/**
 * @file
 * Drupal's states library.
 */

(function ($, Drupal) {
  /**
   * The base States namespace.
   *
   * Having the local states variable allows us to use the States namespace
   * without having to always declare "Drupal.states".
   *
   * @namespace Drupal.states
   */
  const states = {

    /**
     * An array of functions that should be postponed.
     */
    postponed: [],
  };

  Drupal.states = states;

  /**
   * Attaches the states.
   *
   * @type {Drupal~behavior}
   *
   * @prop {Drupal~behaviorAttach} attach
   *   Attaches states behaviors.
   */
  Drupal.behaviors.states = {
    attach(context, settings) {
      const $states = $(context).find('[data-drupal-states]');
      const il = $states.length;
      for (let i = 0; i < il; i++) {
        const config = JSON.parse($states[i].getAttribute('data-drupal-states'));
        Object.keys(config || {}).forEach((state) => {
          new states.Dependent({
            element: $($states[i]),
            state: states.State.sanitize(state),
            constraints: config[state],
          });
        });
      }

      // Execute all postponed functions now.
      while (states.postponed.length) {
        (states.postponed.shift())();
      }
    },
  };

  /**
   * Object representing an element that depends on other elements.
   *
   * @constructor Drupal.states.Dependent
   *
   * @param {object} args
   *   Object with the following keys (all of which are required)
   * @param {jQuery} args.element
   *   A jQuery object of the dependent element
   * @param {Drupal.states.State} args.state
   *   A State object describing the state that is dependent
   * @param {object} args.constraints
   *   An object with dependency specifications. Lists all elements that this
   *   element depends on. It can be nested and can contain
   *   arbitrary AND and OR clauses.
   */
  states.Dependent = function (args) {
    $.extend(this, { values: {}, oldValue: null }, args);

    this.dependees = this.getDependees();
    Object.keys(this.dependees || {}).forEach((selector) => {
      this.initializeDependee(selector, this.dependees[selector]);
    });
  };

  /**
   * Comparison functions for comparing the value of an element with the
   * specification from the dependency settings. If the object type can't be
   * found in this list, the === operator is used by default.
   *
   * @name Drupal.states.Dependent.comparisons
   *
   * @prop {function} RegExp
   * @prop {function} Function
   * @prop {function} Number
   */
  states.Dependent.comparisons = {
    RegExp(reference, value) {
      return reference.test(value);
    },
    Function(reference, value) {
      // The "reference" variable is a comparison function.
      return reference(value);
    },
    Number(reference, value) {
      // If "reference" is a number and "value" is a string, then cast
      // reference as a string before applying the strict comparison in
      // compare().
      // Otherwise numeric keys in the form's #states array fail to match
      // string values returned from jQuery's val().
      return (typeof value === 'string') ? compare(reference.toString(), value) : compare(reference, value);
    },
  };

  states.Dependent.prototype = {

    /**
     * Initializes one of the elements this dependent depends on.
     *
     * @memberof Drupal.states.Dependent#
     *
     * @param {string} selector
     *   The CSS selector describing the dependee.
     * @param {object} dependeeStates
     *   The list of states that have to be monitored for tracking the
     *   dependee's compliance status.
     */
    initializeDependee(selector, dependeeStates) {
      let state;
      const self = this;

      function stateEventHandler(e) {
        self.update(e.data.selector, e.data.state, e.value);
      }

      // Cache for the states of this dependee.
      this.values[selector] = {};

      // eslint-disable-next-line no-restricted-syntax
      for (const i in dependeeStates) {
        if (dependeeStates.hasOwnProperty(i)) {
          state = dependeeStates[i];
          // Make sure we're not initializing this selector/state combination
          // twice.
          if ($.inArray(state, dependeeStates) === -1) {
            continue;
          }

          state = states.State.sanitize(state);

          // Initialize the value of this state.
          this.values[selector][state.name] = null;

