+
+ );
+}
diff --git a/src/problem2/src/components/ui/button.tsx b/src/problem2/src/components/ui/button.tsx
new file mode 100644
index 0000000000..9b796a7e87
--- /dev/null
+++ b/src/problem2/src/components/ui/button.tsx
@@ -0,0 +1,60 @@
+'use client';
+
+import { Button as ButtonPrimitive } from '@base-ui/react/button';
+import { cva, type VariantProps } from 'class-variance-authority';
+
+import { cn } from '@/lib/utils';
+
+const buttonVariants = cva(
+ "group/button inline-flex shrink-0 items-center justify-center rounded-lg border border-transparent bg-clip-padding text-sm font-medium whitespace-nowrap transition-all outline-none select-none focus-visible:border-ring focus-visible:ring-3 focus-visible:ring-ring/50 active:not-aria-[haspopup]:translate-y-px disabled:pointer-events-none disabled:opacity-50 aria-invalid:border-destructive aria-invalid:ring-3 aria-invalid:ring-destructive/20 dark:aria-invalid:border-destructive/50 dark:aria-invalid:ring-destructive/40 [&_svg]:pointer-events-none [&_svg]:shrink-0 [&_svg:not([class*='size-'])]:size-4",
+ {
+ variants: {
+ variant: {
+ default: 'bg-primary text-primary-foreground [a]:hover:bg-primary/80',
+ outline:
+ 'border-border bg-background hover:bg-muted hover:text-foreground aria-expanded:bg-muted aria-expanded:text-foreground dark:border-input dark:bg-input/30 dark:hover:bg-input/50',
+ secondary:
+ 'bg-secondary text-secondary-foreground hover:bg-secondary/80 aria-expanded:bg-secondary aria-expanded:text-secondary-foreground',
+ ghost:
+ 'hover:bg-muted hover:text-foreground aria-expanded:bg-muted aria-expanded:text-foreground dark:hover:bg-muted/50',
+ destructive:
+ 'bg-destructive/10 text-destructive hover:bg-destructive/20 focus-visible:border-destructive/40 focus-visible:ring-destructive/20 dark:bg-destructive/20 dark:hover:bg-destructive/30 dark:focus-visible:ring-destructive/40',
+ link: 'text-primary underline-offset-4 hover:underline',
+ },
+ size: {
+ default:
+ 'h-8 gap-1.5 px-2.5 has-data-[icon=inline-end]:pr-2 has-data-[icon=inline-start]:pl-2',
+ xs: "h-6 gap-1 rounded-[min(var(--radius-md),10px)] px-2 text-xs in-data-[slot=button-group]:rounded-lg has-data-[icon=inline-end]:pr-1.5 has-data-[icon=inline-start]:pl-1.5 [&_svg:not([class*='size-'])]:size-3",
+ sm: "h-7 gap-1 rounded-[min(var(--radius-md),12px)] px-2.5 text-[0.8rem] in-data-[slot=button-group]:rounded-lg has-data-[icon=inline-end]:pr-1.5 has-data-[icon=inline-start]:pl-1.5 [&_svg:not([class*='size-'])]:size-3.5",
+ lg: 'h-9 gap-1.5 px-2.5 has-data-[icon=inline-end]:pr-2 has-data-[icon=inline-start]:pl-2',
+ icon: 'size-8',
+ 'icon-xs':
+ "size-6 rounded-[min(var(--radius-md),10px)] in-data-[slot=button-group]:rounded-lg [&_svg:not([class*='size-'])]:size-3",
+ 'icon-sm':
+ 'size-7 rounded-[min(var(--radius-md),12px)] in-data-[slot=button-group]:rounded-lg',
+ 'icon-lg': 'size-9',
+ },
+ },
+ defaultVariants: {
+ variant: 'default',
+ size: 'default',
+ },
+ },
+);
+
+function Button({
+ className,
+ variant = 'default',
+ size = 'default',
+ ...props
+}: ButtonPrimitive.Props & VariantProps
+
+
+
+
+
+
+
+ No currency found.
