{-# LANGUAGE DeriveDataTypeable         #-}
{-# LANGUAGE FlexibleContexts           #-}
{-# LANGUAGE FlexibleInstances          #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE MultiParamTypeClasses      #-}
{-# LANGUAGE NoMonomorphismRestriction  #-}
{-# LANGUAGE OverloadedStrings          #-}
{-# LANGUAGE RecordWildCards            #-}
{-# LANGUAGE ScopedTypeVariables        #-}
{-# LANGUAGE TypeFamilies               #-}
{-# LANGUAGE UndecidableInstances       #-}

-----------------------------------------------------------------------------
-- |
-- Module      :  Aws.DynamoDb.Core
-- Copyright   :  Soostone Inc, Chris Allen
-- License     :  BSD3
--
-- Maintainer  :  Ozgun Ataman <ozgun.ataman@soostone.com>
-- Stability   :  experimental
--
-- Shared types and utilities for DyanmoDb functionality.
----------------------------------------------------------------------------

module Aws.DynamoDb.Core
    (
    -- * Configuration and Regions
      Region (..)
    , ddbLocal
    , ddbUsEast1
    , ddbUsWest1
    , ddbUsWest2
    , ddbEuWest1
    , ddbEuCentral1
    , ddbApNe1
    , ddbApSe1
    , ddbApSe2
    , ddbSaEast1
    , DdbConfiguration (..)

    -- * DynamoDB values
    , DValue (..)

    -- * Converting to/from 'DValue'
    , DynVal(..)
    , toValue, fromValue
    , Bin (..)

    -- * Defining new 'DynVal' instances
    , DynData(..)
    , DynBinary(..), DynNumber(..), DynString(..)

    -- * Working with key/value pairs
    , Attribute (..)
    , parseAttributeJson
    , attributeJson
    , attributesJson

    , attrTuple
    , attr
    , attrAs
    , text, int, double
    , PrimaryKey (..)
    , hk
    , hrk

    -- * Working with objects (attribute collections)
    , Item
    , item
    , attributes
    , ToDynItem (..)
    , FromDynItem (..)
    , fromItem
    , Parser (..)
    , getAttr
    , getAttr'

    -- * Common types used by operations
    , Conditions (..)
    , conditionsJson
    , expectsJson

    , Condition (..)
    , conditionJson
    , CondOp (..)
    , CondMerge (..)
    , ConsumedCapacity (..)
    , ReturnConsumption (..)
    , ItemCollectionMetrics (..)
    , ReturnItemCollectionMetrics (..)
    , UpdateReturn (..)
    , QuerySelect (..)
    , querySelectJson

    -- * Size estimation
    , DynSize (..)
    , nullAttr

    -- * Responses & Errors
    , DdbResponse (..)
    , DdbErrCode (..)
    , shouldRetry
    , DdbError (..)

    -- * Internal Helpers
    , ddbSignQuery
    , AmazonError (..)
    , ddbResponseConsumer
    , ddbHttp
    , ddbHttps

    ) where


-------------------------------------------------------------------------------
import           Control.Applicative
import qualified Control.Exception            as C
import           Control.Monad
import           Control.Monad.Trans
import           Control.Monad.Trans.Resource (throwM)
import           Crypto.Hash
import           Data.Aeson
import qualified Data.Aeson                   as A
import           Data.Aeson.Types             (Pair, parseEither)
import qualified Data.Aeson.Types             as A
import qualified Data.Attoparsec.ByteString   as AttoB (endOfInput)
import qualified Data.Attoparsec.Text         as Atto
import           Data.Byteable
import qualified Data.ByteString.Base16       as Base16
import qualified Data.ByteString.Base64       as Base64
import qualified Data.ByteString.Char8        as B
import qualified Data.CaseInsensitive         as CI
import           Data.Conduit
import           Data.Conduit.Attoparsec      (sinkParser)
import           Data.Default
import           Data.Function                (on)
import qualified Data.HashMap.Strict          as HM
import           Data.Int
import           Data.IORef
import           Data.List
import qualified Data.Map                     as M
import           Data.Maybe
import           Data.Monoid
import           Data.Proxy
import           Data.Scientific
import qualified Data.Serialize               as Ser
import qualified Data.Set                     as S
import           Data.String
import           Data.Tagged
import qualified Data.Text                    as T
import qualified Data.Text.Encoding           as T
import           Data.Time
import           Data.Typeable
import           Data.Word
import qualified Network.HTTP.Conduit         as HTTP
import qualified Network.HTTP.Types           as HTTP
import           Safe
-------------------------------------------------------------------------------
import           Aws.Core
-------------------------------------------------------------------------------



