handlebars.php/src/Handlebars/Helpers.php

<?php
/**
 * This file is part of Handlebars-php
 * Base on mustache-php https://github.com/bobthecow/mustache.php
 *
 * PHP version 5.3
 *
 * @category  Xamin
 * @package   Handlebars
 * @author    fzerorubigd <fzerorubigd@gmail.com>
 * @author    Behrooz Shabani <everplays@gmail.com>
 * @copyright 2012 (c) ParsPooyesh Co
 * @copyright 2013 (c) Behrooz Shabani
 * @license   MIT <http://opensource.org/licenses/MIT>
 * @version   GIT: $Id$
 * @link      http://xamin.ir
 */

namespace Handlebars;

/**
 * Handlebars helpers
 *
 * a collection of helper function. normally a function like
 * function ($sender, $name, $arguments) $arguments is unscaped arguments and
 * is a string, not array
 *
 * TODO: Add support for an interface with an execute method
 *
 * @category  Xamin
 * @package   Handlebars
 * @author    fzerorubigd <fzerorubigd@gmail.com>
 * @copyright 2012 (c) ParsPooyesh Co
 * @license   MIT <http://opensource.org/licenses/MIT>
 * @version   Release: @package_version@
 * @link      http://xamin.ir
 */

class Helpers
{
    /**
     * @var array array of helpers
     */
    protected $helpers = array();

    /**
     * Create new helper container class
     *
     * @param array      $helpers  array of name=>$value helpers
     * @param array|bool $defaults add defaults helper
     *          (if, unless, each,with, bindAttr)
     *
     * @throws \InvalidArgumentException when $helpers is not an array
     * (or traversable) or helper is not a callable
     */
    public function __construct($helpers = null, $defaults = true)
    {
        if ($defaults) {
            $this->addDefaultHelpers();
        }
        if ($helpers != null) {
            if (!is_array($helpers) && !$helpers instanceof \Traversable) {
                throw new \InvalidArgumentException(
                    'HelperCollection constructor expects an array of helpers'
                );
            }
            foreach ($helpers as $name => $helper) {
                $this->add($name, $helper);
            }
        }
    }


    /**
     * Add default helpers (if unless each with bindAttr)
     *
     * @return void
     */
    protected function addDefaultHelpers()
    {
        $this->add(
            'if',
            function ($template, $context, $args, $source) {
                /**
                 * @var $template \Handlebars\Template
                 * @var $context \Handlebars\Context
                 * @var $args array
                 * @var $source string
                 */
                $tmp = $context->get($args);

                if ($tmp) {
                    $template->setStopToken('else');
                    $buffer = $template->render($context);
                    $template->setStopToken(false);
                    $template->discard($context);
                } else {
                    $template->setStopToken('else');
                    $template->discard($context);
                    $template->setStopToken(false);
                    $buffer = $template->render($context);
                }

                return $buffer;
            }
        );

        $this->add(
            'each',
            function ($template, $context, $args, $source) {
                /**
                 * @var $template \Handlebars\Template
                 * @var $context \Handlebars\Context
                 * @var $args array
                 * @var $source string
                 */
                $tmp = $context->get($args);
                $buffer = '';
                if (is_array($tmp) || $tmp instanceof \Traversable) {
                    $islist = (array_keys($tmp) == range(0, count($tmp) - 1));

                    foreach ($tmp as $key => $var) {
                        if ($islist) {
                            $context->pushIndex($key);
                        } else {
                            $context->pushKey($key);
                        }
                        $context->push($var);
                        $buffer .= $template->render($context);
                        $context->pop();
                        if ($islist) {
                            $context->popIndex();
                        } else {
                            $context->popKey();
                        }
                    }
                }

                return $buffer;
            }
        );

        $this->add(
            'unless',
            function ($template, $context, $args, $source) {
                /**
                 * @var $template \Handlebars\Template
                 * @var $context \Handlebars\Context
                 * @var $args array
                 * @var $source string
                 */
                $tmp = $context->get($args);
                $buffer = '';
                if (!$tmp) {
                    $buffer = $template->render($context);
                }

                return $buffer;
            }
        );

        $this->add(
            'with',
            function ($template, $context, $args, $source) {
                /**
                 * @var $template \Handlebars\Template
                 * @var $context \Handlebars\Context
                 * @var $args array
                 * @var $source string
                 */
                $tmp = $context->get($args);
                $context->push($tmp);
                $buffer = $template->render($context);
                $context->pop();

                return $buffer;
            }
        );

        //Just for compatibility with ember
        $this->add(
            'bindAttr',
            function ($template, $context, $args, $source) {
                /**
                 * @var $template \Handlebars\Template
                 * @var $context \Handlebars\Context
                 * @var $args array
                 * @var $source string
                 */
                return $args;
            }
        );
    }

    /**
     * Add a new helper to helpers
     *
     * @param string   $name   helper name
     * @param callable $helper a function as a helper
     *
     * @throws \InvalidArgumentException if $helper is not a callable
     * @return void
     */
    public function add($name, $helper)
    {
        if (!is_callable($helper)) {
            throw new \InvalidArgumentException("$name Helper is not a callable.");
        }
        $this->helpers[$name] = $helper;
    }

    /**
     * Check if $name helper is available
     *
     * @param string $name helper name
     *
     * @return boolean
     */
    public function has($name)
    {
        return array_key_exists($name, $this->helpers);
    }

    /**
     * Get a helper. __magic__ method :)
     *
     * @param string $name helper name
     *
     * @throws \InvalidArgumentException if $name is not available
     * @return callable helper function
     */
    public function __get($name)
    {
        if (!$this->has($name)) {
            throw new \InvalidArgumentException('Unknown helper :' . $name);
        }

        return $this->helpers[$name];
    }

    /**
     * Check if $name helper is available __magic__ method :)
     *
     * @param string $name helper name
     *
     * @return boolean
     * @see Handlebras_Helpers::has
     */
    public function __isset($name)
    {
        return $this->has($name);
    }

    /**
     * Add a new helper to helpers __magic__ method :)
     *
     * @param string   $name   helper name
     * @param callable $helper a function as a helper
     *
     * @return void
     */
    public function __set($name, $helper)
    {
        $this->add($name, $helper);
    }


    /**
     * Unset a helper
     *
     * @param string $name helper name to remove
     *
     * @return void
     */
    public function __unset($name)
    {
        unset($this->helpers[$name]);
    }

    /**
     * Check whether a given helper is present in the collection.
     *
     * @param string $name helper name
     *
     * @throws \InvalidArgumentException if the requested helper is not present.
     * @return void
     */
    public function remove($name)
    {
        if (!$this->has($name)) {
            throw new \InvalidArgumentException('Unknown helper: ' . $name);
        }

        unset($this->helpers[$name]);
    }

    /**
     * Clear the helper collection.
     *
     * Removes all helpers from this collection
     *
     * @return void
     */
    public function clear()
    {
        $this->helpers = array();
    }

    /**
     * Check whether the helper collection is empty.
     *
     * @return boolean True if the collection is empty
     */
    public function isEmpty()
    {
        return empty($this->helpers);
    }

}