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backend/node_modules/mnemonist/stack.js

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+/**
+ * Mnemonist Stack
+ * ================
+ *
+ * Stack implementation relying on JavaScript arrays, which are fast enough &
+ * correctly optimized for this kind of work.
+ */
+var Iterator = require('obliterator/iterator'),
+    forEach = require('obliterator/foreach');
+
+/**
+ * Stack
+ *
+ * @constructor
+ */
+function Stack() {
+  this.clear();
+}
+
+/**
+ * Method used to clear the stack.
+ *
+ * @return {undefined}
+ */
+Stack.prototype.clear = function() {
+
+  // Properties
+  this.items = [];
+  this.size = 0;
+};
+
+/**
+ * Method used to add an item to the stack.
+ *
+ * @param  {any}    item - Item to add.
+ * @return {number}
+ */
+Stack.prototype.push = function(item) {
+  this.items.push(item);
+  return ++this.size;
+};
+
+/**
+ * Method used to retrieve & remove the last item of the stack.
+ *
+ * @return {any}
+ */
+Stack.prototype.pop = function() {
+  if (this.size === 0)
+    return;
+
+  this.size--;
+  return this.items.pop();
+};
+
+/**
+ * Method used to get the last item of the stack.
+ *
+ * @return {any}
+ */
+Stack.prototype.peek = function() {
+  return this.items[this.size - 1];
+};
+
+/**
+ * Method used to iterate over the stack.
+ *
+ * @param  {function}  callback - Function to call for each item.
+ * @param  {object}    scope    - Optional scope.
+ * @return {undefined}
+ */
+Stack.prototype.forEach = function(callback, scope) {
+  scope = arguments.length > 1 ? scope : this;
+
+  for (var i = 0, l = this.items.length; i < l; i++)
+    callback.call(scope, this.items[l - i - 1], i, this);
+};
+
+/**
+ * Method used to convert the stack to a JavaScript array.
+ *
+ * @return {array}
+ */
+Stack.prototype.toArray = function() {
+  var array = new Array(this.size),
+      l = this.size - 1,
+      i = this.size;
+
+  while (i--)
+    array[i] = this.items[l - i];
+
+  return array;
+};
+
+/**
+ * Method used to create an iterator over a stack's values.
+ *
+ * @return {Iterator}
+ */
+Stack.prototype.values = function() {
+  var items = this.items,
+      l = items.length,
+      i = 0;
+
+  return new Iterator(function() {
+    if (i >= l)
+      return {
+        done: true
+      };
+
+    var value = items[l - i - 1];
+    i++;
+
+    return {
+      value: value,
+      done: false
+    };
+  });
+};
+
+/**
+ * Method used to create an iterator over a stack's entries.
+ *
+ * @return {Iterator}
+ */
+Stack.prototype.entries = function() {
+  var items = this.items,
+      l = items.length,
+      i = 0;
+
+  return new Iterator(function() {
+    if (i >= l)
+      return {
+        done: true
+      };
+
+    var value = items[l - i - 1];
+
+    return {
+      value: [i++, value],
+      done: false
+    };
+  });
+};
+
+/**
+ * Attaching the #.values method to Symbol.iterator if possible.
+ */
+if (typeof Symbol !== 'undefined')
+  Stack.prototype[Symbol.iterator] = Stack.prototype.values;
+
+
+/**
+ * Convenience known methods.
+ */
+Stack.prototype.toString = function() {
+  return this.toArray().join(',');
+};
+
+Stack.prototype.toJSON = function() {
+  return this.toArray();
+};
+
+Stack.prototype.inspect = function() {
+  var array = this.toArray();
+
+  // Trick so that node displays the name of the constructor
+  Object.defineProperty(array, 'constructor', {
+    value: Stack,
+    enumerable: false
+  });
+
+  return array;
+};
+
+if (typeof Symbol !== 'undefined')
+  Stack.prototype[Symbol.for('nodejs.util.inspect.custom')] = Stack.prototype.inspect;
+
+/**
+ * Static @.from function taking an arbitrary iterable & converting it into
+ * a stack.
+ *
+ * @param  {Iterable} iterable   - Target iterable.
+ * @return {Stack}
+ */
+Stack.from = function(iterable) {
+  var stack = new Stack();
+
+  forEach(iterable, function(value) {
+    stack.push(value);
+  });
+
+  return stack;
+};
+
+/**
+ * Static @.of function taking an arbitrary number of arguments & converting it
+ * into a stack.
+ *
+ * @param  {...any} args
+ * @return {Stack}
+ */
+Stack.of = function() {
+  return Stack.from(arguments);
+};
+
+/**
+ * Exporting.
+ */
+module.exports = Stack;