-- Copyright 2020 United States Government as represented by the Administrator
-- of the National Aeronautics and Space Administration. All Rights Reserved.
--
-- Disclaimers
--
-- Licensed under the Apache License, Version 2.0 (the "License"); you may
-- not use this file except in compliance with the License. You may obtain a
-- copy of the License at
--
--      https://www.apache.org/licenses/LICENSE-2.0
--
-- Unless required by applicable law or agreed to in writing, software
-- distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
-- WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
-- License for the specific language governing permissions and limitations
-- under the License.
--
-- | Generate Copilot struct definitions and instances from structs defined in
-- a C header file.
--
-- Working with Copilot structs requires three definitions: the datatype, a
-- @Struct@ instance, and a @Typed@ instance.
--
-- This module converts the C structs into 'Language.Copilot.CStruct.CStruct's,
-- and then converts those 'Language.Copilot.CStruct.CStruct's into Copilot
-- (i.e., Haskell) data type declarations and instance declarations. The result
-- is then printed to a file. This module makes use of
-- "Language.Trans.CStructs2Copilot", which does most of the work.
module Command.CStructs2Copilot
    ( cstructs2Copilot
    , ErrorCode
    )
  where

-- External imports: auxiliary
import Data.String.Extra as S ( safeReadFile )

-- Internal imports: auxiliary
import Command.Result ( Result (..) )
import Data.Location  ( Location (..) )

-- Internal imports: C parsing and AST
import qualified Language.C.AbsC as C ( TranslationUnit )
import qualified Language.C.ParC as C ( myLexer, pTranslationUnit )

-- Internal imports: transformation of C structs to Copilot structs
import Language.Trans.CStructs2Copilot ( cstructs2CopilotDecls )

-- | Generate Copilot struct definitions and instances from structs defined in
-- a C header file.
cstructs2Copilot :: FilePath -- ^ Path to a readable, valid C header file
                             -- containing struct definitions.
                 -> IO (Result ErrorCode)
cstructs2Copilot :: String -> IO (Result ErrorCode)
cstructs2Copilot String
fp = do
    Either String TranslationUnit
source <- String -> IO (Either String TranslationUnit)
parseCFile String
fp

    case TranslationUnit -> Either String [String]
cstructs2CopilotDecls (TranslationUnit -> Either String [String])
-> Either String TranslationUnit -> Either String [String]
forall (m :: * -> *) a b. Monad m => (a -> m b) -> m a -> m b
=<< Either String TranslationUnit
source of
      Right [String]
decls -> [String] -> IO ()
printDecls [String]
decls IO () -> IO (Result ErrorCode) -> IO (Result ErrorCode)
forall a b. IO a -> IO b -> IO b
forall (m :: * -> *) a b. Monad m => m a -> m b -> m b
>> Result ErrorCode -> IO (Result ErrorCode)
forall a. a -> IO a
forall (m :: * -> *) a. Monad m => a -> m a
return Result ErrorCode
forall a. Result a
Success
      Left String
msg    -> Result ErrorCode -> IO (Result ErrorCode)
forall a. a -> IO a
forall (m :: * -> *) a. Monad m => a -> m a
return (Result ErrorCode -> IO (Result ErrorCode))
-> Result ErrorCode -> IO (Result ErrorCode)
forall a b. (a -> b) -> a -> b
$ ErrorCode -> String -> Location -> Result ErrorCode
forall a. a -> String -> Location -> Result a
Error ErrorCode
ecCStructError String
msg (String -> Location
LocationFile String
fp)

  where

    -- Parse a C file, returning 'Left' with some message when there is a parse
    -- error.
    --
    parseCFile :: FilePath -> IO (Either String C.TranslationUnit)
    parseCFile :: String -> IO (Either String TranslationUnit)
parseCFile String
fp' = do
      Either String String
content <- String -> IO (Either String String)
S.safeReadFile String
fp'
      Either String TranslationUnit -> IO (Either String TranslationUnit)
forall a. a -> IO a
forall (m :: * -> *) a. Monad m => a -> m a
return (Either String TranslationUnit
 -> IO (Either String TranslationUnit))
-> Either String TranslationUnit
-> IO (Either String TranslationUnit)
forall a b. (a -> b) -> a -> b
$ [Token] -> Either String TranslationUnit
C.pTranslationUnit ([Token] -> Either String TranslationUnit)
-> (String -> [Token]) -> String -> Either String TranslationUnit
forall b c a. (b -> c) -> (a -> b) -> a -> c
. String -> [Token]
C.myLexer (String -> Either String TranslationUnit)
-> Either String String -> Either String TranslationUnit
forall (m :: * -> *) a b. Monad m => (a -> m b) -> m a -> m b
=<< Either String String
content

    -- Print several Haskell declarations to standard output.
    printDecls :: [ String ] -> IO ()
    printDecls :: [String] -> IO ()
printDecls = String -> IO ()
putStrLn (String -> IO ()) -> ([String] -> String) -> [String] -> IO ()
forall b c a. (b -> c) -> (a -> b) -> a -> c
. [String] -> String
unlines

-- * Error codes

-- | Encoding of reasons why the command can fail.
--
-- The error code used is 1 for user error.
type ErrorCode = Int

-- | Error: the C header file cannot be read due to the file being unreadable
-- or the format being incorrect.
ecCStructError :: ErrorCode
ecCStructError :: ErrorCode
ecCStructError = ErrorCode
1