/template/helper/Form.php

<?php
/**
 * li₃: the most RAD framework for PHP (http://li3.me)
 *
 * Copyright 2009, Union of RAD. All rights reserved. This source
 * code is distributed under the terms of the BSD 3-Clause License.
 * The full license text can be found in the LICENSE.txt file.
 */

namespace lithium\template\helper;

use lithium\aop\Filters;
use lithium\util\Set;
use lithium\util\Inflector;

/**
 * A helper class to facilitate generating, processing and securing HTML forms. By default, `Form`
 * will simply generate HTML forms and widgets, but by creating a form with a _binding object_,
 * the helper can pre-fill form input values, render error messages, and introspect column types.
 *
 * For example, assuming you have created a `Posts` model in your application:
 *
 * In controller code:
 * ```
 * use app\models\Posts;
 * $post = Posts::find(1);
 * return compact('post');
 * ```
 *
 * In view code:
 * ```
 * <?= $this->form->create($post) ?> // Echoes a <form> tag and binds the helper to $post
 * <?= $this->form->text('title') ?> // Echoes an <input /> element, pre-filled with $post's title
 * <?= $this->form->submit('Update') ?> // Echoes a submit button with the title 'Update'
 * <?= $this->form->end() ?> // Echoes a </form> tag & unbinds the form
 * ```
 */
class Form extends \lithium\template\Helper {

	/**
	 * String templates used by this helper.
	 *
	 * @var array
	 */
	protected $_strings = [
		'button'         => '<button{:options}>{:title}</button>',
		'checkbox'       => '<input type="checkbox" name="{:name}"{:options} />',
		'checkbox-multi' => '<input type="checkbox" name="{:name}[]"{:options} />',
		'checkbox-multi-group' => '{:raw}',
		'error'          => '<div{:options}>{:content}</div>',
		'errors'         => '{:raw}',
		'input'          => '<input type="{:type}" name="{:name}"{:options} />',
		'file'           => '<input type="file" name="{:name}"{:options} />',
		'form'           => '<form action="{:url}"{:options}>{:append}',
		'form-end'       => '</form>',
		'hidden'         => '<input type="hidden" name="{:name}"{:options} />',
		'field'          => '<div{:wrap}>{:label}{:input}{:datalist}{:error}</div>',
		'field-checkbox' => '<div{:wrap}>{:input}{:label}{:error}</div>',
		'field-radio'    => '<div{:wrap}>{:input}{:label}{:error}</div>',
		'label'          => '<label for="{:id}"{:options}>{:title}</label>',
		'legend'         => '<legend>{:content}</legend>',
		'option-group'   => '<optgroup label="{:label}"{:options}>{:raw}</optgroup>',
		'password'       => '<input type="password" name="{:name}"{:options} />',
		'radio'          => '<input type="radio" name="{:name}"{:options} />',
		'select'         => '<select name="{:name}"{:options}>{:raw}</select>',
		'select-empty'   => '<option value=""{:options}>&nbsp;</option>',
		'select-multi'   => '<select name="{:name}[]"{:options}>{:raw}</select>',
		'select-option'  => '<option value="{:value}"{:options}>{:title}</option>',
		'submit'         => '<input type="submit" value="{:title}"{:options} />',
		'submit-image'   => '<input type="image" src="{:url}"{:options} />',
		'text'           => '<input type="text" name="{:name}"{:options} />',
		'textarea'       => '<textarea name="{:name}"{:options}>{:value}</textarea>',
		'fieldset'       => '<fieldset{:options}><legend>{:content}</legend>{:raw}</fieldset>',
		'datalist'       => '<datalist{:options}>{:raw}</datalist>',
		'datalist-option' => '<option value="{:value}"></option>'
	];

	/**
	 * Maps method names to template string names, allowing the default template strings to be set
	 * permanently on a per-method basis.
	 *
	 * For example, if all text input fields should be wrapped in `<span />` tags, you can configure
	 * the template string mappings per the following:
	 *
	 * ```
	 * $this->form->config(['templates' => [
	 * 	'text' => '<span><input type="text" name="{:name}"{:options} /></span>'
	 * ]]);
	 * ```
	 *
	 * Alternatively, you can re-map one type as another. This is useful if, for example, you
	 * include your own helper with custom form template strings which do not match the default
	 * template string names.
	 *
	 * ```
	 * // Renders all password fields as text fields
	 * $this->form->config(['templates' => ['password' => 'text']]);
	 * ```
	 *
	 * @var array
	 * @see lithium\template\helper\Form::config()
	 */
	protected $_templateMap = [
		'create' => 'form',
		'end' => 'form-end'
	];

