{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE NoMonomorphismRestriction #-}
{-# LANGUAGE UndecidableInstances #-}
module Symantic.Document.Plain where

import Data.Bool
import Data.Char (Char)
import Data.Eq (Eq(..))
import Data.Function (($), (.), id)
import Data.Functor ((<$>))
import Data.Maybe (Maybe(..))
import Data.Monoid (Monoid(..))
import Data.Ord (Ord(..), Ordering(..))
import Data.Semigroup (Semigroup(..))
import Data.String (String, IsString(..))
import Data.Text (Text)
import Data.Tuple (snd)
import GHC.Natural (minusNatural,quotRemNatural)
import Numeric.Natural (Natural)
import Prelude (fromIntegral, Num(..), pred)
import System.Console.ANSI
import Text.Show (Show(..), showString, showParen)
import qualified Data.Foldable as Fold
import qualified Data.List as List
import qualified Data.Text.Lazy as TL

import Symantic.Document.API

-- * Type 'Plain'
-- | Church encoded for performance concerns.
-- Kind like 'ParsecT' in @megaparsec@ but a little bit different
-- due to the use of 'PlainFit' for implementing 'breakingSpace' correctly
-- when in the left hand side of ('<>').
-- Prepending is done using continuation, like in a difference list.
newtype Plain d = Plain
 { unPlain ::
     {-curr-}PlainInh ->
     {-curr-}PlainState d ->
     {-ok-}( ({-prepend-}(d->d), {-new-}PlainState d) -> PlainFit d) ->
     PlainFit d
     -- NOTE: equivalent to:
     -- ReaderT PlainInh (StateT (PlainState d) (Cont (PlainFit d))) (d->d)
 }
instance (Show d, Monoid d) => Show (Plain d) where
        show = show . runPlain

runPlain :: Monoid d => Plain d -> d
runPlain x =
        unPlain x
         defPlainInh
         defPlainState
         {-k-}(\(px,_sx) fits _overflow ->
                -- NOTE: if px fits, then appending mempty fits
                fits (px mempty) )
         {-fits-}id
         {-overflow-}id

-- ** Type 'PlainState'
data PlainState d = PlainState
 { plainState_buffer          :: ![PlainChunk d]
 , plainState_bufferStart     :: !Column
   -- ^ The 'Column' from which the 'plainState_buffer'
   -- must be written.
 , plainState_bufferWidth     :: !Width
   -- ^ The 'Width' of the 'plainState_buffer' so far.
 , plainState_removableIndent :: !Indent
   -- ^ The amount of 'Indent' added by 'breakspace'
   -- that can be removed by breaking the 'space' into a 'newline'.
 } deriving (Show)

defPlainState :: PlainState d
defPlainState = PlainState
 { plainState_buffer          = mempty
 , plainState_bufferStart     = 0
 , plainState_bufferWidth     = 0
 , plainState_removableIndent = 0
 }

-- ** Type 'PlainInh'
data PlainInh = PlainInh
 { plainInh_width   :: !(Maybe Column)
 , plainInh_justify :: !Bool
 , plainInh_indent  :: !Width
 } deriving (Show)

defPlainInh :: PlainInh
defPlainInh = PlainInh
 { plainInh_width   = Nothing
 , plainInh_justify = False
 , plainInh_indent  = 0
 }

-- ** Type 'PlainFit'
-- | Double continuation to qualify the returned document
-- as fitting or overflowing the given 'plainInh_width'.
-- It's like @('Bool',d)@ in a normal style
-- (a non continuation-passing-style).
type PlainFit d = {-fits-}(d -> d) ->
                  {-overflow-}(d -> d) ->
                  d

-- ** Type 'PlainChunk'
data PlainChunk d
 =   PlainChunk_Ignored d
     -- ^ Ignored by the justification but kept in place.
     -- Used for instance to put ANSI sequences.
 |   PlainChunk_Word (Word d)
 |   PlainChunk_Spaces Width
     -- ^ 'spaces' preserved to be interleaved
     -- correctly with 'PlainChunk_Ignored'.
instance Show d => Show (PlainChunk d) where
        showsPrec p x =
                showParen (p>10) $
                case x of
                 PlainChunk_Ignored d ->
                        showString "Z " .
                        showsPrec 11 d
                 PlainChunk_Word (Word d) ->
                        showString "W " .
                        showsPrec 11 d
                 PlainChunk_Spaces s ->
                        showString "S " .
                        showsPrec 11 s
instance Lengthable d => Lengthable (PlainChunk d) where
        width = \case
         PlainChunk_Ignored{} -> 0
         PlainChunk_Word d -> width d
         PlainChunk_Spaces s -> s
        nullWidth = \case
         PlainChunk_Ignored{} -> True
         PlainChunk_Word d -> nullWidth d
         PlainChunk_Spaces s -> s == 0
instance From [SGR] d => From [SGR] (PlainChunk d) where
        from sgr = PlainChunk_Ignored (from sgr)

