const express = require("express");
const path = require("path");
const BreezeConnect = require("breezeconnect").BreezeConnect;

try {
  require("dotenv").config();
} catch (_) {}

const app = express();
const PORT = Number(process.env.PORT || 7860);

app.use(express.json({ limit: "1mb" }));
app.use(express.static(path.join(__dirname, "public")));

const BREEZE_API_KEY = process.env.BREEZE_API_KEY || "";
const BREEZE_API_SECRET = process.env.BREEZE_API_SECRET || "";

let breeze = null;
let connected = false;
let customer = null;
let lastError = null;

// This Space is designed for a single owner/user. The Breeze session is kept
// in server memory only and is cleared when the Space restarts or logout is used.
function clearSession() {
  breeze = null;
  connected = false;
  customer = null;
}

function isoAt(dateStr, hhmm, endOfMinute = false) {
  const [h, m] = hhmm.split(":").map(Number);
  const ms = endOfMinute ? 59_000 : 0;
  return new Date(Date.UTC(
    Number(dateStr.slice(0, 4)),
    Number(dateStr.slice(5, 7)) - 1,
    Number(dateStr.slice(8, 10)),
    h, m, 0, ms
  )).toISOString();
}

function addDays(dateStr, n) {
  const d = new Date(`${dateStr}T00:00:00Z`);
  d.setUTCDate(d.getUTCDate() + n);
  return d.toISOString().slice(0, 10);
}

function weekday(dateStr) {
  return new Date(`${dateStr}T00:00:00Z`).getUTCDay();
}

function isWeekday(dateStr) {
  const w = weekday(dateStr);
  return w >= 1 && w <= 5;
}

function isEntryDay(dateStr) {
  const w = weekday(dateStr);
  return w >= 1 && w <= 4;
}

function getNextCalendarTradingDay(dateStr) {
  for (let i = 1; i <= 8; i++) {
    const d = addDays(dateStr, i);
    if (isWeekday(d)) return d;
  }
  return null;
}

// Retained from the supplied strategy.
// Mon -> Tue, Tue -> next Tue, Wed -> next Tue, Thu -> next Tue.
function getStrategyExpiry(dateStr) {
  const w = weekday(dateStr);
  const days = { 1: 1, 2: 7, 3: 6, 4: 5 }[w];
  return days == null ? null : addDays(dateStr, days);
}

function roundATM(spot) {
  return Math.round(Number(spot) / 50) * 50;
}

function unwrapSuccess(resp) {
  if (!resp) return [];
  if (Array.isArray(resp)) return resp;
  if (Array.isArray(resp.Success)) return resp.Success;
  if (Array.isArray(resp.success)) return resp.success;
  if (Array.isArray(resp.data)) return resp.data;
  if (resp.Success && typeof resp.Success === "object") return [resp.Success];
  return [];
}

function responseError(resp) {
  if (!resp) return "Empty Breeze response";
  if (resp.Error) return String(resp.Error);
  if (resp.error) return String(resp.error);
  if (resp.Message) return String(resp.Message);
  if (resp.message) return String(resp.message);
  return null;
}

function normalizeBars(resp) {
  return unwrapSuccess(resp)
    .map(x => ({
      datetime: x.datetime || x.dateTime || x.timestamp,
      open: Number(x.open),
      high: Number(x.high),
      low: Number(x.low),
      close: Number(x.close),
      volume: Number(x.volume || 0),
      open_interest: Number(x.open_interest || 0)
    }))
    .filter(x =>
      x.datetime &&
      Number.isFinite(x.open) &&
      Number.isFinite(x.high) &&
      Number.isFinite(x.low) &&
      Number.isFinite(x.close)
    )
    .sort((a, b) => String(a.datetime).localeCompare(String(b.datetime)));
}

function localTimeFromBreeze(dt) {
  // Breeze examples return "YYYY-MM-DD HH:mm:ss" in IST for historical candles.
  const s = String(dt);
  const m = s.match(/(\d{2}):(\d{2}):(\d{2})$/);
  return m ? Number(m[1]) * 60 + Number(m[2]) : null;
}

