{-# LANGUAGE DuplicateRecordFields #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE OverloadedStrings #-}
{-# OPTIONS_GHC -fno-warn-orphans #-}
module Hdoc.DTC.Index where

import Control.Category
import Control.Monad (Monad(..))
import Data.Bool
import Data.Char (Char)
import Data.Default.Class (Default(..))
import Data.Foldable (Foldable(..), concat)
import Data.Function (($), const)
import Data.Functor ((<$>))
import Data.Map.Strict (Map)
import Data.Maybe (Maybe(..), maybe, listToMaybe)
import Data.Monoid (Monoid(..))
import Data.Semigroup (Semigroup(..))
import Data.Sequence ((|>))
import Data.TreeMap.Strict (TreeMap(..))
import Data.TreeSeq.Strict (Tree(..), tree0)
import qualified Data.Char as Char
import qualified Data.List as List
import qualified Data.Map.Strict as Map
import qualified Data.Sequence as Seq
import qualified Data.Strict.Maybe as Strict
import qualified Data.Text.Lazy as TL
import qualified Data.TreeMap.Strict as TreeMap
-- import qualified Data.TreeSeq.Strict as TreeSeq

import Hdoc.DTC.Document
import qualified Hdoc.XML as XML

-- * Type 'PathWord'
type PathWord = TreeMap.Path Word

pathFromWords :: Words -> Maybe PathWord
pathFromWords ws =
	case ws >>= unSpace of
	 p:ps | not (TL.null p) -> Just (TreeMap.path p ps)
	 _ -> Nothing
	where
	unSpace = \case
	 Space  -> []
	 Word w -> [w]

-- * Type 'Irefs'
type Irefs = TreeMap Word [Anchor]

irefsOfTerms :: Terms -> Irefs
irefsOfTerms = TreeMap.fromList const . (>>= f) . concat
	where
	f [] = []
	f ws = maybe [] (\p -> [(p,[])]) $ pathFromWords ws

indexifyWords :: XML.Pos -> Irefs -> Words -> (Irefs, Plain)
indexifyWords section = go mempty
	where
	go :: Plain -> Irefs -> Words -> (Irefs, Plain)
	go acc irefs inp =
		case inp of
		 [] -> (irefs, acc)
		 Space : next ->
			go (acc |> tree0 (PlainText " ")) irefs next
		 Word w : next ->
			case goWords irefs [] inp of
			 Nothing -> go (acc |> tree0 (PlainText w)) irefs next
			 Just (anchor, ls, ns, rs) ->
				let iref_term = List.reverse ls in
				let lines = Seq.fromList $ tree0 . PlainText . plainifyWord <$> iref_term in
				go (acc |> Tree PlainIref
				 { iref_term
				 , iref_anchor=Just anchor
				 } lines) rs ns
	goWords ::
	 Irefs ->
	 Words -> Words ->
	 Maybe (Anchor, Words, Words, Irefs)
	goWords m@(TreeMap irefsByWord) prev inp =
		case inp of
		 [] -> Nothing
		 curr@Space : next -> goWords m (curr:prev) next
		 curr@(Word w) : next ->
			case Map.lookup w irefsByWord of
			 Nothing -> Nothing
			 Just nod@TreeMap.Node{..} ->
				let prev' = curr:prev in
				case node_value of
				 Strict.Nothing
				  | null node_descendants -> Nothing
				  | otherwise ->
					(<$> goWords node_descendants prev' next) $ \(anch, ls, ns, rs) ->
						(anch, ls, ns, TreeMap $
							Map.insert w nod{TreeMap.node_descendants = rs} irefsByWord)
				 Strict.Just anchs ->
					case goWords node_descendants prev' next of
					 Nothing ->
						let anch = Anchor
							 { anchor_count   = maybe def (succNat1 . anchor_count) $ listToMaybe anchs
							 , anchor_section = section } in
						Just (anch, prev', next, TreeMap $
							Map.insert w nod{TreeMap.node_value = Strict.Just $ anch:anchs} irefsByWord)
					 Just (anch, ls, ns, rs) ->
						Just (anch, ls, ns, TreeMap $
							Map.insert w nod{TreeMap.node_descendants = rs} irefsByWord)

wordify :: TL.Text -> Words
wordify = List.reverse . go []
	where
	go :: Words -> TL.Text -> Words
	go acc t =
		case TL.span Char.isAlphaNum t of
		 ("",_) ->
			case TL.span Char.isSpace t of
			 ("",_) ->
				case TL.uncons t of
				 Nothing -> acc
				 Just (c,r) -> go (Word (TL.singleton c) : acc) r
			 (_s,r) -> go (Space : acc) r
		 (w,r) -> go (Word w : acc) r

plainifyWord :: WordOrSpace -> TL.Text
plainifyWord = \case
 Word w -> w
 Space  -> " "

plainifyWords :: Words -> TL.Text
plainifyWords = TL.concat . (plainifyWord <$>)

termsByChar :: Terms -> Map Char Terms
termsByChar =
	foldr (\aliases acc ->
		case aliases of
		 (Word w:_):_ | not (TL.null w) ->
			Map.insertWith (<>)
			 (Char.toUpper $ TL.index w 0)
			 [aliases] acc
		 _ -> acc
		) Map.empty