{-# LANGUAGE CPP #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE DeriveFunctor #-}
{-# LANGUAGE ExistentialQuantification #-}
{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE OverloadedStrings #-}
module Database.Persist.Types.Base where

import qualified Data.Aeson as A
import Control.Exception (Exception)
import Web.PathPieces (PathPiece (..))
import Control.Monad.Trans.Error (Error (..))
import Data.Typeable (Typeable)
import Data.Text (Text, pack)
import qualified Data.Text as T
import qualified Data.Text.Encoding as TE
import Data.Text.Encoding.Error (lenientDecode)
import qualified Data.ByteString.Base64 as B64
import qualified Data.Vector as V
import Control.Arrow (second)
import Data.Time (Day, TimeOfDay, UTCTime)
import Data.Int (Int64)
import qualified Data.Text.Read
import Data.ByteString (ByteString, foldl')
import Data.Bits (shiftL, shiftR)
import qualified Data.ByteString as BS
import qualified Data.ByteString.Char8 as BS8
import Data.Map (Map)
import qualified Data.HashMap.Strict as HM
import Data.Word (Word32)
import Numeric (showHex, readHex)
#if MIN_VERSION_aeson(0, 7, 0)
import qualified Data.Scientific
#else
import qualified Data.Attoparsec.Number as AN
#endif

-- | A 'Checkmark' should be used as a field type whenever a
-- uniqueness constraint should guarantee that a certain kind of
-- record may appear at most once, but other kinds of records may
-- appear any number of times.
--
-- /NOTE:/ You need to mark any @Checkmark@ fields as @nullable@
-- (see the following example).
--
-- For example, suppose there's a @Location@ entity that
-- represents where a user has lived:
--
-- @
-- Location
--     user    UserId
--     name    Text
--     current Checkmark nullable
--
--     UniqueLocation user current
-- @
--
-- The @UniqueLocation@ constraint allows any number of
-- 'Inactive' @Location@s to be @current@.  However, there may be
-- at most one @current@ @Location@ per user (i.e., either zero
-- or one per user).
--
-- This data type works because of the way that SQL treats
-- @NULL@able fields within uniqueness constraints.  The SQL
-- standard says that @NULL@ values should be considered
-- different, so we represent 'Inactive' as SQL @NULL@, thus
-- allowing any number of 'Inactive' records.  On the other hand,
-- we represent 'Active' as @TRUE@, so the uniqueness constraint
-- will disallow more than one 'Active' record.
--
-- /Note:/ There may be DBMSs that do not respect the SQL
-- standard's treatment of @NULL@ values on uniqueness
-- constraints, please check if this data type works before
-- relying on it.
--
-- The SQL @BOOLEAN@ type is used because it's the smallest data
-- type available.  Note that we never use @FALSE@, just @TRUE@
-- and @NULL@.  Provides the same behavior @Maybe ()@ would if
-- @()@ was a valid 'PersistField'.
data Checkmark = Active
                 -- ^ When used on a uniqueness constraint, there
                 -- may be at most one 'Active' record.
               | Inactive
                 -- ^ When used on a uniqueness constraint, there
                 -- may be any number of 'Inactive' records.
    deriving (Eq, Ord, Read, Show, Enum, Bounded)

instance PathPiece Checkmark where
    toPathPiece = pack . show
    fromPathPiece txt =
      case reads (T.unpack txt) of
        [(a, "")] -> Just a
        _         -> Nothing

data IsNullable = Nullable !WhyNullable
                | NotNullable
                  deriving (Eq, Show)

-- | The reason why a field is 'nullable' is very important.  A
-- field that is nullable because of a @Maybe@ tag will have its
-- type changed from @A@ to @Maybe A@.  OTOH, a field that is
-- nullable because of a @nullable@ tag will remain with the same
-- type.
data WhyNullable = ByMaybeAttr
                 | ByNullableAttr
                  deriving (Eq, Show)

data EntityDef = EntityDef
    { entityHaskell :: !HaskellName
    , entityDB      :: !DBName
    , entityId      :: !FieldDef
    , entityAttrs   :: ![Attr]
    , entityFields  :: ![FieldDef]
    , entityUniques :: ![UniqueDef]
    , entityForeigns:: ![ForeignDef]
    , entityDerives :: ![Text]
    , entityExtra   :: !(Map Text [ExtraLine])
    , entitySum     :: !Bool
    }
    deriving (Show, Eq, Read, Ord)

entityPrimary :: EntityDef -> Maybe CompositeDef
entityPrimary t = case fieldReference (entityId t) of
    CompositeRef c -> Just c
    _ -> Nothing

type ExtraLine = [Text]