runPlainChunk :: Spaceable d => PlainChunk d -> d
runPlainChunk = \case
 PlainChunk_Ignored d -> d
 PlainChunk_Word (Word d) -> d
 PlainChunk_Spaces s -> spaces s

instance Semigroup d => Semigroup (Plain d) where
        Plain x <> Plain y = Plain $ \inh st k ->
                x inh st $ \(px,sx) ->
                        y inh sx $ \(py,sy) ->
                                k (px.py,sy)
instance Monoid d => Monoid (Plain d) where
        mempty = Plain $ \_inh st k -> k (id,st)
        mappend = (<>)
instance Spaceable d => Spaceable (Plain d) where
        newline = Plain $ \inh st k ->
                k(\next ->
                        (if plainInh_justify inh then joinLine inh st else mempty) <>
                        newline<>spaces (plainInh_indent inh)<>next
                 , st
                         { plainState_bufferStart      = plainInh_indent inh
                         , plainState_bufferWidth      = 0
                         , plainState_buffer           = mempty
                         }
                 )
        space = spaces 1
        spaces n = Plain $ \inh st@PlainState{..} k fits overflow ->
                let newWidth = plainState_bufferStart + plainState_bufferWidth + n in
                if plainInh_justify inh
                then
                        let newState =
                                case plainState_buffer of
                                 PlainChunk_Spaces s:bs -> st
                                         { plainState_buffer      = PlainChunk_Spaces (s+n):bs
                                         }
                                 _ -> st
                                         { plainState_buffer      = PlainChunk_Spaces n:plainState_buffer
                                         , plainState_bufferWidth = plainState_bufferWidth + 1
                                         }
                        in
                        case plainInh_width inh of
                         Just maxWidth | maxWidth < newWidth ->
                                overflow $ k (id{-(d<>)-}, newState) fits overflow
                         _ -> k (id{-(d<>)-}, newState) fits overflow
                else
                        let newState = st
                                 { plainState_bufferWidth = plainState_bufferWidth + n
                                 } in
                        case plainInh_width inh of
                         Just maxWidth | maxWidth < newWidth ->
                                overflow $ k ((spaces n <>), newState) fits fits
                         _ -> k ((spaces n <>), newState) fits overflow
instance (From (Word s) d, Semigroup d, Lengthable s) =>
         From (Word s) (Plain d) where
        from s = Plain $ \inh st@PlainState{..} k fits overflow ->
                let wordWidth = width s in
                if wordWidth <= 0
                then k (id,st) fits overflow
                else
                        let newBufferWidth = plainState_bufferWidth + wordWidth in
                        let newWidth = plainState_bufferStart + newBufferWidth in
                        if plainInh_justify inh
                        then
                                let newState = st
                                         { plainState_buffer =
                                                PlainChunk_Word (Word (from s)) :
                                                plainState_buffer
                                         , plainState_bufferWidth = newBufferWidth
                                         } in
                                case plainInh_width inh of
                                 Just maxWidth | maxWidth < newWidth ->
                                        overflow $ k (id, newState) fits overflow
                                 _ -> k (id, newState) fits overflow
                        else
                                let newState = st
                                         { plainState_bufferWidth = newBufferWidth
                                         } in
                                case plainInh_width inh of
                                 Just maxWidth | maxWidth < newWidth ->
                                        overflow $ k ((from s <>), newState) fits fits
                                 _ -> k ((from s <>), newState) fits overflow
instance (From (Word s) d, Lengthable s, Spaceable d, Splitable s) =>
         From (Line s) (Plain d) where
        from =
                mconcat .
                List.intersperse breakspace .
                (from <$>) .
                words .
                unLine
instance Spaceable d => Indentable (Plain d) where
        align p = (flushLine <>) $ Plain $ \inh st ->
                let currInd = plainState_bufferStart st + plainState_bufferWidth st in
                unPlain p inh{plainInh_indent=currInd} st
        incrIndent i p = Plain $ \inh ->
                unPlain p inh{plainInh_indent = plainInh_indent inh + i}
        setIndent i p = Plain $ \inh ->
                unPlain p inh{plainInh_indent=i}
        fill m p = Plain $ \inh0 st0 ->
                let col0 = plainState_bufferStart st0 + plainState_bufferWidth st0 in
                let p1 = Plain $ \inh1 st1 ->
                        let col1 = plainState_bufferStart st1 + plainState_bufferWidth st1 in
                        let w | col0 <= col1 = col1`minusNatural`col0
                              | otherwise    = col0`minusNatural`col1 in
                        unPlain
                         (if w<=m
                                then spaces (m`minusNatural`w)
                                else mempty)
                         inh1 st1
                in
                unPlain (p <> p1) inh0 st0
        breakfill m p = Plain $ \inh0 st0 ->
                let col0 = plainState_bufferStart st0 + plainState_bufferWidth st0 in
                let p1 = Plain $ \inh1 st1 ->
                        let col1 = plainState_bufferStart st1 + plainState_bufferWidth st1 in
                        let w | col0 <= col1 = col1`minusNatural`col0
                              | otherwise    = col0`minusNatural`col1 in
                        unPlain
                         (case w`compare`m of
                                 LT -> spaces (m`minusNatural`w)
                                 EQ -> mempty
                                 GT -> setIndent (col0 + m) newline)
                         inh1 st1
                in
                unPlain (p <> p1) inh0 st0
instance (Spaceable d, From (Word Char) d, From (Word String) d) => Listable (Plain d) where
        ul ds =
                catV $
                        (<$> ds) $ \d ->
                                from (Word '-')<>space<>flushLine<>align d<>flushLine
        ol ds =
                catV $ snd $
                        Fold.foldr
                         (\d (i, acc) ->
                                (pred i, (from i<>from (Word '.')<>space<>flushLine<>align d<>flushLine) : acc)
                         ) (Fold.length ds, []) ds
instance Spaceable d => Justifiable (Plain d) where
        justify p = (\x -> flushLine <> x <> flushLine) $ Plain $ \inh ->
                unPlain p inh{plainInh_justify=True}

