ITSSTOOLS/core/oql/expression.class.inc.php

<?php
// Copyright (C) 2010-2017 Combodo SARL
//
//   This file is part of iTop.
//
//   iTop is free software; you can redistribute it and/or modify	
//   it under the terms of the GNU Affero General Public License as published by
//   the Free Software Foundation, either version 3 of the License, or
//   (at your option) any later version.
//
//   iTop is distributed in the hope that it will be useful,
//   but WITHOUT ANY WARRANTY; without even the implied warranty of
//   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//   GNU Affero General Public License for more details.
//
//   You should have received a copy of the GNU Affero General Public License
//   along with iTop. If not, see <http://www.gnu.org/licenses/>


/**
 * General definition of an expression tree (could be OQL, SQL or whatever) 
 *
 * @copyright   Copyright (C) 2010-2017 Combodo SARL
 * @license     http://opensource.org/licenses/AGPL-3.0
 */

class MissingQueryArgument extends CoreException
{
}

abstract class Expression
{
	/**
	 * Perform a deep clone (as opposed to "clone" which does copy a reference to the underlying objects)
	 **/	 	
	public function DeepClone()
	{
		return unserialize(serialize($this));
	}

	// recursive translation of identifiers
	abstract public function GetUnresolvedFields($sAlias, &$aUnresolved);
	abstract public function Translate($aTranslationData, $bMatchAll = true, $bMarkFieldsAsResolved = true);

	// recursive rendering (aArgs used as input by default, or used as output if bRetrofitParams set to True
	abstract public function Render(&$aArgs = null, $bRetrofitParams = false);

	/**
	 * Recursively browse the expression tree
	 * @param Closure $callback
	 * @return mixed
	 */
	abstract public function Browse(Closure $callback);

	abstract public function ApplyParameters($aArgs);
	
	// recursively builds an array of class => fieldname
	abstract public function ListRequiredFields();

	// recursively list field parents ($aTable = array of sParent => dummy)
	abstract public function CollectUsedParents(&$aTable);

	abstract public function IsTrue();
	
	// recursively builds an array of [classAlias][fieldName] => value
	abstract public function ListConstantFields();
	
	public function RequiresField($sClass, $sFieldName)
	{
		// #@# todo - optimize : this is called quite often when building a single query !
		$aRequired = $this->ListRequiredFields();
		if (!in_array($sClass.'.'.$sFieldName, $aRequired)) return false;
		return true;
	}

	public function serialize()
	{
		return base64_encode($this->Render());
	}
	
	static public function unserialize($sValue)
	{
		return self::FromOQL(base64_decode($sValue));
	}

	/**
	 * @param $sConditionExpr
	 * @return Expression
	 */
	static public function FromOQL($sConditionExpr)
	{
		$oOql = new OqlInterpreter($sConditionExpr);
		$oExpression = $oOql->ParseExpression();
		
		return $oExpression;
	}

	static public function FromSQL($sSQL)
	{
		$oSql = new SQLExpression($sSQL);
		return $oSql;
	}

	/**
	 * @param Expression $oExpr
	 * @return Expression
	 */
	public function LogAnd(Expression $oExpr)
	{
		if ($this->IsTrue()) return clone $oExpr;
		if ($oExpr->IsTrue()) return clone $this;
		return new BinaryExpression($this, 'AND', $oExpr);
	}

	/**
	 * @param Expression $oExpr
	 * @return Expression
	 */
	public function LogOr(Expression $oExpr)
	{
		return new BinaryExpression($this, 'OR', $oExpr);
	}
	
	abstract public function RenameParam($sOldName, $sNewName);
	abstract public function RenameAlias($sOldName, $sNewName);

	/**
	 * Make the most relevant label, given the value of the expression
	 * 	 
	 * @param DBSearch oFilter The context in which this expression has been used	 	
	 * @param string sValue The value returned by the query, for this expression	 	
	 * @param string sDefault The default value if no relevant label could be computed	 	
	 * @return The label
	 */	
	public function MakeValueLabel($oFilter, $sValue, $sDefault)
	{
		return $sDefault;
	}
}

class SQLExpression extends Expression
{
	protected $m_sSQL;

	public function __construct($sSQL)
	{
		$this->m_sSQL  = $sSQL;
	}

	public function IsTrue()
	{
		return false;
	}

	// recursive rendering
	public function Render(&$aArgs = null, $bRetrofitParams = false)
	{
		return $this->m_sSQL;
	}

	public function Browse(Closure $callback)
	{
		$callback($this);
	}

	public function ApplyParameters($aArgs)
	{
	}
	
	public function GetUnresolvedFields($sAlias, &$aUnresolved)
	{
	}

	public function Translate($aTranslationData, $bMatchAll = true, $bMarkFieldsAsResolved = true)
	{
		return clone $this;
	}

	public function ListRequiredFields()
	{
		return array();
	}

	public function CollectUsedParents(&$aTable)
	{
	}
	
	public function ListConstantFields()
	{
		return array();
	}
	
	public function RenameParam($sOldName, $sNewName)
	{
		// Do nothing, since there is nothing to rename
	}

	public function RenameAlias($sOldName, $sNewName)
	{
		// Do nothing, since there is nothing to rename
	}
}



class BinaryExpression extends Expression
{
	protected $m_oLeftExpr; // filter code or an SQL expression (later?)
	protected $m_oRightExpr;
	protected $m_sOperator;

