Best friend

My best friend is an alcoholic. And I'm going to lose him. I know it's not my fault, and I'm doing my very best not to be an enabler. But I've witnessed his lows, involving DUIs, rehab, bar fights, and he's even treated me horribly too. I just feel so helpless. I can't just walk away. He's also got a host of mental issues, and I just recently discovered he's a compulsive liar... He's lied to me about things he's created for over a year now. The whole situation we have is strange and bittersweet. But I'm going to lose him to the bottle... Just as I've lost others. I don't know where else to turn.