{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE TemplateHaskell #-}

module Language.PureScript.Environment where

import Prelude.Compat

import Data.Aeson.TH
import Data.Maybe (fromMaybe)
import qualified Data.Aeson as A
import qualified Data.Map as M
import qualified Data.Text as T

import Language.PureScript.Crash
import Language.PureScript.Kinds
import Language.PureScript.Names
import Language.PureScript.TypeClassDictionaries
import Language.PureScript.Types
import qualified Language.PureScript.Constants as C

-- | The @Environment@ defines all values and types which are currently in scope:
data Environment = Environment
  { names :: M.Map (Qualified Ident) (Type, NameKind, NameVisibility)
  -- ^ Values currently in scope
  , types :: M.Map (Qualified (ProperName 'TypeName)) (Kind, TypeKind)
  -- ^ Type names currently in scope
  , dataConstructors :: M.Map (Qualified (ProperName 'ConstructorName)) (DataDeclType, ProperName 'TypeName, Type, [Ident])
  -- ^ Data constructors currently in scope, along with their associated type
  -- constructor name, argument types and return type.
  , typeSynonyms :: M.Map (Qualified (ProperName 'TypeName)) ([(String, Maybe Kind)], Type)
  -- ^ Type synonyms currently in scope
  , typeClassDictionaries :: M.Map (Maybe ModuleName) (M.Map (Qualified (ProperName 'ClassName)) (M.Map (Qualified Ident) TypeClassDictionaryInScope))
  -- ^ Available type class dictionaries
  , typeClasses :: M.Map (Qualified (ProperName 'ClassName)) TypeClassData
  -- ^ Type classes
  } deriving Show

-- | Information about a type class
data TypeClassData = TypeClassData
  { typeClassArguments :: [(String, Maybe Kind)]
  -- ^ A list of type argument names, and their kinds, where kind annotations
  -- were provided.
  , typeClassMembers :: [(Ident, Type)]
  -- ^ A list of type class members and their types. Type arguments listed above
  -- are considered bound in these types.
  , typeClassSuperclasses :: [Constraint]
  -- ^ A list of superclasses of this type class. Type arguments listed above
  -- are considered bound in the types appearing in these constraints.
  , typeClassDependencies :: [FunctionalDependency]
  -- ^ A list of functional dependencies for the type arguments of this class.
  } deriving Show

-- | A functional dependency indicates a relationship between two sets of
-- type arguments in a class declaration.
data FunctionalDependency = FunctionalDependency
  { fdDeterminers :: [Int]
  -- ^ the type arguments which determine the determined type arguments
  , fdDetermined  :: [Int]
  -- ^ the determined type arguments
  } deriving Show

-- |
-- The initial environment with no values and only the default javascript types defined
--
initEnvironment :: Environment
initEnvironment = Environment M.empty primTypes M.empty M.empty M.empty primClasses

-- |
-- The visibility of a name in scope
--
data NameVisibility
  -- |
  -- The name is defined in the current binding group, but is not visible
  --
  = Undefined
  -- |
  -- The name is defined in the another binding group, or has been made visible by a function binder
  --
  | Defined deriving (Show, Eq)

-- |
-- A flag for whether a name is for an private or public value - only public values will be
-- included in a generated externs file.
--
data NameKind
  -- |
  -- A private value introduced as an artifact of code generation (class instances, class member
  -- accessors, etc.)
  --
  = Private
  -- |
  -- A public value for a module member or foreing import declaration
  --
  | Public
  -- |
  -- A name for member introduced by foreign import
  --
  | External
  deriving (Show, Eq)

-- |
-- The kinds of a type
--
data TypeKind
  -- |
  -- Data type
  --
  = DataType [(String, Maybe Kind)] [(ProperName 'ConstructorName, [Type])]
  -- |
  -- Type synonym
  --
  | TypeSynonym
  -- |
  -- Foreign data
  --
  | ExternData
  -- |
  -- A local type variable
  --
  | LocalTypeVariable
  -- |
  -- A scoped type variable
  --
  | ScopedTypeVar
  deriving (Show, Eq)

-- |
-- The type ('data' or 'newtype') of a data type declaration
--
data DataDeclType
  -- |
  -- A standard data constructor
  --
  = Data
  -- |
  -- A newtype constructor
  --
  | Newtype
  deriving (Show, Eq, Ord)

showDataDeclType :: DataDeclType -> String
showDataDeclType Data = "data"
showDataDeclType Newtype = "newtype"

instance A.ToJSON DataDeclType where
  toJSON = A.toJSON . showDataDeclType

instance A.FromJSON DataDeclType where
  parseJSON = A.withText "DataDeclType" $ \str ->
    case str of
      "data" -> return Data
      "newtype" -> return Newtype
      other -> fail $ "invalid type: '" ++ T.unpack other ++ "'"

