From ecdc95accef1450e7c8fd9465e5886d02dc83a26 Mon Sep 17 00:00:00 2001
From: Muthu Kumar <muthukumar@thefeathers.in>
Date: Wed, 16 May 2018 18:47:12 +0530
Subject: [PATCH] [rewrite] Using ES6 classes

---
 example.js     |  25 ------
 index.js       | 258 ++++++++++++++++++++++++++++++++++++++-------------------
 utils/cycle.js | 182 ++++++++++++++++++++++++++++++++++++++++
 utils/index.js |  19 +++++
 4 files changed, 376 insertions(+), 108 deletions(-)
 delete mode 100644 example.js
 create mode 100644 utils/cycle.js
 create mode 100644 utils/index.js

diff --git a/example.js b/example.js
deleted file mode 100644
index c0e906a..0000000
--- a/example.js
+++ /dev/null
@@ -1,25 +0,0 @@
-const infiniteList = require('.');
-
-const increment = i => i + 2;
-const infinite = infiniteList.create(0, increment, 10);
-
-console.log(infinite.top())
-console.log(infinite.last())
-
-console.log(infinite.get(5))
-console.log(infinite.get(5))
-console.log(infinite.get(6))
-console.log(infinite.get(14).next())
-
-console.log(infinite.toString())
-console.log(infinite.top().next().next().toString())
-
-console.log(infinite.take(5))
-
-for(let i of infinite) {
-	if(i.index > 100) break;
-	// console.log(infinite.get(5).value);
-	console.log(i.value.toString());
-}
-
-console.log(infinite.clearCache());
\ No newline at end of file
diff --git a/index.js b/index.js
index efca296..3fb8d2b 100644
--- a/index.js
+++ b/index.js
@@ -1,114 +1,206 @@
-const always = x => _ => x;
+/**
+ * ∞
+ * Infinity: Create infinitely generating lists in JavaScript.
+ * @version 0.2.0
+ * @author Muthu Kumar (MKRhere)
+ */
 
+// Utils
+const { always, isNonZeroFalsy, stringify, areNumbers } = require('./utils');
+
+/**
+ * An item of the InfiniteList class. Created when calling .get(n) on an InfiniteList.
+ * Exposed for instanceof utility sake. Not to be called directly.
+ * @class InfiniteListItem
+ */
 class InfiniteListItem {
-	constructor (list, value, index) {
-		this.value = value,
-		this.index = index,
-		this.next = () => list.get(index + 1),
-		this.previous = () => list.get(index - 1),
-		this[Symbol.iterator] = () => ({
-			next: () => ({
-				done: false,
-				value: list.get(index + 1)
-			})
-		}),
-		this.toString = () => {
-			const val = list.get(i).value;
-			return ( 'InfiniteListItem [ ..., '
-				+ ((typeof val === 'object' && val !== null)
-					? JSON.stringify(val, null, 2)
-					: val.toString())
-				+ ', ... ]' )
+	/**
+	 * Creates an instance of InfiniteListItem.
+	 * @param {any} list Parent list, instance of InfiniteList
+	 * @param {any} value Current value
+	 * @param {any} index Current index
+	 * @memberof InfiniteListItem
+	 */
+	constructor(list, value, index) {
+		this.value = value;
+		this.index = index;
+		this.next = z => (!z ? list.get(index + 1) : list.get(index + z));
+		this.previous = z => (!z ? list.get(index - 1) : list.get(index - z));
+
+		// Check if Symbol exists
+		if (typeof Symbol !== 'undefined' && Symbol.iterator) {
+			/**
+			 * ES6 Symbol.iterator
+			 * @returns {Iterable.<*>}
+			 */
+			this[Symbol.iterator] = () => ({
+				next: () => ({
+					done: false,
+					value: list.get(index + 1)
+				})
+			});
 		}
 	}
+
+	/**
+	 * toString method for pretty printing InfiniteListItem instance.
+	 * @returns {String} Decycled and beautified string
+	 */
+	toString() {
+		return ('InfiniteListItem [ .. ' +
+			stringify(this.value) +
+			' .. ]')
+	};
 }
 
