module World.Lattice
  ( LatticeCell (..)
  , Lattice
  , LatticeRule
  , updateLattice
  , applyLatticeProposals
  ) where


import World.Types 
  (Combinable (..)
  , LatticeProposal (..)
  , LatticePropList (..)
  )


data LatticeCell a b = LatticeCell { kind :: a, flags :: b } deriving (Show, Eq)
type Lattice a b = [[LatticeCell a b]]
type LatticeRule a b = Lattice a b -> Int -> Int -> LatticeCell a b


updateLattice :: (Enum a) => Lattice a b -> [LatticeRule a b] -> Lattice a b
updateLattice lattice rules =
  let
    mapRow = \(row, y) -> map 
      (\((LatticeCell k _), x) ->
        let rule = rules !! (fromEnum k)
        in rule lattice x y
      )
      (zip row [0..])
  in map mapRow (zip lattice [0..])


applyLatticeProposals :: (Combinable b) => Lattice a b -> LatticePropList a b -> Lattice a b
applyLatticeProposals lattice (LatticePropList props) =
  let
    update list idx new =
      let (front, _:back) = splitAt idx list in front ++ (new:back)
    applyProp l (LatticeProposal (x, y) from to flags) = 
      let
        row = l !! y
        cell = row !! x
        cell' = LatticeCell to (combine flags $ cellFlags cell)
      in
        update l y (update row x cell')

    -- replace each cell's flags with the identity
    lattice' = map
      (\row -> map
        (\cell -> cell { flags = identity } )
        row
      )
      lattice
  in
    foldl applyProp lattice' props