Subpart.hs

-- | A type to represent (recursive) subdivisions of a part.
module Music.Parts.Subpart (
          Subpart(..),
          containsSubpart,
          properlyContainsSubpart,
          isSubpartOf,
          isProperSubpartOf,
  ) where

import           Control.Applicative
import           Control.Lens                    (toListOf)
import           Data.Default
import           Data.Functor.Adjunction         (unzipR)
import qualified Data.List
import           Data.Maybe
import           Data.Semigroup
import           Data.Semigroup.Option.Instances
import           Data.Traversable                (traverse)
import           Data.Typeable
import           Text.Numeral.Roman              (toRoman)

import Music.Parts.Division

-- |
-- A subpart is a potentially infinite sequence of divisions, each typically
-- designated using a new index type, i.e. @I.1.2@.
--
-- The empty subpart (also known as 'mempty') represents all the players of the group,
-- or in the context of 'Part', all players of the given instrument.
--
newtype Subpart = Subpart [Division]
    deriving (Eq, Ord, Default, Semigroup, Monoid)

{-
TODO hide internals

Expose

_divisions :: Traversal' Subpart Division

or similar 
-}

instance Show Subpart where
  show (Subpart ps) = Data.List.intercalate "." $ mapFR showDivisionR showDivision $ ps
    where
      mapFR f g []     = []
      mapFR f g (x:xs) = f x : fmap g xs

containsSubpart :: Subpart -> Subpart -> Bool
containsSubpart = flip isSubpartOf

properlyContainsSubpart :: Subpart -> Subpart -> Bool
properlyContainsSubpart = flip isProperSubpartOf

isSubpartOf :: Subpart -> Subpart -> Bool
Subpart x `isSubpartOf` Subpart y = y `Data.List.isPrefixOf` x

isProperSubpartOf :: Subpart -> Subpart -> Bool
x `isProperSubpartOf` y = x `isSubpartOf` y && x /= y