michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: "use strict";
michael@0: 
michael@0: this.EXPORTED_SYMBOLS = ["Dict"];
michael@0: 
michael@0: /**
michael@0:  * Transforms a given key into a property name guaranteed not to collide with
michael@0:  * any built-ins.
michael@0:  */
michael@0: function convert(aKey) {
michael@0:   return ":" + aKey;
michael@0: }
michael@0: 
michael@0: /**
michael@0:  * Transforms a property into a key suitable for providing to the outside world.
michael@0:  */
michael@0: function unconvert(aProp) {
michael@0:   return aProp.substr(1);
michael@0: }
michael@0: 
michael@0: /**
michael@0:  * A dictionary of strings to arbitrary JS objects. This should be used whenever
michael@0:  * the keys are potentially arbitrary, to avoid collisions with built-in
michael@0:  * properties.
michael@0:  *
michael@0:  * @param aInitial An object containing the initial keys and values of this
michael@0:  *                 dictionary. Only the "own" enumerable properties of the
michael@0:  *                 object are considered.
michael@0:  *                 If |aInitial| is a string, it is assumed to be JSON and parsed into an object.
michael@0:  */
michael@0: this.Dict = function Dict(aInitial) {
michael@0:   if (aInitial === undefined)
michael@0:     aInitial = {};
michael@0:   if (typeof aInitial == "string")
michael@0:     aInitial = JSON.parse(aInitial);
michael@0:   var items = {}, count = 0;
michael@0:   // That we don't look up the prototype chain is guaranteed by Iterator.
michael@0:   for (var [key, val] in Iterator(aInitial)) {
michael@0:     items[convert(key)] = val;
michael@0:     count++;
michael@0:   }
michael@0:   this._state = {count: count, items: items};
michael@0:   return Object.freeze(this);
michael@0: }
michael@0: 
michael@0: Dict.prototype = Object.freeze({
michael@0:   /**
michael@0:    * The number of items in the dictionary.
michael@0:    */
michael@0:   get count() {
michael@0:     return this._state.count;
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Gets the value for a key from the dictionary. If the key is not a string,
michael@0:    * it will be converted to a string before the lookup happens.
michael@0:    *
michael@0:    * @param aKey The key to look up
michael@0:    * @param [aDefault] An optional default value to return if the key is not
michael@0:    *                   present. Defaults to |undefined|.
michael@0:    * @returns The item, or aDefault if it isn't found.
michael@0:    */
michael@0:   get: function Dict_get(aKey, aDefault) {
michael@0:     var prop = convert(aKey);
michael@0:     var items = this._state.items;
michael@0:     return items.hasOwnProperty(prop) ? items[prop] : aDefault;
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Sets the value for a key in the dictionary. If the key is a not a string,
michael@0:    * it will be converted to a string before the set happens.
michael@0:    */
michael@0:   set: function Dict_set(aKey, aValue) {
michael@0:     var prop = convert(aKey);
michael@0:     var items = this._state.items;
michael@0:     if (!items.hasOwnProperty(prop))
michael@0:       this._state.count++;
michael@0:     items[prop] = aValue;
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Sets a lazy getter function for a key's value. If the key is a not a string,
michael@0:    * it will be converted to a string before the set happens.
michael@0:    * @param aKey
michael@0:    *        The key to set
michael@0:    * @param aThunk
michael@0:    *        A getter function to be called the first time the value for aKey is
michael@0:    *        retrieved. It is guaranteed that aThunk wouldn't be called more
michael@0:    *        than once.  Note that the key value may be retrieved either
michael@0:    *        directly, by |get|, or indirectly, by |listvalues| or by iterating
michael@0:    *        |values|.  For the later, the value is only retrieved if and when
michael@0:    *        the iterator gets to the value in question.  Also note that calling
michael@0:    *        |has| for a lazy-key does not invoke aThunk.
michael@0:    *
michael@0:    * @note No context is provided for aThunk when it's invoked.
michael@0:    *       Use Function.bind if you wish to run it in a certain context.
michael@0:    */
michael@0:   setAsLazyGetter: function Dict_setAsLazyGetter(aKey, aThunk) {
michael@0:     let prop = convert(aKey);
michael@0:     let items = this._state.items;
michael@0:     if (!items.hasOwnProperty(prop))
michael@0:       this._state.count++;
michael@0: 
michael@0:     Object.defineProperty(items, prop, {
michael@0:       get: function() {
michael@0:         delete items[prop];
michael@0:         return items[prop] = aThunk();
michael@0:       },
michael@0:       configurable: true,
michael@0:       enumerable: true     
michael@0:     });
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Returns whether a key is set as a lazy getter.  This returns
michael@0:    * true only if the getter function was not called already.
