waigo/waigo

"use strict";


const waigo = global.waigo,
  _ = waigo._,
  errors = waigo.load('support/errors'),
  viewObjects = waigo.load('support/viewObjects');


/** 
 * # Form fields
 *
 * This module provides a base `Field` class for use with the `Form` class.
 * Concrete instances of this class are never created - instead one of its
 * subtypes will be instantiated depending on the type of field required.
 *
 * A field is provided a reference to its parent form upon constructions - it
 * uses this primarily to fetch a reference to the form's internal state
 * object, as this is where fields also store their data (rather than within
 * the `Field` instance).
 *
 * The `Field.new()` static method makes it easy to initialise a field of any
 * given type and is the recommended method for creating new field instances.
 */



/** A field validation error. */
const FieldValidationError = exports.FieldValidationError = 
  errors.define('FieldValidationError', errors.MultipleError);

  
/** A field sanitization error. */
const FieldSanitizationError = exports.FieldSanitizationError = 
  errors.define('FieldSanitizationError');




class Field {
  /**
   * A form field.
   * 
   * @param  {Form} form   Parent form
   * @param  {Object} config Configuration options
   * @constructor
   */
  constructor (form, config) {
    this.form = form;
    this.config = config;

    this.sanitizers = [];
    this.validators = [];

    _.each(config.sanitizers || [], (def) => {
      this._addSanitizer(def);
    });

    _.each(config.validators || [], (def) => {
      this._addValidator(def);
    });
  }


  /**
   * Add a validator
   * @param {String|Object|GeneratorFunction} def 
   */
  _addValidator (def) {
    if (_.isGenFn(def)) {
      return this.validators.push({
        fn: def
      });
    }

    var options = {};

    if (def.id) {
      options = _.omit(def, 'id');
      def = def.id;
    }

    this.validators.push({
      fn: waigo.load(`support/forms/validators/${def}`)(options),
      msg: options.msg,
    });
  }


  /**
   * Add a sanitizer
   * @param {String|Object|GeneratorFunction} def 
   */
  _addSanitizer (def) {
    if (_.isGenFn(def)) {
      return this.sanitizers.push({
        fn: def
      });
    }

    var options = {}

    if (def.id) {
      options = _.omit(def, 'id');
      def = def.id;
    }

    this.sanitizers.push({
      fn: waigo.load(`support/forms/sanitizers/${def}`)(options),
      msg: options.msg,
    });
  }


  get name () {
    return this.config.name;
  }


  get label () {
    return this.config.label || this.config.name;
  }

  /**
   * Field original value.
   *
   * This is useful if we wish to check whether the field value has changed 
   * from its previous value.
   */
  get originalValue () {
    return _.get(this.form.state, `${this.name}.originalValue`);
  }

  set originalValue (value) {
    this.form.state[this.name].originalValue = value; 
  }


  get value () {
    return _.get(this.form.state, `${this.name}.value`);
  }

  set value (value) {
    this.form.state[this.name].value = value;
  }


  /**
   * Set the value of this field.
   *
   * This will run the given value through all available sanitizers prior to
   * actually setting it. Subclasses should override this method if they wish to
   * perform any additional processing of the value.
   * 
   * @param {*} val The value.
   * @throws FieldSanitizationError If any errors occur.
   */
  * setSanitizedValue (val) {
    for (let sanitizer of this.sanitizers) {
      let fn = sanitizer.fn,
        msg = sanitizer.msg;

      try {
        val = yield fn(this, val);
      } catch (e) {
        throw new FieldSanitizationError(msg || e.message);
      }
    }

    this.value = val;
  }


  /** 
   * Get whether this field is dirty.
   *
   * It is dirty if its current value is different from its original value.
   * 
   * @return {Boolean}
   */
  isDirty () {
    return this.value !== this.originalValue;
  }



  /**
   * Validate this field's value.
   *
   * @param {Object} [context] Client koa request context.
   *
   * @throws FieldValidationError If validation fails.
   */
  * validate (context) {
    let errors = [];

    // if value is undefined and field is not required then nothing to do
    if (undefined === this.value || null === this.value || '' === this.value) {
      if (!this.config.required) {
        return;
      } else {
        errors.push('Must be set');
      }
    } else {
      for (let validator of this.validators) {
        let fn = validator.fn,
          msg = validator.msg;

        try {
          yield fn(context, this, this.value);
        } catch (err) {
          errors.push(msg || err.message);
        }
      }    
    }

    if (0 < errors.length) {
      throw new FieldValidationError('Field validation failed', 400, errors);
    }
  }
}



/**
 * Get renderable representation of this field.
 *
 * @param {Object} ctx Current request context.
 * 
 * @return {Object}
 */
Field.prototype[viewObjects.METHOD_NAME] = function*(ctx) {
  return _.extend({}, this.config, {
    value: this.value,
    originalValue: this.originalValue,
  });
}




/** 
 * Create a `Field` instance.
 *
 * This will load and intialise an instance of the correct `Field` subtype
 * according to the given field definition.
 * 
 * @param {Form} form The parent form which holds this field's internal state.
 * @param {Object} config The field configuration.
 * @return {Field}
 */
Field.new = function(form, config) {
  let type = config.type,
    FieldClass = waigo.load(`support/forms/fields/${type}`);

  return new FieldClass(form, config);
}




exports.Field = Field;