{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE RecordWildCards #-}

module Blessings
    ( module Export
    , module Blessings
    ) where

import Blessings.Internal as Export (Blessable)
import qualified Blessings.Internal as Bless
import Control.Applicative
import Data.Ix (inRange)
import Data.List (genericDrop)
import Data.String
import Data.Word (Word8)
import qualified Prelude
import Prelude hiding (drop, length, take)

type Ps = Word8
type Pm = [Ps]

data Blessings a
    = Plain a
    | SGR Pm (Blessings a)
    | Append (Blessings a) (Blessings a)
    | Empty
  deriving (Eq, Show)


instance Foldable Blessings where
    foldMap f = \case
        Append t1 t2 -> foldMap f t1 <> foldMap f t2
        Plain s -> f s
        SGR _ t -> foldMap f t
        Empty -> mempty


instance Functor Blessings where
    fmap f = \case
        Append t1 t2 -> Append (fmap f t1) (fmap f t2)
        Plain s -> Plain (f s)
        SGR pm t -> SGR pm (fmap f t)
        Empty -> Empty


instance Semigroup (Blessings a) where
    t <> Empty = t
    Empty <> t = t
    Append t1 t2 <> Append t3 t4 = t1 <> t2 <> t3 <> t4
    Append t1 t2 <> t3 = t1 <> t2 <> t3
    t1 <> t2 = Append t1 t2


instance Monoid (Blessings a) where
    mempty = Empty


instance IsString a => IsString (Blessings a) where
    fromString = Plain . fromString


class IsPm a where
    toPm :: a -> Pm
    fromPm :: Pm -> Maybe a


data FColor = ECMA48FColor Ps   -- ECMA-48 / ISO 6429 / ANSI X3.64
            | Xterm256FColor Ps
            | ISO8613_3FColor Ps Ps Ps
  deriving (Eq, Show)

instance IsPm FColor where
    toPm (ECMA48FColor i) = [i]
    toPm (Xterm256FColor i) = [38,5,i]
    toPm (ISO8613_3FColor r g b) = [38,2,r,g,b]
    fromPm = fromSGRPm SGRPm
               { def8Ps = 39
               , extPs = 38
               , lo8Ps = 30
               , hi8Ps = 37
               , makeECMA48Color = ECMA48FColor
               , makeXterm256Color = Xterm256FColor
               , makeISO8613_3Color = ISO8613_3FColor
               }
           . filterPm sgrBColor


data BColor = ECMA48BColor Ps
            | Xterm256BColor Ps
            | ISO8613_3BColor Ps Ps Ps
  deriving (Eq, Show)


instance IsPm BColor where
    toPm (ECMA48BColor i) = [i]
    toPm (Xterm256BColor i) = [48,5,i]
    toPm (ISO8613_3BColor r g b) = [48,2,r,g,b]
    fromPm = fromSGRPm SGRPm
                 { def8Ps = 49
                 , extPs = 48
                 , lo8Ps = 40
                 , hi8Ps = 47
                 , makeECMA48Color = ECMA48BColor
                 , makeXterm256Color = Xterm256BColor
                 , makeISO8613_3Color = ISO8613_3BColor
               }
           . filterPm sgrFColor


data Blink = Blink | NoBlink
  deriving (Eq, Show)

instance IsPm Blink where
    toPm Blink = [5]
    toPm NoBlink = [25]
    fromPm = rec . filterPm sgrColor
      where
        rec xs = case filter (`elem` ([5,25] :: [Word8])) xs of
            [] -> Nothing
            xs' -> case last xs' of
                5 -> Just Blink
                25 -> Just NoBlink
                _ -> error "filter broken in fromPm :: Pm -> Maybe Blink"


data Bold = Bold | NoBold
  deriving (Eq, Show)

instance IsPm Bold where
    toPm Bold = [1]
    toPm NoBold = [22]
    fromPm = rec . filterPm sgrColor
      where
        rec xs = case filter (`elem` ([1,22] :: [Word8])) xs of
            [] -> Nothing
            xs' -> case last xs' of
                1 -> Just Bold
                22 -> Just NoBold
                _ -> error "filter broken in fromPm :: Pm -> Maybe Bold"


data Underline = Underline | NoUnderline
  deriving (Eq, Show)

instance IsPm Underline where
    toPm Underline = [4]
    toPm NoUnderline = [24]
    fromPm = rec . filterPm sgrColor
      where
        rec xs = case filter (`elem` ([4,24] :: [Word8])) xs of
            [] -> Nothing
            xs' -> case last xs' of
                1 -> Just Underline
                22 -> Just NoUnderline
                _ -> error "filter broken in fromPm :: Pm -> Maybe Underline"


data SGRPm c = SGRPm
    { def8Ps :: Ps
    , extPs :: Ps
    , lo8Ps :: Ps
    , hi8Ps :: Ps
    , makeECMA48Color :: Ps -> c
    , makeXterm256Color :: Ps -> c
    , makeISO8613_3Color :: Ps -> Ps -> Ps -> c
    }


fromSGRPm :: IsPm c => SGRPm c -> Pm -> Maybe c
fromSGRPm SGRPm{..} = rec Nothing
  where
    rec mb_c (x:xs)
        | x == extPs = case xs of
            (2:r:g:b:xs') -> rec (Just $ makeISO8613_3Color r g b) xs'
            (5:i:xs')     -> rec (Just $ makeXterm256Color i) xs'
            _             -> rec mb_c xs
        | x == def8Ps = rec (Just $ makeECMA48Color def8Ps) xs
        | inRange (lo8Ps, hi8Ps) x = rec (Just $ makeECMA48Color x) xs
        | otherwise = rec mb_c xs
    rec mb_c _ = mb_c