michael@0:    * @param aKey
michael@0:    *        The key to look up.
michael@0:    * @returns whether aKey is set as a lazy getter.
michael@0:    */
michael@0:   isLazyGetter: function Dict_isLazyGetter(aKey) {
michael@0:     let descriptor = Object.getOwnPropertyDescriptor(this._state.items,
michael@0:                                                      convert(aKey));
michael@0:     return (descriptor && descriptor.get != null);
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Returns whether a key is in the dictionary. If the key is a not a string,
michael@0:    * it will be converted to a string before the lookup happens.
michael@0:    */
michael@0:   has: function Dict_has(aKey) {
michael@0:     return (this._state.items.hasOwnProperty(convert(aKey)));
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Deletes a key from the dictionary. If the key is a not a string, it will be
michael@0:    * converted to a string before the delete happens.
michael@0:    *
michael@0:    * @returns true if the key was found, false if it wasn't.
michael@0:    */
michael@0:   del: function Dict_del(aKey) {
michael@0:     var prop = convert(aKey);
michael@0:     if (this._state.items.hasOwnProperty(prop)) {
michael@0:       delete this._state.items[prop];
michael@0:       this._state.count--;
michael@0:       return true;
michael@0:     }
michael@0:     return false;
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Returns a shallow copy of this dictionary.
michael@0:    */
michael@0:   copy: function Dict_copy() {
michael@0:     var newItems = {};
michael@0:     for (var [key, val] in this.items)
michael@0:       newItems[key] = val;
michael@0:     return new Dict(newItems);
michael@0:   },
michael@0: 
michael@0:   /*
michael@0:    * List and iterator functions
michael@0:    *
michael@0:    * No guarantees whatsoever are made about the order of elements.
michael@0:    */
michael@0: 
michael@0:   /**
michael@0:    * Returns a list of all the keys in the dictionary in an arbitrary order.
michael@0:    */
michael@0:   listkeys: function Dict_listkeys() {
michael@0:     return [unconvert(k) for (k in this._state.items)];
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Returns a list of all the values in the dictionary in an arbitrary order.
michael@0:    */
michael@0:   listvalues: function Dict_listvalues() {
michael@0:     var items = this._state.items;
michael@0:     return [items[k] for (k in items)];
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Returns a list of all the items in the dictionary as key-value pairs
michael@0:    * in an arbitrary order.
michael@0:    */
michael@0:   listitems: function Dict_listitems() {
michael@0:     var items = this._state.items;
michael@0:     return [[unconvert(k), items[k]] for (k in items)];
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Returns an iterator over all the keys in the dictionary in an arbitrary
michael@0:    * order. No guarantees are made about what happens if the dictionary is
michael@0:    * mutated during iteration.
michael@0:    */
michael@0:   get keys() {
michael@0:     // If we don't capture this._state.items here then the this-binding will be
michael@0:     // incorrect when the generator is executed
michael@0:     var items = this._state.items;
michael@0:     return (unconvert(k) for (k in items));
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Returns an iterator over all the values in the dictionary in an arbitrary
michael@0:    * order. No guarantees are made about what happens if the dictionary is
michael@0:    * mutated during iteration.
michael@0:    */
michael@0:   get values() {
michael@0:     // If we don't capture this._state.items here then the this-binding will be
michael@0:     // incorrect when the generator is executed
michael@0:     var items = this._state.items;
michael@0:     return (items[k] for (k in items));
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Returns an iterator over all the items in the dictionary as key-value pairs
michael@0:    * in an arbitrary order. No guarantees are made about what happens if the
michael@0:    * dictionary is mutated during iteration.
michael@0:    */
michael@0:   get items() {
michael@0:     // If we don't capture this._state.items here then the this-binding will be
michael@0:     // incorrect when the generator is executed
michael@0:     var items = this._state.items;
michael@0:     return ([unconvert(k), items[k]] for (k in items));
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Returns a String representation of this dictionary.
michael@0:    */
michael@0:   toString: function Dict_toString() {
michael@0:     return "{" +
michael@0:       [(key + ": " + val) for ([key, val] in this.items)].join(", ") +
michael@0:       "}";
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Returns a JSON representation of this dictionary.
michael@0:    */
michael@0:   toJSON: function Dict_toJSON() {
michael@0:     let obj = {};
michael@0:     for (let [key, item] of Iterator(this._state.items)) {
michael@0:       obj[unconvert(key)] = item;
michael@0:     }
michael@0:     return JSON.stringify(obj);
michael@0:   },
michael@0: });