{-|
Module      : Verismith.Verilog.Mutate
Description : Functions to mutate the Verilog AST.
Copyright   : (c) 2018-2019, Yann Herklotz
License     : GPL-3
Maintainer  : yann [at] yannherklotz [dot] com
Stability   : experimental
Portability : POSIX

Functions to mutate the Verilog AST from "Verismith.Verilog.AST" to generate more
random patterns, such as nesting wires instead of creating new ones.
-}

{-# LANGUAGE FlexibleInstances #-}

module Verismith.Verilog.Mutate
    ( Mutate(..)
    , inPort
    , findAssign
    , idTrans
    , replace
    , nestId
    , nestSource
    , nestUpTo
    , allVars
    , instantiateMod
    , instantiateMod_
    , instantiateModSpec_
    , filterChar
    , initMod
    , makeIdFrom
    , makeTop
    , makeTopAssert
    , simplify
    , removeId
    , combineAssigns
    , combineAssigns_
    , declareMod
    , fromPort
    )
where

import           Control.Lens
import           Data.Foldable              (fold)
import           Data.Maybe                 (catMaybes, fromMaybe)
import           Data.Text                  (Text)
import qualified Data.Text                  as T
import           Verismith.Circuit.Internal
import           Verismith.Internal
import           Verismith.Verilog.AST
import           Verismith.Verilog.BitVec
import           Verismith.Verilog.CodeGen
import           Verismith.Verilog.Internal

class Mutate a where
    mutExpr :: (Expr -> Expr) -> a -> a

instance Mutate Identifier where
    mutExpr _ = id

instance Mutate Delay where
    mutExpr _ = id

instance Mutate Event where
    mutExpr f (EExpr e) = EExpr $ f e
    mutExpr _ a         = a

instance Mutate BinaryOperator where
    mutExpr _ = id

instance Mutate UnaryOperator where
    mutExpr _ = id

instance Mutate Expr where
    mutExpr f = f

instance Mutate ConstExpr where
    mutExpr _ = id

instance Mutate Task where
    mutExpr f (Task i e) = Task i $ fmap f e

instance Mutate LVal where
    mutExpr f (RegExpr a e) = RegExpr a $ f e
    mutExpr _ a             = a

instance Mutate PortDir where
    mutExpr _ = id

instance Mutate PortType where
    mutExpr _ = id

instance Mutate Range where
    mutExpr _ = id

instance Mutate Port where
    mutExpr _ = id

instance Mutate ModConn where
    mutExpr f (ModConn e)        = ModConn $ f e
    mutExpr f (ModConnNamed a e) = ModConnNamed a $ f e

instance Mutate Assign where
    mutExpr f (Assign a b c) = Assign a b $ f c

instance Mutate ContAssign where
    mutExpr f (ContAssign a e) = ContAssign a $ f e

instance Mutate Statement where
    mutExpr f (TimeCtrl d s)     = TimeCtrl d $ mutExpr f <$> s
    mutExpr f (EventCtrl e s)    = EventCtrl e $ mutExpr f <$> s
    mutExpr f (SeqBlock s)       = SeqBlock $ mutExpr f <$> s
    mutExpr f (BlockAssign a)    = BlockAssign $ mutExpr f a
    mutExpr f (NonBlockAssign a) = NonBlockAssign $ mutExpr f a
    mutExpr f (TaskEnable a)     = TaskEnable $ mutExpr f a
    mutExpr f (SysTaskEnable a)  = SysTaskEnable $ mutExpr f a
    mutExpr f (CondStmnt a b c) = CondStmnt (f a) (mutExpr f <$> b) $ mutExpr f <$> c
    mutExpr f (ForLoop a1 e a2 s) = ForLoop a1 e a2 $ mutExpr f s

