Every dollar accounted for.

/**
 * POC 02 — On-Chain USDC Reserve Ratio
 * Cloudflare Pages Function
 *
 * Reads USDC totalSupply on Base + Ethereum via public RPC,
 * plus the Chainlink USDC/USD price feed, to compute a live
 * reserve confidence indicator.
 *
 * Deploy: Drop into /functions/api/reserve-ratio.js
 * No API keys — uses public RPCs only.
 */

const USDC_BASE = '0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913';
const USDC_ETH  = '0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48';
const CL_USDC   = '0x8fFfFfd4AfB6115b954Bd326cbe7B4BA576818f6';

const RPC_BASE = 'https://mainnet.base.org';
const RPC_ETH  = 'https://eth.llamarpc.com';

const TOTAL_SUPPLY = '0x18160ddd';  // totalSupply()
const LATEST_ROUND = '0xfeaf968c';  // latestRoundData()

async function ethCall(rpc, to, data) {
  const resp = await fetch(rpc, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({
      jsonrpc: '2.0', id: 1,
      method: 'eth_call',
      params: [{ to, data }, 'latest'],
    }),
  });
  const json = await resp.json();
  if (json.error)
    throw new Error(`RPC: ${json.error.message}`);
  return json.result;
}

function hexToBigInt(hex) {
  if (!hex || hex === '0x') return 0n;
  return BigInt(hex);
}

export async function onRequest(context) {
  const headers = {
    'Content-Type': 'application/json',
    'Access-Control-Allow-Origin': '*',
    'Cache-Control': 'public, max-age=60',
  };

  try {
    const [baseSup, ethSup, priceHex] = await Promise.all([
      ethCall(RPC_BASE, USDC_BASE, TOTAL_SUPPLY),
      ethCall(RPC_ETH, USDC_ETH, TOTAL_SUPPLY),
      ethCall(RPC_ETH, CL_USDC, LATEST_ROUND),
    ]);

    const baseSupply = Number(hexToBigInt(baseSup)) / 1e6;
    const ethSupply  = Number(hexToBigInt(ethSup)) / 1e6;

    const pd = priceHex.slice(2);
    const price = Number(hexToBigInt('0x' + pd.slice(64, 128))) / 1e8;
    const updatedAt = Number(hexToBigInt('0x' + pd.slice(192, 256)));

    return new Response(
      JSON.stringify({
        source: 'on-chain',
        timestamp: new Date().toISOString(),
        data: {
          base: { totalSupply: Math.round(baseSupply) },
          ethereum: { totalSupply: Math.round(ethSupply) },
          combined: {
            totalSupply: Math.round(baseSupply + ethSupply),
          },
          chainlinkPrice: {
            pair: 'USDC/USD',
            price,
            updatedAt: new Date(updatedAt * 1000).toISOString(),
          },
          reserveIndicator: {
            value: price,
            interpretation: price >= 0.999
              ? 'Peg holding' : 'Below peg',
          },
        },
      }),
      { status: 200, headers }
    );
  } catch (err) {
    return new Response(
      JSON.stringify({ error: err.message }),
      { status: 502, headers }
    );
  }
}