, mtl

import           Control.Monad.State

import           Aftok
import           Aftok.Types

import           Aftok (UserId)
import           Aftok.Types (Satoshi(..))

  { _raiseAmount :: Satoshi
  , _auctionEnd  :: C.UTCTime

  { _raiseAmount  :: Satoshi
  , _auctionEnd   :: C.UTCTime

data Commitment = Commitment
  { _baseBid :: Bid
  , _commitmentSeconds :: Seconds
  , _commitmentAmount :: Satoshi
  }

bidCommitment :: Satoshi -> Bid -> State Satoshi (Maybe Commitment)
bidCommitment raiseAmount' bid = do
  raised <- get
  case raised of
    -- if the total is fully within the raise amount
    x | x + (bid ^. bidAmount) < raiseAmount' ->
      put (x + bid ^. bidAmount) >> 
      (pure . Just $ Commitment bid (bid ^. bidSeconds) (bid ^. bidAmount))
    -- if the last bid will exceed the raise amount, reduce it to fit
    x | x < raiseAmount' ->
      let remainder = raiseAmount' - x
          winFraction = toRational remainder / toRational (bid ^. bidAmount)
          remainderSeconds = Seconds . round $ winFraction * toRational (bid ^. bidSeconds)
      in  put (x + remainder) >>
          (pure . Just $ Commitment bid (remainderSeconds) remainder)
    -- otherwise, 
    _ -> pure Nothing

import           Aftok.Auction

import           Aftok.Auction (Auction, AuctionId, Bid, BidId)