Aggregate.hs

-- | Aggregate type class.
module Data.CQRS.Aggregate
       ( Aggregate(..)
       ) where

import Data.ByteString (ByteString)

-- | Type class for aggregates.
class Aggregate a where
  -- | Encode aggregate into a ByteString representation. The
  -- representation should contain some metadata (a UUID for example)
  -- which can be used to check reliably whether the encoded
  -- representation is valid upon decoding. This can be used if the
  -- actual aggregate structure changes.
  encodeAggregate :: a -> ByteString
  -- | Decode ByteString to aggregate state. If decoding is not
  -- possible should return 'Nothing'.
  decodeAggregate :: ByteString -> Maybe a