text: 'use strict';
  
  Object.defineProperty(exports, "__esModule", {
    value: true
  });
  
  var _createClass = function () { function defineProperties(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } } return function (Constructor, protoProps, staticProps) { if (protoProps) defineProperties(Constructor.prototype, protoProps); if (staticProps) defineProperties(Constructor, staticProps); return Constructor; }; }();
  
  var _hashIt = require('hash-it');
  
  var _hashIt2 = _interopRequireDefault(_hashIt);
  
  function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
  
  function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }
  
  var Fact = function () {
    /**
     * Returns a new fact instance
     * @param  {string} id - fact unique identifer
     * @param  {object} options
     * @param  {boolean} options.cache - whether to cache the fact's value for future rules
     * @param  {primitive|function} valueOrMethod - constant primitive, or method to call when computing the fact's value
     * @return {Fact}
     */
    function Fact(id, valueOrMethod, options) {
      _classCallCheck(this, Fact);
  
      this.id = id;
      var defaultOptions = { cache: true };
      if (typeof options === 'undefined') {
        options = defaultOptions;
      }
      if (typeof valueOrMethod !== 'function') {
        this.value = valueOrMethod;
        this.type = this.constructor.CONSTANT;
      } else {
        this.calculationMethod = valueOrMethod;
        this.type = this.constructor.DYNAMIC;
      }
  
      if (!this.id) throw new Error('factId required');
  
      this.priority = parseInt(options.priority || 1, 10);
      this.options = Object.assign({}, defaultOptions, options);
      this.cacheKeyMethod = this.defaultCacheKeys;
      return this;
    }
  
    _createClass(Fact, [{
      key: 'isConstant',
      value: function isConstant() {
        return this.type === this.constructor.CONSTANT;
      }
    }, {
      key: 'isDynamic',
      value: function isDynamic() {
        return this.type === this.constructor.DYNAMIC;
      }
  
      /**
       * Return the fact value, based on provided parameters
       * @param  {object} params
       * @param  {Almanac} almanac
       * @return {any} calculation method results
       */
  
    }, {
      key: 'calculate',
      value: function calculate(params, almanac) {
        // if constant fact w/set value, return immediately
        if (Object.prototype.hasOwnProperty.call(this, 'value')) {
          return this.value;
        }
        return this.calculationMethod(params, almanac);
      }
  
      /**
       * Return a cache key (MD5 string) based on parameters
       * @param  {object} obj - properties to generate a hash key from
       * @return {string} MD5 string based on the hash'd object
       */
  
    }, {
      key: 'defaultCacheKeys',
  
  
      /**
       * Default properties to use when caching a fact
       * Assumes every fact is a pure function, whose computed value will only
       * change when input params are modified
       * @param  {string} id - fact unique identifer
       * @param  {object} params - parameters passed to fact calcution method
       * @return {object} id + params
       */
      value: function defaultCacheKeys(id, params) {
        return { params: params, id: id };
      }
  
      /**
       * Generates the fact's cache key(MD5 string)
       * Returns nothing if the fact's caching has been disabled
       * @param  {object} params - parameters that would be passed to the computation method
       * @return {string} cache key
       */
  
    }, {
      key: 'getCacheKey',
      value: function getCacheKey(params) {
        if (this.options.cache === true) {
          var cacheProperties = this.cacheKeyMethod(this.id, params);
          var _hash = Fact.hashFromObject(cacheProperties);
          return _hash;
        }
      }
    }], [{
      key: 'hashFromObject',
      value: function hashFromObject(obj) {
        return (0, _hashIt2.default)(obj);
      }
    }]);
  
    return Fact;
  }();
  
  Fact.CONSTANT = 'CONSTANT';
  Fact.DYNAMIC = 'DYNAMIC';
  
  exports.default = Fact;