// options for all examples
const options = ['Apple', 'Apricot', 'Banana', 'Blackberry', 'Blueberry', 'Cantaloupe', 'Cherry', 'Date', 'Durian', 'Eggplant', 'Fig', 'Grape', 'Guava', 'Huckleberry'];

/*
 * Helper constants and functions
 */

// make it easier for ourselves by putting some values in objects
// in TypeScript, these would be enums
const Keys = {
  Backspace: 'Backspace',
  Clear: 'Clear',
  Down: 'ArrowDown',
  End: 'End',
  Enter: 'Enter',
  Escape: 'Escape',
  Home: 'Home',
  Left: 'ArrowLeft',
  PageDown: 'PageDown',
  PageUp: 'PageUp',
  Right: 'ArrowRight',
  Space: ' ',
  Tab: 'Tab',
  Up: 'ArrowUp'
}

const MenuActions = {
  Close: 0,
  CloseSelect: 1,
  First: 2,
  Last: 3,
  Next: 4,
  Open: 5,
  Previous: 6,
  Select: 7,
  Space: 8,
  Type: 9
}

// filter an array of options against an input string
// returns an array of options that begin with the filter string, case-independent
function filterOptions(options = [], filter, exclude = []) {
  return options.filter((option) => {
    const matches = option.toLowerCase().indexOf(filter.toLowerCase()) === 0;
    return matches && exclude.indexOf(option) < 0;
  });
}

// return an array of exact option name matches from a comma-separated string
function findMatches(options, search) {
  const names = search.split(',');
  return names.map((name) => {
    const match = options.filter((option) => name.trim().toLowerCase() === option.toLowerCase());
    return match.length > 0 ? match[0] : null;
  })
  .filter((option) => option !== null);
}

// return combobox action from key press
function getActionFromKey(key, menuOpen) {
  // handle opening when closed
  if (!menuOpen && key === Keys.Down) {
    return MenuActions.Open;
  }

  // handle keys when open
  if (key === Keys.Down) {
    return MenuActions.Next;
  }
  else if (key === Keys.Up) {
    return MenuActions.Previous;
  }
  else if (key === Keys.Home) {
    return MenuActions.First;
  }
  else if (key === Keys.End) {
    return MenuActions.Last;
  }
  else if (key === Keys.Escape) {
    return MenuActions.Close;
  }
  else if (key === Keys.Enter) {
    return MenuActions.CloseSelect;
  }
  else if (key === Keys.Backspace || key === Keys.Clear || key.length === 1) {
    return MenuActions.Type;
  }
}

// get index of option that matches a string
function getIndexByLetter(options, filter) {
  const firstMatch = filterOptions(options, filter)[0];
  return firstMatch ? options.indexOf(firstMatch) : -1;
}

// get updated option index
function getUpdatedIndex(current, max, action) {
  switch(action) {
    case MenuActions.First:
      return 0;
    case MenuActions.Last:
      return max;
    case MenuActions.Previous:
      return Math.max(0, current - 1);
    case MenuActions.Next:
      return Math.min(max, current + 1);
    default:
      return current;
  }
}

// check if an element is currently scrollable
function isScrollable(element) {
  return element && element.clientHeight < element.scrollHeight;
}

// ensure given child element is within the parent's visible scroll area
function maintainScrollVisibility(activeElement, scrollParent) {
  const { offsetHeight, offsetTop } = activeElement;
  const { offsetHeight: parentOffsetHeight, scrollTop } = scrollParent;

  const isAbove = offsetTop < scrollTop;
  const isBelow = (offsetTop + offsetHeight) > (scrollTop + parentOffsetHeight);

  if (isAbove) {
    scrollParent.scrollTo(0, offsetTop);
  }
  else if (isBelow) {
    scrollParent.scrollTo(0, offsetTop - parentOffsetHeight + offsetHeight);
  }
}

/*
 * Multiselect CSV code
 */
 const MultiselectCSV = function(el, options) {
  // element refs
  this.el = el;
  this.comboEl = el.querySelector('[role=combobox]');
  this.inputEl = el.querySelector('input');
  this.listboxEl = el.querySelector('[role=listbox]');

  // data
  this.idBase = this.inputEl.id;
  this.options = options;
  this.filteredOptions = options;
  this.selectedOptions = [];