	public function __construct($oLeftExpr, $sOperator, $oRightExpr)
	{
		if (!is_object($oLeftExpr))
		{
			throw new CoreException('Expecting an Expression object on the left hand', array('found_type' => gettype($oLeftExpr)));
		}
		if (!is_object($oRightExpr))
		{
			throw new CoreException('Expecting an Expression object on the right hand', array('found_type' => gettype($oRightExpr)));
		}
		if (!$oLeftExpr instanceof Expression)
		{
			throw new CoreException('Expecting an Expression object on the left hand', array('found_class' => get_class($oLeftExpr)));
		}
		if (!$oRightExpr instanceof Expression)
		{
			throw new CoreException('Expecting an Expression object on the right hand', array('found_class' => get_class($oRightExpr)));
		}
		$this->m_oLeftExpr  = $oLeftExpr;
		$this->m_oRightExpr = $oRightExpr;
		$this->m_sOperator  = $sOperator;
	}

	public function IsTrue()
	{
		// return true if we are certain that it will be true
		if ($this->m_sOperator == 'AND')
		{
			if ($this->m_oLeftExpr->IsTrue() && $this->m_oRightExpr->IsTrue()) return true;
		}
		elseif ($this->m_sOperator == 'OR')
		{
			if ($this->m_oLeftExpr->IsTrue() || $this->m_oRightExpr->IsTrue()) return true;
		}
		return false;
	}
	
	public function GetLeftExpr()
	{
		return $this->m_oLeftExpr;
	}

	public function GetRightExpr()
	{
		return $this->m_oRightExpr;
	}

	public function GetOperator()
	{
		return $this->m_sOperator;
	}

	// recursive rendering
	public function Render(&$aArgs = null, $bRetrofitParams = false)
	{
		$sOperator = $this->GetOperator();
		$sLeft = $this->GetLeftExpr()->Render($aArgs, $bRetrofitParams);
		$sRight = $this->GetRightExpr()->Render($aArgs, $bRetrofitParams);
		return "($sLeft $sOperator $sRight)";
	}

	public function Browse(Closure $callback)
	{
		$callback($this);
		$this->m_oLeftExpr->Browse($callback);
		$this->m_oRightExpr->Browse($callback);
	}

	public function ApplyParameters($aArgs)
	{
		if ($this->m_oLeftExpr instanceof VariableExpression)
		{
			$this->m_oLeftExpr = $this->m_oLeftExpr->GetAsScalar($aArgs);
		}
		else //if ($this->m_oLeftExpr instanceof Expression)
		{
			$this->m_oLeftExpr->ApplyParameters($aArgs);
		}
		if ($this->m_oRightExpr instanceof VariableExpression)
		{
			$this->m_oRightExpr = $this->m_oRightExpr->GetAsScalar($aArgs);
		}
		else //if ($this->m_oRightExpr instanceof Expression)
		{
			$this->m_oRightExpr->ApplyParameters($aArgs);
		}
	}
	
	public function GetUnresolvedFields($sAlias, &$aUnresolved)
	{
		$this->GetLeftExpr()->GetUnresolvedFields($sAlias, $aUnresolved);
		$this->GetRightExpr()->GetUnresolvedFields($sAlias, $aUnresolved);
	}

	public function Translate($aTranslationData, $bMatchAll = true, $bMarkFieldsAsResolved = true)
	{
		$oLeft = $this->GetLeftExpr()->Translate($aTranslationData, $bMatchAll, $bMarkFieldsAsResolved);
		$oRight = $this->GetRightExpr()->Translate($aTranslationData, $bMatchAll, $bMarkFieldsAsResolved);
		return new BinaryExpression($oLeft, $this->GetOperator(), $oRight);
	}

	public function ListRequiredFields()
	{
		$aLeft = $this->GetLeftExpr()->ListRequiredFields();
		$aRight = $this->GetRightExpr()->ListRequiredFields();
		return array_merge($aLeft, $aRight);
	}

	public function CollectUsedParents(&$aTable)
	{
		$this->GetLeftExpr()->CollectUsedParents($aTable);
		$this->GetRightExpr()->CollectUsedParents($aTable);
	}
	
	/**
	 * List all constant expression of the form <field> = <scalar> or <field> = :<variable>
	 * Could be extended to support <field> = <function><constant_expression>
	 */
	public function ListConstantFields()
	{
		$aResult = array();
		if ($this->m_sOperator == '=')
		{
			if (($this->m_oLeftExpr instanceof FieldExpression) && ($this->m_oRightExpr instanceof ScalarExpression))
			{
				$aResult[$this->m_oLeftExpr->GetParent()][$this->m_oLeftExpr->GetName()] = $this->m_oRightExpr;
			}
			else if (($this->m_oRightExpr instanceof FieldExpression) && ($this->m_oLeftExpr instanceof ScalarExpression))
			{
				$aResult[$this->m_oRightExpr->GetParent()][$this->m_oRightExpr->GetName()] = $this->m_oLeftExpr;
			}
			else if (($this->m_oLeftExpr instanceof FieldExpression) && ($this->m_oRightExpr instanceof VariableExpression))
			{
				$aResult[$this->m_oLeftExpr->GetParent()][$this->m_oLeftExpr->GetName()] = $this->m_oRightExpr;
			}
			else if (($this->m_oRightExpr instanceof FieldExpression) && ($this->m_oLeftExpr instanceof VariableExpression))
			{
				$aResult[$this->m_oRightExpr->GetParent()][$this->m_oRightExpr->GetName()] = $this->m_oLeftExpr;
			}
		}
		else if ($this->m_sOperator == 'AND')
		{
			// Strictly, this should be done only for the AND operator
			$aResult = array_merge_recursive($this->m_oRightExpr->ListConstantFields(), $this->m_oLeftExpr->ListConstantFields());
		}
		return $aResult;
	}
	
