{-# LANGUAGE NamedFieldPuns #-}
module Hcompta.Format.Ledger.Balance where

import           Hcompta.Model (Transaction)
import qualified Hcompta.Calc.Balance as Balance
import qualified Hcompta.Format.Ledger.Journal as Journal
import           Hcompta.Format.Ledger.Journal (Journal(..))
import qualified Hcompta.Lib.Foldable as Lib.Foldable

-- * The 'Balance.Deviation' type

-- | Return the first 'Transaction' (if any) whose 'Posting's
--   do not sum to a 'Balance' respecting 'Balance.is_inferrable',
--   with the path of 'Journal's leading to that 'Transaction'.
check_equilibrium :: Journal -> Maybe ((Transaction, Balance.Deviation), [Journal])
check_equilibrium =
	Journal.find
	 (\Journal{Journal.transactions} ->
		Lib.Foldable.find
		 (Lib.Foldable.find
			 (\tr -> do
				let bal = Balance.transaction tr Balance.nil
				let dev = Balance.deviation bal
				if Balance.is_equilibrium_inferrable dev
					then Nothing
					else Just (tr, dev)
			 )
		 )
		 transactions
	 )