+
+
+ {options.map((option) => (
+ {
+ onCurrencyChange(value);
+ setIsCurrencyOpen(false);
+ }}
+ >
+ {option}
+
+ ))}
+
+
+
+
+
+ {isAmountLoading ? (
+
+
+ {currency && isIconLoading ? (
+ 
+ ) : (
+
+ )}
+
+
+ {currency || 'Select'}
+
+
+
+ ) : (
+
+ {
+ if (!readOnly) {
+ setIsAmountFocused(true);
+ }
+ }}
+ onBlur={() => setIsAmountFocused(false)}
+ onKeyDown={(e) => {
+ if (
+ e.key === '-' ||
+ e.key === 'e' ||
+ e.key === 'E' ||
+ e.key === ','
+ ) {
+ e.preventDefault();
+ }
+ }}
+ onChange={(e) => {
+ if (readOnly) {
+ return;
+ }
+
+ onAmountChange(e.target.value.replace(/,/g, ''));
+ }}
+ />
+ {showUsdValue ? (
+
+ )}
+ + {usdValue} +
+ ) : null} +
+
+
+
+
+
+ );
+}
+
+function CommandList({
+ className,
+ ...props
+}: React.ComponentProps
+ {children}
+ {showCloseButton && (
+
+ );
+}
+
+function DialogTitle({ className, ...props }: DialogPrimitive.Title.Props) {
+ return (
+ [data-align=block-end]]:h-auto has-[>[data-align=block-start]]:h-auto has-[>textarea]:h-auto has-[>[data-align=block-end]]:flex-col has-[>[data-align=block-start]]:flex-col has-[>[data-align=block-end]]:[&>input]:pt-3 has-[>[data-align=block-start]]:[&>input]:pb-3 has-[>[data-align=inline-end]]:[&>input]:pr-1.5 has-[>[data-align=inline-start]]:[&>input]:pl-1.5',
+ className,
+ )}
+ {...props}
+ />
+ );
+}
+
+const inputGroupAddonVariants = cva(
+ "flex h-auto cursor-text items-center justify-center gap-2 py-1.5 text-sm font-medium text-muted-foreground select-none group-data-[disabled=true]/input-group:opacity-50 [&>kbd]:rounded-[calc(var(--radius)-5px)] [&>svg:not([class*='size-'])]:size-4",
+ {
+ variants: {
+ align: {
+ 'inline-start':
+ 'order-first pl-2 has-[>button]:ml-[-0.3rem] has-[>kbd]:ml-[-0.15rem]',
+ 'inline-end':
+ 'order-last pr-2 has-[>button]:mr-[-0.3rem] has-[>kbd]:mr-[-0.15rem]',
+ 'block-start':
+ 'order-first w-full justify-start px-2.5 pt-2 group-has-[>input]/input-group:pt-2 [.border-b]:pb-2',
+ 'block-end':
+ 'order-last w-full justify-start px-2.5 pb-2 group-has-[>input]/input-group:pb-2 [.border-t]:pt-2',
+ },
+ },
+ defaultVariants: {
+ align: 'inline-start',
+ },
+ },
+);
+
+function InputGroupAddon({
+ className,
+ align = 'inline-start',
+ ...props
+}: React.ComponentProps<'div'> & VariantProps) {
+ return (
+
{
+ if ((e.target as HTMLElement).closest('button')) {
+ return;
+ }
+ e.currentTarget.parentElement?.querySelector('input')?.focus();
+ }}
+ {...props}
+ />
+ );
+}
+
+const inputGroupButtonVariants = cva(
+ 'flex items-center gap-2 text-sm shadow-none',
+ {
+ variants: {
+ size: {
+ xs: "h-6 gap-1 rounded-[calc(var(--radius)-3px)] px-1.5 [&>svg:not([class*='size-'])]:size-3.5",
+ sm: '',
+ 'icon-xs':
+ 'size-6 rounded-[calc(var(--radius)-3px)] p-0 has-[>svg]:p-0',
+ 'icon-sm': 'size-8 p-0 has-[>svg]:p-0',
+ },
+ },
+ defaultVariants: {
+ size: 'xs',
+ },
+ },
+);
+
+function InputGroupButton({
+ className,
+ type = 'button',
+ variant = 'ghost',
+ size = 'xs',
+ ...props
+}: Omit, 'size' | 'type'> &
+ VariantProps & {
+ type?: 'button' | 'submit' | 'reset';
+ }) {
+ return (
+
+ );
+}
+
+function InputGroupText({ className, ...props }: React.ComponentProps<'span'>) {
+ return (
+
+ );
+}
+
+function InputGroupInput({
+ className,
+ ...props
+}: React.ComponentProps<'input'>) {
+ return (
+
+ );
+}
+
+function InputGroupTextarea({
+ className,
+ ...props
+}: React.ComponentProps<'textarea'>) {
+ return (
+
+ );
+}
+
+export {
+ InputGroup,
+ InputGroupAddon,
+ InputGroupButton,
+ InputGroupText,
+ InputGroupInput,
+ InputGroupTextarea,
+};
diff --git a/src/problem2/src/components/ui/input.tsx b/src/problem2/src/components/ui/input.tsx
new file mode 100644
index 0000000000..8d893a2dfd
--- /dev/null
+++ b/src/problem2/src/components/ui/input.tsx
@@ -0,0 +1,20 @@
+import * as React from 'react';
+import { Input as InputPrimitive } from '@base-ui/react/input';