	/**
	 * The data object or list of data objects to which the current form is bound. In order to
	 * be a custom data object, a class must implement the following methods:
	 *
	 * - schema(): Returns an array defining the objects fields and their data types.
	 * - data(): Returns an associative array of the data that this object represents.
	 * - errors(): Returns an associate array of validation errors for the current data set, where
	 *             the keys match keys from `schema()`, and the values are either strings (in cases
	 *             where a field only has one error) or an array (in case of multiple errors),
	 *
	 * For an example of how to implement these methods, see the `lithium\data\Entity` object.
	 *
	 * @see lithium\data\Entity
	 * @see lithium\data\Collection
	 * @see lithium\template\helper\Form::create()
	 * @var mixed A single data object, a `Collection` of multiple data objects, or an array of data
	 *      objects/`Collection`s.
	 */
	protected $_binding = null;

	/**
	 * Array of options used to create the form to which `$_binding` is currently bound.
	 * Overwritten when `end()` is called.
	 *
	 * @var array
	 */
	protected $_bindingOptions = [];

	/**
	 * Constructor.
	 *
	 * @param array $config Configuration options.
	 * @return void
	 */
	public function __construct(array $config = []) {
		$defaults = [
			'base' => [],
			'text' => [],
			'textarea' => [],
			'select' => ['multiple' => false],
			'attributes' => [
				'id' => function($method, $name, $options) {
					if (in_array($method, ['create', 'end', 'label', 'error'])) {
						return;
					}
					if (!$name || ($method === 'hidden' && $name === '_method')) {
						return;
					}
					$info = $this->binding($name);
					$model = $info->class;
					$id = Inflector::camelize(Inflector::slug($info->name));
					return $model ? basename(str_replace('\\', '/', $model)) . $id : $id;
				},
				'name' => function($method, $name, $options) {
					if (!strpos($name, '.')) {
						return $name;
					}
					$name = explode('.', $name);
					$first = array_shift($name);
					return $first . '[' . join('][', $name) . ']';
				}
			],
			'binding' => function($object, $name = null) {
				$result = compact('name') + [
					'data' => null, 'errors' => null, 'class' => null
				];

				if (is_object($object)) {
					$result = compact('name') + [
						'data'   => $object->data($name),
						'errors' => $object->errors($name),
						'class'  => $object->model()
					];
				}
				return (object) $result;
			}
		];
		parent::__construct(Set::merge($defaults, $config));
	}

	/**
	 * Object initializer. Adds a content handler for the `wrap` key in the `field()` method, which
	 * converts an array of properties to an attribute string.
	 *
	 * @return void
	 */
	protected function _init() {
		parent::_init();

		if ($this->_context) {
			$this->_context->handlers(['wrap' => 'attributes']);
		}
	}

	/**
	 * Allows you to configure a default set of options which are included on a per-method basis,
	 * and configure method template overrides.
	 *
	 * To force all `<label />` elements to have a default `class` attribute value of `"foo"`,
	 * simply do the following:
	 *
	 * ```
	 * $this->form->config(['label' => ['class' => 'foo']]);
	 * ```
	 *
	 * Note that this can be overridden on a case-by-case basis, and when overriding, values are
	 * not merged or combined. Therefore, if you wanted a particular `<label />` to have both `foo`
	 * and `bar` as classes, you would have to specify `'class' => 'foo bar'`.
	 *
	 * You can also use this method to change the string template that a method uses to render its
	 * content. For example, the default template for rendering a checkbox is
	 * `'<input type="checkbox" name="{:name}"{:options} />'`. However, suppose you implemented your
	 * own custom UI elements, and you wanted to change the markup used, you could do the following:
	 *
	 * ```
	 * $this->form->config(['templates' => [
	 * 	'checkbox' => '<div id="{:name}" class="ui-checkbox-element"{:options}></div>'
	 * ]]);
	 * ```
	 *
	 * Now, for any calls to `$this->form->checkbox()`, your custom markup template will be applied.
	 * This works for any `Form` method that renders HTML elements.
	 *
	 * @see lithium\template\helper\Form::$_templateMap
	 * @param array $config An associative array where the keys are `Form` method names (or
	 *        `'templates'`, to include a template-overriding sub-array), and the
	 *        values are arrays of configuration options to be included in the `$options`
	 *        parameter of each method specified.
	 * @return array Returns an array containing the currently set per-method configurations, and
	 *         an array of the currently set template overrides (in the `'templates'` array key).
	 */
	public function config(array $config = []) {
		if (!$config) {
			$keys = ['base' => '', 'text' => '', 'textarea' => '', 'attributes' => ''];
			return ['templates' => $this->_templateMap] + array_intersect_key(
				$this->_config, $keys
			);
		}
		if (isset($config['templates'])) {
			$this->_templateMap = $config['templates'] + $this->_templateMap;
			unset($config['templates']);
		}
		return ($this->_config = Set::merge($this->_config, $config)) + [
			'templates' => $this->_templateMap
		];
	}

