feat: add scaleQuantityWithMinimum function to normalize order quantities and implement corresponding tests

src/exchanges/lighter/decimal.ts

@@ -46,6 +46,18 @@ export function decimalToScaled(value: number | string | bigint, decimals: numbe
   return sign === -1 ? -result : result;
 }
 
+export function scaleQuantityWithMinimum(value: number | string | bigint, decimals: number): bigint {
+  const scaled = decimalToScaled(value, decimals);
+  if (scaled !== 0n) {
+    return scaled;
+  }
+  const numeric = typeof value === "bigint" ? Number(value) : Number(value);
+  if (!Number.isFinite(numeric) || numeric === 0) {
+    return scaled;
+  }
+  return numeric < 0 ? -1n : 1n;
+}
+
 export function scaledToDecimalString(value: bigint | number | string, decimals: number): string {
   if (typeof value === "number") {
     if (!Number.isFinite(value)) throw new Error(`Invalid scaled number: ${value}`);

src/exchanges/lighter/gateway.ts

@@ -33,7 +33,7 @@ import {
   IMMEDIATE_OR_CANCEL_EXPIRY_PLACEHOLDER,
   type LighterEnvironment,
 } from "./constants";
-import { decimalToScaled, scaledToDecimalString } from "./decimal";
+import { decimalToScaled, scaledToDecimalString, scaleQuantityWithMinimum } from "./decimal";
 import { lighterOrderToAster, toAccountSnapshot, toDepth, toKlines, toOrders, toTicker } from "./mappers";
 
 interface SimpleEvent<T> {
@@ -888,7 +888,7 @@ export class LighterGateway {
     }
     const side = params.side;
     const isAsk = side === "SELL" ? 1 : 0;
-    const baseAmount = decimalToScaled(params.quantity, this.sizeDecimals);
+    const baseAmount = scaleQuantityWithMinimum(params.quantity, this.sizeDecimals);
     const baseAmountScaledString = scaledToDecimalString(baseAmount, this.sizeDecimals);
     const clientOrderIndex = BigInt(Date.now() % Number.MAX_SAFE_INTEGER);
     let priceScaled = params.price != null ? decimalToScaled(params.price, this.priceDecimals) : null;

tests/lighter/decimal.test.ts

@@ -0,0 +1,27 @@
+import { describe, expect, it } from "vitest";
+
+import { scaleQuantityWithMinimum, scaledToDecimalString, decimalToScaled } from "../../src/exchanges/lighter/decimal";
+
+describe("scaleQuantityWithMinimum", () => {
+  it("raises tiny positive quantities to the minimum step", () => {
+    const scaled = scaleQuantityWithMinimum(0.00001, 4);
+    expect(scaled).toBe(1n);
+    expect(scaledToDecimalString(scaled, 4)).toBe("0.0001");
+  });
+
+  it("raises tiny negative quantities to the negative minimum step", () => {
+    const scaled = scaleQuantityWithMinimum(-0.00001, 4);
+    expect(scaled).toBe(-1n);
+    expect(scaledToDecimalString(scaled, 4)).toBe("-0.0001");
+  });
+
+  it("keeps zero quantities at zero", () => {
+    const scaled = scaleQuantityWithMinimum(0, 4);
+    expect(scaled).toBe(0n);
+  });
+
+  it("preserves values already aligned to the step", () => {
+    const aligned = scaleQuantityWithMinimum(0.0002, 4);
+    expect(aligned).toBe(decimalToScaled(0.0002, 4));
+  });
+});