-- filterPm is used to preprocess Pm before searching with fromPm in
-- order to remove (longer) sequences that could contain subsequences
-- that look like the (shorter) sequences we're searching.
-- E.g. we could find [1] (bold) in any extended color sequence.
-- TODO Can we combine this whole from*Pm with Scanner?
filterPm :: (Pm -> Maybe Word8) -> Pm -> Pm
filterPm f = rec []
  where
    rec ys xs@(xhead:xtail) = maybe (rec (ys ++ [xhead]) xtail)
                                    (rec ys . flip genericDrop xs)
                                    (f xs)
    rec ys _ = ys

sgrColor, sgrFColor, sgrBColor :: Pm -> Maybe Word8

sgrColor xs = sgrFColor xs <|> sgrBColor xs

sgrFColor (38:5:_) = Just 3
sgrFColor (38:2:_) = Just 5
sgrFColor _ = Nothing

sgrBColor (48:5:_) = Just 3
sgrBColor (48:2:_) = Just 5
sgrBColor _ = Nothing


type RenderState = [(FColor, BColor, Blink, Bold, Underline)]


emptyRenderState :: RenderState
emptyRenderState = [(ECMA48FColor 39, ECMA48BColor 49, NoBlink, NoBold, NoUnderline)]


render :: (Blessable a) => RenderState -> Blessings a -> a -> a

render _ (Plain s) y = s <> y

-- TODO merge successive sequences: \ESC[32m\ESC[1m -> \ESC[31;1m
render rs@((fc, bc, bl, b, u):_) (SGR c t) y =
    renderSGR bra <> render rs' t (renderSGR ket <> y)
  where
    fc' = maybe fc id $ fromPm c
    bc' = maybe bc id $ fromPm c
    bl' = maybe bl id $ fromPm c
    b'  = maybe  b id $ fromPm c
    u'  = maybe  u id $ fromPm c
    rs' = (fc', bc', bl', b', u') : rs
    bra = braket >>= fst
    ket = braket >>= snd
    braket =
        (if fc' /= fc then (toPm fc', toPm fc) else ([],[])) :
        (if bc' /= bc then (toPm bc', toPm bc) else ([],[])) :
        (if bl' /= bl then (toPm bl', toPm bl) else ([],[])) :
        (if b'  /=  b then (toPm  b', toPm  b) else ([],[])) :
        (if u'  /=  u then (toPm  u', toPm  u) else ([],[])) : []

render _ (SGR _ _) _ =
    error "render called w/o proper initial state"
    -- where a proper initial state is s.th. like emptyRenderState

render r (Append t1 t2) y =
    render r t1 $ render r t2 y

render _ Empty y = y


renderSGR :: (Blessable a) => Pm -> a
renderSGR [] = mempty
renderSGR pm =
  ("\ESC["<>) . (<>"m") . Bless.intercalate ";" . map Bless.fromWord8 $ pm


stripSGR :: Blessings a -> Blessings a
stripSGR = \case
    Append t1 t2 -> Append (stripSGR t1) (stripSGR t2)
    SGR _ t -> stripSGR t
    Plain x -> Plain x
    Empty -> Empty


pp :: (Blessable a) => Blessings a -> a
pp t = render emptyRenderState t ""


instance Blessable a => Blessable (Blessings a) where
  length (Plain x) = Bless.length x
  length (SGR _ t) = Bless.length t
  length (Append t1 t2) = Bless.length t1 + Bless.length t2
  length Empty = 0

  drop n = \case
      Append t1 t2 ->
          case compare n (Bless.length t1) of
              LT -> Bless.drop n t1 <> t2
              EQ -> t2
              GT -> Bless.drop (n - Bless.length t1) t2
      Plain s ->
          Plain (Bless.drop n s)
      SGR pm t ->
          SGR pm (Bless.drop n t)
      Empty ->
          Empty

  take n = \case
      Append t1 t2 ->
          case compare n (Bless.length t1) of
              LT -> Bless.take n t1
              EQ -> t1
              GT -> t1 <> Bless.take (n - Bless.length t1) t2
      Plain s ->
          Plain (Bless.take n s)
      SGR pm t ->
          SGR pm (Bless.take n t)
      Empty ->
          Empty

  intercalate i = \case
      [] -> mempty
      [t] -> t
      (t:ts) -> t <> i <> Bless.intercalate i ts

  fromWord8 = Plain . Bless.fromWord8