          // Monitor state changes of the specified state for this dependee.
          $(selector).on(`state:${state}`, { selector, state }, stateEventHandler);

          // Make sure the event we just bound ourselves to is actually fired.
          new states.Trigger({ selector, state });
        }
      }
    },

    /**
     * Compares a value with a reference value.
     *
     * @memberof Drupal.states.Dependent#
     *
     * @param {object} reference
     *   The value used for reference.
     * @param {string} selector
     *   CSS selector describing the dependee.
     * @param {Drupal.states.State} state
     *   A State object describing the dependee's updated state.
     *
     * @return {bool}
     *   true or false.
     */
    compare(reference, selector, state) {
      const value = this.values[selector][state.name];
      if (reference.constructor.name in states.Dependent.comparisons) {
        // Use a custom compare function for certain reference value types.
        return states.Dependent.comparisons[reference.constructor.name](reference, value);
      }

        // Do a plain comparison otherwise.
      return compare(reference, value);
    },

    /**
     * Update the value of a dependee's state.
     *
     * @memberof Drupal.states.Dependent#
     *
     * @param {string} selector
     *   CSS selector describing the dependee.
     * @param {Drupal.states.state} state
     *   A State object describing the dependee's updated state.
     * @param {string} value
     *   The new value for the dependee's updated state.
     */
    update(selector, state, value) {
      // Only act when the 'new' value is actually new.
      if (value !== this.values[selector][state.name]) {
        this.values[selector][state.name] = value;
        this.reevaluate();
      }
    },

    /**
     * Triggers change events in case a state changed.
     *
     * @memberof Drupal.states.Dependent#
     */
    reevaluate() {
      // Check whether any constraint for this dependent state is satisfied.
      let value = this.verifyConstraints(this.constraints);

      // Only invoke a state change event when the value actually changed.
      if (value !== this.oldValue) {
        // Store the new value so that we can compare later whether the value
        // actually changed.
        this.oldValue = value;

        // Normalize the value to match the normalized state name.
        value = invert(value, this.state.invert);

        // By adding "trigger: true", we ensure that state changes don't go into
        // infinite loops.
        this.element.trigger({ type: `state:${this.state}`, value, trigger: true });
      }
    },

    /**
     * Evaluates child constraints to determine if a constraint is satisfied.
     *
     * @memberof Drupal.states.Dependent#
     *
     * @param {object|Array} constraints
     *   A constraint object or an array of constraints.
     * @param {string} selector
     *   The selector for these constraints. If undefined, there isn't yet a
     *   selector that these constraints apply to. In that case, the keys of the
     *   object are interpreted as the selector if encountered.
     *
     * @return {bool}
     *   true or false, depending on whether these constraints are satisfied.
     */
    verifyConstraints(constraints, selector) {
      let result;
      if ($.isArray(constraints)) {
        // This constraint is an array (OR or XOR).
        const hasXor = $.inArray('xor', constraints) === -1;
        const len = constraints.length;
        for (let i = 0; i < len; i++) {
          if (constraints[i] !== 'xor') {
            const constraint = this.checkConstraints(constraints[i], selector, i);
            // Return if this is OR and we have a satisfied constraint or if
            // this is XOR and we have a second satisfied constraint.
            if (constraint && (hasXor || result)) {
              return hasXor;
            }
            result = result || constraint;
          }
        }
      }
      // Make sure we don't try to iterate over things other than objects. This
      // shouldn't normally occur, but in case the condition definition is
      // bogus, we don't want to end up with an infinite loop.
      else if ($.isPlainObject(constraints)) {
        // This constraint is an object (AND).
        // eslint-disable-next-line no-restricted-syntax
        for (const n in constraints) {
          if (constraints.hasOwnProperty(n)) {
            result = ternary(result, this.checkConstraints(constraints[n], selector, n));
            // False and anything else will evaluate to false, so return when
            // any false condition is found.
            if (result === false) {
              return false;
            }
          }
        }
      }
      return result;
    },

