// A modem's code (modemCode.ts): six characters derived from the project and
// the modem, the same wherever it is derived; read back as people type it.

import { describe, expect, it } from 'vitest';
import { MODEM_CODE_ALPHABET, MODEM_CODE_LENGTH, modemCode, modemCodeOf, modemCodeText } from '../src/index.js';

const uuid = (number: number) => `00000000-0000-4000-8000-${number.toString(16).padStart(12, '0')}`;

describe("a modem's code", () => {
  it('is six characters one does not misread, the same for the same modem', () => {
    const code = modemCode(uuid(1), uuid(2));
    expect(code).toMatch(new RegExp(`^[${MODEM_CODE_ALPHABET}]{${MODEM_CODE_LENGTH}}$`));
    expect(MODEM_CODE_ALPHABET).not.toMatch(/[01IO]/);
    expect(modemCode(uuid(1), uuid(2))).toBe(code);
    // Pinned: the editor and server F must derive the same code from the same project and modem.
    expect(code).toBe('VKUZ5Q');
  });

  it('differs for a copy of the project and for another modem, and spreads over every character', () => {
    expect(modemCode(uuid(1), uuid(2))).not.toBe(modemCode(uuid(3), uuid(2)));
    expect(modemCode(uuid(1), uuid(2))).not.toBe(modemCode(uuid(1), uuid(3)));
    const codes = Array.from({ length: 20_000 }, (_, index) => modemCode(uuid(index), uuid(7)));
    // 2^30 codes: 20 000 projects meet a handful of times at most.
    expect(new Set(codes).size).toBeGreaterThan(19_990);
    for (let position = 0; position < MODEM_CODE_LENGTH; position += 1) {
      const counts = new Map<string, number>();
      for (const code of codes) counts.set(code[position]!, (counts.get(code[position]!) ?? 0) + 1);
      expect(counts.size, `characters at ${position}`).toBe(MODEM_CODE_ALPHABET.length);
      // Each character about 625 times; none below half of that.
      expect(Math.min(...counts.values()), `rarest character at ${position}`).toBeGreaterThan(300);
    }
  });

  it('is read as typed, without spaces, dashes and small letters, and written in two groups', () => {
    expect(modemCodeOf(' k7f-3qx ')).toBe('K7F3QX');
    expect(modemCodeOf('K7F 3QX')).toBe('K7F3QX');
    for (const text of ['', 'K7F3Q', 'K7F3QXY', 'K7F3Q0', 'K7F3QO', 'K7F3Q1', 'K7F3QI', 'K7F3Q!']) expect(modemCodeOf(text), text).toBeUndefined();
    expect(modemCodeText('K7F3QX')).toBe('K7F-3QX');
  });
});