  // state
  this.activeIndex = 0;
  this.open = false;
}

MultiselectCSV.prototype.init = function() {

  this.inputEl.addEventListener('input', this.onInput.bind(this));
  this.inputEl.addEventListener('blur', this.onInputBlur.bind(this));
  this.inputEl.addEventListener('click', () => this.updateMenuState(true));
  this.inputEl.addEventListener('keydown', this.onInputKeyDown.bind(this));

  this.options.map((option, index) => {
    const optionEl = document.createElement('div');
    optionEl.setAttribute('role', 'option');
    optionEl.id = `${this.idBase}-${index}`;
    optionEl.className = index === 0 ? 'combo-option option-current' : 'combo-option';
    optionEl.setAttribute('aria-selected', 'false');
    optionEl.innerText = option;

    optionEl.addEventListener('click', () => { this.onOptionClick(index); });
    optionEl.addEventListener('mousedown', this.onOptionMouseDown.bind(this));

    this.listboxEl.appendChild(optionEl);
  });
}

MultiselectCSV.prototype.filterOptions = function(value, excludeOptions = []) {
  this.filteredOptions = filterOptions(this.options, value, excludeOptions);

  // hide/show options based on filtering
  const options = this.el.querySelectorAll('[role=option]');
  [...options].forEach((optionEl) => {
    const value = optionEl.innerText;
    if (this.filteredOptions.indexOf(value) > -1) {
      optionEl.style.display = 'block';
    }
    else {
      optionEl.style.display = 'none';
    }
  });
}

MultiselectCSV.prototype.onInput = function() {
  const curValue = this.inputEl.value;
  const currentSearch = curValue.split(',').pop().replace(/^\s+/, '');
  const matchingOptions = findMatches(this.options, curValue);
  this.updateSelectedOptions(matchingOptions, false);
  this.filterOptions(currentSearch, this.selectedOptions);

  // if active option is not in filtered options, set it to first filtered option
  if (this.filteredOptions.indexOf(this.options[this.activeIndex]) < 0) {
    const firstFilteredIndex = Math.max(this.options.indexOf(this.filteredOptions[0]), 0);
    this.onOptionChange(firstFilteredIndex);
  }

  const menuState = this.filteredOptions.length > 0;
  if (this.open !== menuState) {
    this.updateMenuState(menuState, false);
  }
}

MultiselectCSV.prototype.onInputKeyDown = function(event) {
  const { key } = event;

  const max = this.filteredOptions.length - 1;
  const activeFilteredIndex = this.filteredOptions.indexOf(this.options[this.activeIndex]);

  const action = getActionFromKey(key, this.open);

  switch(action) {
    case MenuActions.Next:
    case MenuActions.Last:
    case MenuActions.First:
    case MenuActions.Previous:
      event.preventDefault();
      const nextFilteredIndex = getUpdatedIndex(activeFilteredIndex, max, action);
      const nextRealIndex = this.options.indexOf(this.filteredOptions[nextFilteredIndex]);
      return this.onOptionChange(nextRealIndex);
    case MenuActions.CloseSelect:
      event.preventDefault();
      this.updateOption(this.activeIndex);
      return this.updateMenuState(false);
    case MenuActions.Close:
      event.preventDefault();
      return this.updateMenuState(false);
    case MenuActions.Open:
      return this.updateMenuState(true);
  }
}

MultiselectCSV.prototype.onInputBlur = function() {
  if (this.ignoreBlur) {
    this.ignoreBlur = false;
    return;
  }

  if (this.open) {
    this.processInputString(this.inputEl.value);
    this.updateMenuState(false, false);
  }
}

MultiselectCSV.prototype.onOptionChange = function(index) {
  this.activeIndex = index;
  this.inputEl.setAttribute('aria-activedescendant', `${this.idBase}-${index}`);

  // update active style
  const options = this.el.querySelectorAll('[role=option]');
  [...options].forEach((optionEl) => {
    optionEl.classList.remove('option-current');
  });
  options[index].classList.add('option-current');

  if (this.open && isScrollable(this.listboxEl)) {
    maintainScrollVisibility(options[index], this.listboxEl);
  }
}

MultiselectCSV.prototype.onOptionClick = function(index) {
  this.onOptionChange(index);
  this.updateOption(index);
  this.inputEl.focus();
}

MultiselectCSV.prototype.onOptionMouseDown = function() {
  this.ignoreBlur = true;
}