    /**
     * Checks whether the value matches the requirements for this constraint.
     *
     * @memberof Drupal.states.Dependent#
     *
     * @param {string|Array|object} value
     *   Either the value of a state or an array/object of constraints. In the
     *   latter case, resolving the constraint continues.
     * @param {string} [selector]
     *   The selector for this constraint. If undefined, there isn't yet a
     *   selector that this constraint applies to. In that case, the state key
     *   is propagates to a selector and resolving continues.
     * @param {Drupal.states.State} [state]
     *   The state to check for this constraint. If undefined, resolving
     *   continues. If both selector and state aren't undefined and valid
     *   non-numeric strings, a lookup for the actual value of that selector's
     *   state is performed. This parameter is not a State object but a pristine
     *   state string.
     *
     * @return {bool}
     *   true or false, depending on whether this constraint is satisfied.
     */
    checkConstraints(value, selector, state) {
      // Normalize the last parameter. If it's non-numeric, we treat it either
      // as a selector (in case there isn't one yet) or as a trigger/state.
      if (typeof state !== 'string' || (/[0-9]/).test(state[0])) {
        state = null;
      }
      else if (typeof selector === 'undefined') {
        // Propagate the state to the selector when there isn't one yet.
        selector = state;
        state = null;
      }

      if (state !== null) {
        // Constraints is the actual constraints of an element to check for.
        state = states.State.sanitize(state);
        return invert(this.compare(value, selector, state), state.invert);
      }

        // Resolve this constraint as an AND/OR operator.
      return this.verifyConstraints(value, selector);
    },

    /**
     * Gathers information about all required triggers.
     *
     * @memberof Drupal.states.Dependent#
     *
     * @return {object}
     *   An object describing the required triggers.
     */
    getDependees() {
      const cache = {};
      // Swivel the lookup function so that we can record all available
      // selector- state combinations for initialization.
      const _compare = this.compare;
      this.compare = function (reference, selector, state) {
        (cache[selector] || (cache[selector] = [])).push(state.name);
        // Return nothing (=== undefined) so that the constraint loops are not
        // broken.
      };

      // This call doesn't actually verify anything but uses the resolving
      // mechanism to go through the constraints array, trying to look up each
      // value. Since we swivelled the compare function, this comparison returns
      // undefined and lookup continues until the very end. Instead of lookup up
      // the value, we record that combination of selector and state so that we
      // can initialize all triggers.
      this.verifyConstraints(this.constraints);
      // Restore the original function.
      this.compare = _compare;

      return cache;
    },
  };

  /**
   * @constructor Drupal.states.Trigger
   *
   * @param {object} args
   *   Trigger arguments.
   */
  states.Trigger = function (args) {
    $.extend(this, args);

    if (this.state in states.Trigger.states) {
      this.element = $(this.selector);

      // Only call the trigger initializer when it wasn't yet attached to this
      // element. Otherwise we'd end up with duplicate events.
      if (!this.element.data(`trigger:${this.state}`)) {
        this.initialize();
      }
    }
  };

  states.Trigger.prototype = {

    /**
     * @memberof Drupal.states.Trigger#
     */
    initialize() {
      const trigger = states.Trigger.states[this.state];

      if (typeof trigger === 'function') {
        // We have a custom trigger initialization function.
        trigger.call(window, this.element);
      }
      else {
        Object.keys(trigger || {}).forEach((event) => {
          this.defaultTrigger(event, trigger[event]);
        });
      }

      // Mark this trigger as initialized for this element.
      this.element.data(`trigger:${this.state}`, true);
    },

    /**
     * @memberof Drupal.states.Trigger#
     *
     * @param {jQuery.Event} event
     *   The event triggered.
     * @param {function} valueFn
     *   The function to call.
     */
    defaultTrigger(event, valueFn) {
      let oldValue = valueFn.call(this.element);