-const infiniteList = {
+class InfiniteList {
 	/**
-	 * InfiniteList Constructor. Iterates infinitely until index value is found.
-	 * 
-	 * @param {any} start
-	 * @param {any} next
-	 * @returns InfiniteList instance
+	 * InfiniteList Constructor.
+	 * Iterates infinitely until index value is found.
+	 * Stores cache in closure so when the same index is requested again,
+	 * it's returned immediately.
+	 * @param {*} start Starting value
+	 * @param {Function} next Function to find next item
+	 * Accepts current value and optionally previous value
+	 * @constructs InfiniteList
 	 */
-	create (start, next) {
+	constructor(start, next) {
 
 		// Closure magic!
 		let cache = [];
 		let j = 0;
 
-		// Get list item of index i
-		function get(i) {
+		/**
+		 * Get InfiniteListItem at index.
+		 * @param {Number} index A non-negative integer representing index
+		 * @returns {InfiniteListItem}
+		 */
+		this.get = function (index) {
 
 			// Validation
-			if(
-				// i is a falsy value except 0
-				(!i && i !== 0)
-				// is not a number
-				|| (typeof i !== 'number')
-				// is... not a number
-				|| Number.isNaN(i)
+			if (
+				// i is a non-zero falsy value, or is negative
+				(isNonZeroFalsy(index) || index < 0)
+				|| !areNumbers(index)
 			) return;
 
-			//TODO: Cache limiting. (Removed after unexpected behaviour)
-			
+			//TODO: Cache limiting. (Removed for unexpected behaviour)
+
 			// Initializing first item if it doesn't exist
-			if(!cache[0]) cache[0] = start;
+			if (!cache[0]) cache[0] = start;
 
 			// If index were to be infinity, value and index are infinity
-			if(i === Infinity) return new InfiniteListItem(this, Infinity, Infinity)
+			if (index === Infinity) return new InfiniteListItem(this, Infinity, Infinity)
 
 			// If index exists in cache, return the value
-			if(i in cache) return new InfiniteListItem(this, cache[i], i);
+			if (index in cache) return new InfiniteListItem(this, cache[index], index);
 
 			// If i doesn't exist in cache
-			if(!(i in cache)) {
-				if(cache.length <= i && (cache.length - 1) in cache)
-					while (cache.length <= i)
-						cache[cache.length] = next(cache[cache.length - 1]);
+			if (!(index in cache)) {
+				if (cache.length <= index && (cache.length - 1) in cache)
+					while (cache.length <= index)
+						cache[cache.length] = next(cache[cache.length - 1], cache[cache.length - 2]);
 			}
-			return new InfiniteListItem(this, cache[i], i);
+			return new InfiniteListItem(this, cache[index], index);
 		}
 
-		const take = (from, to) => {
-			const arr = [];
-			let source, target;
-			// "from" number of elements
-			if(!to) { source = 0; target = from; }
-			// "target" is the end index!
-			else { source = from; target = to + 1 };
-			for(let i = source; i < target; i ++) {
-				arr.push(get(i));
+		/**
+		 * Clear cache manually.
+		 * Forces destroy reference to cache, and creates a new cache.
+		 * Old cache will be GC'd.
+		 * @returns {undefined}
+		 */
+		this.clearCache = () => (cache = [], undefined);
+
+		// Check if Symbol exists
+		if (typeof Symbol !== 'undefined' && Symbol.iterator) {
+			/**
+			 * ES6 Symbol.iterator
+			 * @returns {Iterable.<*>}
+			 */
+			this[Symbol.iterator] = function () {
+				return {
+					next: () => ({
+						done: false,
+						value: this.get(j++)
+					})
+				}
 			};
-			return arr;
-		};
-
-		// Clear cache manually.
-		const clearCache = () => (cache = [], undefined);
-
-		const top = function () { return this.get(0) };
-		const end = function () { return this.get(Infinity) };
-		const returns = {
-			get,
-			take,
-			top,
-			first: top,
-			end,
-			last: end,
-			clearCache,
-			[Symbol.iterator]: () => ({
-				next: () => ({
-					done: false,
-					value: get(j++)
-				})
-			}),
-			toString: () => 'InfiniteList [ '
-				+ take(0, 10).map(x => (' ' + x.value.toString()))
-				+ ' ... ]'
-		};
-		return returns;
+		}
 	}
 }
 
