<?php

use SilverStripe\ORM\DataObjectInterface;
use SilverStripe\ORM\FieldType\DBField;
use SilverStripe\ORM\FieldType\DBHTMLText;

/**
 * Represents a field in a form.
 *
 * A FieldList contains a number of FormField objects which make up the whole of a form.
 *
 * In addition to single fields, FormField objects can be "composite", for example, the
 * {@link TabSet} field. Composite fields let us define complex forms without having to resort to
 * custom HTML.
 *
 * To subclass:
 *
 * Define a {@link dataValue()} method that returns a value suitable for inserting into a single
 * database field.
 *
 * For example, you might tidy up the format of a date or currency field. Define {@link saveInto()}
 * to totally customise saving.
 *
 * For example, data might be saved to the filesystem instead of the data record, or saved to a
 * component of the data record instead of the data record itself.
 *
 * A form field can be represented as structured data through {@link FormSchema},
 * including both structure (name, id, attributes, etc.) and state (field value).
 * Can be used by for JSON data which is consumed by a front-end application.
 *
 * @package forms
 * @subpackage core
 */
class FormField extends RequestHandler {

	/** @see $schemaDataType */
	const SCHEMA_DATA_TYPE_STRING = 'String';

	/** @see $schemaDataType */
	const SCHEMA_DATA_TYPE_HIDDEN = 'Hidden';

	/** @see $schemaDataType */
	const SCHEMA_DATA_TYPE_TEXT = 'Text';

	/** @see $schemaDataType */
	const SCHEMA_DATA_TYPE_HTML = 'HTML';

	/** @see $schemaDataType */
	const SCHEMA_DATA_TYPE_INTEGER = 'Integer';

	/** @see $schemaDataType */
	const SCHEMA_DATA_TYPE_DECIMAL = 'Decimal';

	/** @see $schemaDataType */
	const SCHEMA_DATA_TYPE_MULTISELECT = 'MultiSelect';

	/** @see $schemaDataType */
	const SCHEMA_DATA_TYPE_SINGLESELECT = 'SingleSelect';

	/** @see $schemaDataType */
	const SCHEMA_DATA_TYPE_DATE = 'Date';

	/** @see $schemaDataType */
	const SCHEMA_DATA_TYPE_DATETIME = 'DateTime';

	/** @see $schemaDataType */
	const SCHEMA_DATA_TYPE_TIME = 'Time';

	/** @see $schemaDataType */
	const SCHEMA_DATA_TYPE_BOOLEAN = 'Boolean';

	/** @see $schemaDataType */
	const SCHEMA_DATA_TYPE_CUSTOM = 'Custom';

	/** @see $schemaDataType */
	const SCHEMA_DATA_TYPE_STRUCTURAL = 'Structural';

	/**
	 * @var Form
	 */
	protected $form;

	/**
	 * @var string
	 */
	protected $name;

	/**
	 * @var null|string
	 */
	protected $title;

	/**
	 * @var mixed
	 */
	protected $value;

	/**
	 * @var string
	 */
	protected $message;

	/**
	 * @var string
	 */
	protected $messageType;

	/**
	 * @var string
	 */
	protected $extraClass;

	/**
	 * Adds a title attribute to the markup.
	 *
	 * @var string
	 *
	 * @todo Implement in all subclasses
	 */
	protected $description;

	/**
	 * Extra CSS classes for the FormField container.
	 *
	 * @var array
	 */
	protected $extraClasses;

	/**
	 * @config
	 * @var array $default_classes The default classes to apply to the FormField
	 */
	private static $default_classes = [];

	/**
	 * Right-aligned, contextual label for the field.
	 *
	 * @var string
	 */
	protected $rightTitle;

	/**
	 * Left-aligned, contextual label for the field.
	 *
	 * @var string
	 */
	protected $leftTitle;

	/**
	 * Stores a reference to the FieldList that contains this object.
	 *
	 * @var FieldList
	 */
	protected $containerFieldList;

	/**
	 * @var bool
	 */
	protected $readonly = false;

	/**
	 * @var bool
	 */
	protected $disabled = false;

	/**
	 * Custom validation message for the field.
	 *
	 * @var string
	 */
	protected $customValidationMessage = '';

	/**
	 * Name of the template used to render this form field. If not set, then will look up the class
	 * ancestry for the first matching template where the template name equals the class name.
	 *
	 * To explicitly use a custom template or one named other than the form field see
	 * {@link setTemplate()}.
	 *
	 * @var string
	 */
	protected $template;

	/**
	 * Name of the template used to render this form field. If not set, then will look up the class
	 * ancestry for the first matching template where the template name equals the class name.
	 *
	 * To explicitly use a custom template or one named other than the form field see
	 * {@link setFieldHolderTemplate()}.
	 *
	 * @var string
	 */
	protected $fieldHolderTemplate;

