{-# LANGUAGE TupleSections #-}
{-# LANGUAGE ViewPatterns #-}
{-# LANGUAGE RecordWildCards #-}
module Refact.Fixity (applyFixities) where

import SrcLoc

import Refact.Utils
import BasicTypes (Fixity(..), defaultFixity, compareFixity, negateFixity, FixityDirection(..), SourceText(..))
import HsExpr
import RdrName
import HsExtension
import OccName
import Data.Generics hiding (Fixity)
import Data.Maybe
import Language.Haskell.GHC.ExactPrint.Types hiding (GhcPs, GhcTc, GhcRn)

import Control.Monad.State
import qualified Data.Map as Map
import Data.Tuple

-- | Rearrange infix expressions to account for fixity.
-- The set of fixities is wired in and includes all fixities in base.
applyFixities :: Anns -> Module -> (Anns, Module)
applyFixities as m = let (as', m') = swap $ runState (everywhereM (mkM expFix) m) as
                     in (as', m') --error (showAnnData as 0 m ++ showAnnData as' 0 m')

expFix :: LHsExpr GhcPs -> M (LHsExpr GhcPs)
expFix (L loc (OpApp _ l op r)) =
  mkOpAppRn baseFixities loc l op (findFixity baseFixities op) r

expFix e = return e

getIdent :: Expr -> String
getIdent (unLoc -> HsVar _ (L _ n)) = occNameString . rdrNameOcc $ n
getIdent _ = error "Must be HsVar"


moveDelta :: AnnKey -> AnnKey -> M ()
moveDelta old new = do
  a@Ann{..} <- gets (fromMaybe annNone . Map.lookup old)
  modify (Map.insert new (annNone { annEntryDelta = annEntryDelta, annPriorComments = annPriorComments }))
  modify (Map.insert old (a { annEntryDelta = DP (0,0), annPriorComments = []}))

---------------------------
-- Modified from GHC Renamer
mkOpAppRn ::
             [(String, Fixity)]
          -> SrcSpan
          -> LHsExpr GhcPs              -- Left operand; already rearrange
          -> LHsExpr GhcPs -> Fixity            -- Operator and fixity
          -> LHsExpr GhcPs                      -- Right operand (not an OpApp, but might
                                                -- be a NegApp)
          -> M (LHsExpr GhcPs)

-- (e11 `op1` e12) `op2` e2
mkOpAppRn fs loc e1@(L _ (OpApp x1 e11 op1 e12)) op2 fix2 e2
  | nofix_error
  = return $ L loc (OpApp noExt e1 op2 e2)

  | associate_right = do
    new_e <- mkOpAppRn fs loc' e12 op2 fix2 e2
    moveDelta (mkAnnKey e12) (mkAnnKey new_e)
    return $ L loc (OpApp x1 e11 op1 new_e)
  where
    loc'= combineLocs e12 e2
    fix1 = findFixity fs op1
    (nofix_error, associate_right) = compareFixity fix1 fix2

---------------------------
--      (- neg_arg) `op` e2
mkOpAppRn fs loc e1@(L _ (NegApp _ neg_arg neg_name)) op2 fix2 e2
  | nofix_error
  = return (L loc (OpApp noExt e1 op2 e2))

  | associate_right
  = do
      new_e <- mkOpAppRn fs loc' neg_arg op2 fix2 e2
      moveDelta (mkAnnKey neg_arg) (mkAnnKey new_e)
      let res = L loc (NegApp noExt new_e neg_name)
          key = mkAnnKey res
          ak  = AnnKey loc (CN "OpApp")
      opAnn <- gets (fromMaybe annNone . Map.lookup ak)
      negAnns <- gets (fromMaybe annNone . Map.lookup (mkAnnKey e1))
      modify (Map.insert key (annNone { annEntryDelta = annEntryDelta opAnn, annsDP = annsDP negAnns }))
      return res

  where
    loc' = combineLocs neg_arg e2
    (nofix_error, associate_right) = compareFixity negateFixity fix2

---------------------------
--      e1 `op` - neg_arg
mkOpAppRn _ loc e1 op1 fix1 e2@(L _ (NegApp {}))     -- NegApp can occur on the right
  | not associate_right                 -- We *want* right association
  = return $ L loc (OpApp noExt e1 op1 e2)
  where
    (_, associate_right) = compareFixity fix1 negateFixity

---------------------------
--      Default case
mkOpAppRn _ loc e1 op _fix e2                  -- Default case, no rearrangment
  = return $ L loc (OpApp noExt e1 op e2)

findFixity :: [(String, Fixity)] -> Expr -> Fixity
findFixity fs r = askFix fs (getIdent r)

askFix :: [(String, Fixity)] -> String -> Fixity
askFix xs = \k -> lookupWithDefault defaultFixity k xs
    where
        lookupWithDefault def_v k mp1 = fromMaybe def_v $ lookup k mp1



-- | All fixities defined in the Prelude.
preludeFixities :: [(String, Fixity)]
preludeFixities = concat
    [infixr_ 9  ["."]
    ,infixl_ 9  ["!!"]
    ,infixr_ 8  ["^","^^","**"]
    ,infixl_ 7  ["*","/","quot","rem","div","mod",":%","%"]
    ,infixl_ 6  ["+","-"]
    ,infixr_ 5  [":","++"]
    ,infix_  4  ["==","/=","<","<=",">=",">","elem","notElem"]
    ,infixr_ 3  ["&&"]
    ,infixr_ 2  ["||"]
    ,infixl_ 1  [">>",">>="]
    ,infixr_ 1  ["=<<"]
    ,infixr_ 0  ["$","$!","seq"]
    ]

-- | All fixities defined in the base package.
--
--   Note that the @+++@ operator appears in both Control.Arrows and
--   Text.ParserCombinators.ReadP. The listed precedence for @+++@ in
--   this list is that of Control.Arrows.
baseFixities :: [(String, Fixity)]
baseFixities = preludeFixities ++ concat
    [infixl_ 9 ["!","//","!:"]
    ,infixl_ 8 ["shift","rotate","shiftL","shiftR","rotateL","rotateR"]
    ,infixl_ 7 [".&."]
    ,infixl_ 6 ["xor"]
    ,infix_  6 [":+"]
    ,infixl_ 5 [".|."]
    ,infixr_ 5 ["+:+","<++","<+>"] -- fixity conflict for +++ between ReadP and Arrow
    ,infix_  5 ["\\\\"]
    ,infixl_ 4 ["<$>","<$","<*>","<*","*>","<**>"]
    ,infix_  4 ["elemP","notElemP"]
    ,infixl_ 3 ["<|>"]
    ,infixr_ 3 ["&&&","***"]
    ,infixr_ 2 ["+++","|||"]
    ,infixr_ 1 ["<=<",">=>",">>>","<<<","^<<","<<^","^>>",">>^"]
    ,infixl_ 0 ["on"]
    ,infixr_ 0 ["par","pseq"]
    ]

infixr_, infixl_, infix_ :: Int -> [String] -> [(String,Fixity)]
infixr_ = fixity InfixR
infixl_ = fixity InfixL
infix_  = fixity InfixN

-- Internal: help function for the above definitions.
fixity :: FixityDirection -> Int -> [String] -> [(String, Fixity)]
fixity a p = map (,Fixity (SourceText "") p a)