Condition.js

import has from 'lodash/has';
import isSchema from './util/isSchema';

class Condition {
  constructor(refs, options) {
    this.refs = refs;

    if (typeof options === 'function') {
      this.fn = options;
      return;
    }

    if (!has(options, 'is'))
      throw new TypeError('`is:` is required for `when()` conditions');

    if (!options.then && !options.otherwise)
      throw new TypeError(
        'either `then:` or `otherwise:` is required for `when()` conditions',
      );

    let { is, then, otherwise } = options;

    let check =
      typeof is === 'function'
        ? is
        : (...values) => values.every(value => value === is);

    this.fn = function(...args) {
      let options = args.pop();
      let schema = args.pop();
      let branch = check(...args) ? then : otherwise;

      if (!branch) return undefined;
      if (typeof branch === 'function') return branch(schema);
      return schema.concat(branch.resolve(options));
    };
  }

  resolve(base, options) {
    let values = this.refs.map(ref => ref.getValue(options));

    let schema = this.fn.apply(base, values.concat(base, options));

    if (schema === undefined || schema === base) return base;

    if (!isSchema(schema))
      throw new TypeError('conditions must return a schema object');

    return schema.resolve(options);
  }
}

export default Condition;