-module.exports = infiniteList;
-module.exports.InfiniteListItem = InfiniteListItem;
+/**
+ * Takes a given number of elements from the InfiniteList.
+ * @param {Number} from Number of elements or starting index
+ * @param {Number} to Optional ending index
+ * @returns {Array<InfiniteListItem>} An array of InfiniteListItems
+ */
+InfiniteList.prototype.take = function (from, to) {
+	const arr = [];
+
+	if(
+		isNonZeroFalsy(from)
+		|| (from === 0 && isNonZeroFalsy(to)) // Take 0 elements?
+		|| (!areNumbers(from) && isNonZeroFalsy(to))
+	) return arr;
+
+	let source, target;
+	// "from" number of elements
+	if (isNonZeroFalsy(to)) {
+		source = 0;
+		target = from;
+	}
+	// "target" is the end index!
+	else {
+		source = from;
+		target = to + 1
+	};
+
+	for (let i = source; i < target; i++) {
+		arr.push(this.get(i));
+	};
+	return arr;
+};
+
+/**
+ * Returns first element of InfiniteList.
+ * @returns {InfiniteListItem} Instance of InfiniteListItem
+ */
+InfiniteList.prototype.top = function () {
+	return this.get(0)
+};
+
+/**
+ * Returns last element of InfiniteList (Infinity).
+ * @returns {InfiniteListItem} Instance of InfiniteListItem
+ */
+InfiniteList.prototype.end = function () {
+	return this.get(Infinity)
+};
+
+/**
+ * toString method for pretty printing InfiniteList instance.
+ * Snips at 2 elements for arrays and objects, or 5 elements otherwise.
+ * @returns {String} Pretty printed InfiniteList
+ */
+InfiniteList.prototype.toString = function () {
+	const length = typeof this.first() === 'object' ? 2 : 5;
+	return [
+			'InfiniteList [',
+			this
+			.take(length)
+			.map(x => (' ' + stringify(x.value))) +
+			',',
+			'... ]'
+		]
+		.join(' ');
+}
+
+/* Convenience methods */
+InfiniteList.prototype.first = InfiniteList.prototype.top;
+InfiniteList.prototype.last = InfiniteList.prototype.end;
+
+// Exports
+module.exports = InfiniteList;
+module.exports.InfiniteListItem = InfiniteListItem;
\ No newline at end of file
diff --git a/utils/cycle.js b/utils/cycle.js
new file mode 100644
index 0000000..5e63ccb
--- /dev/null
+++ b/utils/cycle.js
@@ -0,0 +1,182 @@
+/*
+    cycle.js
+    2018-05-15
+    Public Domain.
+    NO WARRANTY EXPRESSED OR IMPLIED. USE AT YOUR OWN RISK.
+    This code should be minified before deployment.
+    See http://javascript.crockford.com/jsmin.html
+    USE YOUR OWN COPY. IT IS EXTREMELY UNWISE TO LOAD CODE FROM SERVERS YOU DO
+    NOT CONTROL.
+*/
+
+// The file uses the WeakMap feature of ES6.
+
+/*jslint eval */
+
+/*property
+    $ref, decycle, forEach, get, indexOf, isArray, keys, length, push,
+    retrocycle, set, stringify, test
+*/
+
+if (typeof JSON.decycle !== "function") {
+	JSON.decycle = function decycle(object, replacer) {
+		"use strict";
+
+		// Make a deep copy of an object or array, assuring that there is at most
+		// one instance of each object or array in the resulting structure. The
+		// duplicate references (which might be forming cycles) are replaced with
+		// an object of the form
+
+		//      {"$ref": PATH}
+
+		// where the PATH is a JSONPath string that locates the first occurance.
+
+		// So,
+
+		//      var a = [];
+		//      a[0] = a;
+		//      return JSON.stringify(JSON.decycle(a));
+
+		// produces the string '[{"$ref":"$"}]'.
+
+		// If a replacer function is provided, then it will be called for each value.
+		// A replacer function receives a value and returns a replacement value.
+
+		// JSONPath is used to locate the unique object. $ indicates the top level of
+		// the object or array. [NUMBER] or [STRING] indicates a child element or
+		// property.
+
+		var objects = new WeakMap(); // object to path mappings
+
+		return (function derez(value, path) {
+
+			// The derez function recurses through the object, producing the deep copy.
+
+			var old_path; // The path of an earlier occurance of value
+			var nu; // The new object or array
+
+			// If a replacer function was provided, then call it to get a replacement value.
+
+			if (replacer !== undefined) {
+				value = replacer(value);
+			}
+
+			// typeof null === "object", so go on if this value is really an object but not