newtype HaskellName = HaskellName { unHaskellName :: Text }
    deriving (Show, Eq, Read, Ord)
newtype DBName = DBName { unDBName :: Text }
    deriving (Show, Eq, Read, Ord)

type Attr = Text

data FieldType
    = FTTypeCon (Maybe Text) Text
      -- ^ Optional module and name.
    | FTApp FieldType FieldType
    | FTList FieldType
  deriving (Show, Eq, Read, Ord)

data FieldDef = FieldDef
    { fieldHaskell   :: !HaskellName -- ^ name of the field
    , fieldDB        :: !DBName
    , fieldType      :: !FieldType
    , fieldSqlType   :: !SqlType
    , fieldAttrs     :: ![Attr]    -- ^ user annotations for a field
    , fieldStrict    :: !Bool      -- ^ a strict field in the data type. Default: true
    , fieldReference :: !ReferenceDef
    }
    deriving (Show, Eq, Read, Ord)


-- | There are 3 kinds of references
-- 1) composite (to fields that exist in the record)
-- 2) single field
-- 3) embedded
data ReferenceDef = NoReference
                  | ForeignRef !HaskellName !FieldType -- ^ A ForeignRef has a late binding to the EntityDef it references via HaskellName and has the Haskell type of the foreign key in the form of FieldType
                  | EmbedRef EmbedEntityDef
                  | CompositeRef CompositeDef
                  deriving (Show, Eq, Read, Ord)

-- | An EmbedEntityDef is the same as an EntityDef
-- But it is only used for fieldReference
-- so it only has data needed for embedding
data EmbedEntityDef = EmbedEntityDef
    { embeddedHaskell :: !HaskellName
    , embeddedFields  :: ![EmbedFieldDef]
    } deriving (Show, Eq, Read, Ord)

-- | An EmbedFieldDef is the same as a FieldDef
-- But it is only used for embeddedFields
-- so it only has data needed for embedding
data EmbedFieldDef = EmbedFieldDef
    { emFieldDB       :: !DBName
    , emFieldEmbed :: Maybe EmbedEntityDef
    }
    deriving (Show, Eq, Read, Ord)

toEmbedEntityDef :: EntityDef -> EmbedEntityDef
toEmbedEntityDef ent = EmbedEntityDef
  { embeddedHaskell = entityHaskell ent
  , embeddedFields = map toEmbedFieldDef $ entityFields ent
  }

toEmbedFieldDef :: FieldDef -> EmbedFieldDef
toEmbedFieldDef field =
  EmbedFieldDef { emFieldDB       = fieldDB field
                   , emFieldEmbed = case fieldReference field of
                       EmbedRef em -> Just em
                       _ -> Nothing
                   }

data UniqueDef = UniqueDef
    { uniqueHaskell :: !HaskellName
    , uniqueDBName  :: !DBName
    , uniqueFields  :: ![(HaskellName, DBName)]
    , uniqueAttrs   :: ![Attr]
    }
    deriving (Show, Eq, Read, Ord)

data CompositeDef = CompositeDef
    { compositeFields  :: ![FieldDef]
    , compositeAttrs   :: ![Attr]
    }
    deriving (Show, Eq, Read, Ord)

-- | Used instead of FieldDef
-- to generate a smaller amount of code
type ForeignFieldDef = (HaskellName, DBName)

data ForeignDef = ForeignDef
    { foreignRefTableHaskell       :: !HaskellName
    , foreignRefTableDBName        :: !DBName
    , foreignConstraintNameHaskell :: !HaskellName
    , foreignConstraintNameDBName  :: !DBName
    , foreignFields                :: ![(ForeignFieldDef, ForeignFieldDef)] -- this entity plus the primary entity
    , foreignAttrs                 :: ![Attr]
    , foreignNullable              :: Bool
    }
    deriving (Show, Eq, Read, Ord)

data PersistException
  = PersistError Text -- ^ Generic Exception
  | PersistMarshalError Text
  | PersistInvalidField Text
  | PersistForeignConstraintUnmet Text
  | PersistMongoDBError Text
  | PersistMongoDBUnsupported Text
    deriving (Show, Typeable)

instance Exception PersistException
instance Error PersistException where
    strMsg = PersistError . pack

