import { describe, it, expect } from "vitest";
import { formatBytes } from "./formatBytes";

// TRACES: UR-056 | DR-085 | UT-071
describe("formatBytes", () => {
  it("renders zero and non-positive as '0 B'", () => {
    expect(formatBytes(0)).toBe("0 B");
    expect(formatBytes(-1)).toBe("0 B");
    expect(formatBytes(NaN)).toBe("0 B");
    expect(formatBytes(Infinity)).toBe("0 B");
  });

  it("renders whole bytes below 1 KB", () => {
    expect(formatBytes(1)).toBe("1 B");
    expect(formatBytes(999)).toBe("999 B");
  });

  it("crosses to KB at 1000 bytes (decimal units)", () => {
    expect(formatBytes(1000)).toBe("1 KB");
    expect(formatBytes(1500)).toBe("1.5 KB");
  });

  it("shows 2-3 significant figures", () => {
    expect(formatBytes(340_000_000)).toBe("340 MB");
    expect(formatBytes(1_200_000_000)).toBe("1.2 GB");
    expect(formatBytes(48_000_000)).toBe("48 MB");
  });

  it("trims trailing zeros", () => {
    expect(formatBytes(2_000_000_000)).toBe("2 GB");
    expect(formatBytes(10_000_000)).toBe("10 MB");
  });

  it("scales into large units", () => {
    expect(formatBytes(3_400_000_000)).toBe("3.4 GB");
    expect(formatBytes(1_000_000_000_000)).toBe("1 TB");
  });

  it("uses no decimals at or above 100 of a unit", () => {
    // 123.4 MB → "123 MB" (2-3 sig figs, whole number band)
    expect(formatBytes(123_400_000)).toBe("123 MB");
  });
});