	/**
	 * Creates an HTML form, and optionally binds it to a data object which contains information on
	 * how to render form fields, any data to pre-populate the form with, and any validation errors.
	 * Typically, a data object will be a `Record` object returned from a `Model`, but you can
	 * define your own custom objects as well. For more information on custom data objects, see
	 * `lithium\template\helper\Form::$_binding`.
	 *
	 * @see lithium\template\helper\Form::$_binding
	 * @see lithium\data\Entity
	 * @param mixed $bindings List of objects, or the object to bind the form to. This is usually
	 *        an instance of `Record` or `Document`, or some other class that extends
	 *        `lithium\data\Entity`.
	 * @param array $options Other parameters for creating the form. Available options are:
	 *        - `'url'` _mixed_: A string URL or URL array parameters defining where in the
	 *          application the form should be submitted to.
	 *        - `'action'` _string_: This is a shortcut to be used if you wish to only
	 *          specify the name of the action to submit to, and use the default URL
	 *          parameters (i.e. the current controller, etc.) for generating the remainder
	 *          of the URL. Ignored if the `'url'` key is set.
	 *        - `'type'` _string_: Currently the only valid option is `'file'`. Set this if
	 *          the form will be used for file uploads.
	 *        - `'method'` _string_: Represents the HTTP method with which the form will be
	 *          submitted (`'get'`, `'post'`, `'put'` or `'delete'`). If `'put'` or
	 *          `'delete'`, the request method is simulated using a hidden input field.
	 * @return string Returns a `<form />` open tag with the `action` attribute defined by either
	 *         the `'action'` or `'url'` options (defaulting to the current page if none is
	 *         specified), the HTTP method is defined by the `'method'` option, and any HTML
	 *         attributes passed in `$options`.
	 * @filter
	 */
	public function create($bindings = null, array $options = []) {
		$request = $this->_context ? $this->_context->request() : null;
		$binding = is_array($bindings) ? reset($bindings) : $bindings;

		$defaults = [
			'url' => $request ? $request->params : [],
			'type' => null,
			'action' => null,
			'method' => $binding ? ($binding->exists() ? 'put' : 'post') : 'post'
		];

		list(, $options, $tpl) = $this->_defaults(__FUNCTION__, null, $options);
		list($scope, $options) = $this->_options($defaults, $options);

		$params = compact('scope', 'options', 'bindings');
		$extra = ['method' => __METHOD__] + compact('tpl', 'defaults');

		return Filters::run($this, __FUNCTION__, $params, function($params) use ($extra) {
			$scope = $params['scope'];
			$options = $params['options'];
			$this->_binding = $params['bindings'];
			$append = null;
			$scope['method'] = strtolower($scope['method']);

			if ($scope['type'] === 'file') {
				if ($scope['method'] === 'get') {
					$scope['method'] = 'post';
				}
				$options['enctype'] = 'multipart/form-data';
			}

			if (!($scope['method'] === 'get' || $scope['method'] === 'post')) {
				$append = $this->hidden('_method', ['value' => strtoupper($scope['method'])]);
				$scope['method'] = 'post';
			}

			$url = $scope['action'] ? ['action' => $scope['action']] : $scope['url'];
			$options['method'] = strtolower($scope['method']);
			$this->_bindingOptions = $scope + $options;

			return $this->_render($extra['method'], $extra['tpl'],
				compact('url', 'options', 'append')
			);
		});
	}

	/**
	 * Echoes a closing `</form>` tag and unbinds the `Form` helper from any `Record` or `Document`
	 * object used to generate the corresponding form.
	 *
	 * @return string Returns a closing `</form>` tag.
	 * @filter
	 */
	public function end() {
		list(, $options, $template) = $this->_defaults(__FUNCTION__, null, []);
		$params = compact('options', 'template');

		$result = Filters::run($this, __FUNCTION__, $params, function($params) {
			$this->_bindingOptions = [];
			return $this->_render('end', $params['template'], []);
		});
		unset($this->_binding);
		$this->_binding = null;
		return $result;
	}

	/**
	 * Returns the entity that the `Form` helper is currently bound to.
	 *
	 * @see lithium\template\helper\Form::$_binding
	 * @param string $name If specified, match this field name against the list of bindings
	 * @param string $key If $name specified, where to store relevant $_binding key
	 * @return object Returns an object, usually an instance of `lithium\data\Entity`.
	 */
	public function binding($name = null) {
		if (!$this->_binding) {
			return $this->_config['binding'](null, $name);
		}

