+}
+
+async function _updateStatus(billRunId, status) {
+  return BillRunModel.query().findById(billRunId).patch({ status, updatedAt: timestampForPostgres() })
+}
+
+module.exports = {
+  go
+}