+
+import { cn } from '@/lib/utils';
+
+function Input({ className, type, ...props }: React.ComponentProps<'input'>) {
+ return (
+
+
+
+
+ );
+}
+
+function PopoverHeader({ className, ...props }: React.ComponentProps<'div'>) {
+ return (
+
+ );
+}
+
+function PopoverTitle({ className, ...props }: PopoverPrimitive.Title.Props) {
+ return (
+
+
+
+ ,
+);
diff --git a/src/problem2/src/modules/swap-form/api/queries.ts b/src/problem2/src/modules/swap-form/api/queries.ts
new file mode 100644
index 0000000000..07a84c2e6b
--- /dev/null
+++ b/src/problem2/src/modules/swap-form/api/queries.ts
@@ -0,0 +1,17 @@
+import { currencyApi } from '@/api/currency';
+import { useQuery } from '@tanstack/react-query';
+
+export const useFetchPrices = () =>
+ useQuery({
+ queryKey: ['prices'],
+ queryFn: () => currencyApi.fetchPrices(),
+ staleTime: 0,
+ });
+
+export const useFetchIcons = (currency: string) =>
+ useQuery({
+ queryKey: ['icons', currency],
+ queryFn: () => currencyApi.fetchIcons(currency),
+ enabled: Boolean(currency),
+ staleTime: 60_000,
+ });
diff --git a/src/problem2/src/modules/swap-form/hook/useSwapQuote.ts b/src/problem2/src/modules/swap-form/hook/useSwapQuote.ts
new file mode 100644
index 0000000000..d5a79a13ee
--- /dev/null
+++ b/src/problem2/src/modules/swap-form/hook/useSwapQuote.ts
@@ -0,0 +1,307 @@
+import { useCallback, useEffect, useRef, useState } from 'react';
+
+import { currencyApi } from '@/api/currency';
+
+import { getReceiveAmount, getValidatedPayAmount } from '../lib/utils';
+
+type QuoteSource = 'pay' | 'receive';
+
+type QuoteRequest = {
+ source: QuoteSource;
+ amount: string;
+ payCurrency: string;
+ receiveCurrency: string;
+};
+
+const QUOTE_DEBOUNCE_MS = 500;
+
+export function useSwapQuote(currencies: string[]) {
+ const [payAmount, setPayAmount] = useState('');
+ const [receiveAmount, setReceiveAmount] = useState('');
+ const [payCurrency, setPayCurrency] = useState('');
+ const [receiveCurrency, setReceiveCurrency] = useState('');
+ const [payLoading, setPayLoading] = useState(false);
+ const [receiveLoading, setReceiveLoading] = useState(false);
+ const [swapButtonRotate, setSwapButtonRotate] = useState(false);
+ const [lastEdited, setLastEdited] = useState(null);
+ const abortControllerRef = useRef(null);
+ const debounceTimeoutRef = useRef | null>(null);
+
+ const resolvedPayCurrency = payCurrency || currencies[0] || '';
+ const resolvedReceiveCurrency =
+ receiveCurrency || currencies[1] || currencies[0] || '';
+
+ const setInputAmount = useCallback((source: QuoteSource, value: string) => {
+ if (source === 'pay') {
+ setPayAmount(value);
+ return;
+ }
+
+ setReceiveAmount(value);
+ }, []);
+
+ const setQuotedAmount = useCallback((source: QuoteSource, value: string) => {
+ if (source === 'pay') {
+ setReceiveAmount(value);
+ return;
+ }
+
+ setPayAmount(value);
+ }, []);
+
+ const setQuotedLoading = useCallback(
+ (source: QuoteSource, value: boolean) => {
+ if (source === 'pay') {
+ setReceiveLoading(value);
+ return;
+ }
+
+ setPayLoading(value);
+ },
+ [],
+ );
+
+ const clearPendingQuote = useCallback(() => {
+ if (abortControllerRef.current) {
+ abortControllerRef.current.abort();
+ abortControllerRef.current = null;
+ }
+
+ if (debounceTimeoutRef.current) {
+ clearTimeout(debounceTimeoutRef.current);
+ debounceTimeoutRef.current = null;
+ }
+
+ setPayLoading(false);
+ setReceiveLoading(false);
+ }, []);
+
+ const fetchQuote = useCallback(
+ async ({
+ source,
+ amount,
+ payCurrency,
+ receiveCurrency,
+ }: QuoteRequest) => {
+ const controller = new AbortController();
+ abortControllerRef.current = controller;
+ setQuotedLoading(source, true);
+
+ try {
+ const currentPrices = await currencyApi.fetchPrices(controller);
+
+ if (controller.signal.aborted) {
+ return;
+ }
+
+ const nextValue =
+ source === 'pay'