		$binding = $this->_binding;
		$model = null;
		$key = $name;

		if (is_array($binding)) {
			switch (true) {
				case strpos($name, '.'):
					list($model, $key) = explode('.', $name, 2);
					$binding = isset($binding[$model]) ? $binding[$model] : reset($binding);
				break;
				case isset($binding[$name]):
					$binding = $binding[$name];
					$key = null;
				break;
				default:
					$binding = reset($binding);
				break;
			}
		}
		return $key ? $this->_config['binding']($binding, $key) : $binding;
	}

	/**
	 * Implements alternative input types as method calls against `Form` helper. Enables the
	 * generation of HTML5 input types and other custom input types:
	 *
	 * ``` embed:lithium\tests\cases\template\helper\FormTest::testCustomInputTypes(1-2) ```
	 *
	 * @param string $type The method called, which represents the `type` attribute of the
	 *        `<input />` tag.
	 * @param array $params An array of method parameters passed to the method call. The first
	 *        element should be the name of the input field, and the second should be an array
	 *        of element attributes.
	 * @return string Returns an `<input />` tag of the type specified in `$type`.
	 */
	public function __call($type, array $params = []) {
		$params += [null, []];
		list($name, $options) = $params;
		list($name, $options, $template) = $this->_defaults($type, $name, $options);
		$template = $this->_context->strings($template) ? $template : 'input';
		return $this->_render($type, $template, compact('type', 'name', 'options'));
	}

	/**
	 * Determines if a given method can be called.
	 *
	 * @deprecated
	 * @param string $method Name of the method.
	 * @param boolean $internal Provide `true` to perform check from inside the
	 *                class/object. When `false` checks also for public visibility;
	 *                defaults to `false`.
	 * @return boolean Returns `true` if the method can be called, `false` otherwise.
	 */
	public function respondsTo($method, $internal = false) {
		$message  = '`' . __METHOD__ . '()` has been deprecated. ';
		$message .= "Use `is_callable([<class>, '<method>'])` instead.";
		trigger_error($message, E_USER_DEPRECATED);

		return is_callable([$this, $method], true);
	}

	/**
	 * Generates a form field with a label, input, and error message (if applicable), all contained
	 * within a wrapping element.
	 *
	 * ```
	 *  echo $this->form->field('name');
	 *  echo $this->form->field('present', ['type' => 'checkbox']);
	 *  echo $this->form->field(['email' => 'Enter a valid email']);
	 *  echo $this->form->field(['name','email','phone'], ['div' => false]);
	 * ```
	 *
	 * @param mixed $name The name of the field to render. If the form was bound to an object
	 *        passed in `create()`, `$name` should be the name of a field in that object.
	 *        Otherwise, can be any arbitrary field name, as it will appear in POST data.
	 *        Alternatively supply an array of fields that will use the same options
	 *        [$field1 => $label1, $field2, $field3 => $label3]
	 * @param array $options Rendering options for the form field. The available options are as
	 *        follows:
	 *        - `'label'` _mixed_: A string or array defining the label text and / or
	 *          parameters. By default, the label text is a human-friendly version of `$name`.
	 *          However, you can specify the label manually as a string, or both the label
	 *          text and options as an array, i.e.:
	 *          `['Your Label Title' => ['class' => 'foo', 'other' => 'options']]`.
	 *        - `'type'` _string_: The type of form field to render. Available default options
	 *          are: `'text'`, `'textarea'`, `'select'`, `'checkbox'`, `'password'` or
	 *          `'hidden'`, as well as any arbitrary type (i.e. HTML5 form fields).
	 *        - `'template'` _string_: Defaults to `'template'`, but can be set to any named
	 *          template string, or an arbitrary HTML fragment. For example, to change the
	 *          default wrapper tag from `<div />` to `<li />`, you can pass the following:
	 *          `'<li{:wrap}>{:label}{:input}{:error}</li>'`.
	 *        - `'wrap'` _array_: An array of HTML attributes which will be embedded in the
	 *          wrapper tag.
	 *        - `list` _array|string_: If `'type'` is set to `'select'`, `'list'` is an array of
	 *          key/value pairs representing the `$list` parameter of the `select()` method.
	 *          If `'type'` is set to `'text'`, `'list'` is used to render/reference a corresponding
	 *          `<datalist>` element. It then can either be an array of option values or
	 *          a string to reference an existing `<datalist>`.
	 *        - `error` _array|string|boolean_: Allows to control rendering of error messages.
	 *          By setting this option to `false` any messages are disabled. When an array
	 *          mapping failed rule names to messages, will use these alternative message
