<?php

/**
 * Subclass of {@link DataList} representing a many_many relation.
 *
 * @package framework
 * @subpackage model
 */
class ManyManyList extends RelationList {
	
	protected $joinTable;
	
	protected $localKey;
	
	protected $foreignKey;

	protected $extraFields;

	/**
	 * Create a new ManyManyList object.
	 * 
	 * A ManyManyList object represents a list of DataObject records that correspond to a many-many
	 * relationship.  In addition to, 
	 * 
	 * Generation of the appropriate record set is left up to the caller, using the normal
	 * {@link DataList} methods.  Addition arguments are used to support {@@link add()}
	 * and {@link remove()} methods.
	 * 
	 * @param string $dataClass The class of the DataObjects that this will list.
	 * @param string $joinTable The name of the table whose entries define the content of this many_many relation.
	 * @param string $localKey The key in the join table that maps to the dataClass' PK.
	 * @param string $foreignKey The key in the join table that maps to joined class' PK.
	 * @param string $extraFields A map of field => fieldtype of extra fields on the join table.
	 * 
	 * @example new ManyManyList('Group','Group_Members', 'GroupID', 'MemberID');
	 */
	public function __construct($dataClass, $joinTable, $localKey, $foreignKey, $extraFields = array()) {
		parent::__construct($dataClass);
		$this->joinTable = $joinTable;
		$this->localKey = $localKey;
		$this->foreignKey = $foreignKey;
		$this->extraFields = $extraFields;

		$baseClass = ClassInfo::baseDataClass($dataClass);

		// Join to the many-many join table
		$this->dataQuery->innerJoin($joinTable, "\"$joinTable\".\"$this->localKey\" = \"$baseClass\".\"ID\"");

		// Query the extra fields from the join table
		if($extraFields) $this->dataQuery->selectFromTable($joinTable, array_keys($extraFields));
	}

	protected function foreignIDFilter($id = null) {
		if ($id === null) {
			$id = $this->getForeignID();
		}

		// Apply relation filter
		$key = "\"$this->joinTable\".\"$this->foreignKey\"";
		if(is_array($id)) {
			return array("$key IN (".DB::placeholders($id).")"  => $id);
		} else if($id !== null){
			return array($key => $id);
		}
	}
	
	/**
	 * Return a filter expression for the join table when writing to the join table
	 *
	 * When writing (add, remove, removeByID), we need to filter the join table to just the relevant
	 * entries. However some subclasses of ManyManyList (Member_GroupSet) modify foreignIDFilter to
	 * include additional calculated entries, so we need different filters when reading and when writing
	 *
	 * @param array|integer $id (optional) An ID or an array of IDs - if not provided, will use the current ids
	 * as per getForeignID
	 * @return array Condition In array(SQL => parameters format)
	 */
	protected function foreignIDWriteFilter($id = null) {
		return $this->foreignIDFilter($id);
	}

	/**
	 * Add an item to this many_many relationship
	 * Does so by adding an entry to the joinTable.
	 * 
	 * @param $extraFields A map of additional columns to insert into the joinTable
	 */
	public function add($item, $extraFields = array()) {
		// Ensure nulls or empty strings are correctly treated as empty arrays
		if(empty($extraFields)) $extraFields = array();
		
		// Determine ID of new record
		if(is_numeric($item)) {
			$itemID = $item;
		} elseif($item instanceof $this->dataClass) {
			$itemID = $item->ID;
		} else {
			throw new InvalidArgumentException("ManyManyList::add() expecting a $this->dataClass object, or ID value",
				E_USER_ERROR);
		}

		// Validate foreignID
		$foreignIDs = $this->getForeignID();
		if(empty($foreignIDs)) {
			throw new Exception("ManyManyList::add() can't be called until a foreign ID is set", E_USER_WARNING);
		}

		// Apply this item to each given foreign ID record
		if(!is_array($foreignIDs)) $foreignIDs = array($foreignIDs);
		$baseClass = ClassInfo::baseDataClass($this->dataClass);
		foreach($foreignIDs as $foreignID) {
			
			// Check for existing records for this item
			if($foreignFilter = $this->foreignIDFilter($foreignID)) {
				// With the current query, simply add the foreign and local conditions
				// The query can be a bit odd, especially if custom relation classes
				// don't join expected tables (@see Member_GroupSet for example).
				$query = $this->dataQuery->query()->toSelect();
				$query->addWhere($foreignFilter);
				$query->addWhere(array(
					"\"$baseClass\".\"ID\"" => $itemID
				));
				$hasExisting = ($query->count() > 0);
			} else {
				$hasExisting = false;	
			}
			