-------------------------------------------------------------------------------
-- | Numeric values stored in DynamoDb. Only used in defining new
-- 'DynVal' instances.
newtype DynNumber = DynNumber { unDynNumber :: Scientific }
    deriving (Eq,Show,Read,Ord,Typeable)


-------------------------------------------------------------------------------
-- | String values stored in DynamoDb. Only used in defining new
-- 'DynVal' instances.
newtype DynString = DynString { unDynString :: T.Text }
    deriving (Eq,Show,Read,Ord,Typeable)


-------------------------------------------------------------------------------
-- | Binary values stored in DynamoDb. Only used in defining new
-- 'DynVal' instances.
newtype DynBinary = DynBinary { unDynBinary :: B.ByteString }
    deriving (Eq,Show,Read,Ord,Typeable)


-------------------------------------------------------------------------------
-- | An internally used closed typeclass for values that have direct
-- DynamoDb representations. Based on AWS API, this is basically
-- numbers, strings and binary blobs.
--
-- This is here so that any 'DynVal' haskell value can automatically
-- be lifted to a list or a 'Set' without any instance code
-- duplication.
--
-- Do not try to create your own instances.
class Ord a => DynData a where
    fromData :: a -> DValue
    toData :: DValue -> Maybe a

instance DynData DynNumber where
    fromData (DynNumber i) = DNum i
    toData (DNum i) = Just $ DynNumber i
    toData _ = Nothing

instance DynData (S.Set DynNumber) where
    fromData set = DNumSet (S.map unDynNumber set)
    toData (DNumSet i) = Just $ S.map DynNumber i
    toData _ = Nothing

instance DynData DynString where
    fromData (DynString i) = DString i
    toData (DString i) = Just $ DynString i
    toData _ = Nothing

instance DynData (S.Set DynString) where
    fromData set = DStringSet (S.map unDynString set)
    toData (DStringSet i) = Just $ S.map DynString i
    toData _ = Nothing

instance DynData DynBinary where
    fromData (DynBinary i) = DBinary i
    toData (DBinary i) = Just $ DynBinary i
    toData _ = Nothing

instance DynData (S.Set DynBinary) where
    fromData set = DBinSet (S.map unDynBinary set)
    toData (DBinSet i) = Just $ S.map DynBinary i
    toData _ = Nothing

instance DynData DValue where
    fromData = id
    toData = Just


-------------------------------------------------------------------------------
-- | Class of Haskell types that can be represented as DynamoDb values.
--
-- This is the conversion layer; instantiate this class for your own
-- types and then use the 'toValue' and 'fromValue' combinators to
-- convert in application code.
--
-- Each Haskell type instantiated with this class will map to a
-- DynamoDb-supported type that most naturally represents it.
class DynData (DynRep a) => DynVal a where

    -- | Which of the 'DynData' instances does this data type directly
    -- map to?
    type DynRep a

    -- | Convert to representation
    toRep :: a -> DynRep a

    -- | Convert from representation
    fromRep :: DynRep a -> Maybe a


-------------------------------------------------------------------------------
-- | Any singular 'DynVal' can be upgraded to a list.
instance (DynData (DynRep [a]), DynVal a) => DynVal [a] where
    type DynRep [a] = S.Set (DynRep a)
    fromRep set = mapM fromRep $ S.toList set
    toRep as = S.fromList $ map toRep as