	public function RenameParam($sOldName, $sNewName)
	{
		$this->GetLeftExpr()->RenameParam($sOldName, $sNewName);
		$this->GetRightExpr()->RenameParam($sOldName, $sNewName);
	}

	public function RenameAlias($sOldName, $sNewName)
	{
		$this->GetLeftExpr()->RenameAlias($sOldName, $sNewName);
		$this->GetRightExpr()->RenameAlias($sOldName, $sNewName);
	}
}


class UnaryExpression extends Expression
{
	protected $m_value;

	public function __construct($value)
	{
		$this->m_value = $value;
	}

	public function IsTrue()
	{
		// return true if we are certain that it will be true
		return ($this->m_value == 1);
	}

	public function GetValue()
	{
		return $this->m_value;
	}

	// recursive rendering
	public function Render(&$aArgs = null, $bRetrofitParams = false)
	{
		return CMDBSource::Quote($this->m_value);
	}

	public function Browse(Closure $callback)
	{
		$callback($this);
	}

	public function ApplyParameters($aArgs)
	{
	}
	
	public function GetUnresolvedFields($sAlias, &$aUnresolved)
	{
	}

	public function Translate($aTranslationData, $bMatchAll = true, $bMarkFieldsAsResolved = true)
	{
		return clone $this;
	}

	public function ListRequiredFields()
	{
		return array();
	}

	public function CollectUsedParents(&$aTable)
	{
	}

	public function ListConstantFields()
	{
		return array();
	}
	
	public function RenameParam($sOldName, $sNewName)
	{
		// Do nothing
		// really ? what about :param{$iParamIndex} ??
	}

	public function RenameAlias($sOldName, $sNewName)
	{
		// Do nothing
	}
}

class ScalarExpression extends UnaryExpression
{
	public function __construct($value)
	{
		if (!is_scalar($value) && !is_null($value) && (!$value instanceof OqlHexValue))
		{
			throw new CoreException('Attempt to create a scalar expression from a non scalar', array('var_type'=>gettype($value)));
		}
		parent::__construct($value);
	}

	// recursive rendering
	public function Render(&$aArgs = null, $bRetrofitParams = false)
	{
		if (is_null($this->m_value))
		{
			$sRet = 'NULL';
		}
		else
		{
			$sRet = CMDBSource::Quote($this->m_value);
		}
		return $sRet;
	}

	public function GetAsScalar($aArgs)
	{
		return clone $this;
	}
}

class TrueExpression extends ScalarExpression
{
	public function __construct()
	{
		parent::__construct(1);
	}

	public function IsTrue()
	{
		return true;
	}
}

class FalseExpression extends ScalarExpression
{
	public function __construct()
	{
		parent::__construct(0);
	}

	public function IsTrue()
	{
		return false;
	}
}

class FieldExpression extends UnaryExpression
{
	protected $m_sParent;
	protected $m_sName;

	public function __construct($sName, $sParent = '')
	{
		parent::__construct("$sParent.$sName");

		$this->m_sParent = $sParent;
		$this->m_sName = $sName;
	}

	public function IsTrue()
	{
		// return true if we are certain that it will be true
		return false;
	}

	public function GetParent() {return $this->m_sParent;}
	public function GetName() {return $this->m_sName;}

	public function SetParent($sParent)
	{
		$this->m_sParent = $sParent;
		$this->m_value = $sParent.'.'.$this->m_sName;
	}

	// recursive rendering
	public function Render(&$aArgs = null, $bRetrofitParams = false)
	{
		if (empty($this->m_sParent))
		{
			return "`{$this->m_sName}`";
		}
		return "`{$this->m_sParent}`.`{$this->m_sName}`";
	}

	public function ListRequiredFields()
	{
		return array($this->m_sParent.'.'.$this->m_sName);
	}

	public function CollectUsedParents(&$aTable)
	{
		$aTable[$this->m_sParent] = true;
	}

	public function GetUnresolvedFields($sAlias, &$aUnresolved)
	{
		if ($this->m_sParent == $sAlias)
		{
			// Add a reference to the field
			$aUnresolved[$this->m_sName] = $this;
		}
		elseif ($sAlias == '')
		{
			// An empty alias means "any alias"
			// In such a case, the results are indexed differently
			$aUnresolved[$this->m_sParent][$this->m_sName] = $this;
		}
	}

	public function Translate($aTranslationData, $bMatchAll = true, $bMarkFieldsAsResolved = true)
	{
		if (!array_key_exists($this->m_sParent, $aTranslationData))
		{
			if ($bMatchAll) throw new CoreException('Unknown parent id in translation table', array('parent_id' => $this->m_sParent, 'translation_table' => array_keys($aTranslationData)));
			return clone $this;
		} 
		if (!array_key_exists($this->m_sName, $aTranslationData[$this->m_sParent]))
		{
			if (!array_key_exists('*', $aTranslationData[$this->m_sParent]))
			{
				// #@# debug - if ($bMatchAll) MyHelpers::var_dump_html($aTranslationData, true);
				if ($bMatchAll) throw new CoreException('Unknown name in translation table', array('name' => $this->m_sName, 'parent_id' => $this->m_sParent, 'translation_table' => array_keys($aTranslationData[$this->m_sParent])));
				return clone $this;
			}
			$sNewParent = $aTranslationData[$this->m_sParent]['*'];
			$sNewName = $this->m_sName;
			if ($bMarkFieldsAsResolved)
			{
				$oRet = new FieldExpressionResolved($sNewName, $sNewParent);
			}
			else
			{
				$oRet = new FieldExpression($sNewName, $sNewParent);
			}
		}
		else
		{
			$oRet = $aTranslationData[$this->m_sParent][$this->m_sName];
		}
		return $oRet;
	}

