updates

apps/dashboard/shared/hooks/use-document-totals.ts

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+/**
+ * useDocumentTotals
+ *
+ * Pure calculation hook for invoice-style documents (invoices, bills, estimates,
+ * credit notes, vendor credits, etc.).
+ *
+ * Inputs
+ * ────────────────────────────────────────────────────────────────────────────
+ * lineItems      – flat array of all items (parts + services + expenses)
+ * discountType   – 'no' | 'line_item_level' | 'transaction_level'
+ * discountAmount – used when discountType === 'transaction_level'
+ * taxRate        – percentage (e.g. 15 for 15 %). Undefined → no tax.
+ *
+ * Calculation order
+ * ────────────────────────────────────────────────────────────────────────────
+ * 1. subTotal          = Σ (qty × rate)
+ * 2. lineItemDiscount  = Σ discount_amount  (only when discountType === 'line_item_level')
+ * 3. transactionDiscount = discountAmount   (only when discountType === 'transaction_level')
+ * 4. totalDiscount     = lineItemDiscount + transactionDiscount
+ * 5. afterDiscount     = subTotal - totalDiscount
+ * 6. taxAmount         = afterDiscount × (taxRate / 100)
+ * 7. total             = afterDiscount + taxAmount
+ */
+
+export type DocumentLineItem = {
+    quantity: number
+    rate: number
+    discount_amount?: number
+}
+
+export type UseDocumentTotalsInput = {
+    lineItems: DocumentLineItem[]
+    discountType?: string | null
+    discountAmount?: number
+    taxRate?: number
+}
+
+export type DocumentTotals = {
+    subTotal: number
+    lineItemDiscount: number
+    transactionDiscount: number
+    totalDiscount: number
+    afterDiscount: number
+    taxAmount: number
+    total: number
+    hasLineItems: boolean
+}
+
+export function useDocumentTotals({
+    lineItems,
+    discountType,
+    discountAmount,
+    taxRate,
+}: UseDocumentTotalsInput): DocumentTotals {
+    const subTotal = lineItems.reduce((sum, item) => {
+        const qty = Number(item.quantity) || 0
+        const rate = Number(item.rate) || 0
+        return sum + qty * rate
+    }, 0)
+
+    const lineItemDiscount =
+        discountType === "line_item_level"
+            ? lineItems.reduce((sum, item) => sum + (Number(item.discount_amount) || 0), 0)
+            : 0
+
+    const transactionDiscount =
+        discountType === "transaction_level" ? Number(discountAmount) || 0 : 0
+
+    const totalDiscount = lineItemDiscount + transactionDiscount
+    const afterDiscount = Math.max(0, subTotal - totalDiscount)
+    const taxAmount = taxRate ? afterDiscount * (taxRate / 100) : 0
+    const total = afterDiscount + taxAmount
+
+    return {
+        subTotal,
+        lineItemDiscount,
+        transactionDiscount,
+        totalDiscount,
+        afterDiscount,
+        taxAmount,
+        total,
+        hasLineItems: lineItems.length > 0,
+    }
+}