module AST.Completion where

import Data.Text (Text)
import qualified Data.Text as Text
import Data.Maybe (listToMaybe)
import Data.List (isSubsequenceOf, nub)

import Duplo.Tree
import Duplo.Lattice
import Duplo.Pretty

import AST.Types
import AST.Scope
-- import AST.Parser
import Range
import Product

-- import Debug.Trace


complete
  :: ( Eq (Product xs)
     , Modifies (Product xs)
     , Contains Range xs
     , Contains [ScopedDecl] xs
     , Contains (Maybe Category) xs
     )
  => Range
  -> LIGO (Product xs)
  -> Maybe [Text]
complete r tree = do
  let l = spineTo (leq r . getElem) tree
  word <- listToMaybe l
  let scope   = getElem (extract word)
  let nameCat = getElem (extract word)
  return
    $ filter (isSubseqOf (ppToText word))
    $ nub
    $ map (ppToText . _sdName)
    $ filter (fits nameCat . catFromType)
    $ scope

isSubseqOf :: Text -> Text -> Bool
isSubseqOf l r = isSubsequenceOf (Text.unpack l) (Text.unpack r)

fits :: Maybe Category -> Category -> Bool
fits  Nothing _  = True
fits (Just c) c' = c == c'

catFromType :: ScopedDecl -> Category
catFromType = maybe Variable (either (const Variable) (const Type)) . _sdType