			// Determine entry type
			if(!$hasExisting) {
				// Field values for new record
				$fieldValues = array_merge($extraFields, array(
					"\"{$this->foreignKey}\"" => $foreignID,
					"\"{$this->localKey}\"" => $itemID
				));
				// Create new record
				$insert = new SQLInsert("\"{$this->joinTable}\"", $fieldValues);
				$insert->execute();
			} elseif(!empty($extraFields)) {
				// For existing records, simply update any extra data supplied
				$foreignWriteFilter = $this->foreignIDWriteFilter($foreignID);
				$update = new SQLUpdate("\"{$this->joinTable}\"", $extraFields, $foreignWriteFilter);
				$update->addWhere(array(
					"\"{$this->joinTable}\".\"{$this->localKey}\"" => $itemID
				));
				$update->execute();
			}
		}
	}

	/**
	 * Remove the given item from this list.
	 * Note that for a ManyManyList, the item is never actually deleted, only the join table is affected
	 * @param $itemID The ID of the item to remove.
	 */
	public function remove($item) {
		if(!($item instanceof $this->dataClass)) {
			throw new InvalidArgumentException("ManyManyList::remove() expecting a $this->dataClass object");
		}
		
		return $this->removeByID($item->ID);
	}

	/**
	 * Remove the given item from this list.
	 * Note that for a ManyManyList, the item is never actually deleted, only the join table is affected
	 * @param $itemID The item it
	 */
	public function removeByID($itemID) {
		if(!is_numeric($itemID)) throw new InvalidArgumentException("ManyManyList::removeById() expecting an ID");

		$query = new SQLDelete("\"$this->joinTable\"");

		if($filter = $this->foreignIDWriteFilter($this->getForeignID())) {
			$query->setWhere($filter);
		} else {
			user_error("Can't call ManyManyList::remove() until a foreign ID is set", E_USER_WARNING);
		}
		
		$query->addWhere(array("\"$this->localKey\"" => $itemID));
		$query->execute();
	}

	/**
	 * Remove all items from this many-many join.  To remove a subset of items, filter it first.
	 */
	public function removeAll() {
		$base = ClassInfo::baseDataClass($this->dataClass());

		// Remove the join to the join table to avoid MySQL row locking issues.
		$query = $this->dataQuery();
		$foreignFilter = $query->getQueryParam('Foreign.Filter');
		$query->removeFilterOn($foreignFilter);

		$selectQuery = $query->query();
		$selectQuery->setSelect("\"$base\".\"ID\"");

		$from = $selectQuery->getFrom();
		unset($from[$this->joinTable]);
		$selectQuery->setFrom($from);
		$selectQuery->setOrderBy(); // ORDER BY in subselects breaks MS SQL Server and is not necessary here
		$selectQuery->setDistinct(false);

		// Use a sub-query as SQLite does not support setting delete targets in
		// joined queries.
		$delete = new SQLDelete();
		$delete->setFrom("\"$this->joinTable\"");
		$delete->addWhere($this->foreignIDFilter());
		$subSelect = $selectQuery->sql($parameters);
		$delete->addWhere(array(
			"\"$this->joinTable\".\"$this->localKey\" IN ($subSelect)" => $parameters
		));
		$delete->execute();
	}

	/**
	 * Find the extra field data for a single row of the relationship
	 * join table, given the known child ID.
	 *
	 * @todo Add tests for this / refactor it / something
	 *	
	 * @param string $componentName The name of the component
	 * @param int $itemID The ID of the child for the relationship
	 * @return array Map of fieldName => fieldValue
	 */
	function getExtraData($componentName, $itemID) {
		$result = array();

		if(!is_numeric($itemID)) {
			user_error('ComponentSet::getExtraData() passed a non-numeric child ID', E_USER_ERROR);
		}

		// @todo Optimize into a single query instead of one per extra field
		if($this->extraFields) {
			foreach($this->extraFields as $fieldName => $dbFieldSpec) {
				$query = new SQLSelect("\"$fieldName\"", "\"$this->joinTable\"");
				if($filter = $this->foreignIDWriteFilter($this->getForeignID())) {
					$query->setWhere($filter);
				} else {
					user_error("Can't call ManyManyList::getExtraData() until a foreign ID is set", E_USER_WARNING);
				}
				$query->addWhere("\"$this->localKey\" = {$itemID}");
				$result[$fieldName] = $query->execute()->value();
			}
		}
		
		return $result;
	}

	/**
	 * Gets the join table used for the relationship.
	 *
	 * @return string the name of the table
	 */
	public function getJoinTable() {
		return $this->joinTable;
	}

	/**
	 * Gets the key used to store the ID of the local/parent object.
	 *
	 * @return string the field name
	 */
	public function getLocalKey() {
		return $this->localKey;
	}

	/**
	 * Gets the key used to store the ID of the foreign/child object.
	 *
	 * @return string the field name
	 */
	public function getForeignKey() {
		return $this->foreignKey;
	}

	/**
	 * Gets the extra fields included in the relationship.
	 *
	 * @return array a map of field names to types
	 */
	public function getExtraFields() {
		return $this->extraFields;
	}

}