options-pricer/frontend/assets/strategy-store.js

/**
 * Strategy basket persistence — localStorage-backed.
 * Exposed as window.StrategyStore. No modules, no deps.
 *
 * Stored shape (key "optionsPricer:strategy"):
 * {
 *   v: 1,
 *   symbol: "SPY",
 *   spotSnapshot: 738.18,        // spot when last leg was added (reference only)
 *   updatedAt: "2026-05-13T...Z",
 *   legs: [
 *     { id, symbol, expiry:"YYYY-MM-DD", type:"call"|"put",
 *       strike, side:"long"|"short", qty, entryPrice, iv }
 *   ]
 * }
 */
(function () {
  "use strict";

  const KEY = "optionsPricer:strategy";
  const VERSION = 1;
  const MULTIPLIER = 100; // standard equity option contract size

  function empty() {
    return { v: VERSION, symbol: "", spotSnapshot: 0, updatedAt: null, legs: [] };
  }

  function load() {
    try {
      const raw = localStorage.getItem(KEY);
      if (!raw) return empty();
      const obj = JSON.parse(raw);
      if (!obj || obj.v !== VERSION || !Array.isArray(obj.legs)) return empty();
      // sanitize: drop legs with no usable strike / type
      obj.legs = obj.legs.filter(
        (l) => l && Number.isFinite(Number(l.strike)) && (l.type === "call" || l.type === "put")
      );
      return obj;
    } catch {
      return empty();
    }
  }

  function save(state) {
    const s = state || empty();
    s.v = VERSION;
    s.updatedAt = new Date().toISOString();
    try {
      localStorage.setItem(KEY, JSON.stringify(s));
    } catch (e) {
      console.warn("[StrategyStore] save failed:", e);
    }
    return s;
  }

  function clear() {
    try { localStorage.removeItem(KEY); } catch {}
    return empty();
  }

  /**
   * Add a leg. `leg` should provide: symbol, expiry, type, strike, side, qty, entryPrice, iv.
   * Returns { state, replacedSymbol } — replacedSymbol is the old symbol if the basket
   * was wiped due to a symbol mismatch (caller should have confirmed first via mismatch()).
   */
  function addLeg(leg) {
    const strike = Number(leg && leg.strike);
    if (!Number.isFinite(strike) || strike <= 0) {
      console.warn("[StrategyStore] addLeg: invalid strike", leg);
      return { state: load(), replacedSymbol: null };
    }
    let state = load();
    let replacedSymbol = null;
    if (state.legs.length > 0 && state.symbol && leg.symbol && state.symbol !== leg.symbol) {
      replacedSymbol = state.symbol;
      state = empty();
    }
    state.symbol = leg.symbol || state.symbol || "";
    if (typeof leg.spotSnapshot === "number" && leg.spotSnapshot > 0) {
      state.spotSnapshot = leg.spotSnapshot;
    }
    state.legs.push({
      id: ((typeof crypto !== "undefined" && crypto.randomUUID) ? crypto.randomUUID() : "id-" + Date.now() + "-" + Math.random().toString(36).slice(2)),
      symbol: leg.symbol || state.symbol,
      expiry: leg.expiry,
      type: leg.type,
      strike: strike,
      side: leg.side === "short" ? "short" : "long",
      qty: Math.max(1, Math.round(Number(leg.qty) || 1)),
      entryPrice: Number(leg.entryPrice) || 0,
      iv: Number(leg.iv) || 0,
    });
    save(state);
    return { state, replacedSymbol };
  }

  function removeLeg(id) {
    const state = load();
    state.legs = state.legs.filter((l) => l.id !== id);
    if (state.legs.length === 0) { return clear(); }
    save(state);
    return state;
  }

  function updateLeg(id, patch) {
    const state = load();
    const leg = state.legs.find((l) => l.id === id);
    if (leg) Object.assign(leg, patch);
    save(state);
    return state;
  }

  /** True if adding a leg of `symbol` would wipe an existing different-symbol basket. */
  function mismatch(symbol) {
    const state = load();
    return state.legs.length > 0 && state.symbol && symbol && state.symbol !== symbol
      ? state.symbol
      : null;
  }

  function count() {
    return load().legs.length;
  }

  window.StrategyStore = {
    KEY, VERSION, MULTIPLIER,
    empty, load, save, clear, addLeg, removeLeg, updateLeg, mismatch, count,
  };
})();