fix: implement complete partial payment handling

models/baseModels/AccountingSettings/AccountingSettings.ts

@@ -25,6 +25,7 @@ export class AccountingSettings extends Doc {
   enablePricingRule?: boolean;
   enableERPNextSync?: boolean;
   enablePointOfSaleWithOutInventory?: boolean;
+  enablePartialPayment?: boolean;
 
   static filters: FiltersMap = {
     writeOffAccount: () => ({

models/baseModels/Invoice/Invoice.ts

@@ -838,7 +838,10 @@ export abstract class Invoice extends Transactional {
           if (sinvreturnedDoc.outstandingAmount?.isZero()) {
             return this.grandTotal;
           } else {
-            return this.fyo.pesa(0);
+            const returnAmount = this.grandTotal
+              ?.abs()
+              .sub(sinvreturnedDoc.outstandingAmount as Money);
+            return returnAmount;
           }
         }
 

models/baseModels/Payment/Payment.ts

@@ -42,6 +42,7 @@ export class Payment extends Transactional {
   referenceType?: ModelNameEnum.SalesInvoice | ModelNameEnum.PurchaseInvoice;
   for?: PaymentFor[];
   _accountsMap?: AccountTypeMap;
+  initialAmount?: Money;
 
   async paymentMethodDoc() {
     return (await this.loadAndGetLink('paymentMethod')) as PaymentMethod;
@@ -112,6 +113,7 @@ export class Payment extends Transactional {
     }
 
     await this.validateFor();
+    this.validatePartialAmount();
     this.validateAccounts();
     this.validateTotalReferenceAmount();
     await this.validateReferences();
@@ -445,6 +447,24 @@ export class Payment extends Transactional {
     throw new ValidationError(message);
   }
 
+  validatePartialAmount() {
+    if (!this.fyo.singles.AccountingSettings?.enablePartialPayment) {
+      const amount =
+        (this.amountPaid as Money)?.isZero?.() === false
+          ? (this.amountPaid as Money)
+          : (this.amount as Money);
+      const initialAmount = this.initialAmount as Money;
+      if (amount.lt(initialAmount) && !amount.eq(initialAmount)) {
+        if (this.writeoff?.isZero()) {
+          this.amount = this.initialAmount;
+          throw new ValidationError(
+            this.fyo.t`Enable Partial payment to pay partial amount`
+          );
+        }
+      }
+    }
+  }
+
   async afterSubmit() {
     await super.afterSubmit();
     await this.updateReferenceDocOutstanding();
@@ -703,17 +723,23 @@ export class Payment extends Transactional {
         return;
       }
 
-      const amount = (this.getSum('for', 'amount', false) as Money).abs();
-
-      if ((value as Money).gt(amount)) {
+      if (!this.initialAmount) {
+        this.initialAmount = this.amount as Money;
+      }
+      const moneyValue = value as Money;
+      if (moneyValue.gt(this.initialAmount)) {
         throw new ValidationError(
-          this.fyo.t`Payment amount cannot 
-              exceed ${this.fyo.format(amount, 'Currency')}.`
+          this.fyo.t`Payment amount cannot exceed ${this.fyo.format(
+            this.initialAmount,
+            'Currency'
+          )}.`
         );
-      } else if ((value as Money).isZero()) {
+      } else if (moneyValue.isZero()) {
         throw new ValidationError(
-          this.fyo.t`Payment amount cannot
-              be ${this.fyo.format(value, 'Currency')}.`
+          this.fyo.t`Payment amount cannot be ${this.fyo.format(
+            moneyValue,
+            'Currency'
+          )}.`
         );
       }
     },

models/baseModels/SalesInvoice/SalesInvoice.ts

@@ -115,10 +115,12 @@ export class SalesInvoice extends Invoice {
         ((value as number) || 0) *
         ((loyaltyProgramDoc?.conversionFactor as number) || 0);
 
-      if (this.grandTotal?.lt(loyaltyPoint)) {
-        throw new ValidationError(
-          t`no need ${value as number} points to purchase this item`
-        );
+      if (!this.isReturn) {
+        if (this.grandTotal?.lt(loyaltyPoint)) {
+          throw new ValidationError(
+            t`no need ${value as number} points to purchase this item`
+          );
+        }
       }
     },
   };

schemas/app/AccountingSettings.json

@@ -142,6 +142,13 @@
       "default": false,
       "section": "Features"
     },
+    {
+      "fieldname": "enablePartialPayment",
+      "label": "Enable Partial Payment",
+      "fieldtype": "Check",
+      "default": false,
+      "section": "Features"
+    },
     {
       "fieldname": "fiscalYearStart",
       "label": "Fiscal Year Start Date",