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

/**
 * App-wide settings — commission config, etc.
 * Exposed as window.SettingsStore. localStorage key "optionsPricer:settings".
 *
 * Default plan = IBKR Fixed / Lite:
 *   $0.65 per contract, $1.00 per-order minimum, no per-order maximum.
 *   Source: https://www.interactivebrokers.com/en/pricing/commissions-options.php
 */
(function () {
  "use strict";
  const KEY = "optionsPricer:settings";
  const VERSION = 1;

  const DEFAULTS = {
    v: VERSION,
    commission: {
      plan: "ibkr-fixed",         // ibkr-fixed | ibkr-tiered | custom
      perContract: 0.65,          // $ per option contract
      perOrderMin: 1.00,          // $ minimum per order
      perOrderMax: 0,             // $ cap per order; 0 = none
      applyPerLeg: false,         // true = each leg charged separately; false = whole position counts as one order
    },
  };

  function clone(o) { return JSON.parse(JSON.stringify(o)); }

  function load() {
    try {
      const raw = localStorage.getItem(KEY);
      if (!raw) return clone(DEFAULTS);
      const obj = JSON.parse(raw);
      if (!obj || obj.v !== VERSION) return clone(DEFAULTS);
      // merge over defaults so missing fields fall back
      const out = clone(DEFAULTS);
      if (obj.commission && typeof obj.commission === "object") {
        Object.assign(out.commission, obj.commission);
      }
      return out;
    } catch { return clone(DEFAULTS); }
  }

  function save(s) {
    const out = clone(DEFAULTS);
    if (s && s.commission) Object.assign(out.commission, s.commission);
    try { localStorage.setItem(KEY, JSON.stringify(out)); } catch (e) { console.warn("[SettingsStore] save failed:", e); }
    return out;
  }

  function reset() {
    try { localStorage.removeItem(KEY); } catch {}
    return clone(DEFAULTS);
  }

  /**
   * Estimate commission for a position.
   * legs: [{ qty }, ...]   (only qty matters)
   * Returns { entry, exit, roundTrip } in dollars.
   */
  function estimate(legs) {
    const c = load().commission;
    if (!Array.isArray(legs) || legs.length === 0) return { entry: 0, exit: 0, roundTrip: 0 };

    const orderCost = (contracts) => {
      let v = contracts * c.perContract;
      if (c.perOrderMin > 0) v = Math.max(v, c.perOrderMin);
      if (c.perOrderMax > 0) v = Math.min(v, c.perOrderMax);
      return v;
    };

    let entry;
    if (c.applyPerLeg) {
      entry = legs.reduce((s, l) => s + orderCost(Math.max(1, Math.round(l.qty || 1))), 0);
    } else {
      const total = legs.reduce((s, l) => s + Math.max(1, Math.round(l.qty || 1)), 0);
      entry = orderCost(total);
    }
    const exit = entry;          // assume same fill style on close
    return { entry, exit, roundTrip: entry + exit };
  }

  window.SettingsStore = { KEY, VERSION, DEFAULTS: clone(DEFAULTS), load, save, reset, estimate };
})();