	/**
	 * @var string
	 */
	protected $smallFieldHolderTemplate;

	/**
	 * All attributes on the form field (not the field holder).
	 *
	 * Partially determined based on other instance properties.
	 *
	 * @see getAttributes()
	 *
	 * @var array
	 */
	protected $attributes = [];

	/**
	 * The data type backing the field. Represents the type of value the
	 * form expects to receive via a postback. Should be set in subclasses.
	 *
	 * The values allowed in this list include:
	 *
	 *   - String: Single line text
	 *   - Hidden: Hidden field which is posted back without modification
	 *   - Text: Multi line text
	 *   - HTML: Rich html text
	 *   - Integer: Whole number value
	 *   - Decimal: Decimal value
	 *   - MultiSelect: Select many from source
	 *   - SingleSelect: Select one from source
	 *   - Date: Date only
	 *   - DateTime: Date and time
	 *   - Time: Time only
	 *   - Boolean: Yes or no
	 *   - Custom: Custom type declared by the front-end component. For fields with this type,
	 *     the component property is mandatory, and will determine the posted value for this field.
	 *   - Structural: Represents a field that is NOT posted back. This may contain other fields,
	 *     or simply be a block of stand-alone content. As with 'Custom',
	 *     the component property is mandatory if this is assigned.
	 *
	 * Each value has an equivalent constant, e.g. {@link self::SCHEMA_DATA_TYPE_STRING}.
	 *
	 * @var string
	 */
	 protected $schemaDataType;

	/**
	 * The type of front-end component to render the FormField as.
	 *
	 * @var string
	 */
	protected $schemaComponent;

	/**
	 * Structured schema data representing the FormField.
	 * Used to render the FormField as a ReactJS Component on the front-end.
	 *
	 * @var array
	 */
	protected $schemaData = [];

	private static $casting = array(
		'FieldHolder' => 'HTMLFragment',
		'Field' => 'HTMLFragment',
		'AttributesHTML' => 'HTMLFragment', // property $AttributesHTML version
		'getAttributesHTML' => 'HTMLFragment', // method $getAttributesHTML($arg) version
		'Value' => 'Text',
		'extraClass' => 'Text',
		'ID' => 'Text',
		'isReadOnly' => 'Boolean',
		'HolderID' => 'Text',
		'Title' => 'Text',
		'RightTitle' => 'Text',
		'MessageType' => 'Text',
		'Message' => 'HTMLFragment',
		'Description' => 'HTMLFragment',
	);

	/**
	 * Structured schema state representing the FormField's current data and validation.
	 * Used to render the FormField as a ReactJS Component on the front-end.
	 *
	 * @var array
	 */
	protected $schemaState = [];

	/**
	 * Takes a field name and converts camelcase to spaced words. Also resolves combined field
	 * names with dot syntax to spaced words.
	 *
	 * Examples:
	 *
	 * - 'TotalAmount' will return 'Total Amount'
	 * - 'Organisation.ZipCode' will return 'Organisation Zip Code'
	 *
	 * @param string $fieldName
	 *
	 * @return string
	 */
	public static function name_to_label($fieldName) {
		if(strpos($fieldName, '.') !== false) {
			$parts = explode('.', $fieldName);

			$label = $parts[count($parts) - 2] . ' ' . $parts[count($parts) - 1];
		} else {
			$label = $fieldName;
		}

		return preg_replace('/([a-z]+)([A-Z])/', '$1 $2', $label);
	}

	/**
	 * Construct and return HTML tag.
	 *
	 * @param string $tag
	 * @param array $attributes
	 * @param null|string $content
	 *
	 * @return string
	 */
	public static function create_tag($tag, $attributes, $content = null) {
		$preparedAttributes = '';

		foreach($attributes as $attributeKey => $attributeValue) {
			if(!empty($attributeValue) || $attributeValue === '0' || ($attributeKey == 'value' && $attributeValue !== null)) {
				$preparedAttributes .= sprintf(
					' %s="%s"', $attributeKey, Convert::raw2att($attributeValue)
				);
			}
		}

		if($content || $tag != 'input') {
			return sprintf(
				'<%s%s>%s</%s>', $tag, $preparedAttributes, $content, $tag
			);
		}

		return sprintf(
			'<%s%s />', $tag, $preparedAttributes
		);
	}

	/**
	 * Creates a new field.
	 *
	 * @param string $name The internal field name, passed to forms.
	 * @param null|string $title The human-readable field label.
	 * @param mixed $value The value of the field.
	 */
	public function __construct($name, $title = null, $value = null) {
		$this->name = $name;

		if($title === null) {
			$this->title = self::name_to_label($name);
		} else {
			$this->title = $title;
		}

		if($value !== null) {
			$this->setValue($value);
		}

		parent::__construct();