-------------------------------------------------------------------------------
-- | Any singular 'DynVal' can be upgraded to a 'Set'.
instance (DynData (DynRep (S.Set a)), DynVal a, Ord a) => DynVal (S.Set a) where
    type DynRep (S.Set a) = S.Set (DynRep a)
    fromRep set = fmap S.fromList . mapM fromRep $ S.toList set
    toRep as = S.map toRep as


instance DynVal DValue where
    type DynRep DValue = DValue
    fromRep = Just
    toRep   = id


instance DynVal Int where
    type DynRep Int = DynNumber
    fromRep (DynNumber i) = toIntegral i
    toRep i = DynNumber (fromIntegral i)


instance DynVal Int8 where
    type DynRep Int8 = DynNumber
    fromRep (DynNumber i) = toIntegral i
    toRep i = DynNumber (fromIntegral i)


instance DynVal Int16 where
    type DynRep Int16 = DynNumber
    fromRep (DynNumber i) = toIntegral i
    toRep i = DynNumber (fromIntegral i)


instance DynVal Int32 where
    type DynRep Int32 = DynNumber
    fromRep (DynNumber i) = toIntegral i
    toRep i = DynNumber (fromIntegral i)


instance DynVal Int64 where
    type DynRep Int64 = DynNumber
    fromRep (DynNumber i) = toIntegral i
    toRep i = DynNumber (fromIntegral i)


instance DynVal Word8 where
    type DynRep Word8 = DynNumber
    fromRep (DynNumber i) = toIntegral i
    toRep i = DynNumber (fromIntegral i)


instance DynVal Word16 where
    type DynRep Word16 = DynNumber
    fromRep (DynNumber i) = toIntegral i
    toRep i = DynNumber (fromIntegral i)


instance DynVal Word32 where
    type DynRep Word32 = DynNumber
    fromRep (DynNumber i) = toIntegral i
    toRep i = DynNumber (fromIntegral i)


instance DynVal Word64 where
    type DynRep Word64 = DynNumber
    fromRep (DynNumber i) = toIntegral i
    toRep i = DynNumber (fromIntegral i)


instance DynVal Integer where
    type DynRep Integer = DynNumber
    fromRep (DynNumber i) = toIntegral i
    toRep i = DynNumber (fromIntegral i)


instance DynVal T.Text where
    type DynRep T.Text = DynString
    fromRep (DynString i) = Just i
    toRep i = DynString i


instance DynVal B.ByteString where
    type DynRep B.ByteString = DynBinary
    fromRep (DynBinary i) = Just i
    toRep i = DynBinary i


instance DynVal Double where
    type DynRep Double = DynNumber
    fromRep (DynNumber i) = Just $ toRealFloat i
    toRep i = DynNumber (fromFloatDigits i)


-------------------------------------------------------------------------------
-- | Encoded as number of days
instance DynVal Day where
    type DynRep Day = DynNumber
    fromRep (DynNumber i) = ModifiedJulianDay <$> (toIntegral i)
    toRep (ModifiedJulianDay i) = DynNumber (fromIntegral i)


-------------------------------------------------------------------------------
-- | Losslessly encoded via 'Integer' picoseconds
instance DynVal UTCTime where
    type DynRep UTCTime = DynNumber
    fromRep num = fromTS <$> fromRep num
    toRep x = toRep (toTS x)


-------------------------------------------------------------------------------
pico :: Rational
pico = toRational $ 10 ^ (12 :: Integer)


-------------------------------------------------------------------------------
dayPico :: Integer
dayPico = 86400 * round pico


-------------------------------------------------------------------------------
-- | Convert UTCTime to picoseconds
--
-- TODO: Optimize performance?
toTS :: UTCTime -> Integer
toTS (UTCTime (ModifiedJulianDay i) diff) = i' + diff'
    where
      diff' = floor (toRational diff * pico)
      i' = i * dayPico


-------------------------------------------------------------------------------
-- | Convert picoseconds to UTCTime
--
-- TODO: Optimize performance?
fromTS :: Integer -> UTCTime
fromTS i = UTCTime (ModifiedJulianDay days) diff
    where
      (days, secs) = i `divMod` dayPico
      diff = fromRational ((toRational secs) / pico)


-- | Encoded as 0 and 1.
instance DynVal Bool where
    type DynRep Bool = DynNumber
    fromRep (DynNumber i) = do
        (i' :: Int) <- toIntegral i
        case i' of
          0 -> return False
          1 -> return True
          _ -> Nothing
    toRep b = DynNumber (if b then 1 else 0)



