Reverse previous SROC billing batches in supplementary bill run process

app/services/supplementary-billing/fetch-previous-billing-transactions.service.js

@@ -1,7 +1,8 @@
 'use strict'
 
 /**
- * Fetches the previously billed transactions that match the invoice, licence and year provided
+ * Fetches the previously billed transactions that match the invoice, licence and year provided, removing any debits
+ * which are cancelled out by previous credits.
  * @module FetchPreviousBillingTransactionsService
  */
 
@@ -14,7 +15,29 @@ async function go (billingInvoice, billingInvoiceLicence, financialYearEnding) {
     financialYearEnding
   )
 
-  return billingTransactions
+  return _cleanse(billingTransactions)
+}
+
+/**
+ * Cleanse the billing transactions by cancelling out matching pairs of debits and credits, and return the remaining
+ * debits. We judge a pair of credits and debits to be matching if they have the same number of billable days and the
+ * same charge type.
+ */
+function _cleanse (billingTransactions) {
+  const credits = billingTransactions.filter((transaction) => transaction.isCredit)
+  const debits = billingTransactions.filter((transaction) => !transaction.isCredit)
+
+  for (const credit of credits) {
+    const debitIndex = debits.findIndex((debit) => {
+      return debit.billableDays === credit.billableDays && debit.chargeType === credit.chargeType
+    })
+
+    if (debitIndex > -1) {
+      debits.splice(debitIndex, 1)
+    }
+  }
+
+  return debits
 }
 
 async function _fetch (licenceId, invoiceAccountId, financialYearEnding) {
@@ -70,14 +93,9 @@ async function _fetch (licenceId, invoiceAccountId, financialYearEnding) {
           'bb.status': 'sent',
           'bb.scheme': 'sroc'
         })
-        .orderBy('bb.dateCreated', 'desc')
-        .limit(1)
         .as('validBillingInvoices'),
       'bt.billingInvoiceLicenceId', 'validBillingInvoices.billingInvoiceLicenceId'
     )
-    .where({
-      'bt.isCredit': false
-    })
 }
 
 module.exports = {

test/services/supplementary-billing/fetch-previous-billing-transactions.service.test.js

@@ -41,13 +41,7 @@ describe('Fetch Previous Billing Transactions service', () => {
   describe('when there is a bill run', () => {
     describe('for the same licence and invoice account', () => {
       beforeEach(async () => {
-        const { billingBatchId } = await BillingBatchHelper.add({ status: 'sent' })
-        const { billingInvoiceId } = await BillingInvoiceHelper.add({ invoiceAccountId }, { billingBatchId })
-        const { billingInvoiceLicenceId } = await BillingInvoiceLicenceHelper.add(
-          {},
-          { licenceId },
-          { billingInvoiceId }
-        )
+        const billingInvoiceLicenceId = await _createBillingBatchInvoiceAndLicence(invoiceAccountId, licenceId)
         await BillingTransactionHelper.add({ billingInvoiceLicenceId })
       })
 
@@ -63,14 +57,35 @@ describe('Fetch Previous Billing Transactions service', () => {
 
       describe('followed by another run which credits the previous', () => {
         beforeEach(async () => {
-          const { billingBatchId } = await BillingBatchHelper.add({ status: 'sent' })
-          const { billingInvoiceId } = await BillingInvoiceHelper.add({ invoiceAccountId }, { billingBatchId })
-          const { billingInvoiceLicenceId } = await BillingInvoiceLicenceHelper.add(
-            {},
+          const billingInvoiceLicenceId = await _createBillingBatchInvoiceAndLicence(invoiceAccountId, licenceId)
+          await BillingTransactionHelper.add({ billingInvoiceLicenceId, isCredit: true })
+        })
+
+        it('returns no results', async () => {
+          const result = await FetchPreviousBillingTransactionsService.go(
+            { invoiceAccountId },
             { licenceId },
-            { billingInvoiceId }
+            financialYearEnding
           )
-          await BillingTransactionHelper.add({ billingInvoiceLicenceId, isCredit: true })
+
+          expect(result).to.be.empty()
+        })
+      })
+
+      describe('followed by more runs with equal credits and debits', () => {
+        beforeEach(async () => {
+          const creditsBillingInvoiceLicenceId = await _createBillingBatchInvoiceAndLicence(invoiceAccountId, licenceId)
+          await BillingTransactionHelper.add({
+            billingInvoiceLicenceId: creditsBillingInvoiceLicenceId,
+            isCredit: true
+          })
+          await BillingTransactionHelper.add({
+            billingInvoiceLicenceId: creditsBillingInvoiceLicenceId,
+            isCredit: true
+          })
+
+          const debitBillingInvoiceLicenceId = await _createBillingBatchInvoiceAndLicence(invoiceAccountId, licenceId)
+          await BillingTransactionHelper.add({ billingInvoiceLicenceId: debitBillingInvoiceLicenceId })
         })
 
