module Builtins where

import Code
  ( Builtin(..)
  , Cho(..)
  , Datum(..)
  , Dereferenced(..)
  , Heap(..)
  , Instr(..)
  , Interp(..)
  , InterpFn
  , InterpFn
  , derefHeap
  , heapStruct
  )
import qualified Compiler as Co
import Control.Monad.IO.Class (liftIO)
import Control.Monad.Trans.Class (lift)
import Control.Monad.Trans.State.Lazy (get, gets, modify)
import Data.Functor.Identity (runIdentity)
import Data.List (intercalate)
import qualified Data.Map as M
import Env (PrlgEnv(..), findAtom, findStruct, prlgError)
import qualified IR
import Interpreter (backtrack)
import qualified Operators as O
import System.Console.Haskeline (getInputChar, outputStr, outputStrLn)

bi = Builtin

showTerm itos heap = runIdentity . heapStruct atom struct hrec heap
  where
    atom (Atom a) = pure $ itos M.! a
    atom VoidRef = pure "_"
    struct (Struct (IR.Id h _)) args =
      pure $ itos M.! h ++ "(" ++ intercalate "," args ++ ")"
    hrec (HeapRef hr) ref =
      pure $
      (if hr == ref
         then "_X"
         else "_Rec") ++
      show hr

printLocals :: InterpFn
printLocals = do
  scope <- gets (gvar . cur)
  heap <- gets (heap . cur)
  IR.StrTable _ _ itos <- gets strtable
  flip traverse (M.elems scope) $ \(ref, name) ->
    lift . outputStrLn $
    (maybe "_" id $ itos M.!? name) ++ " = " ++ showTerm itos heap ref
  return Nothing

promptRetry :: InterpFn
promptRetry = do
  last <- gets (null . cho)
  if last
    then return Nothing
    else promptRetry'

promptRetry' :: InterpFn
promptRetry' = do
  x <- lift $ getInputChar "? "
  case x of
    Just ';' -> backtrack
    _ -> return Nothing

write :: InterpFn
write
  --TODO: prlgError on write(Unbound)
 = do
  scope <- gets (hvar . cur)
  heap <- gets (heap . cur)
  IR.StrTable _ _ itos <- gets strtable
  lift . outputStr . showTerm itos heap . fst $ scope M.! 0
  return Nothing

nl :: InterpFn
nl = do
  lift $ outputStrLn ""
  return Nothing

writeln :: InterpFn
writeln = write >> nl

assertFact :: InterpFn
assertFact = do
  scope <- gets (hvar . cur)
  heap <- gets (heap . cur)
  case Co.compileGoal . Co.squashVars <$>
       Co.heapStructPrlgInt Nothing heap (fst $ scope M.! 0) of
    Just (U (Struct s):head) -> do
      addClause s $ head ++ [NoGoal]
      return Nothing
    _ -> prlgError "assert fact failure"

assertClause :: InterpFn
assertClause = do
  scope <- gets (hvar . cur)
  heap <- gets (heap . cur)
  commaId <- findStruct "," 2
  cut <- findAtom "!"
  case Co.squashVars . IR.CallI (IR.Id 0 0) <$>
       traverse (Co.heapStructPrlgInt Nothing heap . fst . (M.!) scope) [0, 1] of
    Just (IR.CallI (IR.Id 0 0) [hs, gs]) ->
      let (U (Struct s):cs) =
            Co.compileGoal hs ++ Co.seqGoals (Co.compileGoals commaId cut gs)
       in do addClause s cs
             return Nothing
    _ -> prlgError "assert clause failure"

retractall :: InterpFn
retractall = prlgError "no retractall yet"

call :: InterpFn
call = do
  ref <- gets (fst . (M.! 0) . hvar . cur)
  heap@(Heap _ hmap) <- gets (heap . cur)
  let exec base struct arity = do
        cur <- gets cur
        modify $ \s ->
          s
            { cur =
                cur
                  { gol =
                      [Call, Goal, U struct] ++
                      [U $ hmap M.! (base + i) | i <- [1 .. arity]] ++ gol cur
                  }
            }
        return Nothing
  case derefHeap heap ref of
    BoundRef addr struct@(Struct IR.Id {IR.arity = arity}) ->
      exec addr struct arity
    BoundRef addr (Atom a) ->
      exec addr (Struct IR.Id {IR.arity = 0, IR.str = a}) 0
    _ -> prlgError "not callable"

{- adding the builtins -}
addOp op = modify $ \s -> s {ops = op : ops s}

addClause struct code =
  modify $ \s ->
    s {defs = M.alter (Just . maybe [code] (\hs -> code : hs)) struct $ defs s}

addProcedure struct heads =
  modify $ \s -> s {defs = M.insert struct heads $ defs s}

addProc n a c = do
  sym <- findStruct n a
  addProcedure sym c

addBi0 n b = addProc n 0 [[Invoke $ bi b]]

addPrelude :: PrlgEnv ()
addPrelude = do
  pure undefined
  {- primitives -}
  addBi0 "true" (pure Nothing)
  addBi0 "fail" backtrack
  addOp $ O.xfx "=" 700
  addProc "=" 2 [[U (LocalRef 0 0), U (LocalRef 0 0), NoGoal]]
  {- clauses -}
  addOp $ O.xfy "," 1000
  addOp $ O.xfx ":-" 1200
  horn2 <- findStruct ":-" 2
  --addOp $ O.fx ":-" 1200
  addProc
    "assert"
    1
    [ [ U (Struct horn2)
      , U (LocalRef 0 0)
      , U (LocalRef 1 0)
      , Cut
      , Invoke (bi assertClause)
      ]
    , [U (LocalRef 0 0), Invoke (bi assertFact)]
    ]
  addProc "retractall" 1 [[U (LocalRef 0 0), Invoke (bi retractall)]]
  addProc "call" 1 [[U (LocalRef 0 0), Invoke (bi call)]]
  {- query tools -}
  addBi0 "print_locals" printLocals
  addBi0 "prompt_retry" promptRetry'
  addBi0 "query" (printLocals >> promptRetry)
  {- IO -}
  addProc "write" 1 [[U (LocalRef 0 0), Invoke (bi write)]]
  addProc "writeln" 1 [[U (LocalRef 0 0), Invoke (bi writeln)]]
  addBi0 "nl" nl
  {- debug -}
  addBi0 "interpreter_trace" (get >>= liftIO . print >> pure Nothing)