build ui for adding and displaying added items

src/App.tsx

@@ -1,3 +0,0 @@
-export default function App() {
-  return <h1 className="text-3xl font-bold text-blue-600 p-4">Bill Generator</h1>
-}

src/components/App.tsx

@@ -0,0 +1,46 @@
+import { useBill } from "../hooks";
+import { BillItemRow } from "./BillItemRow";
+import { ItemForm } from "./ItemForm";
+
+export default function App() {
+  const {
+    bill,
+    computedBill,
+    updateTitle,
+    updateCurrency,
+    updateTax,
+    addItem,
+    removeItem,
+    resetBill,
+  } = useBill();
+  return (
+    <div className="min-h-screen bg-gray-50">
+      <div className="max-w-md mx-auto">
+        <div className="px-4 py-4 flex flex-col gap-4">
+          <ItemForm currency={bill.currency} onAdd={addItem} />
+          {computedBill.items.length > 0 && (
+            <div className="bg-white rounded-2xl px-4 shadow-sm">
+              {computedBill.items.map((item) => (
+                <BillItemRow
+                  key={item.id}
+                  currency={bill.currency}
+                  item={item}
+                  onRemove={removeItem}
+                />
+              ))}
+            </div>
+          )}
+
+          {computedBill.items.length > 0 && (
+            <button
+              className="w-full border border-gray-200 text-gray-400 hover:text-red-400 hover:border-red-200 py-3 rounded-xl text-sm transition-all cursor-pointer"
+              onClick={resetBill}
+            >
+              Clear bill
+            </button>
+          )}
+        </div>
+      </div>
+    </div>
+  );
+}

src/components/BillItemRow.tsx

@@ -0,0 +1,35 @@
+import type { ComputedBillItem } from "../types";
+import { formatCurrency } from "../utils";
+
+interface BillItemRowProps {
+  item: ComputedBillItem;
+  currency: string;
+  onRemove: (id: string) => void;
+}
+
+export function BillItemRow({ item, currency, onRemove }: BillItemRowProps) {
+  return (
+    <div className="flex items-center justify-between border-b border-gray-100 last:border-0 py-3">
+      <div className="flex-1 min-w-0">
+        <p className="text-sm font-medium text-gray-800 truncate">
+          {item.name}
+        </p>
+        <p className="text-xs text-gray-400 mt-0.5">
+          {item.quantity} ☓ {formatCurrency(item.unitPrice, currency)}
+        </p>
+      </div>
+
+      <div className="flex items-center gap-3 ml-3">
+        <span className="text-sm font-semibold text-gray-800">
+          {formatCurrency(item.finalPrice, currency)}
+        </span>
+        <button
+          className="text-gray-300 transition-colors hover:text-red-400 text-large leading-none"
+          onClick={() => onRemove(item.id)}
+        >
+          ☓
+        </button>
+      </div>
+    </div>
+  );
+}