instance Mutate Parameter where
    mutExpr _ = id

instance Mutate LocalParam where
    mutExpr _ = id

instance Mutate ModItem where
    mutExpr f (ModCA (ContAssign a e)) = ModCA . ContAssign a $ f e
    mutExpr f (ModInst a b conns)      = ModInst a b $ mutExpr f conns
    mutExpr f (Initial s)              = Initial $ mutExpr f s
    mutExpr f (Always s)               = Always $ mutExpr f s
    mutExpr _ d@Decl{}                 = d
    mutExpr _ p@ParamDecl{}            = p
    mutExpr _ l@LocalParamDecl{}       = l

instance Mutate ModDecl where
    mutExpr f (ModDecl a b c d e) = ModDecl (mutExpr f a) (mutExpr f b) (mutExpr f c) (mutExpr f d) (mutExpr f e)

instance Mutate Verilog where
    mutExpr f (Verilog a) = Verilog $ mutExpr f a

instance Mutate SourceInfo where
    mutExpr f (SourceInfo a b) = SourceInfo a $ mutExpr f b

instance Mutate a => Mutate [a] where
    mutExpr f a = mutExpr f <$> a

instance Mutate a => Mutate (Maybe a) where
    mutExpr f a = mutExpr f <$> a

instance Mutate a => Mutate (GenVerilog a) where
    mutExpr f (GenVerilog a) = GenVerilog $ mutExpr f a

-- | Return if the 'Identifier' is in a 'ModDecl'.
inPort :: Identifier -> ModDecl -> Bool
inPort i m = inInput
  where
    inInput =
        any (\a -> a ^. portName == i) $ m ^. modInPorts ++ m ^. modOutPorts

-- | Find the last assignment of a specific wire/reg to an expression, and
-- returns that expression.
findAssign :: Identifier -> [ModItem] -> Maybe Expr
findAssign i items = safe last . catMaybes $ isAssign <$> items
  where
    isAssign (ModCA (ContAssign val expr)) | val == i  = Just expr
                                           | otherwise = Nothing
    isAssign _ = Nothing

-- | Transforms an expression by replacing an Identifier with an
-- expression. This is used inside 'transformOf' and 'traverseExpr' to replace
-- the 'Identifier' recursively.
idTrans :: Identifier -> Expr -> Expr -> Expr
idTrans i expr (Id id') | id' == i  = expr
                        | otherwise = Id id'
idTrans _ _ e = e

-- | Replaces the identifier recursively in an expression.
replace :: Identifier -> Expr -> Expr -> Expr
replace = (transform .) . idTrans

-- | Nest expressions for a specific 'Identifier'. If the 'Identifier' is not
-- found, the AST is not changed.
--
-- This could be improved by instead of only using the last assignment to the
-- wire that one finds, to use the assignment to the wire before the current
-- expression. This would require a different approach though.
nestId :: Identifier -> ModDecl -> ModDecl
nestId i m
    | not $ inPort i m
    = let expr = fromMaybe def . findAssign i $ m ^. modItems
      in  m & get %~ replace i expr
    | otherwise
    = m
  where
    get = modItems . traverse . modContAssign . contAssignExpr
    def = Id i

-- | Replaces an identifier by a expression in all the module declaration.
nestSource :: Identifier -> Verilog -> Verilog
nestSource i src = src & getModule %~ nestId i

-- | Nest variables in the format @w[0-9]*@ up to a certain number.
nestUpTo :: Int -> Verilog -> Verilog
nestUpTo i src =
    foldl (flip nestSource) src $ Identifier . fromNode <$> [1 .. i]

allVars :: ModDecl -> [Identifier]
allVars m =
    (m ^.. modOutPorts . traverse . portName)
        <> (m ^.. modInPorts . traverse . portName)

-- $setup
-- >>> import Verismith.Verilog.CodeGen
-- >>> let m = (ModDecl (Identifier "m") [Port Wire False 5 (Identifier "y")] [Port Wire False 5 "x"] [] [])
-- >>> let main = (ModDecl "main" [] [] [] [])