MultiselectCSV.prototype.processInputString = function(inputString) {
  const options = findMatches(this.options, inputString);
  this.updateSelectedOptions(options, true);
}

MultiselectCSV.prototype.updateOption = function(index) {
  const option = this.options[index];
  const selectedIndex = this.selectedOptions.indexOf(option);
  const isSelected = selectedIndex > -1;
  this.filterOptions('');

  if (isSelected) {
    this.selectedOptions.splice(selectedIndex, 1);
    this.updateSelectedOptions(this.selectedOptions, true);
  }

  else {
    this.updateSelectedOptions([...this.selectedOptions, option], true);
  }
}

MultiselectCSV.prototype.updateMenuState = function(open, callFocus = true) {
  this.open = open;

  this.comboEl.setAttribute('aria-expanded', `${open}`);
  open ? this.el.classList.add('open') : this.el.classList.remove('open');
  callFocus && this.inputEl.focus();
}

MultiselectCSV.prototype.updateSelectedOptions = function(options, setInputValue) {
  this.selectedOptions = options;

  if (setInputValue) {
    this.inputEl.value = this.selectedOptions.join(', ');
  }

  // update aria-selected
  const optionEls = this.el.querySelectorAll('[role=option]');
  [...optionEls].forEach((optionEl) => {
    const optionSelected = this.selectedOptions.indexOf(optionEl.innerText) > -1;
    optionEl.setAttribute('aria-selected', `${optionSelected}`);
    optionSelected ? optionEl.classList.add('option-selected') : optionEl.classList.remove('option-selected');
  });

  this.filterOptions('');
}

// init combo
const csvEl = document.querySelector('.js-csv');
const csvComponent = new MultiselectCSV(csvEl, options);
csvComponent.init();

/*
 * Multiselect Combobox w/ Buttons code
 */
 const MultiselectButtons = function(el, options) {
  // element refs
  this.el = el;
  this.comboEl = el.querySelector('[role=combobox]');
  this.inputEl = el.querySelector('input');
  this.listboxEl = el.querySelector('[role=listbox]');

  this.idBase = this.inputEl.id;
  this.selectedEl = document.getElementById(`${this.idBase}-selected`);

  // data
  this.options = options;
  this.filteredOptions = options;

  // state
  this.activeIndex = 0;
  this.open = false;
}

MultiselectButtons.prototype.init = function() {

  this.inputEl.addEventListener('input', this.onInput.bind(this));
  this.inputEl.addEventListener('blur', this.onInputBlur.bind(this));
  this.inputEl.addEventListener('click', () => this.updateMenuState(true));
  this.inputEl.addEventListener('keydown', this.onInputKeyDown.bind(this));

  this.options.map((option, index) => {
    const optionEl = document.createElement('div');
    optionEl.setAttribute('role', 'option');
    optionEl.id = `${this.idBase}-${index}`;
    optionEl.className = index === 0 ? 'combo-option option-current' : 'combo-option';
    optionEl.setAttribute('aria-selected', 'false');
    optionEl.innerText = option;

    optionEl.addEventListener('click', () => { this.onOptionClick(index); });
    optionEl.addEventListener('mousedown', this.onOptionMouseDown.bind(this));

    this.listboxEl.appendChild(optionEl);
  });
}

MultiselectButtons.prototype.filterOptions = function(value) {
  this.filteredOptions = filterOptions(this.options, value);

  // hide/show options based on filtering
  const options = this.el.querySelectorAll('[role=option]');
  [...options].forEach((optionEl) => {
    const value = optionEl.innerText;
    if (this.filteredOptions.indexOf(value) > -1) {
      optionEl.style.display = 'block';
    }
    else {
      optionEl.style.display = 'none';
    }
  });
}

MultiselectButtons.prototype.onInput = function() {
  const curValue = this.inputEl.value;
  this.filterOptions(curValue);

  // if active option is not in filtered options, set it to first filtered option
  if (this.filteredOptions.indexOf(this.options[this.activeIndex]) < 0) {
    const firstFilteredIndex = this.options.indexOf(this.filteredOptions[0]);
    this.onOptionChange(firstFilteredIndex);
  }

  const menuState = this.filteredOptions.length > 0;
  if (this.open !== menuState) {
    this.updateMenuState(menuState, false);
  }
}

