-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-- 
-- $Id$
--
-- PostGIS - Spatial Types for PostgreSQL
-- http://postgis.refractions.net
-- Copyright 2001-2003 Refractions Research Inc.
--
-- This is free software; you can redistribute and/or modify it under
-- the terms of the GNU General Public Licence. See the COPYING file.
--  
-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -


#include "sqldefines.h"


-----------------------------------------------------------------------
-- LONG TERM LOCKING
-----------------------------------------------------------------------

-- UnlockRows(authid)
-- removes all locks held by the given auth
-- returns the number of locks released
CREATEFUNCTION UnlockRows(text)
	RETURNS int
	AS '
DECLARE
	ret int;
BEGIN

	IF NOT LongTransactionsEnabled() THEN
		RAISE EXCEPTION ''Long transaction support disabled, use EnableLongTransaction() to enable.'';
	END IF;

	EXECUTE ''DELETE FROM authorization_table where authid = '' ||
		quote_literal($1);

	GET DIAGNOSTICS ret = ROW_COUNT;

	RETURN ret;
END;
'
LANGUAGE 'plpgsql' _VOLATILE_STRICT;

-- LockRow([schema], table, rowid, auth, [expires]) 
-- Returns 1 if successfully obtained the lock, 0 otherwise
CREATEFUNCTION LockRow(text, text, text, text, timestamp)
	RETURNS int
	AS '
DECLARE
	myschema alias for $1;
	mytable alias for $2;
	myrid   alias for $3;
	authid alias for $4;
	expires alias for $5;
	ret int;
	mytoid oid;
	myrec RECORD;
	
BEGIN

	IF NOT LongTransactionsEnabled() THEN
		RAISE EXCEPTION ''Long transaction support disabled, use EnableLongTransaction() to enable.'';
	END IF;

	EXECUTE ''DELETE FROM authorization_table WHERE expires < now()''; 

#ifdef HAS_SCHEMAS
	SELECT c.oid INTO mytoid FROM pg_class c, pg_namespace n
		WHERE c.relname = mytable
		AND c.relnamespace = n.oid
		AND n.nspname = myschema;
#else
	SELECT c.oid INTO mytoid FROM pg_class c
		WHERE c.relname = mytable;
#endif

	-- RAISE NOTICE ''toid: %'', mytoid;

	FOR myrec IN SELECT * FROM authorization_table WHERE 
		toid = mytoid AND rid = myrid
	LOOP
		IF myrec.authid != authid THEN
			RETURN 0;
		ELSE
			RETURN 1;
		END IF;
	END LOOP;

	EXECUTE ''INSERT INTO authorization_table VALUES (''||
		quote_literal(mytoid)||'',''||quote_literal(myrid)||
		'',''||quote_literal(expires)||
		'',''||quote_literal(authid) ||'')'';

	GET DIAGNOSTICS ret = ROW_COUNT;

	RETURN ret;
END;'
LANGUAGE 'plpgsql' _VOLATILE_STRICT;

-- LockRow(schema, table, rid, authid);
CREATEFUNCTION LockRow(text, text, text, text)
	RETURNS int
	AS
'SELECT LockRow($1, $2, $3, $4, now()::timestamp+''1:00'');'
	LANGUAGE 'sql' _VOLATILE_STRICT;

-- LockRow(table, rid, authid);
CREATEFUNCTION LockRow(text, text, text)
	RETURNS int
	AS
#ifdef HAS_SCHEMAS
'SELECT LockRow(current_schema(), $1, $2, $3, now()::timestamp+''1:00'');'
#else
'SELECT LockRow('''', $1, $2, $3, now()::timestamp+''1:00'');'
#endif
	LANGUAGE 'sql' _VOLATILE_STRICT;

-- LockRow(schema, table, rid, expires);
CREATEFUNCTION LockRow(text, text, text, timestamp)
	RETURNS int
	AS
#ifdef HAS_SCHEMAS
'SELECT LockRow(current_schema(), $1, $2, $3, $4);'
#else
'SELECT LockRow('''', $1, $2, $3, $4);'
#endif
	LANGUAGE 'sql' _VOLATILE_STRICT;


CREATEFUNCTION AddAuth(text)
	RETURNS BOOLEAN
	AS '
DECLARE
	lockid alias for $1;
	okay boolean;
	myrec record;
BEGIN
	-- check to see if table exists
	--  if not, CREATE TEMP TABLE mylock (transid xid, lockcode text)
	okay := ''f'';
	FOR myrec IN SELECT * FROM pg_class WHERE relname = ''temp_lock_have_table'' LOOP
		okay := ''t'';
	END LOOP; 
	IF (okay <> ''t'') THEN 
		CREATE TEMP TABLE temp_lock_have_table (transid xid, lockcode text);
			-- this will only work from pgsql7.4 up
			-- ON COMMIT DELETE ROWS;
	END IF;

	--  INSERT INTO mylock VALUES ( $1)
--	EXECUTE ''INSERT INTO temp_lock_have_table VALUES ( ''||
--		quote_literal(getTransactionID()) || '','' ||
--		quote_literal(lockid) ||'')'';

	INSERT INTO temp_lock_have_table VALUES (getTransactionID(), lockid);

	RETURN true::boolean;
END;
'
LANGUAGE PLPGSQL;
 

-- CheckAuth( <schema>, <table>, <ridcolumn> )
--
-- Returns 0
--
CREATEFUNCTION CheckAuth(text, text, text)
	RETURNS INT
	AS '
DECLARE
#ifdef HAS_SCHEMAS
	schema text;
#endif
BEGIN
	IF NOT LongTransactionsEnabled() THEN
		RAISE EXCEPTION ''Long transaction support disabled, use EnableLongTransaction() to enable.'';
	END IF;

#ifdef HAS_SCHEMAS
	if ( $1 != '''' ) THEN
		schema = $1;
	ELSE
		SELECT current_schema() into schema;
	END IF;
#endif

	-- TODO: check for an already existing trigger ?