async function breezeHistorical(params) {
  if (!breeze || !connected) {
    throw new Error("Breeze is not connected.");
  }

  const resp = await breeze.getHistoricalDatav2(params);
  const err = responseError(resp);
  if (err) throw new Error(err);

  const bars = normalizeBars(resp);
  if (!bars.length) {
    throw new Error("Breeze returned no historical candles for the requested contract/date.");
  }
  return bars;
}

async function getNiftySpotAt1515(dateStr) {
  const bars = await breezeHistorical({
    interval: "1minute",
    fromDate: isoAt(dateStr, "15:15"),
    toDate: isoAt(dateStr, "15:15", true),
    stockCode: "NIFTY",
    exchangeCode: "NSE",
    productType: "cash"
  });

  const bar = bars.find(b => localTimeFromBreeze(b.datetime) === 15 * 60 + 15) || bars[bars.length - 1];
  return { price: bar.close, bar };
}

async function getOptionBars(dateStr, expiryStr, right, strike, fromTime, toTime) {
  return breezeHistorical({
    interval: "1minute",
    fromDate: isoAt(dateStr, fromTime),
    toDate: isoAt(dateStr, toTime, true),
    stockCode: "NIFTY",
    exchangeCode: "NFO",
    productType: "options",
    expiryDate: isoAt(expiryStr, "07:00"),
    right: right.toLowerCase(),
    strikePrice: String(strike)
  });
}

function simulatePosition(entryPrice, bars, targetPts, slPts, squareOffMin) {
  const target = entryPrice + targetPts;
  const sl = entryPrice - slPts;

  for (const b of bars) {
    const min = localTimeFromBreeze(b.datetime);
    if (min == null || min < 9 * 60 + 15) continue;
    if (min > squareOffMin) break;

    // Preserve the supplied strategy's conservative same-candle rule:
    // SL is evaluated before target.
    if (b.low <= sl) {
      return {
        exitPrice: sl,
        exitMin: min,
        reason: "SL"
      };
    }
    if (b.high >= target) {
      return {
        exitPrice: target,
        exitMin: min,
        reason: "TARGET"
      };
    }
  }

  const usable = bars.filter(b => {
    const m = localTimeFromBreeze(b.datetime);
    return m != null && m <= squareOffMin;
  });

  if (!usable.length) {
    return {
      exitPrice: entryPrice,
      exitMin: squareOffMin,
      reason: "NO_NEXT_DAY_DATA"
    };
  }

  const last = usable[usable.length - 1];
  return {
    exitPrice: last.close,
    exitMin: localTimeFromBreeze(last.datetime),
    reason: "NEXT_DAY_SQUAREOFF"
  };
}

function minutesToHHMM(min) {
  const h = Math.floor(min / 60);
  const m = min % 60;
  return `${String(h).padStart(2, "0")}:${String(m).padStart(2, "0")}`;
}

async function runRealBacktest(cfg, progressCb = () => {}) {
  const start = cfg.start;
  const end = cfg.end;
  const targetPts = Number(cfg.targetPts);
  const slPts = Number(cfg.slPts);
  const brokerage = Number(cfg.brokerage);
  const sqOffMin = Number(cfg.sqOffMin);

  if (![targetPts, slPts, brokerage, sqOffMin].every(Number.isFinite)) {
    throw new Error("Invalid backtest parameters.");
  }
  if (start > end) throw new Error("Start date cannot be after end date.");

  const entryDates = [];
  for (let d = start; d <= end; d = addDays(d, 1)) {
    if (isEntryDay(d)) entryDates.push(d);
  }

  const trades = [];
  const daily = [];

  for (let i = 0; i < entryDates.length; i++) {
    const entryDate = entryDates[i];
    progressCb({
      current: i + 1,
      total: entryDates.length,
      message: `FETCHING REAL DATA ${i + 1}/${entryDates.length} · ${entryDate}`
    });

    const nextDay = getNextCalendarTradingDay(entryDate);
    if (!nextDay) continue;

    const expiry = getStrategyExpiry(entryDate);
    if (!expiry) continue;

