EMA Crossover Trend Follower

// Env: FAST_EMA, SLOW_EMA, INTERVAL, TP_PERCENT, SL_PERCENT

async function getCloses(interval, limit) {
  const res = await $.Http.get("https://fapi.binance.com/fapi/v1/klines", {
    symbol: $.Price.symbol,
    interval,
    limit
  });
  if (res.status !== 200) return null;
  const raw = JSON.parse(res.text);
  return raw.map(c => parseFloat(c[4])); // Close prices
}

const FAST_EMA = Number($.Env.FAST_EMA || 9);
const SLOW_EMA = Number($.Env.SLOW_EMA || 21);
const INTERVAL = $.Env.INTERVAL || "15m";
const TP_PERCENT = Number($.Env.TP_PERCENT || 1.5);
const SL_PERCENT = Number($.Env.SL_PERCENT || 1.0);

let S = (await $.Storage.get()) || { position: null, entryPrice: null };
let nextAction = null;

// 1) Manage an existing position first
if (S.position) {
  const roi = $.Strategy.roi(true, S.entryPrice, $.Price.price);
  if (roi !== null) {
    const profit = S.position === "LONG" ? roi : -roi; // shorts invert sign
    if (profit >= TP_PERCENT || profit <= -SL_PERCENT) {
      nextAction = { type: $.Action.EXIT };
    }
  }
}

// 2) Otherwise look for entries / crossover exits
if (!nextAction) {
  const closes = await getCloses(INTERVAL, Math.max(SLOW_EMA * 3, 60));
  if (closes && closes.length > SLOW_EMA) {
    const fast = new $.Ta.EMA(FAST_EMA);
    const slow = new $.Ta.EMA(SLOW_EMA);
    for (const c of closes) {
      fast.update(c);
      slow.update(c);
    }
    if (fast.isStable && slow.isStable) {
      const bullish = fast.getResult() > slow.getResult();

      if (!S.position && bullish) {
        nextAction = { type: $.Action.LONG, side: "LONG" };
      } else if (!S.position && !bullish) {
        nextAction = { type: $.Action.SHORT, side: "SHORT" };
      } else if (S.position === "LONG" && !bullish) {
        nextAction = { type: $.Action.EXIT };
      } else if (S.position === "SHORT" && bullish) {
        nextAction = { type: $.Action.EXIT };
      }
    }
  }
}

if (nextAction) {
  await $.Strategy.action(nextAction.type);
  if (nextAction.type === $.Action.EXIT) {
    S.position = null;
    S.entryPrice = null;
  } else {
    S.position = nextAction.side;
    S.entryPrice = $.Price.price;
  }
}

await $.Storage.set(S);