MultiselectButtons.prototype.onInputKeyDown = function(event) {
  const { key } = event;

  const max = this.filteredOptions.length - 1;
  const activeFilteredIndex = this.filteredOptions.indexOf(this.options[this.activeIndex]);

  const action = getActionFromKey(key, this.open);

  switch(action) {
    case MenuActions.Next:
    case MenuActions.Last:
    case MenuActions.First:
    case MenuActions.Previous:
      event.preventDefault();
      const nextFilteredIndex = getUpdatedIndex(activeFilteredIndex, max, action);
      const nextRealIndex = this.options.indexOf(this.filteredOptions[nextFilteredIndex]);
      return this.onOptionChange(nextRealIndex);
    case MenuActions.CloseSelect:
      event.preventDefault();
      return this.updateOption(this.activeIndex);
    case MenuActions.Close:
      event.preventDefault();
      return this.updateMenuState(false);
    case MenuActions.Open:
      return this.updateMenuState(true);
  }
}

MultiselectButtons.prototype.onInputBlur = function() {
  if (this.ignoreBlur) {
    this.ignoreBlur = false;
    return;
  }

  if (this.open) {
    this.updateMenuState(false, false);
  }
}

MultiselectButtons.prototype.onOptionChange = function(index) {
  this.activeIndex = index;
  this.inputEl.setAttribute('aria-activedescendant', `${this.idBase}-${index}`);

  // update active style
  const options = this.el.querySelectorAll('[role=option]');
  [...options].forEach((optionEl) => {
    optionEl.classList.remove('option-current');
  });
  options[index].classList.add('option-current');

  if (this.open && isScrollable(this.listboxEl)) {
    maintainScrollVisibility(options[index], this.listboxEl);
  }
}

MultiselectButtons.prototype.onOptionClick = function(index) {
  this.onOptionChange(index);
  this.updateOption(index);
  this.inputEl.focus();
}

MultiselectButtons.prototype.onOptionMouseDown = function() {
  this.ignoreBlur = true;
}

MultiselectButtons.prototype.removeOption = function(index) {
  const option = this.options[index];

  // update aria-selected
  const options = this.el.querySelectorAll('[role=option]');
  options[index].setAttribute('aria-selected', 'false');
  options[index].classList.remove('option-selected');

  // remove button
  const buttonEl = document.getElementById(`${this.idBase}-remove-${index}`);
  this.selectedEl.removeChild(buttonEl.parentElement);
}

MultiselectButtons.prototype.selectOption = function(index) {
  const selected = this.options[index];
  this.activeIndex = index;

  // update aria-selected
  const options = this.el.querySelectorAll('[role=option]');
  options[index].setAttribute('aria-selected', 'true');
  options[index].classList.add('option-selected');

  // add remove option button
  const buttonEl = document.createElement('button');
  const listItem = document.createElement('li');
  buttonEl.className = 'remove-option';
  buttonEl.type = 'button';
  buttonEl.id = `${this.idBase}-remove-${index}`;
  buttonEl.setAttribute('aria-describedby', `${this.idBase}-remove`);
  buttonEl.addEventListener('click', () => { this.removeOption(index); });
  buttonEl.innerHTML = selected + ' ';

  listItem.appendChild(buttonEl);
  this.selectedEl.appendChild(listItem);
}

MultiselectButtons.prototype.updateOption = function(index) {
  const option = this.options[index];
  const optionEls = this.el.querySelectorAll('[role=option]');
  const optionEl = optionEls[index];
  const isSelected = optionEl.getAttribute('aria-selected') === 'true';

  if (isSelected) {
    this.removeOption(index);
  }

  else {
    this.selectOption(index);
  }

  this.inputEl.value = '';
  this.filterOptions('');
}

MultiselectButtons.prototype.updateMenuState = function(open, callFocus = true) {
  this.open = open;

  this.comboEl.setAttribute('aria-expanded', `${open}`);
  open ? this.el.classList.add('open') : this.el.classList.remove('open');
  callFocus && this.inputEl.focus();
}

// init multiselect w/ top buttons
const multiButtonEl = document.querySelector('.js-multi-buttons');
const multiButtonComponent = new MultiselectButtons(multiButtonEl, options);
multiButtonComponent.init();

// init multiselect w/ inline buttons
const inlineButtonEl = document.querySelector('.js-inline-buttons');
const inlineButtonComponent = new MultiselectButtons(inlineButtonEl, options);
inlineButtonComponent.init();