<?php

use SilverStripe\Model\Relation;

/**
 * An {@link ArrayList} that represents an unsaved relation.
 *
 * has_many and many_many relations cannot be saved until after the DataObject
 * they're on has been written. This List pretends to be a RelationList and
 * stores the related objects in memory.
 *
 * It can store both saved objects (as IDs) or unsaved objects (as instances
 * of $dataClass). Unsaved objects are then written when the list is saved
 * into an instance of {@link RelationList}.
 *
 * Most methods that alter the list of objects throw LogicExceptions.
 *
 * @package framework
 * @subpackage model
 */
class UnsavedRelationList extends ArrayList implements Relation {

	/**
	 * The DataObject class name that this relation is on
	 *
	 * @var string
	 */
	protected $baseClass;

	/**
	 * The name of the relation
	 *
	 * @var string
	 */
	protected $relationName;

	/**
	 * The DataObject class name that this relation is querying
	 *
	 * @var string
	 */
	protected $dataClass;

	/**
	 * The extra fields associated with the relation
	 *
	 * @var array
	 */
	protected $extraFields = array();

	/**
	 * Create a new UnsavedRelationList
	 *
	 * @param string $dataClass The DataObject class used in the relation
	 */
	public function __construct($baseClass, $relationName, $dataClass) {
		$this->baseClass = $baseClass;
		$this->relationName = $relationName;
		$this->dataClass = $dataClass;
		parent::__construct();
	}

	/**
	 * Add an item to this relationship
	 *
	 * @param $extraFields A map of additional columns to insert into the joinTable in the case of a many_many relation
	 */
	public function add($item, $extraFields = null) {
		$this->push($item, $extraFields);
	}

	/**
	 * Save all the items in this list into the RelationList
	 *
	 * @param RelationList $list
	 */
	public function changeToList(RelationList $list) {
		foreach($this->items as $key => $item) {
			if(is_object($item)) {
				$item->write();
			}
			$list->add($item, $this->extraFields[$key]);
		}
	}

	/**
	 * Pushes an item onto the end of this list.
	 *
	 * @param array|object $item
	 */
	public function push($item, $extraFields = null) {
		if((is_object($item) && !$item instanceof $this->dataClass)
			|| (!is_object($item) && !is_numeric($item))) {
			throw new InvalidArgumentException(
				"UnsavedRelationList::add() expecting a $this->dataClass object, or ID value",
				E_USER_ERROR);
		}
		if(is_object($item) && $item->ID) {
			$item = $item->ID;
		}
		$this->extraFields[] = $extraFields;
		parent::push($item);
	}

	/**
	 * Get the dataClass name for this relation, ie the DataObject ClassName
	 *
	 * @return string
	 */
	public function dataClass() {
		return $this->dataClass;
	}

	/**
	 * Returns an Iterator for this relation.
	 *
	 * @return ArrayIterator
	 */
	public function getIterator() {
		return new ArrayIterator($this->toArray());
	}

	/**
	 * Return an array of the actual items that this relation contains at this stage.
	 * This is when the query is actually executed.
	 *
	 * @return array
	 */
	public function toArray() {
		$items = array();
		foreach($this->items as $key => $item) {
			if(is_numeric($item)) {
				$item = DataObject::get_by_id($this->dataClass, $item);
			}
			if(!empty($this->extraFields[$key])) {
				$item->update($this->extraFields[$key]);
			}
			$items[] = $item;
		}
		return $items;
	}

	/**
	 * Add a number of items to the relation.
	 *
	 * @param array $items Items to add, as either DataObjects or IDs.
	 * @return DataList
	 */
	public function addMany($items) {
		foreach($items as $item) {
			$this->add($item);
		}
		return $this;
	}

	/**
     * Remove all items from this relation.
     */
	public function removeAll() {
		$this->items = array();
		$this->extraFields = array();
	}

	/**
	 * Remove the items from this list with the given IDs
	 *
	 * @param array $items
	 */
	public function removeMany($items) {
		$this->items = array_diff($this->items, $items);
		return $this;
	}

	/**
	 * Removes items from this list which are equal.
	 *
	 * @param string $field unused
	 */
	public function removeDuplicates($field = 'ID') {
		$this->items = array_unique($this->items);
	}

	/**
	 * Sets the Relation to be the given ID list.
	 * Records will be added and deleted as appropriate.
	 *
	 * @param array $idList List of IDs.
	 */
	public function setByIDList($idList) {
		$this->removeAll();
		$this->addMany($idList);
	}

	/**
	 * Returns an array with both the keys and values set to the IDs of the records in this list.
	 *
	 * Does not return the IDs for unsaved DataObjects
	 */
	public function getIDList() {
		// Get a list of IDs of our current items - if it's not a number then object then assume it's a DO.
		$ids = array_map(function($obj) {
			return is_numeric($obj) ? $obj : $obj->ID;
		}, $this->items);

		// Strip out duplicates and anything resolving to False.
		$ids = array_filter(array_unique($ids));

		// Change the array from (1, 2, 3) to (1 => 1, 2 => 2, 3 => 3)
		if ($ids) $ids = array_combine($ids, $ids);

		return $ids;
	}

	/**
	 * Returns the first item in the list
	 *
	 * @return mixed
	 */
	public function first() {
		$item = reset($this->items);
		if(is_numeric($item)) {
			$item = DataObject::get_by_id($this->dataClass, $item);
		}
		if(!empty($this->extraFields[key($this->items)])) {
			$item->update($this->extraFields[key($this->items)]);
		}
		return $item;
	}

	/**
	 * Returns the last item in the list
	 *
	 * @return mixed
	 */
	public function last() {
		$item = end($this->items);
		if(!empty($this->extraFields[key($this->items)])) {
			$item->update($this->extraFields[key($this->items)]);
		}
		return $item;
	}

	/**
	 * Returns an array of a single field value for all items in the list.
	 *
	 * @param string $colName
	 * @return array
	 */
	public function column($colName = 'ID') {
		$list = new ArrayList($this->toArray());
		return $list->column($colName);
	}

	/**
	 * Returns a copy of this list with the relationship linked to the given foreign ID.
	 * @param $id An ID or an array of IDs.
	 */
	public function forForeignID($id) {
		$class = singleton($this->baseClass);
		$class->ID = 1;
		return $class->{$this->relationName}()->forForeignID($id);
	}

	/**
	 * Return the DBField object that represents the given field on the related class.
	 *
	 * @param string $fieldName Name of the field
	 * @return DBField The field as a DBField object
	 */
	public function dbObject($fieldName) {
		return singleton($this->dataClass)->dbObject($fieldName);
	}
}