Moonpie progeess bars

moonPieProgress.test.ts

import { describe, expect, test } from "vitest";
import { moonPieProgress } from "./moonPieProgress.ts";

describe("moonPieProgress", () => {
  test("for for length 4", () => {
    expect.soft(moonPieProgress(0, 4)).toBe("🌑");
    expect.soft(moonPieProgress(1, 4)).toBe("🌘");
    expect.soft(moonPieProgress(2, 4)).toBe("🌗");
    expect.soft(moonPieProgress(3, 4)).toBe("🌖");
    expect.soft(moonPieProgress(4, 4)).toBe("🌕");
  });
  test("for for length 12", () => {
    expect.soft(moonPieProgress(0, 12)).toBe("🌑🌑🌑");
    expect.soft(moonPieProgress(1, 12)).toBe("🌘🌑🌑");
    expect.soft(moonPieProgress(2, 12)).toBe("🌗🌑🌑");
    expect.soft(moonPieProgress(3, 12)).toBe("🌖🌑🌑");
    expect.soft(moonPieProgress(4, 12)).toBe("🌕🌑🌑");
    expect.soft(moonPieProgress(5, 12)).toBe("🌕🌘🌑");
    expect.soft(moonPieProgress(6, 12)).toBe("🌕🌗🌑");
    expect.soft(moonPieProgress(7, 12)).toBe("🌕🌖🌑");
    expect.soft(moonPieProgress(8, 12)).toBe("🌕🌕🌑");
    expect.soft(moonPieProgress(9, 12)).toBe("🌕🌕🌘");
    expect.soft(moonPieProgress(10, 12)).toBe("🌕🌕🌗");
    expect.soft(moonPieProgress(11, 12)).toBe("🌕🌕🌖");
    expect.soft(moonPieProgress(12, 12)).toBe("🌕🌕🌕");
  });
  test("for for length 0", () => {
    expect.soft(moonPieProgress(0, 0)).toBe("");
  });
  test("for for length 1", () => {
    expect.soft(moonPieProgress(0, 1)).toBe("🌑");
    expect.soft(moonPieProgress(1, 1)).toBe("🌘");
  });
  test("for for length 2", () => {
    expect.soft(moonPieProgress(0, 2)).toBe("🌑");
    expect.soft(moonPieProgress(1, 2)).toBe("🌘");
    expect.soft(moonPieProgress(2, 2)).toBe("🌗");
  });
  test("for for length 3", () => {
    expect.soft(moonPieProgress(0, 3)).toBe("🌑");
    expect.soft(moonPieProgress(1, 3)).toBe("🌘");
    expect.soft(moonPieProgress(2, 3)).toBe("🌗");
    expect.soft(moonPieProgress(3, 3)).toBe("🌖");
  });
  test("for for length 7", () => {
    expect.soft(moonPieProgress(0, 7)).toBe("🌑🌑");
    expect.soft(moonPieProgress(1, 7)).toBe("🌘🌑");
    expect.soft(moonPieProgress(2, 7)).toBe("🌗🌑");
    expect.soft(moonPieProgress(3, 7)).toBe("🌖🌑");
    expect.soft(moonPieProgress(4, 7)).toBe("🌕🌑");
    expect.soft(moonPieProgress(5, 7)).toBe("🌕🌘");
    expect.soft(moonPieProgress(6, 7)).toBe("🌕🌗");
    expect.soft(moonPieProgress(7, 7)).toBe("🌕🌖");
  });

  describe("throws when values are out of range #bringYourOwnClamp", () => {
    test("does not accept negative progress", () => {
      expect(() => {
        moonPieProgress(-1, 12);
      }).toThrow(RangeError);
    });
    test("does not accept progress overflow", () => {
      expect(() => {
        moonPieProgress(13, 12);
      }).toThrow(RangeError);
    });
  });
});

moonPieProgress.ts

const lunaCodePoint = 0x25 * 0b11 * 11_51;
const phases = 4;
const emptyString = String.fromCodePoint(lunaCodePoint);
const filledString = String.fromCodePoint(lunaCodePoint + 4);

/**
 * Displays a progress bar using moon emojis.
 * @param i Progress value, between 0 and `length` inclusive
 * @param length Maximum progress value
 * @throws `RangeError` For out of range progress values `i`
 * @returns A string like "🌕🌘🌑"
 */
export function moonPieProgress(i: number, length: number): string {
  const total = Math.ceil(length / phases);
  const filled = Math.floor(i / phases);
  const filledStrings = filledString.repeat(filled);

  const phase = i % phases;

  if (phase === 0) return filledStrings + emptyString.repeat(total - filled);

  const codePointOffset = (8 - phase) % 8;
  const phaseString = String.fromCodePoint(lunaCodePoint + codePointOffset);

  return filledStrings + phaseString + emptyString.repeat(total - filled - 1);
}