module Linker where

import GrammarValue
import Data.Map
import Data.List (find)
import Data.Function (on)

data Rule = Rule {fatherCriterion, childCriterion :: Criterion, ruleWeight :: Double}
true = const True

type Criterion = GValue -> Bool

data Word = Word {wordStr :: String, wordPosition :: Int, wordGV :: GValue}
instance Show Word where
    show (Word str pos _) = str ++ ":" ++ show pos

instance Eq Word where
    (==) = (==) `on` wordPosition
instance Ord Word where
    (<) = (<) `on` wordPosition

type Sentence = [Word]

data JointType = Space | Mark | LeftBracket | RightBracket | SentenceBorder

data Joint = Joint {jointStr :: String, jointType :: JointType}

data Direction = DirLeft | DirRight
    deriving Eq

type Weight = Double

data Link = Link {
    linkFather, linkChild :: Word,
    linkDirection :: Direction,
    linkWeight :: Weight
    }

instance Show Link where
    show (Link f c d w) = "[" ++ (show $ wordPosition f) ++ (if d == DirRight then "->" else "<-") ++ (show $ wordPosition c) ++ ": " ++ show w ++ "]"

type LinkKey = (PartOfSpeech, PartOfSpeech)
type LinkDictionary = Map LinkKey [Rule]

type LinkGraph = Map (Word, Word) Link

possibleLink :: LinkDictionary -> Word -> Word -> Maybe Link
possibleLink dic father child | father == child = Nothing
                              | otherwise = do possibles <- Data.Map.lookup (posOf father, posOf child) dic
                                               match <- find (\rule -> fatherCriterion rule (wordGV father) && childCriterion rule (wordGV child)) possibles
                                               return $ Link father child DirRight (ruleWeight match)
                                where posOf = (gvPOS . wordGV)

possibleLinks :: LinkDictionary -> Sentence -> LinkGraph
possibleLinks dic sentence = possibleLinks' dic empty sentence sentence

possibleLinks' dic acc _ [] = acc
possibleLinks' dic acc sent (w:ws) = possibleLinks' dic (foldr tryInsert acc sent) sent ws
                                     where tryInsert word graph = case possibleLink dic word w of
                                                                       Nothing -> graph
                                                                       Just link -> insert (word, w) link graph

testLinks = fromList [((Verb, Noun), [Rule true true 1]), ((Noun, Noun), [Rule true true 1])]

testSentence = [Word "mama" 1 (GValue Noun Sg Nom TenseUndef), Word "romy" 2 (GValue Noun Sg Gen TenseUndef), Word "myla" 3 (GValue Verb Sg CasusUndef Past)]