-- | Type wrapper for binary data to be written to DynamoDB. Wrap any
-- 'Serialize' instance in there and 'DynVal' will know how to
-- automatically handle conversions in binary form.
newtype Bin a = Bin { getBin :: a }
    deriving (Eq,Show,Read,Ord,Typeable,Enum)


instance (Ser.Serialize a) => DynVal (Bin a) where
    type DynRep (Bin a) = DynBinary
    toRep (Bin i) = DynBinary (Ser.encode i)
    fromRep (DynBinary i) = either (const Nothing) (Just . Bin) $
                            Ser.decode i



-------------------------------------------------------------------------------
-- | Encode a Haskell value.
toValue :: DynVal a  => a -> DValue
toValue a = fromData $ toRep a


-------------------------------------------------------------------------------
-- | Decode a Haskell value.
fromValue :: DynVal a => DValue -> Maybe a
fromValue d = toData d >>= fromRep


toIntegral :: (Integral a, RealFrac a1) => a1 -> Maybe a
toIntegral sc = Just $ floor sc



-- | Value types natively recognized by DynamoDb. We pretty much
-- exactly reflect the AWS API onto Haskell types.
data DValue
    = DNum Scientific
    | DString T.Text
    | DBinary B.ByteString
    -- ^ Binary data will automatically be base64 marshalled.
    | DNumSet (S.Set Scientific)
    | DStringSet (S.Set T.Text)
    | DBinSet (S.Set B.ByteString)
    -- ^ Binary data will automatically be base64 marshalled.
    deriving (Eq,Show,Read,Ord,Typeable)


instance IsString DValue where
    fromString t = DString (T.pack t)

-------------------------------------------------------------------------------
-- | Primary keys consist of either just a Hash key (mandatory) or a
-- hash key and a range key (optional).
data PrimaryKey = PrimaryKey {
      pkHash  :: Attribute
    , pkRange :: Maybe Attribute
    } deriving (Read,Show,Ord,Eq,Typeable)


-------------------------------------------------------------------------------
-- | Construct a hash-only primary key.
--
-- >>> hk "user-id" "ABCD"
--
-- >>> hk "user-id" (mkVal 23)
hk :: T.Text -> DValue -> PrimaryKey
hk k v = PrimaryKey (attr k v) Nothing


-------------------------------------------------------------------------------
-- | Construct a hash-and-range primary key.
hrk :: T.Text                   -- ^ Hash key name
    -> DValue                   -- ^ Hash key value
    -> T.Text                   -- ^ Range key name
    -> DValue                   -- ^ Range key value
    -> PrimaryKey
hrk k v k2 v2 = PrimaryKey (attr k v) (Just (attr k2 v2))


instance ToJSON PrimaryKey where
    toJSON (PrimaryKey h Nothing) = toJSON h
    toJSON (PrimaryKey h (Just r)) =
      let Object p1 = toJSON h
          Object p2 = toJSON r
      in Object (p1 `HM.union` p2)


-- | A key-value pair
data Attribute = Attribute {
      attrName :: T.Text
    , attrVal  :: DValue
    } deriving (Read,Show,Ord,Eq,Typeable)


-- | Convert attribute to a tuple representation
attrTuple :: Attribute -> (T.Text, DValue)
attrTuple (Attribute a b) = (a,b)


-- | Convenience function for constructing key-value pairs
attr :: DynVal a => T.Text -> a -> Attribute
attr k v = Attribute k (toValue v)


-- | 'attr' with type witness to help with cases where you're manually
-- supplying values in code.
--
-- >> item [ attrAs text "name" "john" ]
attrAs :: DynVal a => Proxy a -> T.Text -> a -> Attribute
attrAs _ k v = attr k v


-- | Type witness for 'Text'. See 'attrAs'.
text :: Proxy T.Text
text = Proxy


-- | Type witness for 'Integer'. See 'attrAs'.
int :: Proxy Integer
int = Proxy


-- | Type witness for 'Double'. See 'attrAs'.
double :: Proxy Double
double = Proxy


-- | A DynamoDb object is simply a key-value dictionary.
type Item = M.Map T.Text DValue


-------------------------------------------------------------------------------
-- | Pack a list of attributes into an Item.
item :: [Attribute] -> Item
item = M.fromList . map attrTuple


