feat: Enhance pricing and sales API with free goods and discount scheme support

distribution_fe/lib/api/sales.ts

@@ -21,16 +21,22 @@ export interface ShopPOItemBody {
   itemId: string
   quantity: number
   unitPrice?: number | null
+  /** Free issue accepted from a scheme suggestion; priced 0 by the server. */
+  isFree?: boolean
+  schemeId?: string | null
 }
 
 export interface CreateShopPOBody {
   storeId: string
   items: ShopPOItemBody[]
   raisedByUserId?: string | null
+  /** The one flat/slab discount scheme the user accepted. */
+  discountSchemeIds?: string[]
 }
 
 export interface UpdateShopPOItemsBody {
   items: ShopPOItemBody[]
+  discountSchemeIds?: string[]
 }
 
 export interface ShopPOListParams extends PageParams {
@@ -97,8 +103,12 @@ export const invoices = {
   finalize: (id: string, finalizedByUserId?: string | null, adjustments?: { invoiceItemId: string; adjustedQuantity: number; isRemoved?: boolean }[]) =>
     api.post<InvoiceResponse>(`/invoices/${id}/finalize`, { finalizedByUserId, adjustments }).then(r => r.data),
 
-  updateItems: (id: string, items: { invoiceItemId?: string; itemId?: string; quantity: number; unitPrice?: number | null; isRemoved?: boolean }[], editedByUserId?: string | null) =>
-    api.put<InvoiceResponse>(`/invoices/${id}/items`, { items, editedByUserId }).then(r => r.data),
+  updateItems: (id: string, items: { invoiceItemId?: string; itemId?: string; quantity: number; unitPrice?: number | null; isRemoved?: boolean }[], editedByUserId?: string | null, discountSchemeIds?: string[]) =>
+    api.put<InvoiceResponse>(`/invoices/${id}/items`, { items, editedByUserId, discountSchemeIds }).then(r => r.data),
+
+  /** What the discount and total would be for these unsaved lines (draft editor preview). */
+  previewTotals: (id: string, items: { itemId: string; quantity: number; unitPrice: number; isFree?: boolean; isRemoved?: boolean; schemeId?: string | null }[], discountSchemeIds?: string[]) =>
+    api.post<{ discountAmount: number; totalAmount: number; freeEntitlements: { schemeId: string; quantity: number }[] }>(`/invoices/${id}/preview-totals`, { items, discountSchemeIds }).then(r => r.data),
 
   versions: (id: string) =>
     api.get<InvoiceVersionResponse[]>(`/invoices/${id}/versions`).then(r => r.data),