+			// one of the weird builtin objects.
+
+			if (
+				typeof value === "object" &&
+				value !== null &&
+				!(value instanceof Boolean) &&
+				!(value instanceof Date) &&
+				!(value instanceof Number) &&
+				!(value instanceof RegExp) &&
+				!(value instanceof String)
+			) {
+
+				// If the value is an object or array, look to see if we have already
+				// encountered it. If so, return a {"$ref":PATH} object. This uses an
+				// ES6 WeakMap.
+
+				old_path = objects.get(value);
+				if (old_path !== undefined) {
+					return {
+						$ref: old_path
+					};
+				}
+
+				// Otherwise, accumulate the unique value and its path.
+
+				objects.set(value, path);
+
+				// If it is an array, replicate the array.
+
+				if (Array.isArray(value)) {
+					nu = [];
+					value.forEach(function (element, i) {
+						nu[i] = derez(element, path + "[" + i + "]");
+					});
+				} else {
+
+					// If it is an object, replicate the object.
+
+					nu = {};
+					Object.keys(value).forEach(function (name) {
+						nu[name] = derez(
+							value[name],
+							path + "[" + JSON.stringify(name) + "]"
+						);
+					});
+				}
+				return nu;
+			}
+			return value;
+		}(object, "$"));
+	};
+}
+
+
+if (typeof JSON.retrocycle !== "function") {
+	JSON.retrocycle = function retrocycle($) {
+		"use strict";
+
+		// Restore an object that was reduced by decycle. Members whose values are
+		// objects of the form
+		//      {$ref: PATH}
+		// are replaced with references to the value found by the PATH. This will
+		// restore cycles. The object will be mutated.
+
+		// The eval function is used to locate the values described by a PATH. The
+		// root object is kept in a $ variable. A regular expression is used to
+		// assure that the PATH is extremely well formed. The regexp contains nested
+		// * quantifiers. That has been known to have extremely bad performance
+		// problems on some browsers for very long strings. A PATH is expected to be
+		// reasonably short. A PATH is allowed to belong to a very restricted subset of
+		// Goessner's JSONPath.
+
+		// So,
+		//      var s = '[{"$ref":"$"}]';
+		//      return JSON.retrocycle(JSON.parse(s));
+		// produces an array containing a single element which is the array itself.
+
+		var px = /^\$(?:\[(?:\d+|"(?:[^\\"\u0000-\u001f]|\\(?:[\\"\/bfnrt]|u[0-9a-zA-Z]{4}))*")\])*$/;
+
+		(function rez(value) {
+
+			// The rez function walks recursively through the object looking for $ref
+			// properties. When it finds one that has a value that is a path, then it
+			// replaces the $ref object with a reference to the value that is found by
+			// the path.
+
+			if (value && typeof value === "object") {
+				if (Array.isArray(value)) {
+					value.forEach(function (element, i) {
+						if (typeof element === "object" && element !== null) {
+							var path = element.$ref;
+							if (typeof path === "string" && px.test(path)) {
+								value[i] = eval(path);
+							} else {
+								rez(element);
+							}
+						}
+					});
+				} else {
+					Object.keys(value).forEach(function (name) {
+						var item = value[name];
+						if (typeof item === "object" && item !== null) {
+							var path = item.$ref;
+							if (typeof path === "string" && px.test(path)) {
+								value[name] = eval(path);
+							} else {
+								rez(item);
+							}
+						}
+					});
+				}
+			}
+		}($));
+		return $;
+	};
+}
+
+module.exports = JSON;
\ No newline at end of file
diff --git a/utils/index.js b/utils/index.js
new file mode 100644
index 0000000..1d7460f
--- /dev/null
+++ b/utils/index.js
@@ -0,0 +1,19 @@
+const JSON = require('./cycle');
+
+const always = x => _ => x;
+const isNonZeroFalsy = _ => (
+	(Boolean(_) === false) && _ !== 0
+);
+const stringify = _ => {
+	return ((typeof _ === 'object' && _ !== null) ?
+		JSON.stringify(JSON.decycle(_), null, 2) :
+		_.toString())
+};
+const areNumbers = (...items) => items.every(x => (typeof x === 'number' && x !== NaN));
+
+module.exports = {
+	always,
+	isNonZeroFalsy,
+	stringify,
+	areNumbers
+}
\ No newline at end of file