	/**
	 * Make the most relevant label, given the value of the expression
	 * 	 
	 * @param DBSearch oFilter The context in which this expression has been used	 	
	 * @param string sValue The value returned by the query, for this expression	 	
	 * @param string sDefault The default value if no relevant label could be computed	 	
	 * @return The label
	 */	
	public function MakeValueLabel($oFilter, $sValue, $sDefault)
	{
		$sAttCode = $this->GetName();
		$sParentAlias = $this->GetParent();

		$aSelectedClasses = $oFilter->GetSelectedClasses();
		$sClass = $aSelectedClasses[$sParentAlias];

		$oAttDef = MetaModel::GetAttributeDef($sClass, $sAttCode);
		// Set a default value for the general case
		$sRes = $oAttDef->GetAsHtml($sValue);

		// Exceptions...
		if ($oAttDef->IsExternalKey())
		{
			$sObjClass = $oAttDef->GetTargetClass();
			$iObjKey = (int)$sValue;
			if ($iObjKey > 0)
			{
				$oObject = MetaModel::GetObjectWithArchive($sObjClass, $iObjKey);
				$sRes = $oObject->GetHyperlink();
			}
			else
			{
				// Undefined
				$sRes = DBObject::MakeHyperLink($sObjClass, 0);
			}
		}
		elseif ($oAttDef->IsExternalField())
		{
			if (is_null($sValue))
			{
				$sRes = Dict::S('UI:UndefinedObject');
			}
		}
		return $sRes;
	}

	public function RenameAlias($sOldName, $sNewName)
	{
		if ($this->m_sParent == $sOldName)
		{
			$this->m_sParent = $sNewName;
		}
	}
}

// Has been resolved into an SQL expression
class FieldExpressionResolved extends FieldExpression
{
	public function GetUnresolvedFields($sAlias, &$aUnresolved)
	{
	}

	public function Translate($aTranslationData, $bMatchAll = true, $bMarkFieldsAsResolved = true)
	{
		return clone $this;
	}
}

class VariableExpression extends UnaryExpression
{
	protected $m_sName;

	public function __construct($sName)
	{
		parent::__construct($sName);

		$this->m_sName = $sName;
	}

	public function IsTrue()
	{
		// return true if we are certain that it will be true
		return false;
	}

	public function GetName() {return $this->m_sName;}

	// recursive rendering
	public function Render(&$aArgs = null, $bRetrofitParams = false)
	{
		if (is_null($aArgs))
		{
			return ':'.$this->m_sName;
		}
		elseif (array_key_exists($this->m_sName, $aArgs))
		{
			$res = CMDBSource::Quote($aArgs[$this->m_sName]);
			if (is_array($res))
			{
				$res = implode(', ', $res);
			}
			return $res;
		}
		elseif (($iPos = strpos($this->m_sName, '->')) !== false)
		{
			$sParamName = substr($this->m_sName, 0, $iPos);
			if (array_key_exists($sParamName.'->object()', $aArgs))
			{
				$sAttCode = substr($this->m_sName, $iPos + 2);
				$oObj = $aArgs[$sParamName.'->object()'];
				if ($sAttCode == 'id')
				{
					return CMDBSource::Quote($oObj->GetKey());
				}
				return CMDBSource::Quote($oObj->Get($sAttCode));
			}
		}

		if ($bRetrofitParams)
		{
			$aArgs[$this->m_sName] = null;
			return ':'.$this->m_sName;
		}
		else
		{
			throw new MissingQueryArgument('Missing query argument', array('expecting'=>$this->m_sName, 'available'=>array_keys($aArgs)));
		}
	}

	public function RenameParam($sOldName, $sNewName)
	{
		if ($this->m_sName == $sOldName)
		{
			$this->m_sName = $sNewName;
		}
	}
	
	public function GetAsScalar($aArgs)
	{
		$oRet = null;
		if (array_key_exists($this->m_sName, $aArgs))
		{
			$oRet = new ScalarExpression($aArgs[$this->m_sName]);
		}
		elseif (($iPos = strpos($this->m_sName, '->')) !== false)
		{
			$sParamName = substr($this->m_sName, 0, $iPos);
			if (array_key_exists($sParamName.'->object()', $aArgs))
			{
				$sAttCode = substr($this->m_sName, $iPos + 2);
				$oObj = $aArgs[$sParamName.'->object()'];
				if ($sAttCode == 'id')
				{
					$oRet = new ScalarExpression($oObj->GetKey());
				}
				elseif (MetaModel::IsValidAttCode(get_class($oObj), $sAttCode))
				{
					$oRet = new ScalarExpression($oObj->Get($sAttCode));
				}
				else
				{
					throw new CoreException("Query argument {$this->m_sName} not matching any attribute of class ".get_class($oObj));
				}
			}
		}
		if (is_null($oRet))
		{
			throw new MissingQueryArgument('Missing query argument', array('expecting'=>$this->m_sName, 'available'=>array_keys($aArgs)));
		}
		return $oRet;
	}
}