		$this->setupDefaultClasses();
	}

	/**
	 * Set up the default classes for the form. This is done on construct so that the default classes can be removed
	 * after instantiation
	 */
	protected function setupDefaultClasses() {
		$defaultClasses = self::config()->get('default_classes');
		if ($defaultClasses) {
			foreach ($defaultClasses as $class) {
				$this->addExtraClass($class);
			}
		}
	}

	/**
	 * Return a link to this field.
	 *
	 * @param string $action
	 *
	 * @return string
	 */
	public function Link($action = null) {
		return Controller::join_links($this->form->FormAction(), 'field/' . $this->name, $action);
	}

	/**
	 * Returns the HTML ID of the field.
	 *
	 * The ID is generated as FormName_FieldName. All Field functions should ensure that this ID is
	 * included in the field.
	 *
	 * @return string
	 */
	public function ID() {
		return $this->getTemplateHelper()->generateFieldID($this);
	}

	/**
	 * Returns the HTML ID for the form field holder element.
	 *
	 * @return string
	 */
	public function HolderID() {
		return $this->getTemplateHelper()->generateFieldHolderID($this);
	}

	/**
	 * Returns the current {@link FormTemplateHelper} on either the parent
	 * Form or the global helper set through the {@link Injector} layout.
	 *
	 * To customize a single {@link FormField}, use {@link setTemplate} and
	 * provide a custom template name.
	 *
	 * @return FormTemplateHelper
	 */
	public function getTemplateHelper() {
		if($this->form) {
			return $this->form->getTemplateHelper();
		}

		return Injector::inst()->get('FormTemplateHelper');
	}

	/**
	 * Returns the field name.
	 *
	 * @return string
	 */
	public function getName() {
		return $this->name;
	}

	/**
	 * Returns the field message, used by form validation.
	 *
	 * Use {@link setError()} to set this property.
	 *
	 * @return string
	 */
	public function Message() {
		return $this->message;
	}

	/**
	 * Returns the field message type.
	 *
	 * Arbitrary value which is mostly used for CSS classes in the rendered HTML, e.g "required".
	 *
	 * Use {@link setError()} to set this property.
	 *
	 * @return string
	 */
	public function MessageType() {
		return $this->messageType;
	}

	/**
	 * Returns the field value.
	 *
	 * @return mixed
	 */
	public function Value() {
		return $this->value;
	}

	/**
	 * Method to save this form field into the given {@link DataObject}.
	 *
	 * By default, makes use of $this->dataValue()
	 *
	 * @param DataObjectInterface $record DataObject to save data into
	 */
	public function saveInto(DataObjectInterface $record) {
		if($this->name) {
			$record->setCastedField($this->name, $this->dataValue());
		}
	}

	/**
	 * Returns the field value suitable for insertion into the data object.
	 *
	 * @return mixed
	 */
	public function dataValue() {
		return $this->value;
	}

	/**
	 * Returns the field label - used by templates.
	 *
	 * @return string
	 */
	public function Title() {
		return $this->title;
	}

	/**
	 * Set the title of this formfield.
	 * Note: This expects escaped HTML.
	 *
	 * @param string $title Escaped HTML for title
	 * @return $this
	 */
	public function setTitle($title) {
		$this->title = $title;
		return $this;
	}

	/**
	 * Gets the contextual label than can be used for additional field description.
	 * Can be shown to the right or under the field in question.
	 *
	 * @return string Contextual label text.
	 */
	public function RightTitle() {
		return $this->rightTitle;
	}

	/**
	 * Sets the right title for this formfield
	 * Note: This expects escaped HTML.
	 *
	 * @param string $rightTitle Escaped HTML for title
	 * @return $this
	 */
	public function setRightTitle($rightTitle) {
		$this->rightTitle = $rightTitle;
		return $this;
	}

	/**
	 * @return string
	 */
	public function LeftTitle() {
		return $this->leftTitle;
	}

	/**
	 * @param string $leftTitle
	 *
	 * @return $this
	 */
	public function setLeftTitle($leftTitle) {
		$this->leftTitle = $leftTitle;

		return $this;
	}

	/**
	 * Compiles all CSS-classes. Optionally includes a "nolabel" class if no title was set on the
	 * FormField.
	 *
	 * Uses {@link Message()} and {@link MessageType()} to add validation error classes which can
	 * be used to style the contained tags.
	 *
	 * @return string
	 */
	public function extraClass() {
		$classes = array();