-- | Commit 'plainState_buffer' upto there, so that it won't be justified.
flushLine :: Spaceable d => Plain d
flushLine = Plain $ \_inh st ok ->
        ok
         ( (joinPlainLine (collapseSpaces <$> List.reverse (plainState_buffer st)) <>)
         , st
                 { plainState_bufferStart = plainState_bufferStart st + plainState_bufferWidth st
                 , plainState_bufferWidth = 0
                 , plainState_buffer      = mempty
                 }
         )

collapseSpaces :: PlainChunk d -> PlainChunk d
collapseSpaces = \case
 PlainChunk_Spaces s -> PlainChunk_Spaces (if s > 0 then 1 else 0)
 x -> x

instance Spaceable d => Wrappable (Plain d) where
        setWidth w p = Plain $ \inh ->
                unPlain p inh{plainInh_width=w}
        breakpoint = Plain $ \inh st k fits overflow ->
                let newlineInd = plainInh_indent inh in
                k
                 ( id
                 , st
                         { plainState_removableIndent = newlineInd
                         }
                 )
                 fits
                 {-overflow-}(\_r ->
                        unPlain newline inh st k
                         fits
                         {-overflow-}(
                                if plainState_removableIndent st < newlineInd
                                then overflow
                                else fits
                         )
                 )
        breakspace = Plain $ \inh st k fits overflow ->
                let newlineInd = plainInh_indent inh in
                k
                 ( if plainInh_justify inh then id else (space <>)
                 , st
                         { plainState_buffer =
                                if plainInh_justify inh
                                then case plainState_buffer st of
                                         PlainChunk_Spaces s:bs -> PlainChunk_Spaces (s+1):bs
                                         bs -> PlainChunk_Spaces 1:bs
                                else plainState_buffer st
                         , plainState_bufferWidth      = plainState_bufferWidth st + 1
                         , plainState_removableIndent  = newlineInd
                         }
                 )
                 fits
                 {-overflow-}(\_r ->
                        unPlain newline inh st k
                         fits
                         {-overflow-}(
                                if plainState_removableIndent st < newlineInd
                                then overflow
                                else fits
                         )
                 )
        breakalt x y = Plain $ \inh st k fits overflow ->
                unPlain x inh st k fits
                 {-overflow-}(\_r ->
                        unPlain y inh st k fits overflow
                 )
-- String
instance (From (Word String) d, Spaceable d) =>
         From String (Plain d) where
        from =
                mconcat .
                List.intersperse newline .
                (from <$>) .
                lines
instance (From (Word String) d, Spaceable d) =>
         IsString (Plain d) where
        fromString = from
-- Text
instance (From (Word Text) d, Spaceable d) =>
         From Text (Plain d) where
        from =
                mconcat .
                List.intersperse newline .
                (from <$>) .
                lines
instance (From (Word TL.Text) d, Spaceable d) =>
         From TL.Text (Plain d) where
        from =
                mconcat .
                List.intersperse newline .
                (from <$>) .
                lines
-- Char
instance (From (Word Char) d, Spaceable d) =>
         From Char (Plain d) where
        from ' '  = breakspace
        from '\n' = newline
        from c    = from (Word c)


instance (From [SGR] d, Semigroup d) => From [SGR] (Plain d) where
        from sgr = Plain $ \inh st k ->
                if plainInh_justify inh
                then k (id, st {plainState_buffer = PlainChunk_Ignored (from sgr) : plainState_buffer st})
                else k ((from sgr <>), st)