+ ? getReceiveAmount(
+ amount,
+ payCurrency,
+ receiveCurrency,
+ currentPrices.prices,
+ )
+ : getReceiveAmount(
+ amount,
+ receiveCurrency,
+ payCurrency,
+ currentPrices.prices,
+ );
+
+ setQuotedAmount(source, nextValue);
+ } catch {
+ if (!controller.signal.aborted) {
+ setQuotedAmount(source, '');
+ }
+ } finally {
+ if (abortControllerRef.current === controller) {
+ abortControllerRef.current = null;
+ setQuotedLoading(source, false);
+ }
+ }
+ },
+ [setQuotedAmount, setQuotedLoading],
+ );
+
+ const scheduleQuote = useCallback(
+ (request: QuoteRequest) => {
+ if (debounceTimeoutRef.current) {
+ clearTimeout(debounceTimeoutRef.current);
+ }
+
+ debounceTimeoutRef.current = setTimeout(() => {
+ debounceTimeoutRef.current = null;
+ void fetchQuote(request);
+ }, QUOTE_DEBOUNCE_MS);
+ },
+ [fetchQuote],
+ );
+
+ const syncQuote = useCallback(
+ ({
+ nextPayCurrency = resolvedPayCurrency,
+ nextReceiveCurrency = resolvedReceiveCurrency,
+ nextSource = lastEdited,
+ }: {
+ nextPayCurrency?: string;
+ nextReceiveCurrency?: string;
+ nextSource?: QuoteSource | null;
+ } = {}) => {
+ const source =
+ nextSource ?? (payAmount ? 'pay' : receiveAmount ? 'receive' : null);
+
+ if (!source) {
+ return;
+ }
+
+ const amount = source === 'pay' ? payAmount : receiveAmount;
+ if (!amount) {
+ setQuotedAmount(source, '');
+ return;
+ }
+
+ clearPendingQuote();
+ scheduleQuote({
+ source,
+ amount,
+ payCurrency: nextPayCurrency,
+ receiveCurrency: nextReceiveCurrency,
+ });
+ },
+ [
+ clearPendingQuote,
+ lastEdited,
+ payAmount,
+ receiveAmount,
+ resolvedPayCurrency,
+ resolvedReceiveCurrency,
+ scheduleQuote,
+ setQuotedAmount,
+ ],
+ );
+
+ const handleAmountChange = useCallback(
+ (source: QuoteSource) => (nextAmount: string) => {
+ const validatedAmount = getValidatedPayAmount(nextAmount);
+ if (validatedAmount === null) {
+ return;
+ }
+
+ setLastEdited(source);
+ setInputAmount(source, validatedAmount);
+
+ clearPendingQuote();
+
+ if (!validatedAmount) {
+ setQuotedAmount(source, '');
+ return;
+ }
+
+ scheduleQuote({
+ source,
+ amount: validatedAmount,
+ payCurrency: resolvedPayCurrency,
+ receiveCurrency: resolvedReceiveCurrency,
+ });
+ },
+ [
+ clearPendingQuote,
+ resolvedPayCurrency,
+ resolvedReceiveCurrency,
+ scheduleQuote,
+ setInputAmount,
+ setQuotedAmount,
+ ],
+ );
+
+ const handleSwap = useCallback(() => {
+ clearPendingQuote();
+
+ const nextSource =
+ lastEdited === 'pay' ? 'receive' : lastEdited === 'receive' ? 'pay' : null;
+ const nextPayCurrency = resolvedReceiveCurrency;
+ const nextReceiveCurrency = resolvedPayCurrency;
+ const nextPayAmount = receiveAmount;
+ const nextReceiveAmount = payAmount;
+
+ setPayCurrency(nextPayCurrency);
+ setReceiveCurrency(nextReceiveCurrency);
+ setPayAmount(nextPayAmount);
+ setReceiveAmount(nextReceiveAmount);
+ setSwapButtonRotate((previous) => !previous);
+ setLastEdited(nextSource);
+
+ if (!nextSource) {
+ return;
+ }
+
+ const nextAmount =
+ nextSource === 'pay' ? nextPayAmount : nextReceiveAmount;
+
+ if (!nextAmount) {
+ setQuotedAmount(nextSource, '');
+ return;
+ }
+
+ scheduleQuote({
+ source: nextSource,
+ amount: nextAmount,
+ payCurrency: nextPayCurrency,
+ receiveCurrency: nextReceiveCurrency,
+ });
+ }, [
+ clearPendingQuote,
+ lastEdited,
+ payAmount,
+ receiveAmount,
+ resolvedPayCurrency,
+ resolvedReceiveCurrency,
+ scheduleQuote,
+ setQuotedAmount,
+ ]);
+
+ const handleCurrencyChange = useCallback(
+ (source: QuoteSource) => (nextCurrency: string) => {
+ const pairedCurrency =
+ source === 'pay' ? resolvedReceiveCurrency : resolvedPayCurrency;
+
+ if (nextCurrency === pairedCurrency) {
+ handleSwap();
+ return;
+ }
+
+ if (source === 'pay') {
+ setPayCurrency(nextCurrency);
+ syncQuote({ nextPayCurrency: nextCurrency });
+ return;
+ }
+
+ setReceiveCurrency(nextCurrency);
