{-# LANGUAGE
    UnicodeSyntax
  #-}
-- |A set of auxiliary parser utilities.
module Network.HTTP.Lucu.Parser
    ( atMost
    , finishOff
    , skipManyTill
    , skipWhile1
    , skipSpace1
    , isAlphaNum
    )
    where
import Control.Applicative
import Control.Applicative.Unicode
import Control.Monad.Unicode
import Data.Attoparsec.Char8
import Prelude.Unicode

-- |@'atMost' n v@ is like @'P.many' v@ but accumulates @v@ at most
-- @n@ times.
atMost ∷ Alternative f ⇒ Int → f α → f [α]
{-# INLINEABLE atMost #-}
atMost 0 _ = pure []
atMost n v = ( (:) <$> v ⊛ atMost (n-1) v )
             <|>
             pure []

-- |@'finishOff' p@ is equivalent to @p '>>=' \\a -> 'endOfInput' '>>'
-- 'return' a@.
finishOff ∷ Parser α → Parser α
{-# INLINE finishOff #-}
finishOff = ((endOfInput *>) ∘ return =≪)

-- |Similar to 'manyTill' but discards the result.
skipManyTill ∷ Alternative f ⇒ f α → f β → f ()
{-# INLINEABLE skipManyTill #-}
skipManyTill p end = go
    where
      go = (end *> pure ()) <|> (p *> go)

-- |Similar to 'skipWhile' but consumes at least one character.
skipWhile1 ∷ (Char → Bool) → Parser ()
{-# INLINE skipWhile1 #-}
skipWhile1 p = takeWhile1 p *> pure ()

-- |Similar to 'skipSpace' but consumes at least one whitespace.
skipSpace1 ∷ Parser ()
{-# INLINE skipSpace1 #-}
skipSpace1 = skipMany1 space

-- |@'isAlphaNum' c@ returns 'True' iff @'isDigit' c ||
-- 'isAlpha_ascii' c@.
isAlphaNum ∷ Char → Bool
{-# INLINE isAlphaNum #-}
isAlphaNum c = isDigit c ∨ isAlpha_ascii c