		$classes[] = $this->Type();

		if($this->extraClasses) {
			$classes = array_merge(
				$classes,
				array_values($this->extraClasses)
			);
		}

		if(!$this->Title()) {
			$classes[] = 'nolabel';
		}

		// Allow custom styling of any element in the container based on validation errors,
		// e.g. red borders on input tags.
		//
		// CSS class needs to be different from the one rendered through {@link FieldHolder()}.
		if($this->Message()) {
			$classes[] .= 'holder-' . $this->MessageType();
		}

		return implode(' ', $classes);
	}

	/**
	 * Add one or more CSS-classes to the FormField container.
	 *
	 * Multiple class names should be space delimited.
	 *
	 * @param string $class
	 *
	 * @return $this
	 */
	public function addExtraClass($class) {
		$classes = preg_split('/\s+/', $class);

		foreach ($classes as $class) {
			$this->extraClasses[$class] = $class;
		}

		return $this;
	}

	/**
	 * Remove one or more CSS-classes from the FormField container.
	 *
	 * @param string $class
	 *
	 * @return $this
	 */
	public function removeExtraClass($class) {
		$classes = preg_split('/\s+/', $class);

		foreach ($classes as $class) {
			unset($this->extraClasses[$class]);
		}

		return $this;
	}

	/**
	 * Set an HTML attribute on the field element, mostly an <input> tag.
	 *
	 * Some attributes are best set through more specialized methods, to avoid interfering with
	 * built-in behaviour:
	 *
	 * - 'class': {@link addExtraClass()}
	 * - 'title': {@link setDescription()}
	 * - 'value': {@link setValue}
	 * - 'name': {@link setName}
	 *
	 * Caution: this doesn't work on most fields which are composed of more than one HTML form
	 * field.
	 *
	 * @param string $name
	 * @param string $value
	 *
	 * @return $this
	 */
	public function setAttribute($name, $value) {
		$this->attributes[$name] = $value;

		return $this;
	}

	/**
	 * Get an HTML attribute defined by the field, or added through {@link setAttribute()}.
	 *
	 * Caution: this doesn't work on all fields, see {@link setAttribute()}.
	 *
	 * @return null|string
	 */
	public function getAttribute($name) {
		$attributes = $this->getAttributes();

		if(isset($attributes[$name])) {
			return $attributes[$name];
		}

		return null;
	}

	/**
	 * Allows customization through an 'updateAttributes' hook on the base class.
	 * Existing attributes are passed in as the first argument and can be manipulated,
	 * but any attributes added through a subclass implementation won't be included.
	 *
	 * @return array
	 */
	public function getAttributes() {
		$attributes = array(
			'type' => 'text',
			'name' => $this->getName(),
			'value' => $this->Value(),
			'class' => $this->extraClass(),
			'id' => $this->ID(),
			'disabled' => $this->isDisabled(),
			'readonly' => $this->isReadonly()
		);

		if($this->Required()) {
			$attributes['required'] = 'required';
			$attributes['aria-required'] = 'true';
		}

		$attributes = array_merge($attributes, $this->attributes);

		$this->extend('updateAttributes', $attributes);

		return $attributes;
	}

	/**
	 * Custom attributes to process. Falls back to {@link getAttributes()}.
	 *
	 * If at least one argument is passed as a string, all arguments act as excludes, by name.
	 *
	 * @param array $attributes
	 *
	 * @return string
	 */
	public function getAttributesHTML($attributes = null) {
		$exclude = null;

		if(is_string($attributes)) {
			$exclude = func_get_args();
		}

		if(!$attributes || is_string($attributes)) {
			$attributes = $this->getAttributes();
		}

		$attributes = (array) $attributes;

		$attributes = array_filter($attributes, function ($v) {
			return ($v || $v === 0 || $v === '0');
		});

		if($exclude) {
			$attributes = array_diff_key(
				$attributes,
				array_flip($exclude)
			);
		}

		// Create markup
		$parts = array();

		foreach($attributes as $name => $value) {
			if($value === true) {
				$parts[] = sprintf('%s="%s"', $name, $name);
			} else {
				$parts[] = sprintf('%s="%s"', $name, Convert::raw2att($value));
			}
		}

		return implode(' ', $parts);
	}

	/**
	 * Returns a version of a title suitable for insertion into an HTML attribute.
	 *
	 * @return string
	 */
	public function attrTitle() {
		return Convert::raw2att($this->title);
	}

	/**
	 * Returns a version of a title suitable for insertion into an HTML attribute.
	 *
	 * @return string
	 */
	public function attrValue() {
		return Convert::raw2att($this->value);
	}