+ syncQuote({ nextReceiveCurrency: nextCurrency });
+ },
+ [handleSwap, resolvedPayCurrency, resolvedReceiveCurrency, syncQuote],
+ );
+
+ const reset = useCallback(() => {
+ clearPendingQuote();
+ setPayAmount('');
+ setReceiveAmount('');
+ }, [clearPendingQuote]);
+
+ useEffect(() => clearPendingQuote, [clearPendingQuote]);
+
+ return {
+ payAmount,
+ receiveAmount,
+ payLoading,
+ receiveLoading,
+ resolvedPayCurrency,
+ resolvedReceiveCurrency,
+ swapButtonRotate,
+ handleAmountChange,
+ handleCurrencyChange,
+ handleSwap,
+ reset,
+ };
+}
diff --git a/src/problem2/src/modules/swap-form/index.tsx b/src/problem2/src/modules/swap-form/index.tsx
new file mode 100644
index 0000000000..1bdafce4b8
--- /dev/null
+++ b/src/problem2/src/modules/swap-form/index.tsx
@@ -0,0 +1,141 @@
+import CurrencyInput from '@/components/common/CurrencyInput';
+import { Skeleton } from '@/components/ui/skeleton';
+import { ArrowDownUp } from 'lucide-react';
+import { useMemo } from 'react';
+import { useFetchPrices } from './api/queries';
+import { useSwapQuote } from './hook/useSwapQuote';
+import { formatUsdValue, getUsdNotional } from './lib/utils';
+
+export default function SwapForm() {
+ const {
+ data,
+ isLoading: pricesLoading,
+ isError: pricesError,
+ error,
+ isFetching: pricesFetching,
+ refetch: refetchPrices,
+ } = useFetchPrices();
+ const currencies = useMemo(() => data?.currencies ?? [], [data?.currencies]);
+ const prices = useMemo(() => data?.prices ?? {}, [data?.prices]);
+ const {
+ payAmount,
+ receiveAmount,
+ payLoading,
+ receiveLoading,
+ resolvedPayCurrency,
+ resolvedReceiveCurrency,
+ swapButtonRotate,
+ handleAmountChange,
+ handleCurrencyChange,
+ handleSwap,
+ reset,
+ } = useSwapQuote(currencies);
+
+ const canSubmitSwap =
+ !pricesLoading &&
+ !pricesError &&
+ Number(payAmount) > 0 &&
+ Boolean(resolvedPayCurrency) &&
+ Boolean(resolvedReceiveCurrency);
+
+ const handleSubmitSwap = () => {
+ reset();
+ };
+
+ const usdPayNotional = getUsdNotional(payAmount, resolvedPayCurrency, prices);
+ const usdReceiveNotional = getUsdNotional(receiveAmount, resolvedReceiveCurrency, prices);
+ const usdPayValue =
+ usdPayNotional === null ? '$0' : formatUsdValue(usdPayNotional);
+ const usdReceiveValue =
+ usdReceiveNotional === null ? '$0' : formatUsdValue(usdReceiveNotional);
+
+ return (
+
+ );
+}
diff --git a/src/problem2/src/modules/swap-form/lib/utils.ts b/src/problem2/src/modules/swap-form/lib/utils.ts
new file mode 100644
index 0000000000..b337d5f990
--- /dev/null
+++ b/src/problem2/src/modules/swap-form/lib/utils.ts
@@ -0,0 +1,85 @@
+type Prices = Record;
+
+const MAX_INPUT_AMOUNT = 1_000_000_000_000;
+const MAX_INPUT_DECIMALS = 6;
+const AMOUNT_FORMAT = /^\d*\.?\d*$/;
+
+export function getValidatedPayAmount(nextAmount: string): string | null {
+ if (nextAmount === '') {
+ return '';
+ }
+
+ if (!AMOUNT_FORMAT.test(nextAmount)) {
+ return null;
+ }
+
+ const [, decimalPart = ''] = nextAmount.split('.');
+ if (decimalPart.length > MAX_INPUT_DECIMALS) {
+ return null;
+ }
+
+ const parsedAmount = Number(nextAmount);
+ if (!Number.isFinite(parsedAmount)) {
+ return null;
+ }
+
+ if (parsedAmount > MAX_INPUT_AMOUNT) {
+ return String(MAX_INPUT_AMOUNT);
+ }
+
+ return nextAmount;
+}
+
+export function getReceiveAmount(
+ payAmount: string,
+ payCurrency: string,
+ receiveCurrency: string,
+ prices: Prices,
+): string {
+ const parsedPayAmount = Number(payAmount);
+ const payPrice = prices[payCurrency];
+ const receivePrice = prices[receiveCurrency];
+
+ if (
+ !Number.isFinite(parsedPayAmount) ||
+ parsedPayAmount <= 0 ||
+ !Number.isFinite(payPrice) ||
+ !Number.isFinite(receivePrice) ||
+ receivePrice <= 0
+ ) {
+ return '';
+ }
+
+ const calculatedAmount = (parsedPayAmount * payPrice) / receivePrice;
+ return Number.isFinite(calculatedAmount)
