# Modules

Basic implementation of a module system including tests.

src/FileEval.hs

@@ -1,30 +1,150 @@
 module FileEval where
 
 import Eval
+import Lexer
 import Parser
 import Research
 
+import Data.List       (partition)
+import Control.Monad   (foldM)
 import System.IO
 
 import qualified Data.Map as Map
+import qualified Data.Set as Set
 
 evaluateFileResult :: FilePath -> IO T
 evaluateFileResult filePath = do
   contents <- readFile filePath
-  let asts = parseTricu contents
-  let finalEnv = evalTricu Map.empty asts
-  case Map.lookup "main" finalEnv of
-    Just finalResult -> return finalResult
-    Nothing -> errorWithoutStackTrace "No `main` function detected"
+  let tokens = lexTricu contents
+  let moduleName = case parseProgram tokens of
+        Right ((SModule name) : _) -> name
+        _                          -> ""
+  case parseProgram tokens of
+    Left err -> errorWithoutStackTrace (handleParseError err)
+    Right _ -> do
+      ast <- preprocessFile filePath
+      let finalEnv = mainAlias moduleName $ evalTricu Map.empty ast
+      case Map.lookup "main" finalEnv of
+        Just finalResult -> return finalResult
+        Nothing -> errorWithoutStackTrace "No `main` function detected"
 
 evaluateFile :: FilePath -> IO Env
 evaluateFile filePath = do
   contents <- readFile filePath
-  let asts = parseTricu contents
-  pure $ evalTricu Map.empty asts
+  let tokens = lexTricu contents
+  let moduleName = case parseProgram tokens of
+        Right ((SModule name) : _) -> name
+        _                          -> ""
+  case parseProgram tokens of
+    Left err -> errorWithoutStackTrace (handleParseError err)
+    Right _ -> do
+      ast <- preprocessFile filePath
+      pure $ mainAlias moduleName $ evalTricu Map.empty ast
 
 evaluateFileWithContext :: Env -> FilePath -> IO Env
 evaluateFileWithContext env filePath = do
   contents <- readFile filePath
-  let asts = parseTricu contents
-  pure $ evalTricu env asts
+  let tokens = lexTricu contents
+  let moduleName = case parseProgram tokens of
+        Right ((SModule name) : _) -> name
+        _                          -> ""
+  case parseProgram tokens of
+    Left err -> errorWithoutStackTrace (handleParseError err)
+    Right _ -> do
+      ast <- preprocessFile filePath
+      pure $ mainAlias moduleName $ evalTricu env ast
+
+mainAlias :: String -> Env -> Env
+mainAlias "" env = env
+mainAlias moduleName env =
+  case Map.lookup (moduleName ++ ".main") env of
+    Just value -> Map.insert "main" value env
+    Nothing    -> env
+
+preprocessFile :: FilePath -> IO [TricuAST]
+preprocessFile filePath = preprocessFile' Set.empty filePath
+
+preprocessFile' :: Set.Set FilePath -> FilePath -> IO [TricuAST]
+preprocessFile' inProgress filePath
+  | filePath `Set.member` inProgress = 
+      errorWithoutStackTrace $ "Encountered cyclic import: " ++ filePath
+  | otherwise = do
+      contents <- readFile filePath
+      let tokens = lexTricu contents
+      case parseProgram tokens of
+        Left err -> errorWithoutStackTrace (handleParseError err)
+        Right asts -> do
+          let (moduleName, restAST) = extractModule asts
+          let (imports, nonImports) = partition isImport restAST
+          let newInProgress = Set.insert filePath inProgress
+          importedASTs <- concat <$> mapM (processImport newInProgress) imports
+          let namespacedAST = namespaceDefinitions moduleName nonImports
+          pure $ importedASTs ++ namespacedAST
+  where
+    extractModule :: [TricuAST] -> (String, [TricuAST])
+    extractModule ((SModule name) : xs) = (name, xs)
+    extractModule xs                    = ("", xs)
+
+    isImport :: TricuAST -> Bool
+    isImport (SImport _ _) = True
+    isImport _             = False
+
+    processImport :: Set.Set FilePath -> TricuAST -> IO [TricuAST]
+    processImport inProgress (SImport filePath moduleName) = do
+      importedAST <- preprocessFile' inProgress filePath
+      pure $ namespaceDefinitions moduleName importedAST
+    processImport _ _ = error "Unexpected non-import in processImport"
+
+namespaceDefinitions :: String -> [TricuAST] -> [TricuAST]
+namespaceDefinitions moduleName = map (namespaceDefinition moduleName)
+
+namespaceDefinition :: String -> TricuAST -> TricuAST
+namespaceDefinition "" def = def
+namespaceDefinition moduleName (SDef name args body)
+  | isPrefixed name = SDef name args (namespaceBody moduleName body)
+  | otherwise = SDef (namespaceVariable moduleName name) 
+                        args (namespaceBody moduleName body)
+namespaceDefinition moduleName other =
+  namespaceBody moduleName other
+
+namespaceBody :: String -> TricuAST -> TricuAST
+namespaceBody moduleName (SVar name)
+  | isPrefixed name = SVar name
+  | otherwise = SVar (namespaceVariable moduleName name)
+namespaceBody moduleName (SApp func arg) =
+  SApp (namespaceBody moduleName func) (namespaceBody moduleName arg)
+namespaceBody moduleName (SLambda args body) =
+  SLambda args (namespaceBodyScoped moduleName args body)
+namespaceBody moduleName (SList items) =
+  SList (map (namespaceBody moduleName) items)
+namespaceBody moduleName (TFork left right) =
+  TFork (namespaceBody moduleName left) (namespaceBody moduleName right)
+namespaceBody moduleName (TStem subtree) =
+  TStem (namespaceBody moduleName subtree)
+namespaceBody moduleName (SDef name args body)
+  | isPrefixed name = SDef name args (namespaceBody moduleName body)
+  | otherwise = SDef (namespaceVariable moduleName name) 
+                        args (namespaceBody moduleName body)
+namespaceBody _ other = other
+
+namespaceBodyScoped :: String -> [String] -> TricuAST -> TricuAST
+namespaceBodyScoped moduleName args body = case body of
+  SVar name ->
+    if name `elem` args
+      then SVar name
+      else namespaceBody moduleName (SVar name)
+  SApp func arg -> SApp (namespaceBodyScoped moduleName args func) (namespaceBodyScoped moduleName args arg)
+  SLambda innerArgs innerBody -> SLambda innerArgs (namespaceBodyScoped moduleName (args ++ innerArgs) innerBody)
+  SList items -> SList (map (namespaceBodyScoped moduleName args) items)
+  TFork left right -> TFork (namespaceBodyScoped moduleName args left) (namespaceBodyScoped moduleName args right)
+  TStem subtree -> TStem (namespaceBodyScoped moduleName args subtree)
+  SDef name innerArgs innerBody ->
+    SDef (namespaceVariable moduleName name) innerArgs (namespaceBodyScoped moduleName (args ++ innerArgs) innerBody)
+  other -> other
+
+isPrefixed :: String -> Bool
+isPrefixed name = '.' `elem` name
+
+namespaceVariable :: String -> String -> String
+namespaceVariable "" name = name
+namespaceVariable moduleName name = moduleName ++ "." ++ name