	 *          instead of the ones provided when the validation was originally defined (i.e
	 *          inside the model). The array may contain a `'default'` key which value will
	 *          be used as a fallback message. In absence of a default message, the original
	 *          messages get rendered instead. When providing a string it will be used for
	 *          any error messages.
	 * @return string Returns a form input (the input type is based on the `'type'` option), with
	 *         label and error message, wrapped in a `<div />` element.
	 */
	public function field($name, array $options = []) {
		if (is_array($name)) {
			return $this->_fields($name, $options);
		}
		$method = __FUNCTION__;
		if (isset($options['type']) && !empty($this->_config['field-' . $options['type']])) {
			$method = 'field-' . $options['type'];
		}
		list(, $options, $template) = $this->_defaults($method, $name, $options);
		$defaults = [
			'label' => null,
			'type' => isset($options['list']) ? 'select' : 'text',
			'template' => $template,
			'wrap' => [],
			'list' => null,
			'error' => []
		];
		list($options, $field) = $this->_options($defaults, $options);

		$label = $input = null;
		$wrap = $options['wrap'];
		$type = $options['type'];
		$list = $options['list'];
		$error = $options['error'];
		$template = $options['template'];
		$notText = $template === 'field' && $type !== 'text';

		if ($notText && $this->_context->strings('field-' . $type)) {
			$template = 'field-' . $type;
		}
		if (($options['label'] === null || $options['label']) && $options['type'] !== 'hidden') {
			if (!$options['label']) {
				$options['label'] = Inflector::humanize(preg_replace('/[\[\]\.]/', '_', $name));
			}
			$label = $this->label(isset($options['id']) ? $options['id'] : '', $options['label']);
		}

		$datalist = null;
		if ($type === 'text' && $list) {
			if (is_array($list)) {
				list($list, $datalist) = $this->_datalist($list, $options);
			}
			$field['list'] = $list;
		}

		$call = ($type === 'select') ? [$name, $list, $field] : [$name, $field];
		$input = call_user_func_array([$this, $type], $call);

		if ($error !== false && $this->_binding) {
			$error = $this->error($name, null, ['messages' => $error]);
		} else {
			$error = null;
		}
		return $this->_render(__METHOD__, $template, compact(
			'wrap', 'label', 'input', 'datalist', 'error'
		));
	}

	/**
	 * Helper method used by `Form::field()` for iterating over an array of multiple fields.
	 *
	 * @see lithium\template\helper\Form::field()
	 * @param array $fields An array of fields to render.
	 * @param array $options The array of options to apply to all fields in the `$fields` array. See
	 *        the `$options` parameter of the `field` method for more information.
	 * @return string Returns the fields rendered by `field()`, each separated by a newline.
	 */
	protected function _fields(array $fields, array $options = []) {
		$result = [];

		foreach ($fields as $field => $label) {
			if (is_numeric($field)) {
				$result[] = $this->field($label, $options);
			} else {
				$result[] = $this->field($field, compact('label') + $options);
			}
		}
		return join("\n", $result);
	}

	/**
	 * Generates an HTML button `<button></button>`.
	 *
	 * @param string $title The title of the button.
	 * @param array $options Any options passed are converted to HTML attributes within the
	 *        `<button></button>` tag.
	 * @return string Returns a `<button></button>` tag with the given title and HTML attributes.
	 */
	public function button($title = null, array $options = []) {
		$defaults = ['escape' => true];
		list($scope, $options) = $this->_options($defaults, $options);
		list($title, $options, $template) = $this->_defaults(__METHOD__, $title, $options);

		$arguments = compact('title', 'options');
		return $this->_render(__METHOD__, 'button', $arguments, $scope);
	}

	/**
	 * Generates an HTML `<input type="submit" />` object.
	 *
	 * @param string $title The title of the submit button.
	 * @param array $options Any options passed are converted to HTML attributes within the
	 *        `<input />` tag.
	 * @return string Returns a submit `<input />` tag with the given title and HTML attributes.
	 */
	public function submit($title = null, array $options = []) {
		list($name, $options, $template) = $this->_defaults(__FUNCTION__, null, $options);
		return $this->_render(__METHOD__, $template, compact('title', 'options'));
	}

	/**
	 * Generates an HTML `<textarea>...</textarea>` object.
	 *
	 * @param string $name The name of the field.
	 * @param array $options The options to be used when generating the `<textarea />` tag pair,
	 *        which are as follows:
	 *        - `'value'` _string_: The content value of the field.
	 *        - Any other options specified are rendered as HTML attributes of the element.
	 * @return string Returns a `<textarea>` tag with the given name and HTML attributes.
