harb/kraiken-lib/src/tests/helpers.test.ts

import {
  TAX_RATE_OPTIONS,
  calculateSnatchShortfall,
  decodePositionId,
  getSnatchList,
  isPositionDelinquent,
  minimumTaxRate,
  selectSnatchPositions,
  type SnatchablePosition,
} from "../helpers";
import { uint256ToBytesLittleEndian } from "../subgraph";
import type { Position } from "../__generated__/graphql";
import { PositionStatus } from "../__generated__/graphql";

describe("helpers", () => {
  test("calculateSnatchShortfall returns zero when within cap", () => {
    const outstanding = 100n;
    const desired = 50n;
    const total = 1000n;

    const result = calculateSnatchShortfall(outstanding, desired, total, 2n, 10n);
    expect(result).toBe(0n);
  });

  test("calculateSnatchShortfall returns positive remainder when exceeding cap", () => {
    const outstanding = 200n;
    const desired = 200n;
    const total = 1000n;

    const result = calculateSnatchShortfall(outstanding, desired, total, 2n, 10n);
    expect(result).toBe(200n);
  });

  test("minimumTaxRate finds the lowest tax", () => {
    const rates = [{ taxRate: 0.12 }, { taxRate: 0.05 }, { taxRate: 0.08 }];
    expect(minimumTaxRate(rates, 1)).toBeCloseTo(0.05);
    expect(minimumTaxRate([], 0.42)).toBe(0.42);
  });

  test("selectSnatchPositions chooses cheapest positions first", () => {
    const candidates: SnatchablePosition[] = [
      { id: 1n, stakeShares: 30n, taxRate: 0.05, taxRateIndex: 5 },
      { id: 2n, stakeShares: 40n, taxRate: 0.03, taxRateIndex: 3 },
      { id: 3n, stakeShares: 50n, taxRate: 0.07, taxRateIndex: 7 },
    ];

    const result = selectSnatchPositions(candidates, {
      shortfallShares: 60n,
      maxTaxRate: 0.08,
    });

    expect(result.selected.map((item) => item.id)).toEqual([2n, 1n]);
    expect(result.remainingShortfall).toBe(0n);
    expect(result.coveredShares).toBe(60n);
    expect(result.maxSelectedTaxRateIndex).toBe(5);
  });

  test("selectSnatchPositions keeps track of remaining shortfall", () => {
    const candidates: SnatchablePosition[] = [
      { id: 1n, stakeShares: 10n, taxRate: 0.01 },
      { id: 2n, stakeShares: 10n, taxRate: 0.02 },
    ];

    const result = selectSnatchPositions(candidates, {
      shortfallShares: 50n,
      maxTaxRate: 0.05,
    });

    expect(result.remainingShortfall).toBe(30n);
  });

  test("isPositionDelinquent respects tax rate windows", () => {
    const now = 1_000_000;
    const taxRate = 0.5; // 50%
    const windowSeconds = (365 * 24 * 60 * 60) / taxRate;

    expect(
      isPositionDelinquent(now - windowSeconds + 1, taxRate, now)
    ).toBe(false);
    expect(
      isPositionDelinquent(now - windowSeconds - 10, taxRate, now)
    ).toBe(true);
    expect(isPositionDelinquent(now, 0, now)).toBe(false);
  });

  test("decodePositionId works across representations", () => {
    const id = 12345n;
    const hex = `0x${id.toString(16)}`;
    const bytes = uint256ToBytesLittleEndian(id);

    expect(decodePositionId(id)).toBe(id);
    expect(decodePositionId(hex)).toBe(id);
    expect(decodePositionId(bytes)).toBe(id);
  });

  test("getSnatchList converts subgraph positions", () => {
    const stakeTotalSupply = 1_000_000n * 10n ** 18n;

    const positions: Position[] = [
      {
        __typename: "Position",
        id: uint256ToBytesLittleEndian(1n),
        owner: "0xowner1",
        share: 0.0001,
        creationTime: 0,
        lastTaxTime: 0,
        taxRate: 0.02,
        status: PositionStatus.Active,
      },
      {
        __typename: "Position",
        id: uint256ToBytesLittleEndian(2n),
        owner: "0xowner2",
        share: 0.0002,
        creationTime: 0,
        lastTaxTime: 0,
        taxRate: 0.01,
        status: PositionStatus.Active,
      },
    ];

    const result = getSnatchList(positions, 10n ** 18n, 0.05, stakeTotalSupply);

    expect(result).toEqual([2n]);
  });

  test("tax rate options exported for consumers", () => {
    expect(TAX_RATE_OPTIONS.length).toBeGreaterThan(0);
    expect(TAX_RATE_OPTIONS[0]).toEqual(
      expect.objectContaining({ index: 0, year: 1, decimal: 0.01 })
    );
  });
});