<?php

namespace SilverStripe\ORM\Queries;

/**
 * Represents a list of updates / inserts made to a single row in a table
 *
 * @package framework
 * @subpackage orm
 */
class SQLAssignmentRow {

	/**
	 * List of field values to store for this query
	 *
	 * Each item in this array will be in the form of a single-length array
	 * in the format array('sql' => array($parameters)).
	 * The field name is stored as the key
	 *
	 * E.g.
	 *
	 * <code>$assignments['ID'] = array('?' => array(1));</code>
	 *
	 * This allows for complex, parameterised updates, or explict field values set
	 * without any prameters
	 *
	 * @var array
	 */
	protected $assignments = array();

	/**
	 * Instantiate a new SQLAssignmentRow object with the given values
	 *
	 * @param array $values
	 */
	function __construct(array $values = array()) {
		$this->setAssignments($values);
	}


	/**
	 * Given a key / value pair, extract the predicate and any potential paramaters
	 * in a format suitable for storing internally as a list of paramaterised conditions.
	 *
	 * @param mixed $value Either a literal field value, or an array with
	 * placeholder => parameter(s) as a pair
	 * @return array A single item array in the format array($sql => array($parameters))
	 */
	protected function parseAssignment($value) {
		// Assume string values (or values saved as customised array objects)
		// represent simple assignment
		if(!is_array($value) || isset($value['type'])) {
			return array('?' => array($value));
		}

		// If given as array then extract and check both the SQL as well as the parameter(s)
		// Note that there could be multiple parameters, e.g.
		// array('MAX(?,?)' => array(1,2)) although the container should
		// have a single item
		if(count($value) == 1) {
			foreach($value as $sql => $parameters) {
				if(!is_string($sql)) continue;
				if(!is_array($parameters)) $parameters = array($parameters);

				// @todo Some input sanitisation checking the key contains the
				// correct number of ? placeholders as the number of parameters
				return array($sql => $parameters);
			}
		}

		user_error("Nested field assignments should be given as a single parameterised item array in "
				.  "array('?' => array('value')) format)", E_USER_ERROR);
	}

	/**
	 * Given a list of assignments in any user-acceptible format, normalise the
	 * value to a common array('SQL' => array(parameters)) format
	 *
	 * @param array $predicates List of assignments.
	 * The key of this array should be the field name, and the value the assigned
	 * literal value, or an array with parameterised information.
	 * @return array List of normalised assignments
	 */
	protected function normaliseAssignments(array $assignments) {
		$normalised = array();
		foreach($assignments as $field => $value) {
			$normalised[$field] = $this->parseAssignment($value);
		}
		return $normalised;
	}

	/**
	 * Adds assignments for a list of several fields
	 *
	 * Note that field values must not be escaped, as these will be internally
	 * parameterised by the database engine.
	 *
	 * <code>
	 *
	 * // Basic assignments
	 * $query->addAssignments(array(
	 *		'"Object"."Title"' => 'Bob',
	 *		'"Object"."Description"' => 'Bob was here'
	 * ))
	 *
	 * // Parameterised assignments
	 * $query->addAssignments(array(
	 *		'"Object"."Title"' => array('?' => 'Bob')),
	 *		'"Object"."Description"' => array('?' => null))
	 * ))
	 *
	 * // Complex parameters
	 * $query->addAssignments(array(
	 *		'"Object"."Score"' => array('MAX(?,?)' => array(1, 3))
	 * ));
	 *
	 * // Assigment of literal SQL for a field. The empty array is
	 * // important to denote the zero-number paramater list
	 * $query->addAssignments(array(
	 *		'"Object"."Score"' => array('NOW()' => array())
	 * ));
	 *
	 * </code>
	 *
	 * @param array $assignments The list of fields to assign
	 * @return self The self reference to this row
	 */
	public function addAssignments(array $assignments) {
		$assignments = $this->normaliseAssignments($assignments);
		$this->assignments = array_merge($this->assignments, $assignments);
		return $this;
	}

	/**
	 * Sets the list of assignments to the given list
	 *
	 * @see SQLWriteExpression::addAssignments() for syntax examples
	 *
	 * @param array $assignments
	 * @return self The self reference to this row
	 */
	public function setAssignments(array $assignments) {
		return $this->clear()->addAssignments($assignments);
	}

	/**
	 * Retrieves the list of assignments in parameterised format
	 *
	 * @return array List of assigments. The key of this array will be the
	 * column to assign, and the value a parameterised array in the format
	 * array('SQL' => array(parameters));
	 */
	public function getAssignments() {
		return $this->assignments;
	}

	/**
	 * Set the value for a single field
	 *
	 * E.g.
	 * <code>
	 *
	 * // Literal assignment
	 * $query->assign('"Object"."Description"', 'lorum ipsum');
	 *
	 * // Single parameter
	 * $query->assign('"Object"."Title"', array('?' => 'Bob'));
	 *
	 * // Complex parameters
	 * $query->assign('"Object"."Score"', array('MAX(?,?)' => array(1, 3));
	 * </code>
	 *
	 * @param string $field The field name to update
	 * @param mixed $value The value to assign to this field. This could be an
	 * array containing a parameterised SQL query of any number of parameters,
	 * or a single literal value.
	 * @return self The self reference to this row
	 */
	public function assign($field, $value) {
		return $this->addAssignments(array($field => $value));
	}

	/**
	 * Assigns a value to a field using the literal SQL expression, rather than
	 * a value to be escaped
	 *
	 * @param string $field The field name to update
	 * @param string $sql The SQL to use for this update. E.g. "NOW()"
	 * @return self The self reference to this row
	 */
	public function assignSQL($field, $sql) {
		return $this->assign($field, array($sql => array()));
	}

	/**
	 * Determine if this assignment is empty
	 *
	 * @return boolean Flag indicating that this assignment is empty
	 */
	public function isEmpty() {
		return empty($this->assignments);
	}

	/**
	 * Retrieves the list of columns updated
	 *
	 * @return array
	 */
	public function getColumns() {
		return array_keys($this->assignments);
	}

	/**
	 * Clears all assignment values
	 *
	 * @return self The self reference to this row
	 */
	public function clear() {
		$this->assignments = array();
		return $this;
	}
}