-- | Add a Module Instantiation using 'ModInst' from the first module passed to
-- it to the body of the second module. It first has to make all the inputs into
-- @reg@.
--
-- >>> render $ instantiateMod m main
-- module main;
--   wire [(3'h4):(1'h0)] y;
--   reg [(3'h4):(1'h0)] x;
--   m m1(y, x);
-- endmodule
-- <BLANKLINE>
-- <BLANKLINE>
instantiateMod :: ModDecl -> ModDecl -> ModDecl
instantiateMod m main = main & modItems %~ ((out ++ regIn ++ [inst]) ++)
  where
    out = Decl Nothing <$> m ^. modOutPorts <*> pure Nothing
    regIn =
        Decl Nothing
            <$> (m ^. modInPorts & traverse . portType .~ Reg)
            <*> pure Nothing
    inst = ModInst (m ^. modId)
                   (m ^. modId <> (Identifier . showT $ count + 1))
                   conns
    count =
        length
            .   filter (== m ^. modId)
            $   main
            ^.. modItems
            .   traverse
            .   modInstId
    conns = uncurry ModConnNamed . fmap Id <$> zip (allVars m) (allVars m)

-- | Instantiate without adding wire declarations. It also does not count the
-- current instantiations of the same module.
--
-- >>> GenVerilog $ instantiateMod_ m
-- m m(y, x);
-- <BLANKLINE>
instantiateMod_ :: ModDecl -> ModItem
instantiateMod_ m = ModInst (m ^. modId) (m ^. modId) conns
  where
    conns =
        ModConn
            .   Id
            <$> (m ^.. modOutPorts . traverse . portName)
            ++  (m ^.. modInPorts . traverse . portName)

-- | Instantiate without adding wire declarations. It also does not count the
-- current instantiations of the same module.
--
-- >>> GenVerilog $ instantiateModSpec_ "_" m
-- m m(.y(y), .x(x));
-- <BLANKLINE>
instantiateModSpec_ :: Text -> ModDecl -> ModItem
instantiateModSpec_ outChar m = ModInst (m ^. modId) (m ^. modId) conns
  where
    conns   = zipWith ModConnNamed ids (Id <$> instIds)
    ids     = filterChar outChar (name modOutPorts) <> name modInPorts
    instIds = name modOutPorts <> name modInPorts
    name v = m ^.. v . traverse . portName

filterChar :: Text -> [Identifier] -> [Identifier]
filterChar t ids =
    ids & traverse . _Wrapped %~ (\x -> fromMaybe x . safe head $ T.splitOn t x)

-- | Initialise all the inputs and outputs to a module.
--
-- >>> GenVerilog $ initMod m
-- module m(y, x);
--   output wire [(3'h4):(1'h0)] y;
--   input wire [(3'h4):(1'h0)] x;
-- endmodule
-- <BLANKLINE>
-- <BLANKLINE>
initMod :: ModDecl -> ModDecl
initMod m = m & modItems %~ ((out ++ inp) ++)
  where
    out = Decl (Just PortOut) <$> (m ^. modOutPorts) <*> pure Nothing
    inp = Decl (Just PortIn) <$> (m ^. modInPorts) <*> pure Nothing

-- | Make an 'Identifier' from and existing Identifier and an object with a
-- 'Show' instance to make it unique.
makeIdFrom :: (Show a) => a -> Identifier -> Identifier
makeIdFrom a i = (i <>) . Identifier . ("_" <>) $ showT a

-- | Make top level module for equivalence verification. Also takes in how many
-- modules to instantiate.
makeTop :: Int -> ModDecl -> ModDecl
makeTop i m = ModDecl (m ^. modId) ys (m ^. modInPorts) modIt []
  where
    ys    = yPort . flip makeIdFrom "y" <$> [1 .. i]
    modIt = instantiateModSpec_ "_" . modN <$> [1 .. i]
    modN n =
        m & modId %~ makeIdFrom n & modOutPorts .~ [yPort (makeIdFrom n "y")]

-- | Make a top module with an assert that requires @y_1@ to always be equal to
-- @y_2@, which can then be proven using a formal verification tool.
makeTopAssert :: ModDecl -> ModDecl
makeTopAssert = (modItems %~ (++ [assert])) . makeTop 2
  where
    assert = Always . EventCtrl e . Just $ SeqBlock
        [TaskEnable $ Task "assert" [BinOp (Id "y_1") BinEq (Id "y_2")]]
    e = EPosEdge "clk"