	/**
	 * Set the field value.
	 *
	 * @param mixed $value
	 * @param null|array|DataObject $data {@see Form::loadDataFrom}
	 *
	 * @return $this
	 */
	public function setValue($value) {
		$this->value = $value;
		return $this;
	}

	/**
	 * Set the field name.
	 *
	 * @param string $name
	 *
	 * @return $this
	 */
	public function setName($name) {
		$this->name = $name;

		return $this;
	}

	/**
	 * Set the container form.
	 *
	 * This is called automatically when fields are added to forms.
	 *
	 * @param Form $form
	 *
	 * @return $this
	 */
	public function setForm($form) {
		$this->form = $form;

		return $this;
	}

	/**
	 * Get the currently used form.
	 *
	 * @return Form
	 */
	public function getForm() {
		return $this->form;
	}

	/**
	 * Return true if security token protection is enabled on the parent {@link Form}.
	 *
	 * @return bool
	 */
	public function securityTokenEnabled() {
		$form = $this->getForm();

		if(!$form) {
			return false;
		}

		return $form->getSecurityToken()->isEnabled();
	}

	/**
	 * Sets the error message to be displayed on the form field.
	 *
	 * Allows HTML content, so remember to use Convert::raw2xml().
	 *
	 * @param string $message
	 * @param string $messageType
	 *
	 * @return $this
	 */
	public function setError($message, $messageType) {
		$this->message = $message;
		$this->messageType = $messageType;

		return $this;
	}

	/**
	 * Set the custom error message to show instead of the default format.
	 *
	 * Different from setError() as that appends it to the standard error messaging.
	 *
	 * @param string $customValidationMessage
	 *
	 * @return $this
	 */
	public function setCustomValidationMessage($customValidationMessage) {
		$this->customValidationMessage = $customValidationMessage;

		return $this;
	}

	/**
	 * Get the custom error message for this form field. If a custom message has not been defined
	 * then just return blank. The default error is defined on {@link Validator}.
	 *
	 * @return string
	 */
	public function getCustomValidationMessage() {
		return $this->customValidationMessage;
	}

	/**
	 * Set name of template (without path or extension).
	 *
	 * Caution: Not consistently implemented in all subclasses, please check the {@link Field()}
	 * method on the subclass for support.
	 *
	 * @param string $template
	 *
	 * @return $this
	 */
	public function setTemplate($template) {
		$this->template = $template;

		return $this;
	}

	/**
	 * @return string
	 */
	public function getTemplate() {
		return $this->template;
	}

	/**
	 * @return string
	 */
	public function getFieldHolderTemplate() {
		return $this->fieldHolderTemplate;
	}

	/**
	 * Set name of template (without path or extension) for the holder, which in turn is
	 * responsible for rendering {@link Field()}.
	 *
	 * Caution: Not consistently implemented in all subclasses, please check the {@link Field()}
	 * method on the subclass for support.
	 *
	 * @param string $fieldHolderTemplate
	 *
	 * @return $this
	 */
	public function setFieldHolderTemplate($fieldHolderTemplate) {
		$this->fieldHolderTemplate = $fieldHolderTemplate;

		return $this;
	}

	/**
	 * @return string
	 */
	public function getSmallFieldHolderTemplate() {
		return $this->smallFieldHolderTemplate;
	}

	/**
	 * Set name of template (without path or extension) for the small holder, which in turn is
	 * responsible for rendering {@link Field()}.
	 *
	 * Caution: Not consistently implemented in all subclasses, please check the {@link Field()}
	 * method on the subclass for support.
	 *
	 * @param string $smallFieldHolderTemplate
	 *
	 * @return $this
	 */
	public function setSmallFieldHolderTemplate($smallFieldHolderTemplate) {
		$this->smallFieldHolderTemplate = $smallFieldHolderTemplate;

		return $this;
	}

	/**
	 * Returns the form field.
	 *
	 * Although FieldHolder is generally what is inserted into templates, all of the field holder
	 * templates make use of $Field. It's expected that FieldHolder will give you the "complete"
	 * representation of the field on the form, whereas Field will give you the core editing widget,
	 * such as an input tag.
	 *
	 * @param array $properties
	 * @return DBHTMLText
	 */
	public function Field($properties = array()) {
		$context = $this;

		if(count($properties)) {
			$context = $context->customise($properties);
		}

		$this->extend('onBeforeRender', $this);

		$result = $context->renderWith($this->getTemplates());