	 */
	public function textarea($name, array $options = []) {
		list($name, $options, $template) = $this->_defaults(__FUNCTION__, $name, $options);
		list($scope, $options) = $this->_options(['value' => null], $options);
		$value = isset($scope['value']) ? $scope['value'] : '';
		return $this->_render(__METHOD__, $template, compact('name', 'options', 'value'));
	}

	/**
	 * Generates an HTML `<input type="text" />` object.
	 *
	 * @param string $name The name of the field.
	 * @param array $options All options passed are rendered as HTML attributes.
	 * @return string Returns a `<input />` tag with the given name and HTML attributes.
	 */
	public function text($name, array $options = []) {
		list($name, $options, $template) = $this->_defaults(__FUNCTION__, $name, $options);
		return $this->_render(__METHOD__, $template, compact('name', 'options'));
	}

	/**
	 * Generates an HTML `<datalist></datalist>` object with `<option>` elements.
	 *
	 * @link https://www.w3.org/wiki/HTML/Elements/datalist
	 * @param array $list Valuues, which will be used to render the options of the datalist.
	 * @param array $scope An array of options passed to the parent scope.
	 * @return string Returns a `<datalist>` tag with `<option>` elements.
	 */
	protected function _datalist(array $list, array $scope) {
		$options = [];

		if (isset($scope['id'])) {
			$id = $options['id'] = $scope['id'] . 'List';
		}
		$raw = array_reduce($list, function($carry, $value) {
			return $carry .= $this->_render(__METHOD__, 'datalist-option', compact('value'));
		}, '');

		return [
			isset($options['id']) ? $options['id'] : null,
			$this->_render(__METHOD__, 'datalist', compact('options', 'raw'))
		];
	}

	/**
	 * Generates a `<select />` list using the `$list` parameter for the `<option />` tags. The
	 * default selection will be set to the value of `$options['value']`, if specified.
	 *
	 * For example:
	 * ```
	 * $this->form->select('colors', [1 => 'red', 2 => 'green', 3 => 'blue'], [
	 * 	'id' => 'Colors', 'value' => 2
	 * ]);
	 * // Renders a '<select />' list with options 'red', 'green' and 'blue', with the 'green'
	 * // option as the selection
	 * ```
	 *
	 * @param string $name The `name` attribute of the `<select />` element.
	 * @param array $list An associative array of key/value pairs, which will be used to render the
	 *        list of options.
	 * @param array $options Any HTML attributes that should be associated with the `<select />`
	 *        element. If the `'value'` key is set, this will be the value of the option
	 *        that is selected by default.
	 * @return string Returns an HTML `<select />` element.
	 */
	public function select($name, $list = [], array $options = []) {
		$defaults = ['empty' => false, 'value' => null];
		list($name, $options, $template) = $this->_defaults(__FUNCTION__, $name, $options);
		list($scope, $options) = $this->_options($defaults, $options);

		if ($scope['empty']) {
			$list = ['' => ($scope['empty'] === true) ? '' : $scope['empty']] + $list;
		}
		if ($template === __FUNCTION__ && $scope['multiple']) {
			$template = 'select-multi';
		}
		$raw = $this->_selectOptions($list, $scope);
		return $this->_render(__METHOD__, $template, compact('name', 'options', 'raw'));
	}

	/**
	 * Generator method used by `select()` to produce `<option />` and `<optgroup />` elements.
	 * Generally, this method should not need to be called directly, but through `select()`.
	 *
	 * @param array $list Either a flat key/value array of select menu options, or an array which
	 *        contains key/value elements and/or elements where the keys are `<optgroup />`
	 *        titles and the values are sub-arrays of key/value pairs representing nested
	 *        `<option />` elements.
	 * @param array $scope An array of options passed to the parent scope, including the currently
	 *        selected value of the associated form element.
	 * @return string Returns a string of `<option />` and (optionally) `<optgroup />` tags to be
	 *         embedded in a select element.
	 */
	protected function _selectOptions(array $list, array $scope) {
		$result = "";

		foreach ($list as $value => $title) {
			if (is_array($title)) {
				$label = $value;
				$options = [];

				$raw = $this->_selectOptions($title, $scope);
				$params = compact('label', 'options', 'raw');
				$result .= $this->_render('select', 'option-group', $params);
				continue;
			}
			$selected = (
				(is_array($scope['value']) && in_array($value, $scope['value'])) ||
				($scope['empty'] && empty($scope['value']) && $value === '') ||
				(is_scalar($scope['value']) && ((string) $scope['value'] === (string) $value))
			);
			$options = $selected ? ['selected' => true] : [];
			$params = compact('value', 'title', 'options');
			$result .= $this->_render('select', 'select-option',  $params);
		}
		return $result;
	}

	/**