-------------------------------------------------------------------------------
-- | Unpack an 'Item' into a list of attributes.
attributes :: M.Map T.Text DValue -> [Attribute]
attributes = map (\ (k, v) -> Attribute k v) . M.toList


showT :: Show a => a -> T.Text
showT = T.pack . show


instance ToJSON DValue where
    toJSON (DNum i) = object ["N" .= showT i]
    toJSON (DString i) = object ["S" .= i]
    toJSON (DBinary i) = object ["B" .= (T.decodeUtf8 $ Base64.encode i)]
    toJSON (DNumSet i) = object ["NS" .= map showT (S.toList i)]
    toJSON (DStringSet i) = object ["SS" .= S.toList i]
    toJSON (DBinSet i) = object ["BS" .= map (T.decodeUtf8 . Base64.encode) (S.toList i)]
    toJSON x = error $ "aws: bug: DynamoDB can't handle " ++ show x


instance FromJSON DValue where
    parseJSON o = do
      (obj :: [(T.Text, Value)]) <- M.toList `liftM` parseJSON o
      case obj of
        [("N", numStr)] -> DNum <$> parseScientific numStr
        [("S", str)] -> DString <$> parseJSON str
        [("B", bin)] -> do
            res <- (Base64.decode . T.encodeUtf8) <$> parseJSON bin
            either fail (return . DBinary) res
        [("NS", s)] -> do xs <- mapM parseScientific =<< parseJSON s
                          return $ DNumSet $ S.fromList xs
        [("SS", s)] -> DStringSet <$> parseJSON s
        [("BS", s)] -> do
            xs <- mapM (either fail return . Base64.decode . T.encodeUtf8)
                  =<< parseJSON s
            return $ DBinSet $ S.fromList xs

        x -> fail $ "aws: unknown dynamodb value: " ++ show x

      where
        parseScientific (String str) =
            case Atto.parseOnly Atto.scientific str of
              Left e -> fail ("parseScientific failed: " ++ e)
              Right a -> return a
        parseScientific (Number n) = return n
        parseScientific _ = fail "Unexpected JSON type in parseScientific"


instance ToJSON Attribute where
    toJSON a = object $ [attributeJson a]


-------------------------------------------------------------------------------
-- | Parse a JSON object that contains attributes
parseAttributeJson :: Value -> A.Parser [Attribute]
parseAttributeJson (Object v) = mapM conv $ HM.toList v
    where
      conv (k, o) = Attribute k <$> parseJSON o
parseAttributeJson _ = error "Attribute JSON must be an Object"


-- | Convert into JSON object for AWS.
attributesJson :: [Attribute] -> Value
attributesJson as = object $ map attributeJson as


-- | Convert into JSON pair
attributeJson :: Attribute -> Pair
attributeJson (Attribute nm v) = nm .= v


-------------------------------------------------------------------------------
-- | Errors defined by AWS.
data DdbErrCode
    = AccessDeniedException
    | ConditionalCheckFailedException
    | IncompleteSignatureException
    | InvalidSignatureException
    | LimitExceededException
    | MissingAuthenticationTokenException
    | ProvisionedThroughputExceededException
    | ResourceInUseException
    | ResourceNotFoundException
    | ThrottlingException
    | ValidationException
    | RequestTooLarge
    | InternalFailure
    | InternalServerError
    | ServiceUnavailableException
    | SerializationException
    -- ^ Raised by AWS when the request JSON is missing fields or is
    -- somehow malformed.
    deriving (Read,Show,Eq,Typeable)


-------------------------------------------------------------------------------
-- | Whether the action should be retried based on the received error.
shouldRetry :: DdbErrCode -> Bool
shouldRetry e = go e
    where
      go LimitExceededException = True
      go ProvisionedThroughputExceededException = True
      go ResourceInUseException = True
      go ThrottlingException = True
      go InternalFailure = True
      go InternalServerError = True
      go ServiceUnavailableException = True
      go _ = False


-------------------------------------------------------------------------------
-- | Errors related to this library.
data DdbLibraryError
    = UnknownDynamoErrCode T.Text
    -- ^ A DynamoDB error code we do not know about.
    | JsonProtocolError Value T.Text
    -- ^ A JSON response we could not parse.
    deriving (Show,Eq,Typeable)


