1 files changed, 88 insertions, 0 deletions
diff --git a/lib/Language/Elna/Frontend/SymbolTable.hs b/lib/Language/Elna/Frontend/SymbolTable.hs
new file mode 100644
index 0000000..9ace33f
--- /dev/null
+++ b/lib/Language/Elna/Frontend/SymbolTable.hs
@@ -0,0 +1,88 @@
+module Language.Elna.Frontend.SymbolTable
+    ( SymbolTable
+    , Info(..)
+    , ParameterInfo(..)
+    , builtInSymbolTable
+    , empty
+    , enter
+    , fromList
+    , lookup
+    , member
+    , scope
+    , toMap
+    , update
+    ) where
+
+import Data.HashMap.Strict (HashMap)
+import qualified Data.HashMap.Strict as HashMap
+import Data.List (sort)
+import Data.List.NonEmpty (NonEmpty)
+import qualified Data.List.NonEmpty as NonEmpty
+import Data.Maybe (isJust)
+import Data.Vector (Vector)
+import qualified Data.Vector as Vector
+import Language.Elna.Location (Identifier(..))
+import Language.Elna.Frontend.Types (Type(..), intType)
+import Prelude hiding (lookup)
+
+data SymbolTable = SymbolTable (Maybe SymbolTable) (HashMap Identifier Info)
+    deriving (Eq, Show)
+
+empty :: SymbolTable
+empty = SymbolTable Nothing HashMap.empty
+
+update :: (Info -> Maybe Info) -> Identifier -> SymbolTable -> SymbolTable
+update updater key (SymbolTable parent mappings) = SymbolTable parent
+    $ HashMap.update updater key mappings
+
+scope :: SymbolTable -> SymbolTable -> SymbolTable
+scope parent (SymbolTable _ mappings) = SymbolTable (Just parent) mappings
+
+builtInSymbolTable :: SymbolTable
+builtInSymbolTable = SymbolTable Nothing $ HashMap.fromList
+    [ ("printi", ProcedureInfo empty Vector.empty)
+    , ("int", TypeInfo intType)
+    ]
+
+toMap :: SymbolTable  -> HashMap Identifier Info
+toMap (SymbolTable _ map') = map'
+
+enter :: Identifier -> Info -> SymbolTable -> Maybe SymbolTable
+enter identifier info table@(SymbolTable parent hashTable)
+    | member identifier table = Nothing
+    | otherwise = Just
+        $ SymbolTable parent (HashMap.insert identifier info hashTable)
+
+lookup :: Identifier -> SymbolTable -> Maybe Info
+lookup identifier (SymbolTable parent table)
+    | Just found <- HashMap.lookup identifier table = Just found
+    | Just parent' <- parent = lookup identifier parent'
+    | otherwise = Nothing
+
+member :: Identifier -> SymbolTable -> Bool
+member identifier table =
+    isJust $ lookup identifier table
+
+fromList :: [(Identifier, Info)] -> Either (NonEmpty Identifier) SymbolTable
+fromList elements
+    | Just identifierDuplicates' <- identifierDuplicates =
+        Left identifierDuplicates'
+    | otherwise = Right $ SymbolTable Nothing $ HashMap.fromList elements
+  where
+    identifierDuplicates = NonEmpty.nonEmpty
+        $ fmap NonEmpty.head
+        $ filter ((> 1) . NonEmpty.length)
+        $ NonEmpty.group . sort
+        $ fst <$> elements
+
+data ParameterInfo = ParameterInfo
+    { name :: Identifier
+    , type' :: Type
+    , isReferenceParameter :: Bool
+    } deriving (Eq, Show)
+
+data Info
+    = TypeInfo Type
+    | VariableInfo Bool Type
+    | ProcedureInfo SymbolTable (Vector ParameterInfo)
+    deriving (Eq, Show)