-- ---------------------------------------------------------------------------
--- This library defines various I/O actions to read Curry programs and
--- transform them into the AbstractCurry representation and to write
--- AbstractCurry files.
---
--- Assumption: an abstract Curry program is stored in file with
--- extension `.acy` in the subdirectory `.curry`
---
--- @author Michael Hanus, Bjoern Peemoeller, Jan Tikovsky, Finn Teegen
--- @version August 2024
-- ---------------------------------------------------------------------------

module AbstractCurry.Files where

import Data.Char            ( isSpace )
import System.Directory     ( doesFileExist, getModificationTime
                            , findFileWithSuffix, getFileWithSuffix )
import System.FilePath      ( takeFileName, (</>), (<.>) )
import System.CurryPath     ( getLoadPathForModule, inCurrySubdir
                            , lookupModuleSourceInLoadPath, stripCurrySuffix )
import System.FrontendExec
import ReadShowTerm

import AbstractCurry.Select ( imports )
import AbstractCurry.Types

-- ---------------------------------------------------------------------------
--- I/O action which parses a Curry program and returns the corresponding
--- typed Abstract Curry program.
--- Thus, the argument is the file name without suffix ".curry"
--- or ".lcurry") and the result is a Curry term representing this
--- program.
readCurry :: String -> IO CurryProg
readCurry prog = readCurryWithParseOptions prog (setQuiet True defaultParams)

--- Read an AbstractCurry file with all its imports.
--- @param modname - Module name or file name of Curry module
--- @return a list of curry programs, having the AbstractCurry file as head.
readCurryWithImports :: String -> IO [CurryProg]
readCurryWithImports modname = collect [] [modname]
 where
  collect _        []     = return []
  collect imported (m:ms)
    | m `elem` imported   = collect imported ms
    | otherwise           = do
      p <- readCurry m
      ps <- collect (m:imported) (ms ++ imports p)
      return (p:ps)

tryReadCurryWithImports :: String -> IO (Either [String] [CurryProg])
tryReadCurryWithImports modname = collect [] [modname]
 where
  collect _        []     = return (Right [])
  collect imported (m:ms)
    | m `elem` imported   = collect imported ms
    | otherwise           = do
      eProg <- tryReadCurryFile m
      case eProg of
        Left err                          -> return (Left [err])
        Right prog@(CurryProg _ is _ _ _ _ _ _) -> do
          results <- collect (m:imported) (ms ++ is)
          return (either Left (Right . (prog :)) results)

tryReadCurryFile :: String -> IO (Either String CurryProg)
tryReadCurryFile m = do
  mbSrc <- lookupModuleSourceInLoadPath m
  case mbSrc of
    Nothing      -> cancel $ "Source module '" ++ m ++ "' not found"
    Just (_,srcFile) -> do
      callFrontendWithParams ACY (setQuiet True defaultParams) m
      mbFn <- getLoadPathForModule m >>=
              findFileWithSuffix (abstractCurryFileName m) [""]
      case mbFn of
        Nothing -> cancel $ "AbstractCurry module '" ++ m ++ "' not found"
        Just fn -> do
          ctime <- getModificationTime srcFile
          ftime <- getModificationTime fn
          if ctime > ftime
            then cancel $ "Source file '" ++ srcFile
                    ++ "' is newer than AbstractCurry file '" ++ fn ++ "'"
            else do
              mbProg <- tryParse fn
              case mbProg of
                Left  err -> cancel err
                Right p   -> return (Right p)
 where cancel str = return (Left str)

--- Try to parse an AbstractCurry file.
--- @param fn  - file name of AbstractCurry file
tryParse :: String -> IO (Either String CurryProg)
tryParse fn = do
  exists <- doesFileExist fn
  if not exists
    then cancel $ "AbstractCurry file '" ++ fn ++ "' does not exist"
    else do
      src <- readFile fn
      let (line1, lines) = break (=='\n') src
      if line1 /= "{- "++version++" -}"
        then cancel $ "Could not parse AbstractCurry file '" ++ fn
                   ++ "': incompatible versions"
        else
          case readsUnqualifiedTerm ["AbstractCurry.Types","Prelude"] lines of
            [(p,tl)]  | all isSpace tl -> return (Right p)
            _ -> cancel $ "Could not parse AbstractCurry file '" ++ fn
                          ++ "': no parse"
 where cancel str = return (Left str)

--- I/O action which parses a Curry program and returns the corresponding
--- untyped AbstractCurry program.
--- The argument is the file name without suffix ".curry"
--- or ".lcurry") and the result is a Curry term representing this
--- program.
--- In an untyped AbstractCurry program, the type signatures
--- of operations are the type signatures provided by the programmer
--- (and not the type signatures inferred by the front end).
--- If the programmer has not provided an explicit type signature,
--- the function declaration contains the type `(CTCons ("Prelude","untyped")`.
readUntypedCurry :: String -> IO CurryProg
readUntypedCurry prog =
  readUntypedCurryWithParseOptions prog (setQuiet True defaultParams)