    // Real NIFTY cash price at 15:15 determines ATM.
    const spotResult = await getNiftySpotAt1515(entryDate);
    const atm = roundATM(spotResult.price);

    let dayPnl = 0;

    for (const right of ["call", "put"]) {
      // Real entry premium at 15:15.
      const entryBars = await getOptionBars(
        entryDate,
        expiry,
        right,
        atm,
        "15:15",
        "15:15"
      );

      const entryBar =
        entryBars.find(b => localTimeFromBreeze(b.datetime) === 15 * 60 + 15) ||
        entryBars[entryBars.length - 1];

      if (!entryBar) {
        throw new Error(`No ${right.toUpperCase()} entry candle for ${entryDate} ${atm} ${expiry}.`);
      }

      const entryPrice = entryBar.close;

      // Real next-trading-day option bars.
      const nextBars = await getOptionBars(
        nextDay,
        expiry,
        right,
        atm,
        "09:15",
        minutesToHHMM(sqOffMin)
      );

      const exit = simulatePosition(
        entryPrice,
        nextBars,
        targetPts,
        slPts,
        sqOffMin
      );

      const qty = 65;
      const gross = (exit.exitPrice - entryPrice) * qty;
      const net = gross - brokerage;
      dayPnl += net;

      trades.push({
        entryDate,
        entryTime: "15:15",
        exitDate: nextDay,
        exitTime: minutesToHHMM(exit.exitMin),
        dayHeld: 1,
        right: right.toUpperCase() === "CALL" ? "CE" : "PE",
        strike: atm,
        expiry,
        lots: 1,
        qty,
        entry: entryPrice,
        exit: exit.exitPrice,
        gross,
        brokerage,
        net,
        reason: exit.reason,
        spotAtEntry: spotResult.price
      });
    }

    daily.push({
      entryDate,
      entryTime: "15:15",
      exitDate: nextDay,
      exitTime: minutesToHHMM(sqOffMin),
      pnl: dayPnl
    });
  }

  let cum = 0;
  for (const d of daily) {
    cum += d.pnl;
    d.cum = cum;
    d.result = d.pnl > 0 ? "PROFIT" : d.pnl < 0 ? "LOSS" : "FLAT";
  }

  return { trades, daily };
}

function calculateMetrics(trades) {
  const pnl = trades.map(t => Number(t.net));
  if (!pnl.length) {
    return {
      trades: 0, wins: 0, losses: 0, winRate: 0,
      grossProfit: 0, grossLoss: 0, brokerage: 0, netPnl: 0,
      avgTrade: 0, avgWin: 0, avgLoss: 0,
      maxProfit: 0, maxLoss: 0, profitFactor: 0,
      maxDrawdown: 0, expectancy: 0
    };
  }

  const wins = pnl.filter(v => v > 0);
  const losses = pnl.filter(v => v < 0);
  const grossProfit = wins.reduce((a, b) => a + b, 0);
  const grossLoss = Math.abs(losses.reduce((a, b) => a + b, 0));
  const netPnl = pnl.reduce((a, b) => a + b, 0);

  let eq = 0;
  let peak = 0;
  let dd = 0;
  for (const v of pnl) {
    eq += v;
    peak = Math.max(peak, eq);
    dd = Math.min(dd, eq - peak);
  }

  return {
    trades: pnl.length,
    wins: wins.length,
    losses: losses.length,
    winRate: wins.length / pnl.length * 100,
    grossProfit,
    grossLoss,
    brokerage: trades.reduce((a, t) => a + Number(t.brokerage || 0), 0),
    netPnl,
    avgTrade: netPnl / pnl.length,
    avgWin: wins.length ? grossProfit / wins.length : 0,
    avgLoss: losses.length ? -grossLoss / losses.length : 0,
    maxProfit: Math.max(...pnl),
    maxLoss: Math.min(...pnl),
    profitFactor: grossLoss > 0 ? grossProfit / grossLoss : null,
    maxDrawdown: dd,
    expectancy: netPnl / pnl.length
  };
}