-- |
-- Construct a ProperName in the Prim module
--
primName :: String -> Qualified (ProperName a)
primName = Qualified (Just $ ModuleName [ProperName C.prim]) . ProperName

-- |
-- Construct a type in the Prim module
--
primTy :: String -> Type
primTy = TypeConstructor . primName

-- |
-- Type constructor for functions
--
tyFunction :: Type
tyFunction = primTy "Function"

-- |
-- Type constructor for strings
--
tyString :: Type
tyString = primTy "String"

-- |
-- Type constructor for strings
--
tyChar :: Type
tyChar = primTy "Char"

-- |
-- Type constructor for numbers
--
tyNumber :: Type
tyNumber = primTy "Number"

-- |
-- Type constructor for integers
--
tyInt :: Type
tyInt = primTy "Int"

-- |
-- Type constructor for booleans
--
tyBoolean :: Type
tyBoolean = primTy "Boolean"

-- |
-- Type constructor for arrays
--
tyArray :: Type
tyArray = primTy "Array"

-- |
-- Type constructor for records
--
tyRecord :: Type
tyRecord = primTy "Record"

-- |
-- Check whether a type is a record
--
isObject :: Type -> Bool
isObject = isTypeOrApplied tyRecord

-- |
-- Check whether a type is a function
--
isFunction :: Type -> Bool
isFunction = isTypeOrApplied tyFunction

isTypeOrApplied :: Type -> Type -> Bool
isTypeOrApplied t1 (TypeApp t2 _) = t1 == t2
isTypeOrApplied t1 t2 = t1 == t2

-- |
-- Smart constructor for function types
--
function :: Type -> Type -> Type
function t1 = TypeApp (TypeApp tyFunction t1)

-- |
-- The primitive types in the external javascript environment with their
-- associated kinds. There are also pseudo `Fail` and `Partial` types
-- that correspond to the classes with the same names.
--
primTypes :: M.Map (Qualified (ProperName 'TypeName)) (Kind, TypeKind)
primTypes =
  M.fromList
    [ (primName "Function", (FunKind Star (FunKind Star Star), ExternData))
    , (primName "Array",    (FunKind Star Star, ExternData))
    , (primName "Record",   (FunKind (Row Star) Star, ExternData))
    , (primName "String",   (Star, ExternData))
    , (primName "Char",     (Star, ExternData))
    , (primName "Number",   (Star, ExternData))
    , (primName "Int",      (Star, ExternData))
    , (primName "Boolean",  (Star, ExternData))
    , (primName "Partial",  (Star, ExternData))
    , (primName "Fail",     (FunKind Symbol Star, ExternData))
    , (primName "TypeString", (FunKind Star Symbol, ExternData))
    , (primName "TypeConcat", (FunKind Symbol (FunKind Symbol Symbol), ExternData))
    ]

-- |
-- The primitive class map. This just contains the `Fail` and `Partial`
-- classes. `Partial` is used as a kind of magic constraint for partial
-- functions. `Fail` is used for user-defined type errors.
--
primClasses :: M.Map (Qualified (ProperName 'ClassName)) TypeClassData
primClasses =
  M.fromList
    [ (primName "Partial", (TypeClassData [] [] [] []))
    , (primName "Fail",    (TypeClassData [("message", Just Symbol)] [] [] []))
    ]

-- |
-- Finds information about data constructors from the current environment.
--
lookupConstructor :: Environment -> Qualified (ProperName 'ConstructorName) -> (DataDeclType, ProperName 'TypeName, Type, [Ident])
lookupConstructor env ctor =
  fromMaybe (internalError "Data constructor not found") $ ctor `M.lookup` dataConstructors env

-- |
-- Checks whether a data constructor is for a newtype.
--
isNewtypeConstructor :: Environment -> Qualified (ProperName 'ConstructorName) -> Bool
isNewtypeConstructor e ctor = case lookupConstructor e ctor of
  (Newtype, _, _, _) -> True
  (Data, _, _, _) -> False

-- |
-- Finds information about values from the current environment.
--
lookupValue :: Environment -> Qualified Ident -> Maybe (Type, NameKind, NameVisibility)
lookupValue env ident = ident `M.lookup` names env

$(deriveJSON (defaultOptions { sumEncoding = ObjectWithSingleField }) ''TypeKind)
$(deriveJSON (defaultOptions { sumEncoding = ObjectWithSingleField }) ''FunctionalDependency)