Implement API functions for market data retrieval

src/lib/api.ts

@@ -0,0 +1,30 @@
+export async function api<T>(path: string, init?: RequestInit) {
+  const res = await fetch(`/api${path}`, { ...init })
+  if (!res.ok) {
+    const text = await res.text().catch(() => '')
+    throw new Error(`API ${res.status}: ${text}`)
+  }
+  return (await res.json()) as T
+}
+
+export type MarketItem = {
+  id: string
+  symbol: string
+  name: string
+  image: string
+  current_price: number
+  market_cap: number
+  price_change_percentage_24h: number
+  price_change_percentage_7d_in_currency?: number
+}
+
+export function getMarkets(vs = 'usd', page = 1, perPage = 100) {
+  return api<MarketItem[]>(`/markets?vs=${vs}&page=${page}&per_page=${perPage}`)
+}
+
+export type Kline = [number, string, string, string, string, string, number, string, number, string, string, string]
+
+export function getBinanceKlines(symbol = 'BTCUSDT', interval = '1m', limit = 500) {
+  const sp = new URLSearchParams({ symbol, interval, limit: String(limit) })
+  return api<Kline[]>(`/binance/klines?${sp.toString()}`)
+}