<?php
class OOM_Expr {
	var $_orig;
	var $_expr;
	var $_op;
	var $_lparen;
	var $_rparen;

	function OOM_Expr ($expr = NULL, $op = NULL, $lparen = '(', $rparen = ')') {
		$this->_op = $op;
		$this->_lparen = $lparen;
		$this->_rparen = $rparen;
		$this->assign($expr);
	}
	function value () { return $this->_orig; }
	function count () {
		$tally = 0;
		foreach ($this->_expr as $operand):
			if (is_a($operand, "OOM_Expr")):
				$tally = $tally + $operand->count();
			else:
				$tally = $tally + count($operand);
			endif;
		endforeach;
		return $tally;
	}
	function assign ($expr) {
		$this->_orig = $expr;
		if (is_array($expr)):
			$this->_expr = $expr;
		elseif (is_a($expr, "OOM_Expr") or is_numeric($expr) or is_string($expr)):
			$this->_expr = array($expr);
		else:
			$this->_expr = array();
		endif;
	}
	function merge ($expr) {
		if (is_array($expr)):
			$this->_expr = array_merge($this->_expr, $expr);
		elseif (is_a($expr, "OOM_Expr") or is_numeric($expr) or is_string($expr)):
			array_push($this->_expr, $expr);
		endif;
	}		
	function evaluate ($operand) {
		$ret = NULL;
		if (is_numeric($operand) or is_string($operand)):
			$ret = $operand;
		elseif (is_a($operand, "OOM_Expr") and $operand->count() > 0):
			$ret = $operand->to_string();
		endif;
		return $ret;
	}
	function to_string () {
		$ret = NULL;
		foreach ($this->_expr as $operand):
			$o = $this->evaluate($operand);
			if (!is_null($o)):
				$ret = (is_null($ret) ? '' : $ret.' '.$this->_op.' ')
					.$this->_lparen.$o.$this->_rparen;
			endif;
		endforeach;
		return $ret;
	}
}
class OOM_And extends OOM_Expr { function OOM_And ($expr = NULL) { OOM_Expr::OOM_Expr($expr, 'AND'); } }
class OOM_Or extends OOM_Expr { function OOM_Or ($expr = NULL) { OOM_Expr::OOM_Expr($expr, 'OR'); } }
class OOM_Literal extends OOM_Expr {
	function OOM_Literal ($expr = NULL) { OOM_Expr::OOM_Expr($expr, NULL); }
	function assign ($expr) {
		$this->_orig = $expr;
		if (is_null($expr)): $this->_expr = array("NULL");
		elseif (is_bool($expr)): $this->_expr = array(($expr) ? 1 : 0);
		elseif (is_numeric($expr)): $this->_expr = array($expr);
		elseif (is_string($expr)): $this->_expr = array("'".mysql_escape_string($expr)."'");
		elseif (is_a($expr, "OOM_Expr")): $this->_expr = array($expr);
		else: $this->_expr = array();
		endif;
	}
}
class OOM_List extends OOM_Expr { function OOM_List ($expr, $lparen = '', $rparen = '') { OOM_Expr::OOM_Expr($expr, ',', $lparen, $rparen); } }

class OOM_Literal_Row extends OOM_Expr {
	var $_raw = NULL;
	function OOM_Literal_Row ($expr, $op, $glue, $lparen = '(', $rparen = ')') {
		$arr = NULL;
		if (is_a($expr, "OOM_Literal_Row")):
			$this->_raw = $expr->raw();
		elseif (is_array($expr)):
			$this->_raw = $expr;
		endif;
		
		if (is_array($this->_raw)):
			foreach ($this->_raw as $key => $value):
				$lit =& new OOM_Literal($value);
				$arr[] = $key . $glue . $lit->to_string();
				unset($lit);
			endforeach;
		endif;
		OOM_Expr::OOM_Expr($arr, $op, $lparen, $rparen);
	}
	function raw () { return $this->_raw; }
}
class OOM_Pick_Out_Row extends OOM_Literal_Row { function OOM_Pick_Out_Row ($expr) { OOM_Literal_Row::OOM_Literal_Row($expr, 'AND', '<=>'); } }
class OOM_Set_Row extends OOM_Literal_Row { function OOM_Set_Row ($expr) { OOM_Literal_Row::OOM_Literal_Row($expr, ',', '=', '', ''); } }
class OOM_Condition_Clause extends OOM_And {
	var $_word;
	function OOM_Condition_Clause ($word, $expr = NULL) { $this->_word = $word; OOM_And::OOM_And($expr); }
	function to_clause () {
		if ($this->count() > 0):
			$ret = $this->_word.' '.$this->to_string();
		else:
			$ret = '';
		endif;
		return $ret;
	}
}
class OOM_Where extends OOM_Condition_Clause { function OOM_Where ($expr = NULL) { OOM_Condition_Clause::OOM_Condition_Clause("WHERE", $expr); } }
class OOM_Having extends OOM_Condition_Clause { function OOM_Having ($expr = NULL) { OOM_Condition_Clause::OOM_Condition_Clause("HAVING", $expr); } }
?>