-- packages/acs-events/sql/postgres/oracle-compat-create.sql
--
-- Functions to ease porting from Postgres to Oracle
--
-- @author jowell@jsabino.com
-- @creation-date 2001-06-26
--
-- $Id: oracle-compat-create.sql,v 1.5.4.1 2017/04/21 15:50:24 gustafn Exp $



-- added
select define_function_args('dow_to_int','weekday');

--
-- procedure dow_to_int/1
--
     --
     -- Convert string to day of the week
     --
     -- Note that the output of extract(dow from timestamp) and to_char(timestamp,'D')
     -- are different!  to_char is more consistent with Oracle, so we only use to_char.
     --
     -- @author jowell@jsabino.com
     --
     -- @param weekday       Day of the week string to be converted to Postgres int representation
     --
     -- @return integer corresponding to Postgres representation of day of the week (Sunday = 0)
     --

CREATE OR REPLACE FUNCTION dow_to_int(
   dow_to_int__weekday varchar

) RETURNS integer AS $$
DECLARE
       v_dow			integer;
BEGIN
       -- Brute force (what can I say?).
       select (case trim(upper(dow_to_int__weekday))
	             when 'SUNDAY'    then 1
	             when 'SUN'       then 1
		     when 'MONDAY'    then 2
		     when 'MON'	then 2
		     when 'TUESDAY'	then 3
		     when 'TUES'	then 3
		     when 'TUE'	then 3
		     when 'WEDNESDAY' then 4
		     when 'WED'	then 4
		     when 'WEDS'	then 4
		     when 'THURSDAY'  then 5
		     when 'THURS'	then 5
		     when 'THUR'	then 5
		     when 'THU'	then 5
		     when 'FRIDAY'	then 6
		     when 'FRI'	then 6
		     when 'SATURDAY'	then 7
		     when 'SAT'	then 7
		     else -1
		end) into v_dow
       from dual;
	
       if v_dow < 0 
       then 
	   raise exception 'Day of the week unknown';
       end if;

       return v_dow;

END;
$$ LANGUAGE plpgsql;




-- added
select define_function_args('to_interval','number,units');

--
-- procedure to_interval/2
--
     --
     -- Convert an integer to the specified interval
     --
     -- Utility function so we do not have to remember how to escape
     -- double quotes when we typecast an integer to an interval
     --
     -- @author jowell@jsabino.com
     --
     -- @param interval_number       Integer to convert to interval
     -- @param interval_units                Interval units
     --
     -- @return interval equivalent of interval_number, in interval_units units
     --  

CREATE OR REPLACE FUNCTION to_interval(
   interval__number integer,
   interval__units varchar

) RETURNS interval AS $$
	
DECLARE    
BEGIN
	-- We should probably do unit checking at some point
	return ('''' || interval__number || ' ' || interval__units || '''')::interval;

END;
$$ LANGUAGE plpgsql;




-- added
select define_function_args('next_day','somedate,weekday');

--
-- procedure next_day/2
--
     --
     -- Equivalent of Oracle next_day function
     --
     -- @author jowell@jsabino.com
     --
     -- @param somedate      Reference date
     -- @param weekday       Day of the week to find
     --
     -- @return The date of the next weekday that is later than somedate
     --
CREATE OR REPLACE FUNCTION next_day(
   next_day__somedate timestamptz,
   next_day__weekday varchar

) RETURNS timestamptz AS $$
DECLARE
       v_dow			integer;
       v_ref_dow		integer;
       v_add_days		integer;
BEGIN
	-- I can't find a function that converts days of the week to
	-- the corresponding integer value, so I roll my own (above)
	-- We avoid extract(dow from timestamp) because of incompatible output with to_char.
	v_ref_dow := dow_to_int(next_day__weekday);
	v_dow := to_number(to_char(next_day__somedate,'D'),'9');
	
	-- If next_day___weekday is the same day of the week as
	-- next_day__somedate, we add a full week.
	if v_dow < v_ref_dow
	then
	     v_add_days := v_ref_dow - v_dow;
        else
	     v_add_days := v_ref_dow - v_dow + 7;
	end if;

	-- Do date math
	return next_day__somedate + to_interval(v_add_days,'days');

END;
$$ LANGUAGE plpgsql;



-- added
select define_function_args('add_months','somedate,n_months');

--
-- procedure add_months/2
--
     --
     -- Equivalent of Oracle add_months function
     --
     -- @author jowell@jsabino.com
     --
     -- @param somedate      Reference date
     -- @param n_months      Day of the week to find
     --
     -- @return The date plus n_months full months
     --
CREATE OR REPLACE FUNCTION add_months(
   add_months__somedate timestamptz,
   add_months__n_months integer

) RETURNS timestamptz AS $$
DECLARE
BEGIN
	-- Date math magic
	return add_months__somedate + to_interval(add_months__n_months,'months');

END;
$$ LANGUAGE plpgsql;



-- added
select define_function_args('last_day','somedate');

--
-- procedure last_day/1
--
     --
     -- Equivalent of Oracle last_day function
     --
     -- @author jowell@jsabino.com
     --
     -- @param somedate      Reference date
     --
     -- @return The last day of the month containing somedate
     --

CREATE OR REPLACE FUNCTION last_day(
   last_day__somedate timestamptz
) RETURNS timestamptz AS $$
DECLARE
       v_month			integer;
       v_targetmonth		integer;
       v_date			timestamptz;
       v_targetdate		timestamptz;
BEGIN
	
       -- Initial values
       v_targetdate := last_day__somedate;
       v_targetmonth := extract(month from last_day__somedate);

       -- Add up to 31 days to the given date, stop if month changes.
       FOR i IN 1..31 LOOP

	    v_date := last_day__somedate + to_interval(i,'days');
	    v_month := extract(month from v_date);

	    if v_month != v_targetmonth
	    then
		exit;
	    else
	       v_targetdate := v_date;
	    end if;

       END LOOP;
	
       return v_targetdate;

END;
$$ LANGUAGE plpgsql;