// Temporary, until we implement functions and expression casting!
// ... or until we implement a real full text search based in the MATCH() expression
class ListExpression extends Expression
{
	protected $m_aExpressions;

	public function __construct($aExpressions)
	{
		$this->m_aExpressions = $aExpressions;
	}

	public static function FromScalars($aScalars)
	{
		$aExpressions = array();
		foreach($aScalars as $value)
		{
			$aExpressions[] = new ScalarExpression($value);
		}
		return new ListExpression($aExpressions);
	}

	public function IsTrue()
	{
		// return true if we are certain that it will be true
		return false;
	}

	public function GetItems()
	{
		return $this->m_aExpressions;
	}

	// recursive rendering
	public function Render(&$aArgs = null, $bRetrofitParams = false)
	{
		$aRes = array();
		foreach ($this->m_aExpressions as $oExpr)
		{
			$aRes[] = $oExpr->Render($aArgs, $bRetrofitParams);
		}
		return '('.implode(', ', $aRes).')';
	}

	public function Browse(Closure $callback)
	{
		$callback($this);
		foreach ($this->m_aExpressions as $oExpr)
		{
			$oExpr->Browse($callback);
		}
	}

	public function ApplyParameters($aArgs)
	{
		$aRes = array();
		foreach ($this->m_aExpressions as $idx => $oExpr)
		{
			if ($oExpr instanceof VariableExpression)
			{
				$this->m_aExpressions[$idx] = $oExpr->GetAsScalar();
			}
			else
			{
				$oExpr->ApplyParameters($aArgs);
			}
		}
	}
	
	public function GetUnresolvedFields($sAlias, &$aUnresolved)
	{
		foreach ($this->m_aExpressions as $oExpr)
		{
			$oExpr->GetUnresolvedFields($sAlias, $aUnresolved);
		}
	}

	public function Translate($aTranslationData, $bMatchAll = true, $bMarkFieldsAsResolved = true)
	{
		$aRes = array();
		foreach ($this->m_aExpressions as $oExpr)
		{
			$aRes[] = $oExpr->Translate($aTranslationData, $bMatchAll, $bMarkFieldsAsResolved);
		}
		return new ListExpression($aRes);
	}

	public function ListRequiredFields()
	{
		$aRes = array();
		foreach ($this->m_aExpressions as $oExpr)
		{
			$aRes = array_merge($aRes, $oExpr->ListRequiredFields());
		}
		return $aRes;
	}
	
	public function CollectUsedParents(&$aTable)
	{
		foreach ($this->m_aExpressions as $oExpr)
		{
			$oExpr->CollectUsedParents($aTable);
		}
	}

	public function ListConstantFields()
	{
		$aRes = array();
		foreach ($this->m_aExpressions as $oExpr)
		{
			$aRes = array_merge($aRes, $oExpr->ListConstantFields());
		}
		return $aRes;
	}
	
	public function RenameParam($sOldName, $sNewName)
	{
		$aRes = array();
		foreach ($this->m_aExpressions as $key => $oExpr)
		{
			$this->m_aExpressions[$key] = $oExpr->RenameParam($sOldName, $sNewName);
		}
	}	

	public function RenameAlias($sOldName, $sNewName)
	{
		$aRes = array();
		foreach ($this->m_aExpressions as $key => $oExpr)
		{
			$oExpr->RenameAlias($sOldName, $sNewName);
		}
	}	
}


class FunctionExpression extends Expression
{
	protected $m_sVerb;
	protected $m_aArgs; // array of expressions

	public function __construct($sVerb, $aArgExpressions)
	{
		$this->m_sVerb = $sVerb;
		$this->m_aArgs = $aArgExpressions;
	}

	public function IsTrue()
	{
		// return true if we are certain that it will be true
		return false;
	}

	public function GetVerb()
	{
		return $this->m_sVerb;
	}

	public function GetArgs()
	{
		return $this->m_aArgs;
	}

	// recursive rendering
	public function Render(&$aArgs = null, $bRetrofitParams = false)
	{
		$aRes = array();
		foreach ($this->m_aArgs as $iPos => $oExpr)
		{
			$aRes[] = $oExpr->Render($aArgs, $bRetrofitParams);
		}
		return $this->m_sVerb.'('.implode(', ', $aRes).')';
	}

	public function Browse(Closure $callback)
	{
		$callback($this);
		foreach ($this->m_aArgs as $iPos => $oExpr)
		{
			$oExpr->Browse($callback);
		}
	}

	public function ApplyParameters($aArgs)
	{
		$aRes = array();
		foreach ($this->m_aArgs as $idx => $oExpr)
		{
			if ($oExpr instanceof VariableExpression)
			{
				$this->m_aArgs[$idx] = $oExpr->GetAsScalar($aArgs);
			}
			else
			{
				$oExpr->ApplyParameters($aArgs);
			}
		}
	}

	public function GetUnresolvedFields($sAlias, &$aUnresolved)
	{
		foreach ($this->m_aArgs as $oExpr)
		{
			$oExpr->GetUnresolvedFields($sAlias, $aUnresolved);
		}
	}

	public function Translate($aTranslationData, $bMatchAll = true, $bMarkFieldsAsResolved = true)
	{
		$aRes = array();
		foreach ($this->m_aArgs as $oExpr)
		{
			$aRes[] = $oExpr->Translate($aTranslationData, $bMatchAll, $bMarkFieldsAsResolved);
		}
		return new FunctionExpression($this->m_sVerb, $aRes);
	}