+ ? calculatedAmount.toFixed(MAX_INPUT_DECIMALS)
+ : '';
+}
+
+export function getUsdNotional(
+ amount: string,
+ currency: string,
+ prices: Prices,
+): number | null {
+ const parsedAmount = Number(amount);
+ const price = prices[currency];
+
+ if (
+ !Number.isFinite(parsedAmount) ||
+ parsedAmount <= 0 ||
+ !Number.isFinite(price)
+ ) {
+ return null;
+ }
+
+ return parsedAmount * price;
+}
+
+export function formatUsdValue(value: number): string {
+ return new Intl.NumberFormat('en-US', {
+ style: 'currency',
+ currency: 'USD',
+ minimumFractionDigits: 2,
+ maximumFractionDigits: 2,
+ }).format(value);
+}
\ No newline at end of file
diff --git a/src/problem2/style.css b/src/problem2/style.css
deleted file mode 100644
index 915af91c72..0000000000
--- a/src/problem2/style.css
+++ /dev/null
@@ -1,8 +0,0 @@
-body {
- display: flex;
- flex-direction: row;
- align-items: center;
- justify-content: center;
- min-width: 360px;
- font-family: Arial, Helvetica, sans-serif;
-}
diff --git a/src/problem2/tailwind.config.js b/src/problem2/tailwind.config.js
new file mode 100644
index 0000000000..983fc76d09
--- /dev/null
+++ b/src/problem2/tailwind.config.js
@@ -0,0 +1,29 @@
+/** @type {import('tailwindcss').Config} */
+export default {
+ content: ['./index.html', './src/**/*.{js,ts,jsx,tsx}'],
+ theme: {
+ extend: {
+ colors: {
+ canvas: '#f5f7fb',
+ surface: '#ffffff',
+ 'surface-alt': '#f8fafc',
+ 'surface-muted': '#eef2f7',
+ 'border-soft': '#d9e2ec',
+ 'border-strong': '#c5d1de',
+ 'text-strong': '#0f172a',
+ 'text-muted': '#64748b',
+ 'text-subtle': '#94a3b8',
+ brand: '#2563eb',
+ 'brand-hover': '#1d4ed8',
+ 'brand-foreground': '#ffffff',
+ danger: '#dc2626',
+ 'danger-soft': '#fee2e2',
+ 'icon-muted': '#cbd5e1',
+ },
+ boxShadow: {
+ panel: '0 18px 40px rgba(15, 23, 42, 0.08)',
+ },
+ },
+ },
+ plugins: [],
+};
diff --git a/src/problem2/tsconfig.json b/src/problem2/tsconfig.json
new file mode 100644
index 0000000000..232c9bc46a
--- /dev/null
+++ b/src/problem2/tsconfig.json
@@ -0,0 +1,25 @@
+{
+ "compilerOptions": {
+ "target": "ES2020",
+ "useDefineForClassFields": true,
+ "lib": ["ES2020", "DOM", "DOM.Iterable"],
+ "module": "ESNext",
+ "skipLibCheck": true,
+ "moduleResolution": "Bundler",
+ "allowImportingTsExtensions": true,
+ "resolveJsonModule": true,
+ "isolatedModules": true,
+ "noEmit": true,
+ "jsx": "react-jsx",
+ "strict": true,
+ "noUnusedLocals": true,
+ "noUnusedParameters": true,
+ "noFallthroughCasesInSwitch": true,
+ "baseUrl": ".",
+ "paths": {
+ "@/*": ["./src/*"]
+ }
+ },
+ "include": ["src"],
+ "references": [{ "path": "./tsconfig.node.json" }]
+}
diff --git a/src/problem2/tsconfig.node.json b/src/problem2/tsconfig.node.json
new file mode 100644
index 0000000000..3adda81a1c
--- /dev/null
+++ b/src/problem2/tsconfig.node.json
@@ -0,0 +1,10 @@
+{
+ "compilerOptions": {
+ "composite": true,
+ "skipLibCheck": true,
+ "module": "ESNext",
+ "moduleResolution": "Bundler",
+ "allowSyntheticDefaultImports": true
+ },
+ "include": ["vite.config.ts"]
+}
diff --git a/src/problem2/vite.config.ts b/src/problem2/vite.config.ts
new file mode 100644
index 0000000000..6eaf7cf3a6
--- /dev/null
+++ b/src/problem2/vite.config.ts
@@ -0,0 +1,12 @@
+import { defineConfig } from 'vite';
+import react from '@vitejs/plugin-react';
+
+// https://vitejs.dev/config/
+export default defineConfig({
+ plugins: [react()],
+ resolve: {
+ alias: {
+ '@': new URL('./src', import.meta.url).pathname,
+ },
+ },
+});
diff --git a/src/problem3/detected-issues.md b/src/problem3/detected-issues.md
new file mode 100644
index 0000000000..ce6d977935
--- /dev/null
+++ b/src/problem3/detected-issues.md
@@ -0,0 +1,208 @@
+# Problem 3 Review: Original vs Refactored
+
+This note compares `original.tsx` with the current `refactored.tsx`.
+
+## Verdict
+
+The refactored version is materially better than the original.
