/*

Purpose of this function is to break down the tag expressions

We can separate operators on left and rigth side.

Left ones are AND and OR as they require an operator on left side to

be valid. Right side is NOT.

In each iteration we breakdown string into parts

*/

function valid_tag_expression(a_tags in varchar2) return number is

l_left_side_expression varchar2(10) := '[|&,]';

l_left_side_regex varchar2(50) := '([^|&,]*)[|&,](.*)';

l_left_side varchar2(4000);

l_rigth_side_expression varchar2(10) := '[!-]';

l_right_side_regex varchar2(50) := '([!-])([^!-].*)';

l_right_side varchar2(4000);

l_tags varchar2(4000) := a_tags;

l_result number :=1;

begin

--Validate that we have closed up all brackets

if regexp_count(l_tags,'\(') <> regexp_count(l_tags,'\)') then

l_result := 0;

end if;

--Remove brackets as we dont evaluate expression only validate.

l_tags := replace(replace(l_tags,'('),')');

--Check if there are any left side operators for first in order from left to right

if regexp_count(l_tags,l_left_side_expression) > 0 then

--Extract left part of operator and remaining of string to right

l_left_side := regexp_replace(l_tags,l_left_side_regex,'\1');

l_right_side := regexp_replace(l_tags,l_left_side_regex,'\2');

--If left side is null that means that we used left side operator without

-- left and right e.g. |test

if l_left_side is null then

l_result := 0;

else

--Extract right side from left side expression if there is any !-

--Remove first negation tag to see if there is double negation

l_left_side := regexp_replace(l_left_side,l_right_side_regex,'\2');

end if;

--check that on right side there is no extra negation

if regexp_count(l_left_side,l_rigth_side_expression) > 0 then

l_result := 0;

end if;

--Now process right side of string

if l_right_side is not null then

l_result := least(l_result,valid_tag_expression(l_right_side));

else

l_result := 0;

end if;

else

--We just process single tag.

l_left_side := l_tags;

l_left_side := regexp_replace(l_left_side,l_right_side_regex,'\2');

if regexp_count(l_left_side,l_rigth_side_expression) > 0 then

l_result := 0;

end if;

end if;

return l_result;

end;

procedure build_tag_expression_filter(a_tags in varchar2,a_expression_tab in out t_expression_tab,a_parent_id varchar2 default null) is

l_left_side_expression varchar2(10) := '[|&,]';

l_left_side_regex varchar2(50) := '([^|&,]*)([|&,])(.*)';

l_left_side varchar2(4000);

l_rigth_side_expression varchar2(10) := '[!-]';

l_right_side_regex varchar2(50) := '([!-])([^!-].*)';

l_right_side varchar2(4000);

l_tags varchar2(4000) := a_tags;

l_result number :=1;

l_expression_rec t_expression_rec;

begin

if a_expression_tab is null then

a_expression_tab := t_expression_tab();

end if;

l_expression_rec.id := sys_guid();

l_expression_rec.parent_id := a_parent_id;

if instr(substr(l_tags,1,1),'(',1,1) + instr(substr(l_tags,-1,1),')',-1,1) = 2 then

if regexp_count(l_tags,l_right_side_regex) = 1 then

l_expression_rec.negated :=1;

l_tags := trim (leading '!' from l_tags);

end if;

l_expression_rec.left_bracket := 1;

l_tags := trim(leading '(' from l_tags);

l_expression_rec.right_bracket := 1;

l_tags := trim(trailing ')' from l_tags);

end if;

--Check if there are any left side operators for first in order from left to right

if regexp_count(l_tags,l_left_side_expression) > 0 then

--Extract left part of operator and remaining of string to right

--if there are bracketc extract it and record it

l_left_side := regexp_replace(l_tags,l_left_side_regex,'\1');

l_expression_rec.log_operator := regexp_replace(l_tags,l_left_side_regex,'\2');

l_right_side := regexp_replace(l_tags,l_left_side_regex,'\3');

a_expression_tab.extend;

a_expression_tab(a_expression_tab.last) := l_expression_rec;

build_tag_expression_filter(l_left_side,a_expression_tab,l_expression_rec.id);

build_tag_expression_filter(l_right_side,a_expression_tab,l_expression_rec.id);

else

if instr(substr(l_tags,1,1),'(',1,1) + instr(substr(l_tags,-1,1),')',-1,1) = 2 then

if regexp_count(l_tags,l_right_side_regex) = 1 then

l_expression_rec.negated :=1;

l_tags := trim (leading '!' from l_tags);

end if;

l_expression_rec.left_bracket := 1;

l_tags := trim(leading '(' from l_tags);

l_expression_rec.right_bracket := 1;

l_tags := trim(trailing ')' from l_tags);

end if;

l_expression_rec.expression := l_tags;

a_expression_tab.extend;

a_expression_tab(a_expression_tab.last) := l_expression_rec;

end if;

end;

end;

function convert_postfix_to_infix_where_sql(a_postfix_exp in ut_varchar2_list)

end;

/*

* Return number 1 or 0 if the list of tags is valid expression

*/

function valid_tag_expression(a_tags in varchar2) return number;

/*

* Return number 1 or 0 if the list of tags is valid expression

*/

procedure build_tag_expression_filter(a_tags in varchar2,a_expression_tab in out t_expression_tab,a_parent_id varchar2 default null);

function convert_postfix_to_infix_where_sql(a_postfix_exp in ut_varchar2_list) return varchar2;