	public function ListRequiredFields()
	{
		$aRes = array();
		foreach ($this->m_aArgs as $oExpr)
		{
			$aRes = array_merge($aRes, $oExpr->ListRequiredFields());
		}
		return $aRes;
	}
	
	public function CollectUsedParents(&$aTable)
	{
		foreach ($this->m_aArgs as $oExpr)
		{
			$oExpr->CollectUsedParents($aTable);
		}
	}

	public function ListConstantFields()
	{
		$aRes = array();
		foreach ($this->m_aArgs as $oExpr)
		{
			$aRes = array_merge($aRes, $oExpr->ListConstantFields());
		}
		return $aRes;
	}
	
	public function RenameParam($sOldName, $sNewName)
	{
		foreach ($this->m_aArgs as $key => $oExpr)
		{
			$this->m_aArgs[$key] = $oExpr->RenameParam($sOldName, $sNewName);
		}
	}

	public function RenameAlias($sOldName, $sNewName)
	{
		foreach ($this->m_aArgs as $key => $oExpr)
		{
			$oExpr->RenameAlias($sOldName, $sNewName);
		}
	}

	/**
	 * Make the most relevant label, given the value of the expression
	 * 	 
	 * @param DBSearch oFilter The context in which this expression has been used	 	
	 * @param string sValue The value returned by the query, for this expression	 	
	 * @param string sDefault The default value if no relevant label could be computed	 	
	 * @return The label
	 */	
	public function MakeValueLabel($oFilter, $sValue, $sDefault)
	{
		static $aWeekDayToString = null;
		if (is_null($aWeekDayToString))
		{
			// Init the correspondance table
			$aWeekDayToString = array(
				0 => Dict::S('DayOfWeek-Sunday'),
				1 => Dict::S('DayOfWeek-Monday'),
				2 => Dict::S('DayOfWeek-Tuesday'),
				3 => Dict::S('DayOfWeek-Wednesday'),
				4 => Dict::S('DayOfWeek-Thursday'),
				5 => Dict::S('DayOfWeek-Friday'),
				6 => Dict::S('DayOfWeek-Saturday')
			);
		}
		static $aMonthToString = null;
		if (is_null($aMonthToString))
		{
			// Init the correspondance table
			$aMonthToString = array(
				1 => Dict::S('Month-01'),
				2 => Dict::S('Month-02'),
				3 => Dict::S('Month-03'),
				4 => Dict::S('Month-04'),
				5 => Dict::S('Month-05'),
				6 => Dict::S('Month-06'),
				7 => Dict::S('Month-07'),
				8 => Dict::S('Month-08'),
				9 => Dict::S('Month-09'),
				10 => Dict::S('Month-10'),
				11 => Dict::S('Month-11'),
				12 => Dict::S('Month-12'),
			);
		}

		$sRes = $sDefault;
		if (strtolower($this->m_sVerb) == 'date_format')
		{
			$oFormatExpr = $this->m_aArgs[1];
			if ($oFormatExpr->Render() == "'%w'")
			{
				if (isset($aWeekDayToString[(int)$sValue]))
				{
					$sRes = $aWeekDayToString[(int)$sValue];
				}
			}
			elseif ($oFormatExpr->Render() == "'%Y-%m'")
			{
				// yyyy-mm => "yyyy month"
				$iMonth = (int) substr($sValue, -2); // the two last chars
				$sRes = substr($sValue, 0, 4).' '.$aMonthToString[$iMonth];
			}
			elseif ($oFormatExpr->Render() == "'%Y-%m-%d'")
			{
				// yyyy-mm-dd => "month d"
				$iMonth = (int) substr($sValue, 5, 2);
				$sRes = $aMonthToString[$iMonth].' '.(int)substr($sValue, -2);
			}
		}
		return $sRes;
	}
}

class IntervalExpression extends Expression
{
	protected $m_oValue; // expression
	protected $m_sUnit;

	public function __construct($oValue, $sUnit)
	{
		$this->m_oValue = $oValue;
		$this->m_sUnit = $sUnit;
	}

	public function IsTrue()
	{
		// return true if we are certain that it will be true
		return false;
	}

	public function GetValue()
	{
		return $this->m_oValue;
	}

	public function GetUnit()
	{
		return $this->m_sUnit;
	}

	// recursive rendering
	public function Render(&$aArgs = null, $bRetrofitParams = false)
	{
		return 'INTERVAL '.$this->m_oValue->Render($aArgs, $bRetrofitParams).' '.$this->m_sUnit;
	}

	public function Browse(Closure $callback)
	{
		$callback($this);
		$this->m_oValue->Browse($callback);
	}

	public function ApplyParameters($aArgs)
	{
		if ($this->m_oValue instanceof VariableExpression)
		{
			$this->m_oValue = $this->m_oValue->GetAsScalar($aArgs);
		}
		else
		{
			$this->m_oValue->ApplyParameters($aArgs);
		}
	}
		
	public function GetUnresolvedFields($sAlias, &$aUnresolved)
	{
		$this->m_oValue->GetUnresolvedFields($sAlias, $aUnresolved);
	}

	public function Translate($aTranslationData, $bMatchAll = true, $bMarkFieldsAsResolved = true)
	{
		return new IntervalExpression($this->m_oValue->Translate($aTranslationData, $bMatchAll, $bMarkFieldsAsResolved), $this->m_sUnit);
	}