	EXECUTE ''CREATE TRIGGER check_auth BEFORE UPDATE OR DELETE ON '' 
#ifdef HAS_SCHEMAS
		|| quote_ident(schema) || ''.'' || quote_ident($2)
#else
		|| quote_ident($2)
#endif
		||'' FOR EACH ROW EXECUTE PROCEDURE CheckAuthTrigger(''
		|| quote_literal($3) || '')'';

	RETURN 0;
END;
'
LANGUAGE 'plpgsql';

-- CheckAuth(<table>, <ridcolumn>)
CREATEFUNCTION CheckAuth(text, text)
	RETURNS INT
	AS
	'SELECT CheckAuth('''', $1, $2)'
	LANGUAGE 'SQL';

CREATEFUNCTION CheckAuthTrigger()
	RETURNS trigger AS 
	'@MODULE_FILENAME@', 'check_authorization'
	LANGUAGE C;

CREATEFUNCTION GetTransactionID()
	RETURNS xid AS 
	'@MODULE_FILENAME@', 'getTransactionID'
	LANGUAGE C;


--
-- Enable Long transactions support
--
--  Creates the authorization_table if not already existing
--
CREATEFUNCTION EnableLongTransactions()
	RETURNS TEXT
	AS '
DECLARE
	query text;
	exists bool;
	rec RECORD;

BEGIN

	exists = ''f'';
	FOR rec IN SELECT * FROM pg_class WHERE relname = ''authorization_table''
	LOOP
		exists = ''t'';
	END LOOP;

	IF NOT exists
	THEN
		query = ''CREATE TABLE authorization_table (
			toid oid, -- table oid
			rid text, -- row id
			expires timestamp,
			authid text
		)'';
		EXECUTE query;
	END IF;

	exists = ''f'';
	FOR rec IN SELECT * FROM pg_class WHERE relname = ''authorized_tables''
	LOOP
		exists = ''t'';
	END LOOP;

	IF NOT exists THEN
		query = ''CREATE VIEW authorized_tables AS '' ||
			''SELECT '' ||
#ifdef HAS_SCHEMAS
			''n.nspname as schema, '' ||
#endif
			''c.relname as table, trim('' ||
			quote_literal(chr(92) || ''000'') ||
			'' from t.tgargs) as id_column '' ||
			''FROM pg_trigger t, pg_class c, pg_proc p '' ||
#ifdef HAS_SCHEMAS
			'', pg_namespace n '' ||
#endif
			''WHERE p.proname = '' || quote_literal(''checkauthtrigger'') ||
#ifdef HAS_SCHEMAS
			'' AND c.relnamespace = n.oid'' ||
#endif
			'' AND t.tgfoid = p.oid and t.tgrelid = c.oid'';
		EXECUTE query;
	END IF;

	RETURN ''Long transactions support enabled'';
END;
'
LANGUAGE 'plpgsql';

--
-- Check if Long transactions support is enabled
--
CREATEFUNCTION LongTransactionsEnabled()
	RETURNS bool
AS '
DECLARE
	rec RECORD;
BEGIN
	FOR rec IN SELECT oid FROM pg_class WHERE relname = ''authorized_tables''
	LOOP
		return ''t'';
	END LOOP;
	return ''f'';
END;
'
LANGUAGE 'plpgsql';

--
-- Disable Long transactions support
--
--  (1) Drop any long_xact trigger 
--  (2) Drop the authorization_table
--  (3) KEEP the authorized_tables view
--
CREATEFUNCTION DisableLongTransactions()
	RETURNS TEXT
	AS '
DECLARE
	query text;
	exists bool;
	rec RECORD;

BEGIN

	--
	-- Drop all triggers applied by CheckAuth()
	--
	FOR rec IN
		SELECT c.relname, t.tgname, t.tgargs FROM pg_trigger t, pg_class c, pg_proc p
		WHERE p.proname = ''checkauthtrigger'' and t.tgfoid = p.oid and t.tgrelid = c.oid
	LOOP
		EXECUTE ''DROP TRIGGER '' || quote_ident(rec.tgname) ||
			'' ON '' || quote_ident(rec.relname);
	END LOOP;

	--
	-- Drop the authorization_table table
	--
	FOR rec IN SELECT * FROM pg_class WHERE relname = ''authorization_table'' LOOP
		DROP TABLE authorization_table;
	END LOOP;

	--
	-- Drop the authorized_tables view
	--
	FOR rec IN SELECT * FROM pg_class WHERE relname = ''authorized_tables'' LOOP
		DROP VIEW authorized_tables;
	END LOOP;

	RETURN ''Long transactions support disabled'';
END;
'
LANGUAGE 'plpgsql';

---------------------------------------------------------------
-- END
---------------------------------------------------------------