-- | A raw value which can be stored in any backend and can be marshalled to
-- and from a 'PersistField'.
data PersistValue = PersistText Text
                  | PersistByteString ByteString
                  | PersistInt64 Int64
                  | PersistDouble Double
                  | PersistRational Rational
                  | PersistBool Bool
                  | PersistDay Day
                  | PersistTimeOfDay TimeOfDay
                  | PersistUTCTime UTCTime
                  | PersistNull
                  | PersistList [PersistValue]
                  | PersistMap [(Text, PersistValue)]
                  | PersistObjectId ByteString -- ^ Intended especially for MongoDB backend
                  | PersistDbSpecific ByteString -- ^ Using 'PersistDbSpecific' allows you to use types specific to a particular backend
-- For example, below is a simple example of the PostGIS geography type:
--
-- @
-- data Geo = Geo ByteString
-- 
-- instance PersistField Geo where
--   toPersistValue (Geo t) = PersistDbSpecific t
-- 
--   fromPersistValue (PersistDbSpecific t) = Right $ Geo $ Data.ByteString.concat ["'", t, "'"]
--   fromPersistValue _ = Left "Geo values must be converted from PersistDbSpecific"
-- 
-- instance PersistFieldSql Geo where
--   sqlType _ = SqlOther "GEOGRAPHY(POINT,4326)"
-- 
-- toPoint :: Double -> Double -> Geo
-- toPoint lat lon = Geo $ Data.ByteString.concat ["'POINT(", ps $ lon, " ", ps $ lat, ")'"]
--   where ps = Data.Text.pack . show
-- @
-- 
-- If Foo has a geography field, we can then perform insertions like the following:
-- 
-- @
-- insert $ Foo (toPoint 44 44)
-- @
--
    deriving (Show, Read, Eq, Typeable, Ord)


instance PathPiece PersistValue where
    fromPathPiece t =
        case Data.Text.Read.signed Data.Text.Read.decimal t of
            Right (i, t')
                | T.null t' -> Just $ PersistInt64 i
            _ -> case reads $ T.unpack t of
                    [(fks, "")] -> Just $ PersistList fks
                    _ -> Just $ PersistText t
    toPathPiece x =
        case fromPersistValueText x of
            Left e -> error $ T.unpack e
            Right y -> y

fromPersistValueText :: PersistValue -> Either Text Text
fromPersistValueText (PersistText s) = Right s
fromPersistValueText (PersistByteString bs) =
    Right $ TE.decodeUtf8With lenientDecode bs
fromPersistValueText (PersistInt64 i) = Right $ T.pack $ show i
fromPersistValueText (PersistDouble d) = Right $ T.pack $ show d
fromPersistValueText (PersistRational r) = Right $ T.pack $ show r
fromPersistValueText (PersistDay d) = Right $ T.pack $ show d
fromPersistValueText (PersistTimeOfDay d) = Right $ T.pack $ show d
fromPersistValueText (PersistUTCTime d) = Right $ T.pack $ show d
fromPersistValueText PersistNull = Left "Unexpected null"
fromPersistValueText (PersistBool b) = Right $ T.pack $ show b
fromPersistValueText (PersistList _) = Left "Cannot convert PersistList to Text"
fromPersistValueText (PersistMap _) = Left "Cannot convert PersistMap to Text"
fromPersistValueText (PersistObjectId _) = Left "Cannot convert PersistObjectId to Text"
fromPersistValueText (PersistDbSpecific _) = Left "Cannot convert PersistDbSpecific to Text"

instance A.ToJSON PersistValue where
    toJSON (PersistText t) = A.String $ T.cons 's' t
    toJSON (PersistByteString b) = A.String $ T.cons 'b' $ TE.decodeUtf8 $ B64.encode b
    toJSON (PersistInt64 i) = A.Number $ fromIntegral i
    toJSON (PersistDouble d) = A.Number $
#if MIN_VERSION_aeson(0, 7, 0)
        Data.Scientific.fromFloatDigits
#else
        AN.D
#endif
        d
    toJSON (PersistRational r) = A.String $ T.pack $ 'r' : show r
    toJSON (PersistBool b) = A.Bool b
    toJSON (PersistTimeOfDay t) = A.String $ T.pack $ 't' : show t
    toJSON (PersistUTCTime u) = A.String $ T.pack $ 'u' : show u
    toJSON (PersistDay d) = A.String $ T.pack $ 'd' : show d
    toJSON PersistNull = A.Null
    toJSON (PersistList l) = A.Array $ V.fromList $ map A.toJSON l
    toJSON (PersistMap m) = A.object $ map (second A.toJSON) m
    toJSON (PersistDbSpecific b) = A.String $ T.cons 'p' $ TE.decodeUtf8 $ B64.encode b
    toJSON (PersistObjectId o) =
      A.toJSON $ showChar 'o' $ showHexLen 8 (bs2i four) $ showHexLen 16 (bs2i eight) ""
        where
         (four, eight) = BS8.splitAt 4 o