	public function ListRequiredFields()
	{
		return array();
	}

	public function CollectUsedParents(&$aTable)
	{
	}

	public function ListConstantFields()
	{
		return array();
	}
	
	public function RenameParam($sOldName, $sNewName)
	{
		$this->m_oValue->RenameParam($sOldName, $sNewName);
	}	

	public function RenameAlias($sOldName, $sNewName)
	{
		$this->m_oValue->RenameAlias($sOldName, $sNewName);
	}	
}

class CharConcatExpression extends Expression
{
	protected $m_aExpressions;

	public function __construct($aExpressions)
	{
		$this->m_aExpressions = $aExpressions;
	}

	public function IsTrue()
	{
		// return true if we are certain that it will be true
		return false;
	}

	public function GetItems()
	{
		return $this->m_aExpressions;
	}

	// recursive rendering
	public function Render(&$aArgs = null, $bRetrofitParams = false)
	{
		$aRes = array();
		foreach ($this->m_aExpressions as $oExpr)
		{
			$sCol = $oExpr->Render($aArgs, $bRetrofitParams);
			// Concat will be globally NULL if one single argument is null ! 
			$aRes[] = "COALESCE($sCol, '')";
		}
		return "CAST(CONCAT(".implode(', ', $aRes).") AS CHAR)";
	}

	public function Browse(Closure $callback)
	{
		$callback($this);
		foreach ($this->m_aExpressions as $oExpr)
		{
			$oExpr->Browse($callback);
		}
	}

	public function ApplyParameters($aArgs)
	{
		$aRes = array();
		foreach ($this->m_aExpressions as $idx => $oExpr)
		{
			if ($oExpr instanceof VariableExpression)
			{
				$this->m_aExpressions[$idx] = $oExpr->GetAsScalar();
			}
			else
			{
				$this->m_aExpressions->ApplyParameters($aArgs);
			}
		}
	}

	public function GetUnresolvedFields($sAlias, &$aUnresolved)
	{
		foreach ($this->m_aExpressions as $oExpr)
		{
			$oExpr->GetUnresolvedFields($sAlias, $aUnresolved);
		}
	}

	public function Translate($aTranslationData, $bMatchAll = true, $bMarkFieldsAsResolved = true)
	{
		$aRes = array();
		foreach ($this->m_aExpressions as $oExpr)
		{
			$aRes[] = $oExpr->Translate($aTranslationData, $bMatchAll, $bMarkFieldsAsResolved);
		}
		return new CharConcatExpression($aRes);
	}

	public function ListRequiredFields()
	{
		$aRes = array();
		foreach ($this->m_aExpressions as $oExpr)
		{
			$aRes = array_merge($aRes, $oExpr->ListRequiredFields());
		}
		return $aRes;
	}

	public function CollectUsedParents(&$aTable)
	{
		foreach ($this->m_aExpressions as $oExpr)
		{
			$oExpr->CollectUsedParents($aTable);
		}
	}

	public function ListConstantFields()
	{
		$aRes = array();
		foreach ($this->m_aExpressions as $oExpr)
		{
			$aRes = array_merge($aRes, $oExpr->ListConstantFields());
		}
		return $aRes;
	}

	public function RenameParam($sOldName, $sNewName)
	{
		foreach ($this->m_aExpressions as $key => $oExpr)
		{
			$this->m_aExpressions[$key] = $oExpr->RenameParam($sOldName, $sNewName);
		}
	}	

	public function RenameAlias($sOldName, $sNewName)
	{
		foreach ($this->m_aExpressions as $key => $oExpr)
		{
			$oExpr->RenameAlias($sOldName, $sNewName);
		}
	}	
}


class CharConcatWSExpression extends CharConcatExpression
{
	protected $m_separator;

	public function __construct($separator, $aExpressions)
	{
		$this->m_separator = $separator;
		parent::__construct($aExpressions);
	}

	// recursive rendering
	public function Render(&$aArgs = null, $bRetrofitParams = false)
	{
		$aRes = array();
		foreach ($this->m_aExpressions as $oExpr)
		{
			$sCol = $oExpr->Render($aArgs, $bRetrofitParams);
			// Concat will be globally NULL if one single argument is null ! 
			$aRes[] = "COALESCE($sCol, '')";
		}
		$sSep = CMDBSource::Quote($this->m_separator);
		return "CAST(CONCAT_WS($sSep, ".implode(', ', $aRes).") AS CHAR)";
	}

	public function Browse(Closure $callback)
	{
		$callback($this);
		foreach ($this->m_aExpressions as $oExpr)
		{
			$oExpr->Browse($callback);
		}
	}

	public function Translate($aTranslationData, $bMatchAll = true, $bMarkFieldsAsResolved = true)
	{
		$aRes = array();
		foreach ($this->m_aExpressions as $oExpr)
		{
			$aRes[] = $oExpr->Translate($aTranslationData, $bMatchAll, $bMarkFieldsAsResolved);
		}
		return new CharConcatWSExpression($this->m_separator, $aRes);
	}
}


class QueryBuilderExpressions
{
	/**
	 * @var Expression
	 */
	protected $m_oConditionExpr;
	/**
	 * @var Expression[]
	 */
	protected $m_aSelectExpr;
	/**
	 * @var Expression[]
	 */
	protected $m_aGroupByExpr;
	/**
	 * @var Expression[]
	 */
	protected $m_aJoinFields;
	/**
	 * @var string[]
	 */
	protected $m_aClassIds;