      // Attach the event callback.
      this.element.on(event, $.proxy(function (e) {
        const value = valueFn.call(this.element, e);
        // Only trigger the event if the value has actually changed.
        if (oldValue !== value) {
          this.element.trigger({ type: `state:${this.state}`, value, oldValue });
          oldValue = value;
        }
      }, this));

      states.postponed.push($.proxy(function () {
        // Trigger the event once for initialization purposes.
        this.element.trigger({ type: `state:${this.state}`, value: oldValue, oldValue: null });
      }, this));
    },
  };

  /**
   * This list of states contains functions that are used to monitor the state
   * of an element. Whenever an element depends on the state of another element,
   * one of these trigger functions is added to the dependee so that the
   * dependent element can be updated.
   *
   * @name Drupal.states.Trigger.states
   *
   * @prop empty
   * @prop checked
   * @prop value
   * @prop collapsed
   */
  states.Trigger.states = {
    // 'empty' describes the state to be monitored.
    empty: {
      // 'keyup' is the (native DOM) event that we watch for.
      keyup() {
        // The function associated with that trigger returns the new value for
        // the state.
        return this.val() === '';
      },
    },

    checked: {
      change() {
        // prop() and attr() only takes the first element into account. To
        // support selectors matching multiple checkboxes, iterate over all and
        // return whether any is checked.
        let checked = false;
        this.each(function () {
          // Use prop() here as we want a boolean of the checkbox state.
          // @see http://api.jquery.com/prop/
          checked = $(this).prop('checked');
          // Break the each() loop if this is checked.
          return !checked;
        });
        return checked;
      },
    },

    // For radio buttons, only return the value if the radio button is selected.
    value: {
      keyup() {
        // Radio buttons share the same :input[name="key"] selector.
        if (this.length > 1) {
          // Initial checked value of radios is undefined, so we return false.
          return this.filter(':checked').val() || false;
        }
        return this.val();
      },
      change() {
        // Radio buttons share the same :input[name="key"] selector.
        if (this.length > 1) {
          // Initial checked value of radios is undefined, so we return false.
          return this.filter(':checked').val() || false;
        }
        return this.val();
      },
    },

    collapsed: {
      collapsed(e) {
        return (typeof e !== 'undefined' && 'value' in e) ? e.value : !this.is('[open]');
      },
    },
  };

  /**
   * A state object is used for describing the state and performing aliasing.
   *
   * @constructor Drupal.states.State
   *
   * @param {string} state
   *   The name of the state.
   */
  states.State = function (state) {
    /**
     * Original unresolved name.
     */
    this.pristine = state;
    this.name = state;

    // Normalize the state name.
    let process = true;
    do {
      // Iteratively remove exclamation marks and invert the value.
      while (this.name.charAt(0) === '!') {
        this.name = this.name.substring(1);
        this.invert = !this.invert;
      }

      // Replace the state with its normalized name.
      if (this.name in states.State.aliases) {
        this.name = states.State.aliases[this.name];
      }
      else {
        process = false;
      }
    } while (process);
  };

  /**
   * Creates a new State object by sanitizing the passed value.
   *
   * @name Drupal.states.State.sanitize
   *
   * @param {string|Drupal.states.State} state
   *   A state object or the name of a state.
   *
   * @return {Drupal.states.state}
   *   A state object.
   */
  states.State.sanitize = function (state) {
    if (state instanceof states.State) {
      return state;
    }

    return new states.State(state);
  };

  /**
   * This list of aliases is used to normalize states and associates negated
   * names with their respective inverse state.
   *
   * @name Drupal.states.State.aliases
   */
  states.State.aliases = {
    enabled: '!disabled',
    invisible: '!visible',
    invalid: '!valid',
    untouched: '!touched',
    optional: '!required',
    filled: '!empty',
    unchecked: '!checked',
    irrelevant: '!relevant',
    expanded: '!collapsed',
    open: '!collapsed',
    closed: 'collapsed',
    readwrite: '!readonly',
  };

  states.State.prototype = {

    /**
     * @memberof Drupal.states.State#
     */
    invert: false,

    /**
     * Ensures that just using the state object returns the name.
     *
     * @memberof Drupal.states.State#
     *
     * @return {string}
     *   The name of the state.
     */
    toString() {
      return this.name;
    },
  };