		// Trim whitespace from the result, so that trailing newlines are supressed. Works for strings and HTMLText values
		if(is_string($result)) {
			$result = trim($result);
		} else if($result instanceof DBField) {
			$result->setValue(trim($result->getValue()));
		}

		return $result;
	}

	/**
	 * Returns a "field holder" for this field.
	 *
	 * Forms are constructed by concatenating a number of these field holders.
	 *
	 * The default field holder is a label and a form field inside a div.
	 *
	 * @see FieldHolder.ss
	 *
	 * @param array $properties
	 *
	 * @return DBHTMLText
	 */
	public function FieldHolder($properties = array()) {
		$context = $this;

		if(count($properties)) {
			$context = $this->customise($properties);
		}

		return $context->renderWith($this->getFieldHolderTemplates());
	}

	/**
	 * Returns a restricted field holder used within things like FieldGroups.
	 *
	 * @param array $properties
	 *
	 * @return string
	 */
	public function SmallFieldHolder($properties = array()) {
		$context = $this;

		if(count($properties)) {
			$context = $this->customise($properties);
		}

		return $context->renderWith($this->getSmallFieldHolderTemplates());
	}

	/**
	 * Returns an array of templates to use for rendering {@link FieldHolder}.
	 *
	 * @return array
	 */
	public function getTemplates() {
		return $this->_templates($this->getTemplate());
	}

	/**
	 * Returns an array of templates to use for rendering {@link FieldHolder}.
	 *
	 * @return array
	 */
	public function getFieldHolderTemplates() {
		return $this->_templates(
			$this->getFieldHolderTemplate(),
			'_holder'
		);
	}

	/**
	 * Returns an array of templates to use for rendering {@link SmallFieldHolder}.
	 *
	 * @return array
	 */
	public function getSmallFieldHolderTemplates() {
		return $this->_templates(
			$this->getSmallFieldHolderTemplate(),
			'_holder_small'
		);
	}


	/**
	 * Generate an array of class name strings to use for rendering this form field into HTML.
	 *
	 * @param string $customTemplate
	 * @param string $customTemplateSuffix
	 *
	 * @return array
	 */
	private function _templates($customTemplate = null, $customTemplateSuffix = null) {
		$matches = array();

		foreach(array_reverse(ClassInfo::ancestry($this)) as $className) {
			$matches[] = $className . $customTemplateSuffix;

			if($className == "FormField") {
				break;
			}
		}

		if($customTemplate) {
			array_unshift($matches, $customTemplate);
		}

		return $matches;
	}

	/**
	 * Returns true if this field is a composite field.
	 *
	 * To create composite field types, you should subclass {@link CompositeField}.
	 *
	 * @return bool
	 */
	public function isComposite() {
		return false;
	}

	/**
	 * Returns true if this field has its own data.
	 *
	 * Some fields, such as titles and composite fields, don't actually have any data. It doesn't
	 * make sense for data-focused methods to look at them. By overloading hasData() to return
	 * false, you can prevent any data-focused methods from looking at it.
	 *
	 * @see FieldList::collateDataFields()
	 *
	 * @return bool
	 */
	public function hasData() {
		return true;
	}

	/**
	 * @return bool
	 */
	public function isReadonly() {
		return $this->readonly;
	}

	/**
	 * Sets a read-only flag on this FormField.
	 *
	 * Use performReadonlyTransformation() to transform this instance.
	 *
	 * Setting this to false has no effect on the field.
	 *
	 * @param bool $readonly
	 *
	 * @return $this
	 */
	public function setReadonly($readonly) {
		$this->readonly = $readonly;

		return $this;
	}

	/**
	 * @return bool
	 */
	public function isDisabled() {
		return $this->disabled;
	}

	/**
	 * Sets a disabled flag on this FormField.
	 *
	 * Use performDisabledTransformation() to transform this instance.
	 *
	 * Setting this to false has no effect on the field.
	 *
	 * @param bool $disabled
	 *
	 * @return $this
	 */
	public function setDisabled($disabled) {
		$this->disabled = $disabled;

		return $this;
	}

	/**
	 * Returns a read-only version of this field.
	 *
	 * @return FormField
	 */
	public function performReadonlyTransformation() {
		$readonlyClassName = $this->class . '_Readonly';

		if(ClassInfo::exists($readonlyClassName)) {
			$clone = $this->castedCopy($readonlyClassName);
		} else {
			$clone = $this->castedCopy('ReadonlyField');
		}

		$clone->setReadonly(true);

		return $clone;
	}

	/**
	 * Return a disabled version of this field.
	 *
	 * Tries to find a class of the class name of this field suffixed with "_Disabled", failing
	 * that, finds a method {@link setDisabled()}.
	 *
	 * @return FormField
	 */
	public function performDisabledTransformation() {
		$disabledClassName = $this->class . '_Disabled';

		if(ClassInfo::exists($disabledClassName)) {
			$clone = $this->castedCopy($disabledClassName);
		} else {
			$clone = clone $this;
		}