	public function __construct(DBObjectSearch $oSearch, $aGroupByExpr = null)
	{
		$this->m_oConditionExpr = $oSearch->GetCriteria();
		if (!$oSearch->GetShowObsoleteData())
		{
			foreach ($oSearch->GetSelectedClasses() as $sAlias => $sClass)
			{
				if (MetaModel::IsObsoletable($sClass))
				{
					$oNotObsolete = new BinaryExpression(new FieldExpression('obsolescence_flag', $sAlias), '=', new ScalarExpression(0));
					$this->m_oConditionExpr = $this->m_oConditionExpr->LogAnd($oNotObsolete);
				}
			}
		}
		$this->m_aSelectExpr = array();
		$this->m_aGroupByExpr = $aGroupByExpr;
		$this->m_aJoinFields = array();

		$this->m_aClassIds = array();
		foreach($oSearch->GetJoinedClasses() as $sClassAlias => $sClass)
		{
			$this->m_aClassIds[$sClassAlias] = new FieldExpression('id', $sClassAlias);
		}
	}

	public function GetSelect()
	{
		return $this->m_aSelectExpr;
	}

	public function GetGroupBy()
	{
		return $this->m_aGroupByExpr;
	}

	public function GetCondition()
	{
		return $this->m_oConditionExpr;
	}

	/**
	 * @return Expression|mixed
	 */
	public function PopJoinField()
	{
		return array_pop($this->m_aJoinFields);
	}

	/**
	 * @param string $sAttAlias
	 * @param Expression $oExpression
	 */
	public function AddSelect($sAttAlias, Expression $oExpression)
	{
		$this->m_aSelectExpr[$sAttAlias] = $oExpression;
	}

	/**
	 * @param Expression $oExpression
	 */
	public function AddCondition(Expression $oExpression)
	{
		$this->m_oConditionExpr = $this->m_oConditionExpr->LogAnd($oExpression);
	}

	/**
	 * @param Expression $oExpression
	 */
	public function PushJoinField(Expression $oExpression)
	{
		array_push($this->m_aJoinFields, $oExpression);
	}

	/**
	 * Get tables representing the queried objects
	 * Could be further optimized: when the first join is an outer join, then the rest can be omitted	 
	 */	 	
	public function GetMandatoryTables(&$aTables = null)
	{
		if (is_null($aTables)) $aTables = array();

		foreach($this->m_aClassIds as $sClass => $oExpression)
		{
			$oExpression->CollectUsedParents($aTables);
		}
	}

	public function GetUnresolvedFields($sAlias, &$aUnresolved)
	{
		$this->m_oConditionExpr->GetUnresolvedFields($sAlias, $aUnresolved);
		foreach($this->m_aSelectExpr as $sColAlias => $oExpr)
		{
			$oExpr->GetUnresolvedFields($sAlias, $aUnresolved);
		}
		if ($this->m_aGroupByExpr)
		{
			foreach($this->m_aGroupByExpr as $sColAlias => $oExpr)
			{
				$oExpr->GetUnresolvedFields($sAlias, $aUnresolved);
			}
		}
		foreach($this->m_aJoinFields as $oExpression)
		{
			$oExpression->GetUnresolvedFields($sAlias, $aUnresolved);
		}
	}

	public function Translate($aTranslationData, $bMatchAll = true, $bMarkFieldsAsResolved = true)
	{
		$this->m_oConditionExpr = $this->m_oConditionExpr->Translate($aTranslationData, $bMatchAll, $bMarkFieldsAsResolved);
		foreach($this->m_aSelectExpr as $sColAlias => $oExpr)
		{
			$this->m_aSelectExpr[$sColAlias] = $oExpr->Translate($aTranslationData, $bMatchAll, $bMarkFieldsAsResolved);
		}
		if ($this->m_aGroupByExpr)
		{
			foreach($this->m_aGroupByExpr as $sColAlias => $oExpr)
			{
				$this->m_aGroupByExpr[$sColAlias] = $oExpr->Translate($aTranslationData, $bMatchAll, $bMarkFieldsAsResolved);
			}
		}
		foreach($this->m_aJoinFields as $index => $oExpression)
		{
			$this->m_aJoinFields[$index] = $oExpression->Translate($aTranslationData, $bMatchAll, $bMarkFieldsAsResolved);
		}

		foreach($this->m_aClassIds as $sClass => $oExpression)
		{
			$this->m_aClassIds[$sClass] = $oExpression->Translate($aTranslationData, $bMatchAll, $bMarkFieldsAsResolved);
		}
	}

	public function RenameParam($sOldName, $sNewName)
	{
		$this->m_oConditionExpr->RenameParam($sOldName, $sNewName);
		foreach($this->m_aSelectExpr as $sColAlias => $oExpr)
		{
			$this->m_aSelectExpr[$sColAlias] = $oExpr->RenameParam($sOldName, $sNewName);
		}
		if ($this->m_aGroupByExpr)
		{
			foreach($this->m_aGroupByExpr as $sColAlias => $oExpr)
			{
				$this->m_aGroupByExpr[$sColAlias] = $oExpr->RenameParam($sOldName, $sNewName);
			}
		}
		foreach($this->m_aJoinFields as $index => $oExpression)
		{
			$this->m_aJoinFields[$index] = $oExpression->RenameParam($sOldName, $sNewName);
		}
	}
}