Implement API proxy with CORS support

worker/index.ts

@@ -0,0 +1,57 @@
+export interface Env {
+  CG_KEY?: string
+}
+
+const CORS_HEADERS = {
+  'access-control-allow-origin': '*',
+  'access-control-allow-headers': 'Content-Type, Authorization',
+  'access-control-allow-methods': 'GET, OPTIONS',
+}
+
+function json(data: unknown, init: ResponseInit = {}) {
+  return new Response(JSON.stringify(data), {
+    headers: { 'content-type': 'application/json', ...CORS_HEADERS },
+    ...init,
+  })
+}
+
+async function proxyFetch(url: string, headers: Record<string, string> = {}) {
+  const res = await fetch(url, { headers })
+  if (!res.ok) {
+    const text = await res.text().catch(() => '')
+    return json({ error: true, status: res.status, body: text }, { status: res.status })
+  }
+  const data = await res.json()
+  return json(data, { headers: { 'cache-control': 'max-age=10' } })
+}
+
+export default {
+  async fetch(req: Request, env: Env) {
+    if (req.method === 'OPTIONS') return new Response(null, { headers: CORS_HEADERS })
+
+    const url = new URL(req.url)
+    const { pathname, searchParams } = url
+
+    if (pathname === '/api/health') return json({ ok: true, ts: Date.now() })
+
+    if (pathname === '/api/markets') {
+      const vs = searchParams.get('vs') ?? 'usd'
+      const page = searchParams.get('page') ?? '1'
+      const perPage = searchParams.get('per_page') ?? '100'
+      const target = `https://api.coingecko.com/api/v3/coins/markets?vs_currency=${vs}&order=market_cap_desc&per_page=${perPage}&page=${page}&price_change_percentage=1h,24h,7d`
+      const headers: Record<string, string> = {}
+      if (env.CG_KEY) headers['x-cg-demo-api-key'] = env.CG_KEY
+      return proxyFetch(target, headers)
+    }
+
+    if (pathname === '/api/binance/klines') {
+      const symbol = searchParams.get('symbol') ?? 'BTCUSDT'
+      const interval = searchParams.get('interval') ?? '1m'
+      const limit = searchParams.get('limit') ?? '500'
+      const target = `https://api.binance.com/api/v3/klines?symbol=${symbol}&interval=${interval}&limit=${limit}`
+      return proxyFetch(target)
+    }
+
+    return json({ error: 'Not found' }, { status: 404 })
+  },
+}