		$clone->setDisabled(true);

		return $clone;
	}

	/**
	 * @param FormTransformation $transformation
	 *
	 * @return mixed
	 */
	public function transform(FormTransformation $transformation) {
		return $transformation->transform($this);
	}

	/**
	 * @param string $class
	 *
	 * @return int
	 */
	public function hasClass($class) {
		$patten = '/' . strtolower($class) . '/i';

		$subject = strtolower($this->class . ' ' . $this->extraClass());

		return preg_match($patten, $subject);
	}

	/**
	 * Returns the field type.
	 *
	 * The field type is the class name with the word Field dropped off the end, all lowercase.
	 *
	 * It's handy for assigning HTML classes. Doesn't signify the <input type> attribute.
	 *
	 * @see {link getAttributes()}.
	 *
	 * @return string
	 */
	public function Type() {
		$type = new ReflectionClass($this);
		return strtolower(preg_replace('/Field$/', '', $type->getShortName()));
	}

	/**
	 * @deprecated 4.0 Use FormField::create_tag()
	 *
	 * @param string $tag
	 * @param array $attributes
	 * @param null|string $content
	 *
	 * @return string
	 */
	public function createTag($tag, $attributes, $content = null) {
		Deprecation::notice('4.0', 'Use FormField::create_tag()');

		return self::create_tag($tag, $attributes, $content);
	}

	/**
	 * Abstract method each {@link FormField} subclass must implement, determines whether the field
	 * is valid or not based on the value.
	 *
	 * @todo Make this abstract.
	 *
	 * @param Validator
	 *
	 * @return bool
	 */
	public function validate($validator) {
		return true;
	}

	/**
	 * Describe this field, provide help text for it.
	 *
	 * By default, renders as a <span class="description"> underneath the form field.
	 *
	 * @param string $description
	 *
	 * @return $this
	 */
	public function setDescription($description) {
		$this->description = $description;

		return $this;
	}

	/**
	 * @return string
	 */
	public function getDescription() {
		return $this->description;
	}

	/**
	 * @return string
	 */
	public function debug() {
		return sprintf(
			'%s (%s: %s : <span style="color:red;">%s</span>) = %s',
			$this->class,
			$this->name,
			$this->title,
			$this->message,
			$this->value
		);
	}

	/**
	 * This function is used by the template processor. If you refer to a field as a $ variable, it
	 * will return the $Field value.
	 *
	 * @return string
	 */
	public function forTemplate() {
		return $this->Field();
	}

	/**
	 * @return bool
	 */
	public function Required() {
		if($this->form && ($validator = $this->form->Validator)) {
			return $validator->fieldIsRequired($this->name);
		}

		return false;
	}

	/**
	 * Set the FieldList that contains this field.
	 *
	 * @param FieldList $containerFieldList
	 *
	 * @return FieldList
	 */
	public function setContainerFieldList($containerFieldList) {
		$this->containerFieldList = $containerFieldList;

		return $this;
	}

	/**
	 * Get the FieldList that contains this field.
	 *
	 * @return FieldList
	 */
	public function getContainerFieldList() {
		return $this->containerFieldList;
	}

	/**
	 * @return null|FieldList
	 */
	public function rootFieldList() {
		if(is_object($this->containerFieldList)) {
			return $this->containerFieldList->rootFieldList();
		}

		user_error(
			"rootFieldList() called on $this->class object without a containerFieldList",
			E_USER_ERROR
		);

		return null;
	}

	/**
	 * Returns another instance of this field, but "cast" to a different class. The logic tries to
	 * retain all of the instance properties, and may be overloaded by subclasses to set additional
	 * ones.
	 *
	 * Assumes the standard FormField parameter signature with its name as the only mandatory
	 * argument. Mainly geared towards creating *_Readonly or *_Disabled subclasses of the same
	 * type, or casting to a {@link ReadonlyField}.
	 *
	 * Does not copy custom field templates, since they probably won't apply to the new instance.
	 *
	 * @param mixed $classOrCopy Class name for copy, or existing copy instance to update
	 *
	 * @return FormField
	 */
	public function castedCopy($classOrCopy) {
		$field = $classOrCopy;

		if(!is_object($field)) {
			$field = new $classOrCopy($this->name);
		}

		$field
			->setValue($this->value)
			->setForm($this->form)
			->setTitle($this->Title())
			->setLeftTitle($this->LeftTitle())
			->setRightTitle($this->RightTitle())
			->addExtraClass($this->extraClass())
			->setDescription($this->getDescription());

