import assert from 'node:assert/strict';
import test from 'node:test';
import {
  distanceParts,
  formatDistanceText,
  kilometreDigits,
} from './distanceFormat.js';

test('a distance switches to kilometres where its metres round to 1,000', () => {
  assert.equal(formatDistanceText(999.4), '999 m');
  assert.equal(formatDistanceText(999.5), '1.0 km');
  assert.equal(formatDistanceText(999.6), '1.0 km');
  assert.equal(formatDistanceText(994, { metreStep: 10 }), '990 m');
  assert.equal(formatDistanceText(995, { metreStep: 10 }), '1.0 km');
});

test('kilometres drop their decimal where the tenth rounds to 10.0', () => {
  assert.equal(kilometreDigits(9949), 1);
  assert.equal(kilometreDigits(9950), 0);
  assert.equal(formatDistanceText(9949), '9.9 km');
  assert.equal(formatDistanceText(9950), '10 km');
  assert.equal(formatDistanceText(9960), '10 km');
  assert.equal(formatDistanceText(99950), '100 km');
});

test('metres below exactBelowM stay whole while the rest round to the step', () => {
  const options = { metreStep: 10, exactBelowM: 100 };
  assert.equal(formatDistanceText(8, options), '8 m');
  assert.equal(formatDistanceText(99.4, options), '99 m');
  assert.equal(formatDistanceText(846, options), '850 m');
  assert.deepEqual(distanceParts(846, options), {
    value: 850,
    unit: 'm',
    digits: 0,
  });
});

test('a negative or non-finite distance has no parts', () => {
  for (const value of [-1, Number.NaN, Infinity, -Infinity, null, undefined]) {
    assert.equal(distanceParts(value), null);
    assert.equal(formatDistanceText(value), null);
  }
  assert.equal(formatDistanceText(0), '0 m');
});

test('kilometres come back rounded, so toFixed and Intl agree', () => {
  assert.deepEqual(distanceParts(1450), { value: 1.5, unit: 'km', digits: 1 });
  assert.equal(formatDistanceText(1450), '1.5 km');
  assert.equal(formatDistanceText(1150), '1.2 km');
});