joinLine ::
 Spaceable d =>
 PlainInh -> PlainState d -> d
joinLine PlainInh{..} PlainState{..} =
        case plainInh_width of
         Nothing -> joinPlainLine $ List.reverse plainState_buffer
         Just maxWidth ->
                if maxWidth < plainState_bufferStart
                || maxWidth < plainInh_indent
                then joinPlainLine $ List.reverse plainState_buffer
                else
                        let superfluousSpaces = Fold.foldr
                                 (\c acc ->
                                        acc + case c of
                                         PlainChunk_Ignored{} -> 0
                                         PlainChunk_Word{} -> 0
                                         PlainChunk_Spaces s -> s`minusNatural`(min 1 s))
                                 0 plainState_buffer in
                        let minBufferWidth =
                                -- NOTE: cap the spaces at 1,
                                -- to let justifyWidth decide where to add spaces.
                                plainState_bufferWidth`minusNatural`superfluousSpaces in
                        let justifyWidth =
                                -- NOTE: when minBufferWidth is not breakable,
                                -- the width of justification can be wider than
                                -- what remains to reach maxWidth.
                                max minBufferWidth $
                                        maxWidth`minusNatural`plainState_bufferStart
                        in
                        let wordCount = countWords plainState_buffer in
                        unLine $ padPlainLineInits justifyWidth $
                         (minBufferWidth,wordCount,List.reverse plainState_buffer)

-- | @('countWords' ps)@ returns the number of words in @(ps)@
-- clearly separated by spaces.
countWords :: [PlainChunk d] -> Natural
countWords = go False 0
 where
        go inWord acc = \case
         [] -> acc
         PlainChunk_Word{}:xs ->
                if inWord
                then go inWord acc xs
                else go True (acc+1) xs
         PlainChunk_Spaces s:xs
          | s == 0    -> go inWord acc xs
          | otherwise -> go False acc xs
         PlainChunk_Ignored{}:xs -> go inWord acc xs

-- | @('justifyPadding' a b)@ returns the padding lengths
-- to reach @(a)@ in @(b)@ pads,
-- using the formula: @(a '==' m'*'(q '+' q'+'1) '+' ('r'-'m)'*'(q'+'1) '+' (b'-'r'-'m)'*'q)@
-- where @(q+1)@ and @(q)@ are the two padding lengths used and @(m = min (b-r) r)@.
--
-- A simple implementation of 'justifyPadding' could be:
-- @
-- 'justifyPadding' a b =
--   'join' ('List.replicate' m [q,q'+'1])
--   <> ('List.replicate' (r'-'m) (q'+'1)
--   <> ('List.replicate' ((b'-'r)'-'m) q
--   where
--   (q,r) = a`divMod`b
--   m = 'min' (b-r) r
-- @
justifyPadding :: Natural -> Natural -> [Natural]
justifyPadding a b = go r (b-r) -- NOTE: r >= 0 && b-r >= 0 due to 'divMod'
        where
        (q,r) = a`quotRemNatural`b

        go 0  bmr = List.replicate (fromIntegral bmr) q    -- when min (b-r) r == b-r
        go rr 0   = List.replicate (fromIntegral rr) (q+1) -- when min (b-r) r == r
        go rr bmr = q:(q+1) : go (rr`minusNatural`1) (bmr`minusNatural`1)

padPlainLineInits ::
 Spaceable d =>
 Width -> (Natural, Natural, [PlainChunk d]) -> Line d
padPlainLineInits maxWidth (lineWidth,wordCount,line) = Line $
        if maxWidth <= lineWidth
                -- The gathered line reached or overreached the maxWidth,
                -- hence no padding id needed.
        || wordCount <= 1
                -- The case maxWidth <= lineWidth && wordCount == 1
                -- can happen if first word's length is < maxWidth
                -- but second word's len is >= maxWidth.
        then joinPlainLine line
        else
                -- Share the missing spaces as evenly as possible
                -- between the words of the line.
                padPlainLine line $ justifyPadding (maxWidth-lineWidth) (wordCount-1)

-- | Just concat 'PlainChunk's with no justification.
joinPlainLine :: Monoid d => Spaceable d => [PlainChunk d] -> d
joinPlainLine = mconcat . (runPlainChunk <$>)

-- | Interleave 'PlainChunk's with 'Width's from 'justifyPadding'.
padPlainLine :: Spaceable d => [PlainChunk d] -> [Width] -> d
padPlainLine = go
        where
        go (w:ws) lls@(l:ls) =
                case w of
                 PlainChunk_Spaces _s -> spaces (fromIntegral (l+1)) <> go ws ls
                 _ -> runPlainChunk w <> go ws lls
        go (w:ws) [] = runPlainChunk w <> go ws []
        go [] _ls = mempty