	 * Generates an HTML `<input type="checkbox" />` object.
	 *
	 * @param string $name The name of the field.
	 * @param array $options Options to be used when generating the checkbox `<input />` element:
	 *        - `'checked'` _boolean_: Whether or not the field should be checked by default.
	 *        - `'value'` _mixed_: if specified, it will be used as the 'value' html
	 *          attribute and no hidden input field will be added.
	 *        - Any other options specified are rendered as HTML attributes of the element.
	 * @return string Returns a `<input />` tag with the given name and HTML attributes.
	 */
	public function checkbox($name, array $options = []) {
		$defaults = ['value' => '1', 'hidden' => true];
		$options += $defaults;
		$default = $options['value'];
		$key = $name;
		$out = '';

		list($name, $options, $template) = $this->_defaults(__FUNCTION__, $name, $options);
		list($scope, $options) = $this->_options($defaults, $options);

		if (!isset($options['checked'])) {
			$options['checked'] = ($this->binding($key)->data == $default);
		}
		if ($scope['hidden']) {
			$out = $this->hidden($name, ['value' => '', 'id' => false]);
		}
		$options['value'] = $scope['value'];
		return $out . $this->_render(__METHOD__, $template, compact('name', 'options'));
	}

	/**
	 * Generates an HTML `<input type="radio" />` object.
	 *
	 * @param string $name The name of the field
	 * @param array $options All options to be used when generating the radio `<input />` element:
	 *        - `'checked'` _boolean_: Whether or not the field should be selected by default.
	 *        - `'value'` _mixed_: if specified, it will be used as the 'value' html
	 *          attribute. Defaults to `1`
	 *        - Any other options specified are rendered as HTML attributes of the element.
	 * @return string Returns a `<input />` tag with the given name and attributes
	 */
	public function radio($name, array $options = []) {
		$defaults = ['value' => '1'];
		$options += $defaults;
		$default = $options['value'];
		$key = $name;

		list($name, $options, $template) = $this->_defaults(__FUNCTION__, $name, $options);
		list($scope, $options) = $this->_options($defaults, $options);

		if (!isset($options['checked'])) {
			$options['checked'] = ($this->binding($key)->data == $default);
		}

		$options['value'] = $scope['value'];
		return $this->_render(__METHOD__, $template, compact('name', 'options'));
	}

	/**
	 * Generates an HTML `<input type="password" />` object.
	 *
	 * @param string $name The name of the field.
	 * @param array $options An array of HTML attributes with which the field should be rendered.
	 * @return string Returns a `<input />` tag with the given name and HTML attributes.
	 */
	public function password($name, array $options = []) {
		list($name, $options, $template) = $this->_defaults(__FUNCTION__, $name, $options);
		unset($options['value']);
		return $this->_render(__METHOD__, $template, compact('name', 'options'));
	}

	/**
	 * Generates an HTML `<input type="hidden" />` object.
	 *
	 * @param string $name The name of the field.
	 * @param array $options An array of HTML attributes with which the field should be rendered.
	 * @return string Returns a `<input />` tag with the given name and HTML attributes.
	 */
	public function hidden($name, array $options = []) {
		list($name, $options, $template) = $this->_defaults(__FUNCTION__, $name, $options);
		return $this->_render(__METHOD__, $template, compact('name', 'options'));
	}

	/**
	 * Generates an HTML `<label></label>` object.
	 *
	 * @param string $id The DOM ID of the field that the label is for.
	 * @param string $title The content inside the `<label></label>` object.
	 * @param array $options Besides HTML attributes, this parameter allows one additional flag:
	 *        - `'escape'` _boolean_: Defaults to `true`. Indicates whether the title of the
	 *          label should be escaped. If `false`, it will be treated as raw HTML.
	 * @return string Returns a `<label>` tag for the name and with HTML attributes.
	 */
	public function label($id, $title = null, array $options = []) {
		$defaults = ['escape' => true];

		if (is_array($title)) {
			$options = current($title);
			$title = key($title);
		}
		$title = $title ?: Inflector::humanize(str_replace('.', '_', $id));

		list($name, $options, $template) = $this->_defaults(__FUNCTION__, $id, $options);
		list($scope, $options) = $this->_options($defaults, $options);

		if (strpos($id, '.')) {
			$generator = $this->_config['attributes']['id'];
			$id = $generator(__METHOD__, $id, $options);
		}
		return $this->_render(__METHOD__, $template, compact('id', 'title', 'options'), $scope);
	}

	/**
	 * Generates an error message for a field which is part of an object bound to a form in
	 * `create()`.
	 *
	 * @param string $name The name of the field for which to render an error.
	 * @param mixed $key If more than one error is present for `$name`, a key may be specified.
