import { describe, it, expect } from "vitest";
import { EMPTY, displayValue } from "./placeholder";

describe("displayValue", () => {
  it("returns the canonical placeholder for null and undefined", () => {
    expect(displayValue(null)).toBe(EMPTY);
    expect(displayValue(undefined)).toBe(EMPTY);
  });

  it("treats empty and whitespace-only strings as no value", () => {
    expect(displayValue("")).toBe(EMPTY);
    expect(displayValue("   ")).toBe(EMPTY);
    expect(displayValue("\t\n ")).toBe(EMPTY);
  });

  it("returns non-blank strings verbatim (including surrounding content)", () => {
    expect(displayValue("hello")).toBe("hello");
    expect(displayValue("  padded  ")).toBe("  padded  ");
    expect(displayValue("0")).toBe("0");
  });

  it("stringifies finite numbers, including zero and negatives", () => {
    expect(displayValue(0)).toBe("0");
    expect(displayValue(42)).toBe("42");
    expect(displayValue(-1.5)).toBe("-1.5");
  });

  it("returns the placeholder for non-finite numbers", () => {
    expect(displayValue(NaN)).toBe(EMPTY);
    expect(displayValue(Infinity)).toBe(EMPTY);
    expect(displayValue(-Infinity)).toBe(EMPTY);
  });

  it("stringifies booleans and bigints", () => {
    expect(displayValue(true)).toBe("true");
    expect(displayValue(false)).toBe("false");
    expect(displayValue(10n)).toBe("10");
  });

  it("falls back to the placeholder for non-primitive values", () => {
    expect(displayValue({})).toBe(EMPTY);
    expect(displayValue([])).toBe(EMPTY);
    expect(displayValue(() => "x")).toBe(EMPTY);
    expect(displayValue(Symbol("s"))).toBe(EMPTY);
  });
});