Add Balanced Payments API

Summary: Adds the Balanced PHP API to externals/. Ref T2787.

Test Plan: Used in next diff.

Reviewers: btrahan, chad

Reviewed By: chad

CC: aran, aurelijus

Maniphest Tasks: T2787

Differential Revision: https://secure.phabricator.com/D5764

externals/restful/src/RESTful/Pagination.php

@@ -0,0 +1,90 @@
+<?php
+
+namespace RESTful;
+
+class Pagination implements \IteratorAggregate, \ArrayAccess
+{
+    public $resource,
+        $uri;
+
+    protected $_page,
+        $_offset = 0,
+        $_size = 25;
+
+    public function __construct($resource, $uri, $data = null)
+    {
+        $this->resource = $resource;
+        $this->uri = $uri;
+        if ($data != null) {
+            $this->_page = new Page($resource, $uri, $data);
+        } else {
+            $this->_page = null;
+        }
+    }
+
+    protected function _getPage($offset = null)
+    {
+        if ($this->_page == null) {
+            $this->_offset = ($offset == null) ? 0 : $offset * $this->_size;
+            $uri = $this->_buildUri();
+            $this->_page = new Page($this->resource, $uri);
+        } elseif ($offset != null) {
+            $offset = $offset * $this->_size;
+            if ($offset != $this->_offset) {
+                $this->_offset = $offset;
+                $uri = $this->_buildUri();
+                $this->_page = new Page($this->resource, $uri);
+            }
+        }
+
+        return $this->_page;
+    }
+
+    public function total()
+    {
+        return floor($this->_getPage()->total / $this->_size);
+    }
+
+    protected function _buildUri($offset = null)
+    {
+        # TODO: hacky but works for now
+        $offset = ($offset == null) ? $this->_offset : $offset;
+        if (strpos($this->uri, '?') === false) {
+            $uri = $this->uri . '?';
+        } else {
+            $uri = $this->uri . '&';
+        }
+        $uri = $uri . 'offset=' . strval($offset);
+
+        return $uri;
+    }
+
+    // IteratorAggregate
+    public function getIterator()
+    {
+        $uri = $this->_buildUri($offset = 0);
+
+        return new PaginationIterator($this->resource, $uri);
+    }
+
+    // ArrayAccess
+    public function offsetSet($offset, $value)
+    {
+        throw new \BadMethodCallException(get_class($this) . ' array access is read-only');
+    }
+
+    public function offsetExists($offset)
+    {
+        return (0 <= $offset && $offset < $this->total());
+    }
+
+    public function offsetUnset($offset)
+    {
+        throw new \BadMethodCallException(get_class($this) . ' array access is read-only');
+    }
+
+    public function offsetGet($offset)
+    {
+        return $this->_getPage($offset);
+    }
+}