import { describe, it, expect } from "vitest";
import { computeFeeBreakdown } from "./fee.js";

const TREASURY = "6dNVUMrJ8C8C8C8C8C8C8C8C8C8C8C8C8C8C8C8C8C8";

describe("computeFeeBreakdown", () => {
  it("takes a 5% base fee of the gross (500 bps of 1_000_000 = 50_000; net 950_000)", () => {
    const fee = computeFeeBreakdown({
      grossLamports: 1_000_000n,
      feeBps: 500,
      treasury: TREASURY,
    });
    expect(fee.grossLamports).toBe("1000000");
    expect(fee.feeBps).toBe(500);
    expect(fee.feeLamports).toBe("50000");
    expect(fee.totalToTreasuryLamports).toBe("50000");
    expect(fee.netToUserLamports).toBe("950000");
    expect(fee.treasury).toBe(TREASURY);
    // No contribution requested → fields omitted.
    expect(fee.contributionBps).toBeUndefined();
    expect(fee.contributionLamports).toBeUndefined();
  });

  it("adds an optional contribution on top of the base fee", () => {
    const fee = computeFeeBreakdown({
      grossLamports: 1_000_000n,
      feeBps: 500, // 50_000
      contributionBps: 200, // 20_000
      treasury: TREASURY,
    });
    expect(fee.feeLamports).toBe("50000");
    expect(fee.contributionBps).toBe(200);
    expect(fee.contributionLamports).toBe("20000");
    expect(fee.totalToTreasuryLamports).toBe("70000");
    expect(fee.netToUserLamports).toBe("930000");
  });

  it("caps the contribution at maxContributionBps", () => {
    const fee = computeFeeBreakdown({
      grossLamports: 1_000_000n,
      feeBps: 500,
      contributionBps: 5_000, // requested 50%
      maxContributionBps: 300, // capped to 3% = 30_000
      treasury: TREASURY,
    });
    expect(fee.contributionBps).toBe(300);
    expect(fee.contributionLamports).toBe("30000");
    expect(fee.totalToTreasuryLamports).toBe("80000"); // 50_000 + 30_000
    expect(fee.netToUserLamports).toBe("920000");
  });

  it("never lets the total exceed gross (net is never negative)", () => {
    const fee = computeFeeBreakdown({
      grossLamports: 1_000_000n,
      feeBps: 9_000, // 90%
      contributionBps: 9_000, // +90% → would be 180% of gross
      maxContributionBps: 10_000,
      treasury: TREASURY,
    });
    expect(BigInt(fee.totalToTreasuryLamports)).toBeLessThanOrEqual(1_000_000n);
    expect(fee.totalToTreasuryLamports).toBe("1000000");
    expect(fee.netToUserLamports).toBe("0");
    expect(BigInt(fee.netToUserLamports)).toBeGreaterThanOrEqual(0n);
  });

  it("0 bps → 0 fee, full amount to the user", () => {
    const fee = computeFeeBreakdown({
      grossLamports: 1_000_000n,
      feeBps: 0,
      treasury: TREASURY,
    });
    expect(fee.feeLamports).toBe("0");
    expect(fee.totalToTreasuryLamports).toBe("0");
    expect(fee.netToUserLamports).toBe("1000000");
  });

  it("accepts a string gross and stays exact for large u64 values", () => {
    const fee = computeFeeBreakdown({
      grossLamports: "18446744073709551615", // u64 max
      feeBps: 500,
      treasury: TREASURY,
    });
    expect(fee.grossLamports).toBe("18446744073709551615");
    // 5% of u64 max, BigInt-exact.
    expect(fee.feeLamports).toBe("922337203685477580");
  });
});