converting Oracle to postgres

Here is a copy of my function in oracle.

Create Or Replace FUNCTION SET_USERNAME

( eventtype IN varchar2,

message IN varchar2)

RETURN varchar2 IS

username varchar2(30);

pos1 number(7);

pos2 number(7);

BEGIN

if eventtype = 'AUDIT_SUCCESS' then

pos1 := instr(message, 'User Name:') + 10;

pos2 := instr(message, 'Domain');

return substr(message, pos1, pos2-pos1);

elsif eventtype = 'AUDIT_FAILURE' then

pos1 := instr(message, 'User Name:') + 10;

pos2 := instr(message, 'Domain:');

if (pos1 = 0 or pos2 = 0) then

pos1 := instr(message, 'Account Name:') + 13;

pos2 := instr(message, 'Target Domain:');

end if;

return substr(message, pos1, pos2-pos1);

end if;

return '' ;

EXCEPTION

WHEN others THEN

return '' ;

END;

How do I get it to work in postgres

Please help me with the SQL commands

Thanks

Robert Stewart

Division of Communications

Office of Infrastructure Services

Governors Office for Technology

Commonwealth of Kentucky

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