         -- taken from crypto-api
         bs2i :: ByteString -> Integer
         bs2i bs = foldl' (\i b -> (i `shiftL` 8) + fromIntegral b) 0 bs
         {-# INLINE bs2i #-}

         -- showHex of n padded with leading zeros if necessary to fill d digits
         -- taken from Data.BSON
         showHexLen :: (Show n, Integral n) => Int -> n -> ShowS
         showHexLen d n = showString (replicate (d - sigDigits n) '0') . showHex n  where
             sigDigits 0 = 1
             sigDigits n' = truncate (logBase (16 :: Double) $ fromIntegral n') + 1

instance A.FromJSON PersistValue where
    parseJSON (A.String t0) =
        case T.uncons t0 of
            Nothing -> fail "Null string"
            Just ('p', t) -> either (fail "Invalid base64") (return . PersistDbSpecific)
                           $ B64.decode $ TE.encodeUtf8 t
            Just ('s', t) -> return $ PersistText t
            Just ('b', t) -> either (fail "Invalid base64") (return . PersistByteString)
                           $ B64.decode $ TE.encodeUtf8 t
            Just ('t', t) -> fmap PersistTimeOfDay $ readMay t
            Just ('u', t) -> fmap PersistUTCTime $ readMay t
            Just ('d', t) -> fmap PersistDay $ readMay t
            Just ('r', t) -> fmap PersistRational $ readMay t
            Just ('o', t) -> maybe (fail "Invalid base64") (return . PersistObjectId) $
                              fmap (i2bs (8 * 12) . fst) $ headMay $ readHex $ T.unpack t
            Just (c, _) -> fail $ "Unknown prefix: " ++ [c]
      where
        headMay []    = Nothing
        headMay (x:_) = Just x
        readMay :: (Read a, Monad m) => T.Text -> m a
        readMay t =
            case reads $ T.unpack t of
                (x, _):_ -> return x
                [] -> fail "Could not read"

        -- taken from crypto-api
        -- |@i2bs bitLen i@ converts @i@ to a 'ByteString' of @bitLen@ bits (must be a multiple of 8).
        i2bs :: Int -> Integer -> BS.ByteString
        i2bs l i = BS.unfoldr (\l' -> if l' < 0 then Nothing else Just (fromIntegral (i `shiftR` l'), l' - 8)) (l-8)
        {-# INLINE i2bs #-}


#if MIN_VERSION_aeson(0, 7, 0)
    parseJSON (A.Number n) = return $
        if fromInteger (floor n) == n
            then PersistInt64 $ floor n
            else PersistDouble $ fromRational $ toRational n
#else
    parseJSON (A.Number (AN.I i)) = return $ PersistInt64 $ fromInteger i
    parseJSON (A.Number (AN.D d)) = return $ PersistDouble d
#endif
    parseJSON (A.Bool b) = return $ PersistBool b
    parseJSON A.Null = return $ PersistNull
    parseJSON (A.Array a) = fmap PersistList (mapM A.parseJSON $ V.toList a)
    parseJSON (A.Object o) =
        fmap PersistMap $ mapM go $ HM.toList o
      where
        go (k, v) = fmap ((,) k) $ A.parseJSON v

-- | A SQL data type. Naming attempts to reflect the underlying Haskell
-- datatypes, eg SqlString instead of SqlVarchar. Different SQL databases may
-- have different translations for these types.
data SqlType = SqlString
             | SqlInt32
             | SqlInt64
             | SqlReal
             | SqlNumeric Word32 Word32
             | SqlBool
             | SqlDay
             | SqlTime
             | SqlDayTime -- ^ Always uses UTC timezone
             | SqlBlob
             | SqlOther T.Text -- ^ a backend-specific name
    deriving (Show, Read, Eq, Typeable, Ord)

data PersistFilter = Eq | Ne | Gt | Lt | Ge | Le | In | NotIn
                   | BackendSpecificFilter T.Text
    deriving (Read, Show)

data UpdateException = KeyNotFound String
                     | UpsertError String
    deriving Typeable
instance Show UpdateException where
    show (KeyNotFound key) = "Key not found during updateGet: " ++ key
    show (UpsertError msg) = "Error during upsert: " ++ msg
instance Exception UpdateException

data OnlyUniqueException = OnlyUniqueException String deriving Typeable
instance Show OnlyUniqueException where
    show (OnlyUniqueException uniqueMsg) =
      "Expected only one unique key, got " ++ uniqueMsg
instance Exception OnlyUniqueException


data PersistUpdate = Assign | Add | Subtract | Multiply | Divide
                   | BackendSpecificUpdate T.Text
    deriving (Read, Show)