	 *        If `$key` is not set in the array of errors, or if `$key` is `true`, the first
	 *        available error is used.
	 * @param array $options Any rendering options or HTML attributes to be used when rendering
	 *        the error.
	 * @return string Returns a rendered error message based on the `'error'` string template.
	 */
	public function error($name, $key = null, array $options = []) {
		$defaults = ['class' => 'error', 'messages' => []];
		list(, $options, $template) = $this->_defaults(__FUNCTION__, $name, $options);
		$options += $defaults;

		if (is_array($options['messages'])) {
			$messages = $options['messages'] + ['default' => null];
		} else {
			$messages = ['default' => $options['messages']];
		}
		unset($options['messages']);

		$params = compact('name', 'key', 'messages', 'options', 'template');

		return Filters::run($this, __FUNCTION__, $params, function($params) {
			$options = $params['options'];
			$template = $params['template'];
			$messages = $params['messages'];

			if (isset($options['value'])) {
				unset($options['value']);
			}
			if (!$content = $this->binding($params['name'])->errors) {
				return null;
			}
			$result = '';

			if (!is_array($content)) {
				return $this->_render(__METHOD__, $template, compact('content', 'options'));
			}
			$errors = $content;

			if ($params['key'] === null) {
				foreach ($errors as $rule => $content) {
					if (isset($messages[$rule])) {
						$content = $messages[$rule];
					} elseif ($messages['default']) {
						$content = $messages['default'];
					}
					$result .= $this->_render(__METHOD__, $template, compact('content', 'options'));
				}
				return $result;
			}

			$key = $params['key'];
			$content = !isset($errors[$key]) || $key === true ? reset($errors) : $errors[$key];
			return $this->_render(__METHOD__, $template, compact('content', 'options'));
		});
	}

	/**
	 * Builds the defaults array for a method by name, according to the config.
	 *
	 * @param string $method The name of the method to create defaults for.
	 * @param string $name The `$name` supplied to the original method.
	 * @param string $options `$options` from the original method.
	 * @return array Defaults array contents.
	 */
	protected function _defaults($method, $name, $options) {
		$params = compact('method', 'name', 'options');

		return Filters::run($this, __FUNCTION__, $params, function($params) {
			$method = $params['method'];
			$name = $params['name'];
			$options = $params['options'];

			$methodConfig = isset($this->_config[$method]) ? $this->_config[$method] : [];
			$options += $methodConfig + $this->_config['base'];
			$options = $this->_generators($method, $name, $options);

			$hasValue = (
				(!isset($options['value']) || $options['value'] === null) &&
				$name && $value = $this->binding($name)->data
			);
			$isZero = (isset($value) && ($value === 0 || $value === "0"));

			if ($hasValue || $isZero) {
				$options['value'] = $value;
			}
			if (isset($options['value']) && !$isZero) {
				$isZero = ($options['value'] === 0 || $options['value'] === "0");
			}
			if (isset($options['default']) && empty($options['value']) && !$isZero) {
				$options['value'] = $options['default'];
			}
			unset($options['default']);

			$generator = $this->_config['attributes']['name'];
			$name = $generator($method, $name, $options);

			$tplKey = isset($options['template']) ? $options['template'] : $method;
			$template = isset($this->_templateMap[$tplKey]) ? $this->_templateMap[$tplKey] : $tplKey;
			return [$name, $options, $template];
		});
	}

	/**
	 * Iterates over the configured attribute generators, and modifies the settings for a tag.
	 *
	 * @param string $method The name of the helper method which was called, i.e. `'text'`,
	 *        `'select'`, etc.
	 * @param string $name The name of the field whose attributes are being generated. Some helper
	 *        methods, such as `create()` and `end()`, are not field-based, and therefore
	 *        will have no name.
	 * @param array $options The options and HTML attributes that will be used to generate the
	 *        helper output.
	 * @return array Returns the value of the `$options` array, modified by the attribute generators
	 *         added in the `'attributes'` key of the helper's configuration. Note that if a
	 *         generator is present for a field whose value is `false`, that field will be removed
	 *         from the array.
	 */
	protected function _generators($method, $name, $options) {
		foreach ($this->_config['attributes'] as $key => $generator) {
			if ($key === 'name') {
				continue;
			}
			if ($generator && !isset($options[$key])) {
				if (($attr = $generator($method, $name, $options)) !== null) {
					$options[$key] = $attr;
				}
				continue;
			}
			if ($generator && $options[$key] === false) {
				unset($options[$key]);
			}
		}
		return $options;
	}
}

?>