/**
 * Cloudflare Pages Function
 * /api/nse
 * Full Market Proxy (NSE + BSE + MCX)
 */

const CORS = {
  "Access-Control-Allow-Origin": "*",
  "Access-Control-Allow-Methods": "GET, OPTIONS",
  "Content-Type": "application/json",
  "Cache-Control": "no-store"
};

/* NSE Index Mapping */
const NSE_INDEX = {
  NIFTY: "NIFTY 50",
  BANKNIFTY: "NIFTY BANK",
  FINNIFTY: "NIFTY FIN SERVICE",
  MIDCPNIFTY: "NIFTY MIDCAP SELECT",
  NIFTYNXT50: "NIFTY NEXT 50"
};

/* ───────── NSE FETCH WITH SESSION ───────── */

async function fetchNSE(url) {
  const headers = {
    "User-Agent": "Mozilla/5.0",
    "Accept": "application/json",
    "Referer": "https://www.nseindia.com/"
  };

  const home = await fetch("https://www.nseindia.com", { headers });
  const cookie = home.headers.get("set-cookie");

  const res = await fetch(url, {
    headers: { ...headers, "Cookie": cookie || "" }
  });

  if (!res.ok) throw new Error("NSE HTTP " + res.status);
  return res.json();
}

/* ───────── SPOT DATA (ALL MARKETS) ───────── */

async function getSpots() {

  const spots = {};

  /* NSE INDICES */
  try {
    const data = await fetchNSE(
      "https://www.nseindia.com/api/allIndices"
    );

    for (const row of data.data || []) {
      for (const [key, name] of Object.entries(NSE_INDEX)) {
        if (row.index === name && row.last) {
          spots[key] = parseFloat(row.last);
        }
      }
    }
  } catch (err) {}

  /* BSE SENSEX */
  try {
    const res = await fetch(
      "https://api.bseindia.com/BseIndiaAPI/api/GetSensexData/w"
    );
    const data = await res.json();

    if (data?.Data?.CurrVal) {
      spots["SENSEX"] =
        parseFloat(data.Data.CurrVal.replace(/,/g, ""));
    }
  } catch (err) {}

  /* MCX COMMODITIES */
  try {
    const res = await fetch(
      "https://www.mcxindia.com/api/marketplace/getBestIndicativeRates"
    );
    const data = await res.json();
    const list = data?.data || [];

    for (const item of list) {
      const sym = (item.symbol || "").toUpperCase();
      const price = parseFloat(item.rate || 0);

      if (sym.includes("GOLDM")) spots["GOLDMINI"] = price;
      if (sym.includes("GOLD") && !sym.includes("MINI"))
        spots["GOLD"] = price;

      if (sym.includes("SILVERM"))
        spots["SILVERMINI"] = price;
      if (sym.includes("SILVER"))
        spots["SILVER"] = price;

      if (sym.includes("CRUDE"))
        spots["CRUDEOIL"] = price;

      if (sym.includes("NATURAL"))
        spots["NATURALGAS"] = price;

      if (sym.includes("COPPER"))
        spots["COPPER"] = price;

      if (sym.includes("ALUMINIUM"))
        spots["ALUMINIUM"] = price;
    }

  } catch (err) {}

  return spots;
}

/* ───────── OPTION CHAIN (NSE ONLY) ───────── */

async function getChain(symbol, expiry) {

  const url =
    `https://www.nseindia.com/api/option-chain-indices?symbol=${symbol}`;

  const data = await fetchNSE(url);

  const records = data.records?.data || [];
  const expiryDates = data.records?.expiryDates || [];

  const filtered = expiry
    ? records.filter(r => r.expiryDate === expiry)
    : records;

  const strikes = filtered.map(r => ({
    strike: r.strikePrice,

    CE: r.CE ? {
      ltp: r.CE.lastPrice,
      iv: r.CE.impliedVolatility,
      oi: r.CE.openInterest,
      volume: r.CE.totalTradedVolume,
      change: r.CE.change
    } : null,

    PE: r.PE ? {
      ltp: r.PE.lastPrice,
      iv: r.PE.impliedVolatility,
      oi: r.PE.openInterest,
      volume: r.PE.totalTradedVolume,
      change: r.PE.change
    } : null
  }));

  return {
    symbol,
    spot: data.records?.underlyingValue || null,
    expiryDates,
    strikes
  };
}

/* ───────── MAIN HANDLER ───────── */

export async function onRequest({ request }) {

  if (request.method === "OPTIONS")
    return new Response(null, {
      status: 204,
      headers: CORS
    });

  const url = new URL(request.url);
  const type = url.searchParams.get("type");

  try {

    /* SPOT */
    if (type === "spot") {
      const spots = await getSpots();

      return new Response(
        JSON.stringify({ ok: true, spots }),
        { headers: CORS }
      );
    }

    /* OPTION CHAIN */
    if (type === "chain") {
      const symbol =
        url.searchParams.get("symbol") || "NIFTY";
      const expiry =
        url.searchParams.get("expiry") || null;

      const chain =
        await getChain(symbol, expiry);

      return new Response(
        JSON.stringify({ ok: true, ...chain }),
        { headers: CORS }
      );
    }

    return new Response(
      JSON.stringify({ ok: false }),
      { status: 400, headers: CORS }
    );

  } catch (err) {

    return new Response(
      JSON.stringify({
        ok: false,
        error: err.message
      }),
      { status: 502, headers: CORS }
    );
  }
}