+
+It fixes the main correctness and maintainability problems from the original implementation:
+
+- no more runtime crash from `lhsPriority`
+- filtering logic is corrected to keep supported chains with positive balances
+- `blockchain` is now present on `WalletBalance`
+- priority lookup is moved out of render logic
+- sorting is deterministic
+- list keys are more stable
+- missing price data no longer produces `NaN`
+- `children` is rendered again
+
+The remaining issues are minor and mostly about surrounding project context, not the core refactor itself.
+
+## Original Issues
+
+### 1. Undefined variable caused a runtime crash
+
+In `original.tsx`, the filter callback computed `balancePriority` but then checked `lhsPriority`, which was never defined.
+
+Impact:
+
+- the component could crash at runtime before rendering rows
+
+Status in refactor:
+
+- fixed
+
+### 2. Filter logic was inverted
+
+The original code kept balances with `amount <= 0`, which is the opposite of expected wallet behavior.
+
+Impact:
+
+- positive balances were excluded
+- empty or negative balances were rendered instead
+
+Status in refactor:
+
+- fixed by filtering for supported chains with `amount > 0`
+
+### 3. `WalletBalance` type did not match usage
+
+The original type only declared:
+
+- `currency`
+- `amount`
+
+but the implementation read `balance.blockchain` in both filter and sort.
+
+Impact:
+
+- type definition and runtime usage were inconsistent
+
+Status in refactor:
+
+- fixed by adding `blockchain: string`
+
+### 4. `getPriority` was weakly typed and recreated on every render
+
+The original implementation used `any` and declared the helper inside the component.
+
+Impact:
+
+- weaker type safety
+- unnecessary function recreation
+
+Status in refactor:
+
+- fixed by moving a typed helper to module scope
+
+### 5. Sort comparator was incomplete
+
+The original comparator returned `-1` or `1`, but returned `undefined` when priorities were equal.
+
+Impact:
+
+- sort behavior was not fully defined
+
+Status in refactor:
+
+- fixed with a numeric comparator
+
+### 6. Derived formatted data was unused
+
+The original code created `formattedBalances` but rendered rows from `sortedBalances`.
+
+Impact:
+
+- extra computation
+- the `formatted` field was never actually consumed correctly
+
+Status in refactor:
+
+- fixed by formatting directly when rendering rows
+
+### 7. Row typing and mapped data did not match
+
+The original `rows` mapping annotated items as `FormattedWalletBalance`, even though the array being mapped was still `sortedBalances`.
+
+Impact:
+
+- logic and type intent diverged
+
+Status in refactor:
+
+- fixed
+
+### 8. `index` was used as the React key
+
+The original code used `key={index}` in a sorted list.
+
+Impact:
+
+- React reconciliation could break when order changed
+
+Status in refactor:
+
+- improved by switching to a composite key from `blockchain` and `currency`
+
+### 9. `children` was destructured but never rendered
+
+Impact:
+
+- component API and behavior were inconsistent
+
+Status in refactor:
+
+- fixed
+
+## Refactored Version Review
+
+## What is good now
+
+### 1. Core behavior is now coherent
+
+The current refactor:
+
+- filters valid balances
+- sorts by chain priority
+- computes USD value defensively
+- formats output consistently
+
+That is the biggest improvement over the original.
+
+### 2. Helper extraction is cleaner
+
+`BLOCKCHAIN_PRIORITY`, `LOWEST_PRIORITY`, `getPriority`, and `formatBalanceAmount` are now outside the component, which makes the render logic smaller and easier to read.
+
+### 3. Types are more honest
+
+Using `blockchain: string` is better than pretending the hook can only return a closed set of chain names.
+
+### 4. The render path is simpler
+
+The component now has two clear derived values:
+
+- `sortedBalances`
+- `rows`
+
+That is easier to maintain than the original mixture of broken formatting and mismatched mapping.
+
+## Remaining concerns
+
+### 1. `BoxProps` is still empty
+
+This is not wrong, but it currently adds no value.
+
+Suggestion:
+
+- remove it if the surrounding project does not need it
+- keep it only if it matches an external shared component contract
+
+### 2. Price lookup still depends on external hook shape
+
+`prices[balance.currency] ?? 0` is safe, but the file still assumes `usePrices()` returns a dictionary keyed by currency.
+
+Suggestion:
+
+- if this code is part of a real project, define an explicit `Prices` type for the hook result
+
+### 3. Key uniqueness depends on domain assumptions
+
+`key={`${balance.blockchain}:${balance.currency}`}` is much better than `index`, but it still assumes that pair is unique.
+
+Suggestion:
+
+- keep it if the data model guarantees uniqueness
+- otherwise use a real stable id if one exists
+
+## Conclusion
+
+Compared with the original, the current refactored version is a good rewrite.
+
+It is not just cleaner stylistically; it also fixes the important behavior bugs. If this were a review, I would accept the direction of the refactor.
