fix(vouchers): undo reversals on delete

This commit updates the voucher delete method to undo the "reversal"
flag on the reversed record if the voucher has been removed.  It is
currently a naive method - simply attempt to remove the value if it is
present.  This can be improved in the future by checking the transaction
types first.

Closes #2207.

server/controllers/finance/vouchers.js

@@ -246,8 +246,11 @@ function create(req, res, next) {
  * @function safelyDeleteVoucher
  *
  * @description
- * This function deletes a voucher from the system.  It assumes that
- * checks have already been made for referencing transactions.
+ * This function deletes a voucher from the system.  The method first checks
+ * that a transaction can be deleted using the shared transaction library.
+ * After removing the voucher, it also updates and "reversal" flags if necessary
+ * to ensure that cash payments and invoices do not maintain broken links to
+ * vouchers that have been deleted.
  */
 function safelyDeleteVoucher(guid) {
   const DELETE_TRANSACTION = `
@@ -266,6 +269,25 @@ function safelyDeleteVoucher(guid) {
     DELETE FROM document_map WHERE uuid = ?;
   `;
 
+  // NOTE(@jniles) - this is a naive way of undoing reversals.  If no value is
+  // matched, nothing happens.  This can be improved in the future by first
+  // checking if the voucher's transaction_type is a reversal type, and then
+  // performing or skipping this step based on that result.
+
+  const TOGGLE_INVOICE_REVERSAL = `
+    UPDATE invoice
+      JOIN voucher ON invoice.uuid = voucher.reference_uuid
+      SET invoice.reversed = 0
+      WHERE voucher.uuid = ?;
+  `;
+
+  const TOGGLE_CASH_REVERSAL = `
+    UPDATE cash
+      JOIN voucher ON cash.uuid = voucher.reference_uuid
+      SET cash.reversed = 0
+      WHERE voucher.uuid = ?;
+  `;
+
   return shared.isRemovableTransaction(guid)
     .then(() => {
       const binaryUuid = db.bid(guid);
@@ -275,7 +297,9 @@ function safelyDeleteVoucher(guid) {
         .addQuery(DELETE_TRANSACTION, binaryUuid)
         .addQuery(DELETE_TRANSACTION_HISTORY, binaryUuid)
         .addQuery(DELETE_VOUCHER, binaryUuid)
-        .addQuery(DELETE_DOCUMENT_MAP, binaryUuid);
+        .addQuery(DELETE_DOCUMENT_MAP, binaryUuid)
+        .addQuery(TOGGLE_INVOICE_REVERSAL, binaryUuid)
+        .addQuery(TOGGLE_CASH_REVERSAL, binaryUuid);
 
       return transaction.execute();
     });

server/models/schema.sql

@@ -1397,7 +1397,7 @@ CREATE TABLE `purchase` (
   `user_id`         SMALLINT(5) UNSIGNED NOT NULL,
   `payment_method`  TEXT,
   `note`            TEXT,
-  `status_id`       TINYINT(3) UNSIGNED NOT NULL,   
+  `status_id`       TINYINT(3) UNSIGNED NOT NULL,
   PRIMARY KEY (`uuid`),
   UNIQUE KEY `purchase_1` (`project_id`, `reference`),
   KEY `project_id` (`project_id`),