class Validator {
  constructor(form, constraints, onChange = true) {
    this.form = form;
    this.constraints = constraints;
    this.ON_CHANGE = onChange;
    this.ERROR = 'has-error';
  };

  init() {
    this._validate();
  };

  checkPresence(input) {
    return (input.value.length >= 1) ? true : false;
  };

  checkEmail(input) {
    let email = input.value;
    let re = /^(([^<>()\[\]\\.,;:\s@"]+(\.[^<>()\[\]\\.,;:\s@"]+)*)|(".+"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/;
    return re.test(String(email).toLowerCase());
  };

  handleFormSubmit(e, form) {
    let errors = this.validate(form, this.constraints);
    let keys = Object.keys(errors);

    if (keys.length) {
      for (let i = 0; i < keys.length; i++) {
        let inputs = form.querySelectorAll('input[name="'+keys[i]+'"], textarea[name="'+keys[i]+'"], select[name="'+keys[i]+'"]');
        for (let j = 0; j < inputs.length; j++) {
          if (inputs[j].name === keys[i]) {
            e.preventDefault();
            inputs[j].classList.add(this.ERROR);
            if (this.addError) {
              this.addError(inputs[j]);
            };
          };
        };
      };
    } else {
      if (this.removeAllErrors) {
        this.removeAllErrors(e, form);
      };
      if (this.showSuccess) {
        this.showSuccess(e, form);
      };
    };

  };

  handleChangeInput(input, error) {
    if (error) {
      input.classList.add(this.ERROR);
      if (this.addError) {
        this.addError(input);
      };
    } else {
      input.classList.remove(this.ERROR);
      if (this.removeError) {
        this.removeError(input);
      };
    };
  };

  validate(form, constraints) {
    let inputs = [].slice.call(form.querySelectorAll('input, select, textarea'));
    let errors = {};
    inputs.forEach((input) => {
      let name = input.name;
      let error = this.validateInput(input, constraints[name]);
      if (error) {
        errors[name] = error;
      };
    });
    return errors;
  };

  validateInput(input, constraint) {
    if (constraint === 'presence' && !this.checkPresence(input)) {
      return input.name;
    };
    if (constraint === 'email' && !this.checkEmail(input)) {
      return input.name;
    };
    if (typeof constraint === 'function' && !constraint(input)) {
      return input.name;
    };
  };

  _validate() {
    this.form.addEventListener('submit', (e) => {
      this.handleFormSubmit(e, this.form);
    }, false);

    if (this.ON_CHANGE) {
      let inputs = [].slice.call(this.form.querySelectorAll('input, select, textarea'));
      inputs.forEach((input) => {
        input.addEventListener('change', (e) => {
          let errors = this.validate(this.form, this.constraints);
          this.handleChangeInput(e.currentTarget, errors[e.currentTarget.name]);
        }, false);
      });
    };
  };
};

const $forms = $('.js-form-valid');

function checkLength(input) {
  return (input.value.length > 5) ? true : false;
};

function checkCheckbox(input) {
  return input.checked ? true : false;
};



$forms.each(function(index, el) {
  let validator = new Validator(el, {
    username: checkLength,
    email: 'email',
    checkbox: checkCheckbox,
    comment: 'presence'
  });

  validator.removeAllErrors = (e, form) => {

  };
  validator.addError = (input) => {

  };
  validator.removeError = (input) => {

  };
  validator.showSuccess = (e, form) => {

  };
  validator.init();
});