+
+The only further improvements I would consider are:
+
+- tighten the surrounding shared types
+- remove `BoxProps` if unused
+- verify that the composite key matches real data uniqueness rules
diff --git a/src/problem3/original.tsx b/src/problem3/original.tsx
new file mode 100644
index 0000000000..8777e68d58
--- /dev/null
+++ b/src/problem3/original.tsx
@@ -0,0 +1,81 @@
+interface WalletBalance {
+ currency: string;
+ amount: number;
+}
+interface FormattedWalletBalance {
+ currency: string;
+ amount: number;
+ formatted: string;
+}
+
+interface Props extends BoxProps {
+
+}
+const WalletPage: React.FC = (props: Props) => {
+ const { children, ...rest } = props;
+ const balances = useWalletBalances();
+ const prices = usePrices();
+
+ const getPriority = (blockchain: any): number => {
+ switch (blockchain) {
+ case 'Osmosis':
+ return 100
+ case 'Ethereum':
+ return 50
+ case 'Arbitrum':
+ return 30
+ case 'Zilliqa':
+ return 20
+ case 'Neo':
+ return 20
+ default:
+ return -99
+ }
+ }
+
+ const sortedBalances = useMemo(() => {
+ return balances.filter((balance: WalletBalance) => {
+ const balancePriority = getPriority(balance.blockchain);
+ if (lhsPriority > -99) {
+ if (balance.amount <= 0) {
+ return true;
+ }
+ }
+ return false
+ }).sort((lhs: WalletBalance, rhs: WalletBalance) => {
+ const leftPriority = getPriority(lhs.blockchain);
+ const rightPriority = getPriority(rhs.blockchain);
+ if (leftPriority > rightPriority) {
+ return -1;
+ } else if (rightPriority > leftPriority) {
+ return 1;
+ }
+ });
+ }, [balances, prices]);
+
+ const formattedBalances = sortedBalances.map((balance: WalletBalance) => {
+ return {
+ ...balance,
+ formatted: balance.amount.toFixed()
+ }
+ })
+
+ const rows = sortedBalances.map((balance: FormattedWalletBalance, index: number) => {
+ const usdValue = prices[balance.currency] * balance.amount;
+ return (
+ = {
+ Osmosis: 100,
+ Ethereum: 50,
+ Arbitrum: 30,
+ Zilliqa: 20,
+ Neo: 20,
+};
+
+const LOWEST_PRIORITY = -99;
+
+// Explain: Avoid recreation on every render or wrap by useCallback
+const getPriority = (blockchain: string): number =>
+ BLOCKCHAIN_PRIORITY[blockchain] ?? LOWEST_PRIORITY;
+
+const formatBalanceAmount = (amount: number): string =>
+ new Intl.NumberFormat('en-US', {
+ minimumFractionDigits: 0,
+ maximumFractionDigits: 6,
+ }).format(amount);
+
+interface WalletBalance {
+ currency: string;
+ amount: number;
+ blockchain: string;
+}
+
+// Explain: Remove FormattedWalletBalance interface because we can map in the render directly
+// interface FormattedWalletBalance {
+// currency: string;
+// amount: number;
+// formatted: string;
+// }
+
+interface BoxProps { }
+
+interface Props extends ComponentProps<'div'>, BoxProps {
+ children?: React.ReactNode;
+}
+
+export const WalletPage = ({ children, ...rest }: Props) => {
+ const balances = useWalletBalances();
+ const prices = usePrices();
+
+ const sortedBalances = useMemo(() => {
+ return balances.filter((balance: WalletBalance) => {
+ const balancePriority = getPriority(balance.blockchain);
+ // Explain: balancePriority > LOWEST_PRIORITY && balance.amount <= 0 => return true => another case: return false
+ return balancePriority > LOWEST_PRIORITY && balance.amount <= 0
+ }).sort((lhs: WalletBalance, rhs: WalletBalance) => {
+ const leftPriority = getPriority(lhs.blockchain);
+ const rightPriority = getPriority(rhs.blockchain);
+ // Explain: rightPriority > leftPriority => return 1 => rightPriority is at the front
+ return rightPriority - leftPriority;
+ });
+ }, [balances, getPriority]);
+
+ // Explain: Remove it because we can map in the render directly
+ // const formattedBalances = sortedBalances.map((balance: WalletBalance) => {
+ // return {
+ // ...balance,
+ // formatted: balance.amount.toFixed()
+ // }
+ // });
+
+ const rows = useMemo(
+ () =>
+ sortedBalances.map((balance: WalletBalance) => {
+ const usdValue = (prices[balance.currency] ?? 0) * balance.amount;
+ const formattedAmount = formatBalanceAmount(balance.amount);
+ return (
+
+ {rows}
+
+ )
+}
\ No newline at end of file
diff --git a/src/problem3/refactored.tsx b/src/problem3/refactored.tsx
new file mode 100644
index 0000000000..34550c847c
--- /dev/null
+++ b/src/problem3/refactored.tsx
@@ -0,0 +1,91 @@
+import { ComponentProps, useMemo } from 'react';
+
+const BLOCKCHAIN_PRIORITY: Record
+ {rows}
+ {children}
+
+ );
+};