app.get("/api/health", (req, res) => {
  res.json({
    ok: true,
    service: "selva-option-backtest",
    port: PORT,
    breezeConfigured: Boolean(BREEZE_API_KEY && BREEZE_API_SECRET),
    connected
  });
});

app.get("/api/status", (req, res) => {
  res.json({
    connected,
    customer,
    breezeConfigured: Boolean(BREEZE_API_KEY && BREEZE_API_SECRET),
    lastError
  });
});

app.get("/api/login-url", (req, res) => {
  if (!BREEZE_API_KEY) {
    return res.status(500).json({ error: "BREEZE_API_KEY is missing in Hugging Face Secrets." });
  }
  const url = `https://api.icicidirect.com/apiuser/login?api_key=${encodeURIComponent(BREEZE_API_KEY)}`;
  res.json({ url });
});

app.post("/api/connect", async (req, res) => {
  try {
    if (!BREEZE_API_KEY || !BREEZE_API_SECRET) {
      return res.status(500).json({
        error: "BREEZE_API_KEY / BREEZE_API_SECRET are not configured in Hugging Face Secrets."
      });
    }

    const apiSession = String(req.body?.apiSession || "").trim();
    if (!apiSession) {
      return res.status(400).json({ error: "API Session is required." });
    }

    const bc = new BreezeConnect({ appKey: BREEZE_API_KEY });
    const sessionResp = await bc.generateSession(BREEZE_API_SECRET, apiSession);

    const sessionErr = responseError(sessionResp);
    if (sessionErr) {
      clearSession();
      lastError = sessionErr;
      return res.status(401).json({ error: sessionErr });
    }

    // generateSession mutates the Breeze client with the access token/session.
    let details = null;
    try {
      const detailResp = await bc.getCustomerDetails(apiSession);
      details = unwrapSuccess(detailResp)[0] || null;
      const detailErr = responseError(detailResp);
      if (detailErr) {
        // Session itself is still valid; do not fail solely because details call
        // is unavailable in a particular SDK version.
        lastError = detailErr;
      }
    } catch (e) {
      lastError = e.message;
    }

    breeze = bc;
    connected = true;
    customer = details;
    lastError = null;

    res.json({
      ok: true,
      connected: true,
      customer
    });
  } catch (e) {
    clearSession();
    lastError = e.message;
    res.status(500).json({ error: e.message });
  }
});

app.post("/api/logout", (req, res) => {
  clearSession();
  lastError = null;
  res.json({ ok: true });
});

app.post("/api/backtest", async (req, res) => {
  if (!connected || !breeze) {
    return res.status(401).json({ error: "Connect Breeze before running the backtest." });
  }

  const cfg = {
    start: String(req.body?.start || ""),
    end: String(req.body?.end || ""),
    targetPts: Number(req.body?.targetPts ?? 20),
    slPts: Number(req.body?.slPts ?? 10),
    brokerage: Number(req.body?.brokerage ?? 40),
    sqOffMin: (() => {
      const s = String(req.body?.sqOff || "15:10");
      const [h, m] = s.split(":").map(Number);
      return h * 60 + m;
    })()
  };

  try {
    lastError = null;
    const result = await runRealBacktest(cfg);
    res.json({
      ok: true,
      source: "ICICI DIRECT BREEZE HISTORICAL DATA",
      strategy: {
        entry: "15:15",
        legs: ["ATM CE", "ATM PE"],
        qty: 65,
        targetPts: cfg.targetPts,
        slPts: cfg.slPts,
        squareOff: String(req.body?.sqOff || "15:10")
      },
      ...result,
      metrics: calculateMetrics(result.trades)
    });
  } catch (e) {
    lastError = e.message;
    res.status(500).json({ error: e.message });
  }
});

app.get("*", (req, res) => {
  res.sendFile(path.join(__dirname, "public", "index.html"));
});

app.listen(PORT, "0.0.0.0", () => {
  console.log(`Selva Option Backtest listening on 0.0.0.0:${PORT}`);
});