         it('returns no results', async () => {
@@ -83,17 +98,42 @@ describe('Fetch Previous Billing Transactions service', () => {
           expect(result).to.be.empty()
         })
       })
+
+      describe('followed by more runs with unequal credits and debits', () => {
+        beforeEach(async () => {
+          const unmatchedBillingInvoiceLicenceId = await _createBillingBatchInvoiceAndLicence(
+            invoiceAccountId,
+            licenceId
+          )
+          await BillingTransactionHelper.add({
+            billingInvoiceLicenceId: unmatchedBillingInvoiceLicenceId,
+            billableDays: 30,
+            isCredit: true
+          })
+
+          const matchedBillingInvoiceLicenceId = await _createBillingBatchInvoiceAndLicence(invoiceAccountId, licenceId)
+          await BillingTransactionHelper.add({
+            billingInvoiceLicenceId: matchedBillingInvoiceLicenceId,
+            isCredit: true
+          })
+          await BillingTransactionHelper.add({ billingInvoiceLicenceId: matchedBillingInvoiceLicenceId })
+        })
+
+        it('returns results', async () => {
+          const result = await FetchPreviousBillingTransactionsService.go(
+            { invoiceAccountId },
+            { licenceId },
+            financialYearEnding
+          )
+
+          expect(result).to.have.length(1)
+        })
+      })
     })
 
     describe('but for a different licence', () => {
       beforeEach(async () => {
-        const { billingBatchId } = await BillingBatchHelper.add({ status: 'sent' })
-        const { billingInvoiceId } = await BillingInvoiceHelper.add({ invoiceAccountId }, { billingBatchId })
-        const { billingInvoiceLicenceId } = await BillingInvoiceLicenceHelper.add(
-          {},
-          { licenceId: '66498337-e6a6-4a2a-9fb7-e39f43410f80' },
-          { billingInvoiceId }
-        )
+        const billingInvoiceLicenceId = await _createBillingBatchInvoiceAndLicence(invoiceAccountId, '66498337-e6a6-4a2a-9fb7-e39f43410f80')
         await BillingTransactionHelper.add({ billingInvoiceLicenceId })
       })
 
@@ -110,15 +150,9 @@ describe('Fetch Previous Billing Transactions service', () => {
 
     describe('but for a different invoice account', () => {
       beforeEach(async () => {
-        const { billingBatchId } = await BillingBatchHelper.add({ status: 'sent' })
-        const { billingInvoiceId } = await BillingInvoiceHelper.add(
-          { invoiceAccountId: 'b0b75e7a-e80a-4c28-9ac9-33b3a850722b' },
-          { billingBatchId }
-        )
-        const { billingInvoiceLicenceId } = await BillingInvoiceLicenceHelper.add(
-          {},
-          { licenceId },
-          { billingInvoiceId }
+        const billingInvoiceLicenceId = await _createBillingBatchInvoiceAndLicence(
+          'b0b75e7a-e80a-4c28-9ac9-33b3a850722b',
+          licenceId
         )
         await BillingTransactionHelper.add({ billingInvoiceLicenceId })
       })
@@ -135,3 +169,15 @@ describe('Fetch Previous Billing Transactions service', () => {
     })
   })
 })
+
+async function _createBillingBatchInvoiceAndLicence (invoiceAccountId, licenceId) {
+  const { billingBatchId } = await BillingBatchHelper.add({ status: 'sent' })
+  const { billingInvoiceId } = await BillingInvoiceHelper.add({ invoiceAccountId }, { billingBatchId })
+  const { billingInvoiceLicenceId } = await BillingInvoiceLicenceHelper.add(
+    {},
+    { licenceId },
+    { billingInvoiceId }
+  )
+
+  return billingInvoiceLicenceId
+}