import { merge } from 'lodash';
import { s__ } from '~/locale';

/**
 * Validation messages will take priority based on the property order.
 *
 * For example:
 * { valueMissing: {...}, urlTypeMismatch: {...} }
 *
 * `valueMissing` will be displayed the user has entered a value
 *  after that, if the input is not a valid URL then `urlTypeMismatch` will show
 */
const defaultFeedbackMap = {
  valueMissing: {
    isInvalid: el => el.validity?.valueMissing,
    message: s__('Please fill out this field.'),
  },
  urlTypeMismatch: {
    isInvalid: el => el.type === 'url' && el.validity?.typeMismatch,
    message: s__('Please enter a valid URL format, ex: http://www.example.com/home'),
  },
};

const getFeedbackForElement = (feedbackMap, el) =>
  Object.values(feedbackMap).find(f => f.isInvalid(el))?.message || el.validationMessage;

const focusFirstInvalidInput = e => {
  const { target: formEl } = e;
  const invalidInput = formEl.querySelector('input:invalid');

  if (invalidInput) {
    invalidInput.focus();
  }
};

const isEveryFieldValid = form => Object.values(form.fields).every(({ state }) => state === true);

const createValidator = (context, feedbackMap) => ({ el, reportInvalidInput = false }) => {
  const { form } = context;
  const { name } = el;

  if (!name) {
    if (process.env.NODE_ENV === 'development') {
      // eslint-disable-next-line no-console
      console.warn(
        '[gitlab] the validation directive requires the given input to have "name" attribute',
      );
    }
    return;
  }

  const formField = form.fields[name];
  const isValid = el.checkValidity();

  // This makes sure we always report valid fields - this can be useful for cases where the consuming
  // component's logic depends on certain fields being in a valid state.
  // Invalid input, on the other hand, should only be reported once we want to display feedback to the user.
  // (eg.: After a field has been touched and moved away from, a submit-button has been clicked, ...)
  formField.state = reportInvalidInput ? isValid : isValid || null;
  formField.feedback = reportInvalidInput ? getFeedbackForElement(feedbackMap, el) : '';

  form.state = isEveryFieldValid(form);
};

/**
 * Takes an object that allows to add or change custom feedback messages.
 *
 * The passed in object will be merged with the built-in feedback
 * so it is possible to override a built-in message.
 *
 * @example
 * validate({
 *   tooLong: {
 *     check: el => el.validity.tooLong === true,
 *     message: 'Your custom feedback'
 *   }
 * })
 *
 * @example
 *   validate({
 *     valueMissing: {
 *       message: 'Your custom feedback'
 *     }
 *   })
 *
 * @param {Object<string, { message: string, isValid: ?function}>} customFeedbackMap
 * @returns {{ inserted: function, update: function }} validateDirective
 */
export default function(customFeedbackMap = {}) {
  const feedbackMap = merge(defaultFeedbackMap, customFeedbackMap);
  const elDataMap = new WeakMap();

  return {
    inserted(el, binding, { context }) {
      const { arg: showGlobalValidation } = binding;
      const { form: formEl } = el;

      const validate = createValidator(context, feedbackMap);
      const elData = { validate, isTouched: false, isBlurred: false };

      elDataMap.set(el, elData);

      el.addEventListener('input', function markAsTouched() {
        elData.isTouched = true;
        // once the element has been marked as touched we can stop listening on the 'input' event
        el.removeEventListener('input', markAsTouched);
      });

      el.addEventListener('blur', function markAsBlurred({ target }) {
        if (elData.isTouched) {
          elData.isBlurred = true;
          validate({ el: target, reportInvalidInput: true });
          // this event handler can be removed, since the live-feedback in `update` takes over
          el.removeEventListener('blur', markAsBlurred);
        }
      });

      if (formEl) {
        formEl.addEventListener('submit', focusFirstInvalidInput);
      }

      validate({ el, reportInvalidInput: showGlobalValidation });
    },
    update(el, binding) {
      const { arg: showGlobalValidation } = binding;
      const { validate, isTouched, isBlurred } = elDataMap.get(el);
      const showValidationFeedback = showGlobalValidation || (isTouched && isBlurred);

      validate({ el, reportInvalidInput: showValidationFeedback });
    },
  };
}