-- | Potential errors raised by DynamoDB
data DdbError = DdbError {
      ddbStatusCode :: Int
    -- ^ 200 if successful, 400 for client errors and 500 for
    -- server-side errors.
    , ddbErrCode    :: DdbErrCode
    , ddbErrMsg     :: T.Text
    } deriving (Show,Eq,Typeable)


instance C.Exception DdbError
instance C.Exception DdbLibraryError


-- | Response metadata that is present in every DynamoDB response.
data DdbResponse = DdbResponse {
      ddbrCrc   :: Maybe T.Text
    , ddbrMsgId :: Maybe T.Text
    }


instance Loggable DdbResponse where
    toLogText (DdbResponse id2 rid) =
        "DynamoDB: request ID=" `mappend`
        fromMaybe "<none>" rid `mappend`
        ", x-amz-id-2=" `mappend`
        fromMaybe "<none>" id2

instance Monoid DdbResponse where
    mempty = DdbResponse Nothing Nothing
    mappend a b = DdbResponse (ddbrCrc a `mplus` ddbrCrc b) (ddbrMsgId a `mplus` ddbrMsgId b)


data Region = Region {
      rUri  :: B.ByteString
    , rName :: B.ByteString
    } deriving (Eq,Show,Read,Typeable)


data DdbConfiguration qt = DdbConfiguration {
      ddbcRegion   :: Region
    -- ^ The regional endpoint. Ex: 'ddbUsEast'
    , ddbcProtocol :: Protocol
    -- ^ 'HTTP' or 'HTTPS'
    , ddbcPort     :: Maybe Int
    -- ^ Port override (mostly for local dev connection)
    } deriving (Show,Typeable)

instance Default (DdbConfiguration NormalQuery) where
    def = DdbConfiguration ddbUsEast1 HTTPS Nothing

instance DefaultServiceConfiguration (DdbConfiguration NormalQuery) where
  defServiceConfig = ddbHttps ddbUsEast1
  debugServiceConfig = ddbHttp ddbUsEast1


-------------------------------------------------------------------------------
-- | DynamoDb local connection (for development)
ddbLocal :: Region
ddbLocal = Region "127.0.0.1" "local"

ddbUsEast1 :: Region
ddbUsEast1 = Region "dynamodb.us-east-1.amazonaws.com" "us-east-1"

ddbUsWest1 :: Region
ddbUsWest1 = Region "dynamodb.us-west-1.amazonaws.com" "us-west-1"

ddbUsWest2 :: Region
ddbUsWest2 = Region "dynamodb.us-west-2.amazonaws.com" "us-west-2"

ddbEuWest1 :: Region
ddbEuWest1 = Region "dynamodb.eu-west-1.amazonaws.com" "eu-west-1"

ddbEuCentral1 :: Region
ddbEuCentral1 = Region "dynamodb.eu-central-1.amazonaws.com" "eu-central-1"

ddbApNe1 :: Region
ddbApNe1 = Region "dynamodb.ap-northeast-1.amazonaws.com" "ap-northeast-1"

ddbApSe1 :: Region
ddbApSe1 = Region "dynamodb.ap-southeast-1.amazonaws.com" "ap-southeast-1"

ddbApSe2 :: Region
ddbApSe2 = Region "dynamodb.ap-southeast-2.amazonaws.com" "ap-southeast-2"

ddbSaEast1 :: Region
ddbSaEast1 = Region "dynamodb.sa-east-1.amazonaws.com" "sa-east-1"

ddbHttp :: Region -> DdbConfiguration NormalQuery
ddbHttp endpoint = DdbConfiguration endpoint HTTP Nothing

ddbHttps :: Region -> DdbConfiguration NormalQuery
ddbHttps endpoint = DdbConfiguration endpoint HTTPS Nothing


ddbSignQuery
    :: A.ToJSON a
    => B.ByteString
    -> a
    -> DdbConfiguration qt
    -> SignatureData
    -> SignedQuery
ddbSignQuery target body di sd
    = SignedQuery {
        sqMethod = Post
      , sqProtocol = ddbcProtocol di
      , sqHost = host
      , sqPort = fromMaybe (defaultPort (ddbcProtocol di)) (ddbcPort di)
      , sqPath = "/"
      , sqQuery = []
      , sqDate = Just $ signatureTime sd
      , sqAuthorization = Just auth
      , sqContentType = Just "application/x-amz-json-1.0"
      , sqContentMd5 = Nothing
      , sqAmzHeaders = amzHeaders ++ maybe [] (\tok -> [("x-amz-security-token",tok)]) (iamToken credentials)
      , sqOtherHeaders = []
      , sqBody = Just $ HTTP.RequestBodyLBS bodyLBS
      , sqStringToSign = canonicalRequest
      }
    where
        credentials = signatureCredentials sd