src/components/ItemForm.tsx

@@ -0,0 +1,91 @@
+import { useState } from "react";
+import type { BillItemForm } from "../types";
+
+interface ItemFormProps {
+  currency: string;
+  onAdd: (form: BillItemForm) => void;
+}
+
+const emptyForm: BillItemForm = {
+  name: "",
+  quantity: 1,
+  unitPrice: 0,
+};
+
+export function ItemForm({ currency, onAdd }: ItemFormProps) {
+  const [form, setForm] = useState<BillItemForm>(emptyForm);
+  const [error, setError] = useState<string | null>(null);
+
+  function handleSubmit() {
+    if (!form.name.trim()) {
+      setError("Item name is required");
+      return;
+    }
+    if (form.quantity <= 0) {
+      setError("Quantity must be greater than 0");
+      return;
+    }
+    if (form.unitPrice <= 0) {
+      setError("Price must be greater than 0");
+      return;
+    }
+    onAdd(form);
+    setForm(emptyForm);
+    setError(null);
+  }
+
+  return (
+    <div className="bg-white rounded-2xl p-4 shadow-sm">
+      <h2 className="text-sm font-semibold text-gray-500 uppercase tracking-wide mb-3">
+        Add Item
+      </h2>
+
+      <div className="flex flex-col gap-3">
+        <input
+          type="text"
+          placeholder="Item name"
+          value={form.name}
+          onChange={(e) =>
+            setForm((prev) => ({ ...prev, name: e.target.value }))
+          }
+          className="w-full border border-gray-200 rounded-xl px-4 py-3 text-sm focus:outline-none focus:ring-2 focus:ring-indigo-400"
+        />
+
+        <div className="flex gap-2">
+          <input
+            type="number"
+            placeholder="Qty"
+            value={form.quantity}
+            min={1}
+            onChange={(e) =>
+              setForm((prev) => ({ ...prev, quantity: Number(e.target.value) }))
+            }
+            className="w-1/3 border border-gray-200 rounded-xl px-4 py-3 text-sm focus:outline-none focus:ring-2 focus:ring-indigo-400"
+          />
+          <input
+            type="number"
+            placeholder={`Unit price (${currency})`}
+            value={form.unitPrice}
+            min={0}
+            onChange={(e) =>
+              setForm((prev) => ({
+                ...prev,
+                unitPrice: Number(e.target.value),
+              }))
+            }
+            className="w-2/3 border border-gray-200 rounded-xl px-4 py-3 text-sm focus:outline-none focus:ring-2 focus:ring-indigo-400"
+          />
+        </div>
+
+        {error && <p className="text-red-500 text-xs px-1">{error}</p>}
+
+        <button
+          onClick={handleSubmit}
+          className="w-full bg-indigo-500 hover:bg-indigo-600 active:scale-95 text-white font-semibold py-3 rounded-xl text-sm transition-all"
+        >
+          + Add Item
+        </button>
+      </div>
+    </div>
+  );
+}

src/hooks/index.ts

@@ -0,0 +1 @@
+export * from "./useBill";

src/hooks/useBill.ts

@@ -0,0 +1,78 @@
+import { useCallback, useState } from "react";
+import { Currency, TaxType } from "../types";
+import type { Bill, BillItem, BillItemForm, ComputedBill } from "../types";
+import { computeBill, generateId } from "../utils";
+
+export function useBill() {
+  const [bill, setBill] = useState<Bill>({
+    id: generateId(),
+    title: "New Bill",
+    currency: Currency.INR,
+    createdAt: new Date(),
+    taxPercent: 18,
+    taxType: TaxType.GST,
+    items: [],
+  });
+
+  const computedBill: ComputedBill = computeBill(bill);
+
+  const updateTitle = useCallback((title: string) => {
+    setBill((prev) => ({ ...prev, title }));
+  }, []);
+
+  const updateCurrency = useCallback((currency: Currency) => {
+    setBill((prev) => ({ ...prev, currency }));
+  }, []);
+
+  const updateTax = useCallback((taxType: TaxType, taxPercent: number) => {
+    setBill((prev) => ({ ...prev, taxType, taxPercent }));
+  }, []);
+
+  const addItem = useCallback((form: BillItemForm) => {
+    const newItem: BillItem = {
+      ...form,
+      id: generateId(),
+    };
+    setBill((prev) => ({ ...prev, items: [...prev.items, newItem] }));
+  }, []);
+
+  const updateItem = useCallback((id: string, form: BillItemForm) => {
+    setBill((prev) => ({
+      ...prev,
+      items: prev.items.map((item) =>
+        item.id === id ? { ...item, ...form } : item,
+      ),
+    }));
+  }, []);
+
+  const removeItem = useCallback((id: string) => {
+    setBill((prev) => ({
+      ...prev,
+      items: prev.items.filter((item) => item.id !== id),
+    }));
+  }, []);
+
+  const resetBill = useCallback(() => {
+    setBill({
+      id: generateId(),
+      title: "New Bill",
+      currency: Currency.INR,
+      createdAt: new Date(),
+      taxPercent: 18,
+      taxType: TaxType.GST,
+      items: [],
+    });
+  }, []);
+
+  return {
+    bill,
+    computedBill,
+    updateTitle,
+    updateCurrency,
+    updateTax,
+    addItem,
+    updateItem,
+    removeItem,
+    resetBill,
+  };
+}

src/main.tsx

@@ -1,10 +1,10 @@
-import { StrictMode } from 'react'
-import { createRoot } from 'react-dom/client'
-import './index.css'
-import App from './App.tsx'
+import { StrictMode } from "react";
+import { createRoot } from "react-dom/client";
+import "./index.css";
+import App from "./components/App";
 