  /**
   * Global state change handlers. These are bound to "document" to cover all
   * elements whose state changes. Events sent to elements within the page
   * bubble up to these handlers. We use this system so that themes and modules
   * can override these state change handlers for particular parts of a page.
   */

  const $document = $(document);
  $document.on('state:disabled', (e) => {
    // Only act when this change was triggered by a dependency and not by the
    // element monitoring itself.
    if (e.trigger) {
      $(e.target)
        .prop('disabled', e.value)
        .closest('.js-form-item, .js-form-submit, .js-form-wrapper')
        .toggleClass('form-disabled', e.value)
        .find('select, input, textarea')
        .prop('disabled', e.value);

      // Note: WebKit nightlies don't reflect that change correctly.
      // See https://bugs.webkit.org/show_bug.cgi?id=23789
    }
  });

  $document.on('state:required', (e) => {
    if (e.trigger) {
      if (e.value) {
        const label = `label${e.target.id ? `[for=${e.target.id}]` : ''}`;
        const $label = $(e.target).attr({ required: 'required', 'aria-required': 'aria-required' }).closest('.js-form-item, .js-form-wrapper').find(label);
        // Avoids duplicate required markers on initialization.
        if (!$label.hasClass('js-form-required').length) {
          $label.addClass('js-form-required form-required');
        }
      }
      else {
        $(e.target)
          .removeAttr('required aria-required')
          .closest('.js-form-item, .js-form-wrapper')
          .find('label.js-form-required')
          .removeClass('js-form-required form-required');
      }
    }
  });

  $document.on('state:visible', (e) => {
    if (e.trigger) {
      $(e.target).closest('.js-form-item, .js-form-submit, .js-form-wrapper').toggle(e.value);
    }
  });

  $document.on('state:checked', (e) => {
    if (e.trigger) {
      $(e.target).prop('checked', e.value);
    }
  });

  $document.on('state:collapsed', (e) => {
    if (e.trigger) {
      if ($(e.target).is('[open]') === e.value) {
        $(e.target).find('> summary').trigger('click');
      }
    }
  });

  /**
   * These are helper functions implementing addition "operators" and don't
   * implement any logic that is particular to states.
   */

  /**
   * Bitwise AND with a third undefined state.
   *
   * @function Drupal.states~ternary
   *
   * @param {*} a
   *   Value a.
   * @param {*} b
   *   Value b
   *
   * @return {bool}
   *   The result.
   */
  function ternary(a, b) {
    if (typeof a === 'undefined') {
      return b;
    }
    else if (typeof b === 'undefined') {
      return a;
    }

    return a && b;
  }

  /**
   * Inverts a (if it's not undefined) when invertState is true.
   *
   * @function Drupal.states~invert
   *
   * @param {*} a
   *   The value to maybe invert.
   * @param {bool} invertState
   *   Whether to invert state or not.
   *
   * @return {bool}
   *   The result.
   */
  function invert(a, invertState) {
    return (invertState && typeof a !== 'undefined') ? !a : a;
  }

  /**
   * Compares two values while ignoring undefined values.
   *
   * @function Drupal.states~compare
   *
   * @param {*} a
   *   Value a.
   * @param {*} b
   *   Value b.
   *
   * @return {bool}
   *   The comparison result.
   */
  function compare(a, b) {
    if (a === b) {
      return typeof a === 'undefined' ? a : true;
    }

    return typeof a === 'undefined' || typeof b === 'undefined';
  }
}(jQuery, Drupal));