--- I/O action which reads a typed Curry program from a file (with extension
--- ".acy") with respect to some parser options.
--- This I/O action is used by the standard action 'readCurry'.
--- It is currently predefined only in Curry2Prolog.
--- @param progfile - the program file name (without suffix ".curry")
--- @param options - parameters passed to the front end

readCurryWithParseOptions :: String -> FrontendParams -> IO CurryProg
readCurryWithParseOptions progname options = do
  let modname = takeFileName progname
  mbsrc <- lookupModuleSourceInLoadPath progname
  case mbsrc of
    Nothing -> do -- no source file, try to find AbstractCurry file in load path:
      loadpath <- getLoadPathForModule progname
      filename <- getFileWithSuffix (abstractCurryFileName modname) [""] loadpath
      readAbstractCurryFile filename
    Just (dir,_) -> do
      callFrontendWithParams ACY options progname
      readAbstractCurryFile (abstractCurryFileName (dir </> modname))

--- I/O action which reads an untyped Curry program from a file (with extension
--- ".uacy") with respect to some parser options. For more details
--- see function 'readCurryWithParseOptions'
--- In an untyped AbstractCurry program, the type signatures
--- of operations are the type signatures provided by the programmer
--- (and not the type signatures inferred by the front end).
--- If the programmer has not provided an explicit type signature,
--- the function declaration contains the type `(CTCons ("Prelude","untyped")`.
readUntypedCurryWithParseOptions :: String -> FrontendParams -> IO CurryProg
readUntypedCurryWithParseOptions progname options = do
  let modname = takeFileName progname
  mbsrc <- lookupModuleSourceInLoadPath progname
  case mbsrc of
    Nothing -> do -- no source file, try to find AbstractCurry file in load path:
      loadpath <- getLoadPathForModule progname
      filename <- getFileWithSuffix (untypedAbstractCurryFileName modname) [""]
                                loadpath
      readAbstractCurryFile filename
    Just (dir,_) -> do
      callFrontendWithParams UACY options progname
      readAbstractCurryFile (untypedAbstractCurryFileName (dir </> modname))

--- Transforms a name of a Curry program (with or without suffix ".curry"
--- or ".lcurry") into the name of the file containing the
--- corresponding AbstractCurry program.
abstractCurryFileName :: String -> String
abstractCurryFileName prog = inCurrySubdir (stripCurrySuffix prog) <.> "acy"

--- Transforms a name of a Curry program (with or without suffix ".curry"
--- or ".lcurry") into the name of the file containing the
--- corresponding untyped AbstractCurry program.
untypedAbstractCurryFileName :: String -> String
untypedAbstractCurryFileName prog =
  inCurrySubdir (stripCurrySuffix prog) <.> "uacy"

--- I/O action which reads an AbstractCurry program from a file in ".acy"
--- format. In contrast to <CODE>readCurry</CODE>, this action does not parse
--- a source program. Thus, the argument must be the name of an existing
--- file (with suffix ".acy") containing an AbstractCurry program in ".acy"
--- format and the result is a Curry term representing this program.
--- It is currently predefined only in Curry2Prolog.
readAbstractCurryFile :: String -> IO CurryProg
readAbstractCurryFile filename = do
  exacy <- doesFileExist filename
  if exacy
   then readExistingACY filename
   else do let subdirfilename = inCurrySubdir filename
           exdiracy <- doesFileExist subdirfilename
           if exdiracy
            then readExistingACY subdirfilename
            else error ("EXISTENCE ERROR: AbstractCurry file '"++filename++
                        "' does not exist")
 where
   readExistingACY fname = do
     filecontents <- readFile fname
     let (line1,lines) = break (=='\n') filecontents
     if line1 == "{- "++version++" -}"
      then return (readUnqualifiedTerm ["AbstractCurry.Types","Prelude"] lines)
      else error $ "AbstractCurry: incompatible file found: "++fname

--- Tries to read an AbstractCurry file and returns
---
---  * Left err  , where err specifies the error occurred
---  * Right prog, where prog is the AbstractCurry program
tryReadACYFile :: String -> IO (Maybe CurryProg)
tryReadACYFile fn = do
  exists <- doesFileExist fn
  if exists
    then tryRead fn
    else do
      let fn' = inCurrySubdir fn
      exists' <- doesFileExist fn'
      if exists'
        then tryRead fn'
        else cancel
 where
  tryRead file = do
    src <- readFile file
    let (line1,lines) = break (=='\n') src
    if line1 /= "{- "++version++" -}"
      then error $ "AbstractCurry: incompatible file found: "++fn
      else
        case readsUnqualifiedTerm ["AbstractCurry.Types","Prelude"] lines of
          []       -> cancel
          [(p,tl)] -> if all isSpace tl
                        then return $ Just p
                        else cancel
          _        -> cancel
  cancel = return Nothing

--- Writes an AbstractCurry program into a file in ".acy" format.
--- The first argument must be the name of the target file
--- (with suffix ".acy").
writeAbstractCurryFile :: String -> CurryProg -> IO ()
writeAbstractCurryFile file prog = writeFile file (showTerm prog)

------------------------------------------------------------------------------