{-# LANGUAGE OverloadedStrings #-}

-- | Support for CPP.
module Ormolu.Processing.Cpp
  ( cppLines,
    eraseCppLines,
  )
where

import Data.IntSet (IntSet)
import Data.IntSet qualified as IntSet
import Data.Maybe (isJust)
import Data.Text (Text)
import Data.Text qualified as T

-- | State of the CPP processor.
data State
  = -- | Outside of CPP directives
    Outside
  | -- | In a conditional expression, with a positive nesting count
    InConditional Int
  | -- | In a continuation (after @\\@), but not in a conditional expression
    InContinuation
  deriving (State -> State -> Bool
(State -> State -> Bool) -> (State -> State -> Bool) -> Eq State
forall a. (a -> a -> Bool) -> (a -> a -> Bool) -> Eq a
$c== :: State -> State -> Bool
== :: State -> State -> Bool
$c/= :: State -> State -> Bool
/= :: State -> State -> Bool
Eq, Key -> State -> ShowS
[State] -> ShowS
State -> String
(Key -> State -> ShowS)
-> (State -> String) -> ([State] -> ShowS) -> Show State
forall a.
(Key -> a -> ShowS) -> (a -> String) -> ([a] -> ShowS) -> Show a
$cshowsPrec :: Key -> State -> ShowS
showsPrec :: Key -> State -> ShowS
$cshow :: State -> String
show :: State -> String
$cshowList :: [State] -> ShowS
showList :: [State] -> ShowS
Show)

-- | Return an 'IntSet' containing all lines which are affected by CPP.
cppLines :: Text -> IntSet
cppLines :: Text -> IntSet
cppLines Text
input = [Key] -> IntSet
IntSet.fromAscList ([Key] -> IntSet) -> [Key] -> IntSet
forall a b. (a -> b) -> a -> b
$ State -> [(Text, Key)] -> [Key]
forall {a}. State -> [(Text, a)] -> [a]
go State
Outside (Text -> [Text]
T.lines Text
input [Text] -> [Key] -> [(Text, Key)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [Key
1 ..])
  where
    go :: State -> [(Text, a)] -> [a]
go State
_ [] = []
    go State
state ((Text
line, a
i) : [(Text, a)]
ls)
      | (Text -> Bool) -> [Text] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any Text -> Bool
for [Text
"define ", Text
"include ", Text
"undef "] =
          a
i a -> [a] -> [a]
forall a. a -> [a] -> [a]
: State -> [(Text, a)] -> [a]
go State
contState [(Text, a)]
ls
      | (Text -> Bool) -> [Text] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any Text -> Bool
for [Text
"ifdef ", Text
"ifndef ", Text
"if "] =
          let state' :: State
state' = case State
state of
                InConditional Key
nc -> Key -> State
InConditional (Key
nc Key -> Key -> Key
forall a. Num a => a -> a -> a
+ Key
1)
                State
_ -> Key -> State
InConditional Key
1
           in a
i a -> [a] -> [a]
forall a. a -> [a] -> [a]
: State -> [(Text, a)] -> [a]
go State
state' [(Text, a)]
ls
      | Text -> Bool
for Text
"endif" =
          let state' :: State
state' = case State
state of
                InConditional Key
nc | Key
nc Key -> Key -> Bool
forall a. Ord a => a -> a -> Bool
> Key
1 -> Key -> State
InConditional (Key
nc Key -> Key -> Key
forall a. Num a => a -> a -> a
- Key
1)
                State
_ -> State
Outside
           in a
i a -> [a] -> [a]
forall a. a -> [a] -> [a]
: State -> [(Text, a)] -> [a]
go State
state' [(Text, a)]
ls
      | Bool
otherwise =
          let is :: [a]
is = case State
state of
                State
Outside -> []
                State
_ -> [a
i]
              state' :: State
state' = case State
state of
                State
InContinuation -> State
contState
                State
_ -> State
state
           in [a]
is [a] -> [a] -> [a]
forall a. Semigroup a => a -> a -> a
<> State -> [(Text, a)] -> [a]
go State
state' [(Text, a)]
ls
      where
        for :: Text -> Bool
for Text
directive = Maybe Text -> Bool
forall a. Maybe a -> Bool
isJust (Maybe Text -> Bool) -> Maybe Text -> Bool
forall a b. (a -> b) -> a -> b
$ do
          Text
s <- Text -> Text
T.stripStart (Text -> Text) -> Maybe Text -> Maybe Text
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> Text -> Text -> Maybe Text
T.stripPrefix Text
"#" Text
line
          Text -> Text -> Maybe Text
T.stripPrefix Text
directive Text
s
        contState :: State
contState =
          if Text
"\\" Text -> Text -> Bool
`T.isSuffixOf` Text
line Bool -> Bool -> Bool
&& Bool -> Bool
not Bool
inConditional
            then State
InContinuation
            else State
Outside
          where
            inConditional :: Bool
inConditional = case State
state of
              InConditional {} -> Bool
True
              State
_ -> Bool
False

-- | Replace all lines affected by CPP with blank lines.
eraseCppLines :: Text -> Text
eraseCppLines :: Text -> Text
eraseCppLines Text
input =
  [Text] -> Text
T.unlines ([Text] -> Text)
-> ([(Text, Key)] -> [Text]) -> [(Text, Key)] -> Text
forall b c a. (b -> c) -> (a -> b) -> a -> c
. ((Text, Key) -> Text) -> [(Text, Key)] -> [Text]
forall a b. (a -> b) -> [a] -> [b]
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap (Text, Key) -> Text
forall {a}. IsString a => (a, Key) -> a
eraseCpp ([(Text, Key)] -> Text) -> [(Text, Key)] -> Text
forall a b. (a -> b) -> a -> b
$ Text -> [Text]
T.lines Text
input [Text] -> [Key] -> [(Text, Key)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [Key
1 ..]
  where
    linesToErase :: IntSet
linesToErase = Text -> IntSet
cppLines Text
input
    eraseCpp :: (a, Key) -> a
eraseCpp (a
x, Key
i) =
      if Key
i Key -> IntSet -> Bool
`IntSet.member` IntSet
linesToErase
        then a
"\n"
        else a
x