<?php

use SilverStripe\Model\Relation;

/**
 * Represents a SelectField that may potentially have multiple selections, and may have
 * a {@link ManyManyList} as a data source.
 */
abstract class MultiSelectField extends SelectField {

	/**
	 * List of items to mark as checked, and may not be unchecked
	 *
	 * @var array
	 */
	protected $defaultItems = array();

	/**
	 * Extracts the value of this field, normalised as an array.
	 * Scalar values will return a single length array, even if empty
	 *
	 * @return array List of values as an array
	 */
	public function getValueArray() {
		return $this->getListValues($this->Value());
	}

	/**
	 * Default selections, regardless of the {@link setValue()} settings.
	 * Note: Items marked as disabled through {@link setDisabledItems()} can still be
	 * selected by default through this method.
	 *
	 * @param array $items Collection of array keys, as defined in the $source array
	 * @return $this Self reference
	 */
	public function setDefaultItems($items) {
		$this->defaultItems = $this->getListValues($items);
		return $this;
	}

	/**
	 * Default selections, regardless of the {@link setValue()} settings.
	 *
	 * @return array
	 */
	public function getDefaultItems() {
		return $this->defaultItems;
	}

	/**
	 * Load a value into this MultiSelectField
	 */
	public function setValue($val, $obj = null) {
		// If we're not passed a value directly,
		// we can look for it in a relation method on the object passed as a second arg
		if($obj instanceof DataObject) {
			$this->loadFrom($obj);
		} else {
			return parent::setValue($val);
		}
		return $this;
	}

	/**
	 * Load the value from the dataobject into this field
	 *
	 * @param DataObjectInterface $record
	 */
	public function loadFrom(DataObjectInterface $record) {
		$fieldName = $this->getName();
		if(empty($fieldName) || empty($record)) {
			return;
		}

		$relation = $record->hasMethod($fieldName)
			? $record->$fieldName()
			: null;

		// Detect DB relation or field
		if($relation instanceof Relation) {
			// Load ids from relation
			$value = array_values($relation->getIDList());
			parent::setValue($value);
		} elseif($record->hasField($fieldName)) {
			$value = $this->stringDecode($record->$fieldName);
			parent::setValue($value);
		}
	}


	/**
	 * Save the current value of this MultiSelectField into a DataObject.
	 * If the field it is saving to is a has_many or many_many relationship,
	 * it is saved by setByIDList(), otherwise it creates a comma separated
	 * list for a standard DB text/varchar field.
	 *
	 * @param DataObject $record The record to save into
	 */
	public function saveInto(DataObjectInterface $record) {
		$fieldName = $this->getName();
		if(empty($fieldName) || empty($record)) {
			return;
		}

		$relation = $record->hasMethod($fieldName)
			? $record->$fieldName()
			: null;

		// Detect DB relation or field
		$items = $this->getValueArray();
		if($relation instanceof Relation) {
			// Save ids into relation
			$relation->setByIDList($items);
		} elseif($record->hasField($fieldName)) {
			// Save dataValue into field
			$record->$fieldName = $this->stringEncode($items);
		}

	}

	/**
	 * Encode a list of values into a string, or null if empty (to simplify empty checks)
	 *
	 * @param array $value
	 * @return string|null
	 */
	public function stringEncode($value) {
		return $value
			? json_encode(array_values($value))
			: null;
	}

	/**
	 * Extract a string value into an array of values
	 *
	 * @param string $value
	 * @return array
	 */
	protected function stringDecode($value) {
		// Handle empty case
		if(empty($value)) {
			return array();
		}

		// If json deserialisation fails, then fallover to legacy format
		$result = json_decode($value, true);
		if($result !== false) {
			return $result;
		}

		throw new \InvalidArgumentException("Invalid string encoded value for multi select field");
	}

	/**
	 * Validate this field
	 *
	 * @param Validator $validator
	 * @return bool
	 */
	public function validate($validator) {
		$values = $this->getValueArray();
		$validValues = $this->getValidValues();

		// Filter out selected values not in the data source
		$self = $this;
		$invalidValues = array_filter(
			$values,
			function($userValue) use ($self, $validValues) {
				foreach($validValues as $formValue) {
					if($self->isSelectedValue($formValue, $userValue)) {
						return false;
					}
				}
				return true;
			}
		);
		if(empty($invalidValues)) {
			return true;
		}

		// List invalid items
		$validator->validationError(
			$this->getName(),
			_t(
				'MultiSelectField.SOURCE_VALIDATION',
				"Please select values within the list provided. Invalid option(s) {value} given",
				array('value' => implode(',', $invalidValues))
			),
			"validation"
		);
		return false;
	}

	/**
	 * Transforms the source data for this CheckboxSetField
	 * into a comma separated list of values.
	 *
	 * @return ReadonlyField
	 */
	public function performReadonlyTransformation() {
		$source = $this->getSource();

		// Map selected values to titles
		$data = array();
		foreach($this->getValueArray() as $value) {
			if(array_key_exists($value, $source)) {
				$data[] = $source[$value];
			} else {
				$data[] = $value;
			}
		}
		$values = implode(', ', $data);

		$field = $this->castedCopy('ReadonlyField');
		$field->setValue($values);

		return $field;
	}
}