/**
 * The rules of a Knob (#378): where a value sits on the turn, and what a drag and the wheel make of it.
 */
import { describe, expect, it } from 'vitest';
import {
  draggedValue,
  KNOB_TRAVEL,
  knobOrigin,
  knobPosition,
  knobValue,
  wheeledValue,
} from '../../src/ui/knob';

const threshold = { min: -100, max: 0, step: 0.5 };
const attack = { min: 0, max: 1, step: 0.001, taper: 3 };
const makeup = { min: -24, max: 24, step: 0.5 };

describe('a knob', () => {
  it('turns evenly without a taper, and gives the low end more of the turn with one', () => {
    expect(knobPosition(-50, threshold)).toBeCloseTo(0.5, 9);
    expect(knobValue(0.5, threshold)).toBe(-50);
    // An attack of 3 ms is an eighth of the way round, not three thousandths.
    expect(knobPosition(0.003, attack)).toBeCloseTo(0.144, 3);
    expect(knobValue(knobPosition(0.003, attack), attack)).toBe(0.003);
    expect(knobValue(-1, attack)).toBe(0);
    expect(knobValue(2, attack)).toBe(1);
  });

  it('turns up as it is dragged up, a tenth as far with Shift', () => {
    expect(draggedValue(-50, -KNOB_TRAVEL / 2, false, threshold)).toBe(0);
    expect(draggedValue(-50, KNOB_TRAVEL / 4, false, threshold)).toBe(-75);
    expect(draggedValue(-50, -KNOB_TRAVEL / 2, true, threshold)).toBe(-45);
    expect(draggedValue(-50, KNOB_TRAVEL * 10, false, threshold)).toBe(-100);
  });

  it('moves at least one step, however short the drag', () => {
    expect(draggedValue(-50, -1, true, threshold)).toBe(-49.5);
    expect(draggedValue(-50, 1, true, threshold)).toBe(-50.5);
    expect(draggedValue(0, -1, true, threshold)).toBe(0);
    expect(draggedValue(-50, 0, false, threshold)).toBe(-50);
  });

  it('notches up on the wheel turned up, and down on it turned down', () => {
    expect(wheeledValue(-50, -100, threshold)).toBe(-48);
    expect(wheeledValue(-50, 100, threshold)).toBe(-52);
    expect(wheeledValue(0.003, -100, attack)).toBeGreaterThan(0.003);
  });

  it('has 0 straight up on a bipolar range, and gives the small numbers either way most of the turn (#386)', () => {
    const slide = { min: -2000, max: 2000, step: 1, taper: 3, bipolar: true };
    expect(knobPosition(0, slide)).toBe(0.5);
    expect(knobPosition(2000, slide)).toBe(1);
    expect(knobPosition(-2000, slide)).toBe(0);
    // 250 st/s, an eighth of the reach, is halfway up the right half; even it would be at 0.5625.
    expect(knobPosition(250, slide)).toBeCloseTo(0.75, 9);
    expect(knobPosition(-250, slide)).toBeCloseTo(0.25, 9);
    expect(knobValue(0.75, slide)).toBe(250);
    expect(knobValue(0.5, slide)).toBe(0);
    for (const value of [-1200, -7, 0, 3, 640])
      expect(knobValue(knobPosition(value, slide), slide)).toBe(value);
    expect(knobOrigin(slide)).toBe(0.5);
    expect(draggedValue(0, -1, true, slide)).toBe(1);
  });

  it('fills its arc from 0 when the range has it inside, else from the low end', () => {
    expect(knobOrigin(makeup)).toBeCloseTo(0.5, 9);
    expect(knobOrigin(threshold)).toBe(0);
    expect(knobOrigin(attack)).toBe(0);
  });
});