{-# LANGUAGE OverloadedStrings #-}

-- | Ketiv/Qere — the dual reading.
--
-- Architecture §3.1:
--   "A specification position that holds two authoritative values."
--   Ketiv = what is written (stored form).
--   Qere  = what is read (executed form).
--
-- At no point in the processing chain should a dual reading
-- collapse to a single value. Both readings are preserved.
module Shoresh.KetivQere
  ( DualReading(..)
  , SpecValue(..)
  , bothReadings
  , isDual
  , hasDualReadings
  ) where

import Shoresh.Types (Reference)
import Data.Text (Text)

-- | A position in the specification that holds two authoritative values.
data DualReading = DualReading
  { ketiv :: !Text      -- ^ What is written (stored form)
  , qere  :: !Text      -- ^ What is read (executed form)
  , drRef :: !Reference -- ^ Where in Torah this occurs
  } deriving (Eq, Show)

-- | A specification value: either single or dual.
data SpecValue
  = Single !Text
  | DualVal !DualReading
  deriving (Show)

-- | Retrieve both readings without collapsing.
-- Single values return the same text for both.
-- Dual values return (ketiv, qere).
bothReadings :: SpecValue -> (Text, Text)
bothReadings (Single t)   = (t, t)
bothReadings (DualVal dr) = (ketiv dr, qere dr)

-- | Check if a SpecValue is a dual reading.
isDual :: SpecValue -> Bool
isDual (Single _)  = False
isDual (DualVal _) = True

-- | Check if a list of spec values contains any dual readings.
hasDualReadings :: [SpecValue] -> Bool
hasDualReadings = any isDual