-createRoot(document.getElementById('root')!).render(
+createRoot(document.getElementById("root")!).render(
   <StrictMode>
     <App />
   </StrictMode>,
-)
+);

src/types/index.ts

@@ -0,0 +1,51 @@
+export interface BillItem {
+  id: string;
+  name: string;
+  quantity: number;
+  unitPrice: number;
+}
+
+export enum Currency {
+  INR = "INR",
+  USD = "USD",
+}
+
+export enum TaxType {
+  None = "NONE",
+  GST = "GST",
+  VAT = "VAT",
+}
+
+export interface Bill {
+  id: string;
+  title: string;
+  currency: Currency;
+  taxType: TaxType;
+  taxPercent: number;
+  items: BillItem[];
+  createdAt: Date;
+}
+
+export type ComputedBillItem = BillItem & {
+  finalPrice: number;
+};
+
+// export interface ComputedBillItem extends BillItem {
+//     finalPrice: number;
+// }
+
+// export type ComputedBill = Bill & {
+//   subtotal: number;
+//   taxAmount: number;
+//   total: number;
+//   items: ComputedBillItem[];
+// };
+
+export interface ComputedBill extends Bill {
+  subtotal: number;
+  taxAmount: number;
+  total: number;
+  items: ComputedBillItem[];
+}
+
+export type BillItemForm = Omit<BillItem, "id">;

src/utils/calculator.ts

@@ -0,0 +1,47 @@
+import type { Bill, BillItem, ComputedBill, ComputedBillItem } from "../types";
+
+export function findById<T extends { id: string }>(
+  items: T[],
+  id: string,
+): T | undefined {
+  return items.find((item) => item.id === id);
+}
+
+export function computeItem(item: BillItem): ComputedBillItem {
+  return {
+    ...item,
+    finalPrice: item.unitPrice * item.quantity,
+  };
+}
+
+export function computeBill(bill: Bill): ComputedBill {
+  const computedItems = bill.items.map(computeItem);
+
+  const subtotal = computedItems.reduce(
+    (sum, item) => sum + item.finalPrice,
+    0,
+  );
+
+  const taxAmount = (subtotal * bill.taxPercent) / 100;
+  const total = subtotal + taxAmount;
+
+  return {
+    ...bill,
+    items: computedItems,
+    subtotal,
+    taxAmount,
+    total,
+  };
+}
+
+export function formatCurrency(amount: number, currency: string): string {
+  return new Intl.NumberFormat("en-IN", {
+    style: "currency",
+    currency,
+    minimumFractionDigits: 2,
+  }).format(amount);
+}
+
+export function generateId(): string {
+  return Math.random().toString(36).slice(2, 9);
+}

src/utils/index.ts

@@ -0,0 +1 @@
+export * from "./calculator";

tsconfig.app.json

@@ -18,7 +18,7 @@
     /* Linting */
     "noUnusedLocals": true,
     "noUnusedParameters": true,
-    "erasableSyntaxOnly": true,
+    "erasableSyntaxOnly": false,
     "noFallthroughCasesInSwitch": true
   },
   "include": ["src"]

tsconfig.node.json

@@ -17,7 +17,7 @@
     /* Linting */
     "noUnusedLocals": true,
     "noUnusedParameters": true,
-    "erasableSyntaxOnly": true,
+    "erasableSyntaxOnly": false,
     "noFallthroughCasesInSwitch": true
   },
   "include": ["vite.config.ts"]