module Text.Authoring.Label 
       ( Label(..),(<>),(./), fromValue)
       where

import           Data.Monoid
import           Data.String (IsString(..))
import           Data.Typeable
import           Data.Text (pack)
import           Text.LaTeX (raw)

-- | 'Label's are used to create a unique reference label
--   within a paper.
data Label 
  = FromType !TypeRep 
  | FromString !String
  | Ap !Label !Label
  | Empty
  deriving (Eq, Ord)

instance Monoid Label where
  mempty = Empty
  mappend Empty x = x
  mappend x Empty = x
  mappend x y = Ap x y

instance IsString Label where
  fromString = FromString

instance Show Label where
  show (FromType r) = show r
  show (FromString s) = s
  show (Ap a b) = show a ++ "." ++ show b

infixl 1 ./

-- | Create a label from the type of a value.
fromValue :: Typeable t => t -> Label
fromValue = FromType . typeOf

-- | Create a slightly different version of the label.
(./) :: Show a => Label -> a -> Label
l ./ x = Ap l (FromString $ show x)