halfred/lib/immutable_stack.js

parses JSON HAL resources (Hypertext Application Language)

'use strict';

/*
 * A very naive copy-on-write immutable stack. Since the size of the stack
 * is equal to the depth of the embedded resources for one HAL resource, the bad
 * performance for the copy-on-write approach is probably not a problem at all.
 * Might be replaced by a smarter solution later. Or not. Whatever.
 */
function ImmutableStack() {
  if (arguments.length >= 1) {
    this._array = arguments[0];
  } else {
    this._array = [];
  }
}

ImmutableStack.prototype.array = function() {
  return this._array;
};

ImmutableStack.prototype.isEmpty = function(array) {
  return this._array.length === 0;
};

ImmutableStack.prototype.push = function(element) {
  var array = this._array.slice(0);
  array.push(element);
  return new ImmutableStack(array);
};

ImmutableStack.prototype.pop = function() {
  var array = this._array.slice(0, this._array.length - 1);
  return new ImmutableStack(array);
};

ImmutableStack.prototype.peek = function() {
  if (this.isEmpty()) {
    throw new Error('can\'t peek on empty stack');
  }
  return this._array[this._array.length - 1];
};

module.exports = ImmutableStack;