		// Only include built-in attributes, ignore anything set through getAttributes().
		// Those might change important characteristics of the field, e.g. its "type" attribute.
		foreach($this->attributes as $attributeKey => $attributeValue) {
			$field->setAttribute($attributeKey, $attributeValue);
		}

		return $field;
	}

	/**
	 * Sets the component type the FormField will be rendered as on the front-end.
	 *
	 * @param string $componentType
	 * @return FormField
	 */
	public function setSchemaComponent($componentType) {
		$this->schemaComponent = $componentType;
		return $this;
	}

	/**
	 * Gets the type of front-end component the FormField will be rendered as.
	 *
	 * @return string
	 */
	public function getSchemaComponent() {
		return $this->schemaComponent;
	}

	/**
	 * Sets the schema data used for rendering the field on the front-end.
	 * Merges the passed array with the current `$schemaData` or {@link getSchemaDataDefaults()}.
	 * Any passed keys that are not defined in {@link getSchemaDataDefaults()} are ignored.
	 * If you want to pass around ad hoc data use the `data` array e.g. pass `['data' => ['myCustomKey' => 'yolo']]`.
	 *
	 * @param array $schemaData - The data to be merged with $this->schemaData.
	 * @return FormField
	 *
	 * @todo Add deep merging of arrays like `data` and `attributes`.
	 */
	public function setSchemaData($schemaData = []) {
		$current = $this->getSchemaData();

		$this->schemaData = array_merge($current, array_intersect_key($schemaData, $current));
		return $this;
	}

	/**
	 * Gets the schema data used to render the FormField on the front-end.
	 *
	 * @return array
	 */
	public function getSchemaData() {
		return array_merge($this->getSchemaDataDefaults(), $this->schemaData);
	}

	/**
	 * @todo Throw exception if value is missing, once a form field schema is mandatory across the CMS
	 *
	 * @return string
	 */
	public function getSchemaDataType() {
		return $this->schemaDataType;
	}

	/**
	 * Gets the defaults for $schemaData.
	 * The keys defined here are immutable, meaning undefined keys passed to {@link setSchemaData()} are ignored.
	 * Instead the `data` array should be used to pass around ad hoc data.
	 *
	 * @return array
	 */
	public function getSchemaDataDefaults() {
		return [
			'name' => $this->getName(),
			'id' => $this->ID(),
			'type' => $this->getSchemaDataType(),
			'component' => $this->getSchemaComponent(),
			'holder_id' => null,
			'title' => $this->Title(),
			'source' => null,
			'extraClass' => $this->ExtraClass(),
			'description' => $this->getDescription(),
			'rightTitle' => $this->RightTitle(),
			'leftTitle' => $this->LeftTitle(),
			'readOnly' => $this->isReadOnly(),
			'disabled' => $this->isDisabled(),
			'customValidationMessage' => $this->getCustomValidationMessage(),
			'attributes' => [],
			'data' => [],
		];
	}

	/**
	 * Sets the schema data used for rendering the field on the front-end.
	 * Merges the passed array with the current `$schemaData` or {@link getSchemaDataDefaults()}.
	 * Any passed keys that are not defined in {@link getSchemaDataDefaults()} are ignored.
	 * If you want to pass around ad hoc data use the `data` array e.g. pass `['data' => ['myCustomKey' => 'yolo']]`.
	 *
	 * @param array $schemaData - The data to be merged with $this->schemaData.
	 * @return FormField
	 *
	 * @todo Add deep merging of arrays like `data` and `attributes`.
	 */
	public function setSchemaState($schemaState = []) {
		$current = $this->getSchemaState();

		$this->schemaState = array_merge($current, array_intersect_key($schemaState, $current));
		return $this;
	}

	/**
	 * Gets the schema state used to render the FormField on the front-end.
	 *
	 * @return array
	 */
	public function getSchemaState() {
		return array_merge($this->getSchemaStateDefaults(), $this->schemaState);
	}

	/**
	 * Gets the defaults for $schemaState.
	 * The keys defined here are immutable, meaning undefined keys passed to {@link setSchemaState()} are ignored.
	 * Instead the `data` array should be used to pass around ad hoc data.
	 * Includes validation data if the field is associated to a {@link Form},
	 * and {@link Form->validate()} has been called.
	 *
	 * @return array
	 */
	public function getSchemaStateDefaults() {
		$field = $this;
		$form = $this->getForm();
		$validator = $form ? $form->getValidator() : null;
		$errors = $validator ? (array)$validator->getErrors() : [];
		$messages = array_filter(array_map(function($error) use ($field) {
			if($error['fieldName'] === $field->getName()) {
				return [
					'value' => $error['message'],
					'type' => $error['messageType']
				];
			}
		}, $errors));

		return [
			'id' => $this->ID(),
			'value' => $this->Value(),
			'valid' => (count($messages) === 0),
			'messages' => (array)$messages,
			'data' => [],
		];
	}

}