/**
  * This file is a factory for DOM UI elements.
  */

/**
  * Returns a settings container that includes a section and a heading.
  */
export function settingsContainer({id, label, level=2}) {

  const container = document.createElement('section');
  container.id = id;
  container.innerHTML = `<h${level}>${label}</h${level}>`;
  return container;
};

/**
  * Returns a slider that includes a label, and can optionally be set to
  * "shift" to a different step. (eg. we use this for π mode, where frequency
  * and amplitude are mapped to π/8 increments.
  */
export function slider({
  id,
  min,
  max,
  step,
  shiftStep,
  get,
  set,
  label = '',
  className
}) {

  const sliderContainer = document.createElement('section');
  sliderContainer.classList.add('slider');
  sliderContainer.classList.add(className);
  const labelElement = document.createElement('label');
  labelElement.setAttribute('for', id);
  labelElement.innerHTML = label;
  const slider = document.createElement('input');
  slider.id = id;
  slider.type = 'range';
  slider.min = min;
  slider.max = max;
  slider.step = step;
  slider.value = get().toString();

  if (shiftStep) {
    document.addEventListener('keydown', function(event) {
      if (event.shiftKey) {
        slider.classList.add('shifted');
        slider.step = shiftStep;
      }
    });

    document.addEventListener('keyup', function(event) {
      if (event.key === 'Shift') {
        slider.classList.remove('shifted');
        slider.step = step;
      }
    });

    document.addEventListener('touchstart', function(event) {
      if (event.touches.length == 3) {
        if (slider.classList.contains('shifted')) {
          slider.classList.remove('shifted');
          slider.step = step;
        } else {
          slider.classList.add('shifted');
          slider.step = shiftStep;
        }
      }
    });
  }

  slider.addEventListener('input', () => set(slider.value));

  sliderContainer.appendChild(labelElement);
  sliderContainer.appendChild(slider);
  return sliderContainer;
}