-- | Provide declarations for all the ports that are passed to it. If they are
-- registers, it should assign them to 0.
declareMod :: [Port] -> ModDecl -> ModDecl
declareMod ports = initMod . (modItems %~ (fmap decl ports ++))
  where
    decl p@(Port Reg _ _ _) = Decl Nothing p (Just 0)
    decl p                  = Decl Nothing p Nothing

-- | Simplify an 'Expr' by using constants to remove 'BinaryOperator' and
-- simplify expressions. To make this work effectively, it should be run until
-- no more changes were made to the expression.
--
-- >>> GenVerilog . simplify $ (Id "x") + 0
-- x
--
-- >>> GenVerilog . simplify $ (Id "y") + (Id "x")
-- (y + x)
simplify :: Expr -> Expr
simplify (BinOp (Number (BitVec _ 1)) BinAnd e)   = e
simplify (BinOp e BinAnd (Number (BitVec _ 1)))   = e
simplify (BinOp (Number (BitVec _ 0)) BinAnd _)   = Number 0
simplify (BinOp _ BinAnd (Number (BitVec _ 0)))   = Number 0
simplify (BinOp e BinPlus (Number (BitVec _ 0)))  = e
simplify (BinOp (Number (BitVec _ 0)) BinPlus e)  = e
simplify (BinOp e BinMinus (Number (BitVec _ 0))) = e
simplify (BinOp (Number (BitVec _ 0)) BinMinus e) = e
simplify (BinOp e BinTimes (Number (BitVec _ 1))) = e
simplify (BinOp (Number (BitVec _ 1)) BinTimes e) = e
simplify (BinOp _ BinTimes (Number (BitVec _ 0))) = Number 0
simplify (BinOp (Number (BitVec _ 0)) BinTimes _) = Number 0
simplify (BinOp e BinOr (Number (BitVec _ 0)))    = e
simplify (BinOp (Number (BitVec _ 0)) BinOr e)    = e
simplify (BinOp e BinLSL (Number (BitVec _ 0)))   = e
simplify (BinOp (Number (BitVec _ 0)) BinLSL e)   = e
simplify (BinOp e BinLSR (Number (BitVec _ 0)))   = e
simplify (BinOp (Number (BitVec _ 0)) BinLSR e)   = e
simplify (BinOp e BinASL (Number (BitVec _ 0)))   = e
simplify (BinOp (Number (BitVec _ 0)) BinASL e)   = e
simplify (BinOp e BinASR (Number (BitVec _ 0)))   = e
simplify (BinOp (Number (BitVec _ 0)) BinASR e)   = e
simplify (UnOp UnPlus e)                          = e
simplify e                                        = e

-- | Remove all 'Identifier' that do not appeare in the input list from an
-- 'Expr'. The identifier will be replaced by @1'b0@, which can then later be
-- simplified further.
--
-- >>> GenVerilog . removeId ["x"] $ Id "x" + Id "y"
-- (x + (1'h0))
removeId :: [Identifier] -> Expr -> Expr
removeId i = transform trans
  where
    trans (Id ident) | ident `notElem` i = Number 0
                     | otherwise         = Id ident
    trans e = e

combineAssigns :: Port -> [ModItem] -> [ModItem]
combineAssigns p a =
    a
        <> [ ModCA
             .   ContAssign (p ^. portName)
             .   UnOp UnXor
             .   fold
             $   Id
             <$> assigns
           ]
    where assigns = a ^.. traverse . modContAssign . contAssignNetLVal

combineAssigns_ :: Bool -> Port -> [Port] -> ModItem
combineAssigns_ comb p ps =
    ModCA
        .   ContAssign (p ^. portName)
        .   (if comb then UnOp UnXor else id)
        .   fold
        $   Id
        <$> ps
        ^.. traverse
        .   portName

fromPort :: Port -> Identifier
fromPort (Port _ _ _ i) = i