how to stop sunroof leaking peugeot 405?

my electric sunroof does not work, it appears to be stuck in the closed position but it lets in water which drips through the courtesy light fitting and if bad covers the whole roof.if i go sharply downhill to the right a lot of water runs away through the drains by the drivers door.is this problem a drainage one , and how do i fix it, or does the sunroof need sealing?