        Region{..} = ddbcRegion di
        host = rUri

        sigTime = fmtTime "%Y%m%dT%H%M%SZ" $ signatureTime sd

        bodyLBS = A.encode body
        bodyHash = Base16.encode $ toBytes (hashlazy bodyLBS :: Digest SHA256)

        -- for some reason AWS doesn't want the x-amz-security-token in the canonical request
        amzHeaders = [ ("x-amz-date", sigTime)
                     , ("x-amz-target", dyApiVersion <> target)
                     ]

        canonicalHeaders = sortBy (compare `on` fst) $ amzHeaders ++
                           [("host", host),
                            ("content-type", "application/x-amz-json-1.0")]

        canonicalRequest = B.concat $ intercalate ["\n"] (
                                    [ ["POST"]
                                    , ["/"]
                                    , [] -- query string
                                    ] ++
                                    map (\(a,b) -> [CI.foldedCase a,":",b]) canonicalHeaders ++
                                    [ [] -- end headers
                                    , intersperse ";" (map (CI.foldedCase . fst) canonicalHeaders)
                                    , [bodyHash]
                                    ])

        auth = authorizationV4 sd HmacSHA256 rName "dynamodb"
                               "content-type;host;x-amz-date;x-amz-target"
                               canonicalRequest

data AmazonError = AmazonError {
      aeType    :: T.Text
    , aeMessage :: Maybe T.Text
    }

instance FromJSON AmazonError where
    parseJSON (Object v) = AmazonError
        <$> v .: "__type"
        <*> (Just <$> (v .: "message" <|> v .: "Message") <|> pure Nothing)
    parseJSON _ = error $ "aws: unexpected AmazonError message"




-------------------------------------------------------------------------------
ddbResponseConsumer :: A.FromJSON a => IORef DdbResponse -> HTTPResponseConsumer a
ddbResponseConsumer ref resp = do
    val <- HTTP.responseBody resp $$+- sinkParser (A.json' <* AttoB.endOfInput)
    case statusCode of
      200 -> rSuccess val
      _   -> rError val
  where

    header = fmap T.decodeUtf8 . flip lookup (HTTP.responseHeaders resp)
    amzId = header "x-amzn-RequestId"
    amzCrc = header "x-amz-crc32"
    meta = DdbResponse amzCrc amzId
    tellMeta = liftIO $ tellMetadataRef ref meta

    rSuccess val =
      case A.fromJSON val of
        A.Success a -> return a
        A.Error err -> do
            tellMeta
            throwM $ JsonProtocolError val (T.pack err)

    rError val = do
      tellMeta
      case parseEither parseJSON val of
        Left e ->
          throwM $ JsonProtocolError val (T.pack e)

        Right err'' -> do
          let e = T.drop 1 . snd . T.breakOn "#" $ aeType err''
          errCode <- readErrCode e
          throwM $ DdbError statusCode errCode (fromMaybe "" $ aeMessage err'')

    readErrCode txt =
        let txt' = T.unpack txt
        in case readMay txt' of
             Just e -> return $ e
             Nothing -> throwM (UnknownDynamoErrCode txt)

    HTTP.Status{..} = HTTP.responseStatus resp


-- | Conditions used by mutation operations ('PutItem', 'UpdateItem',
-- etc.). The default 'def' instance is empty (no condition).
data Conditions = Conditions CondMerge [Condition]
    deriving (Eq,Show,Read,Ord,Typeable)

instance Default Conditions where
    def = Conditions CondAnd []



expectsJson :: Conditions -> [A.Pair]
expectsJson = conditionsJson "Expected"


-- | JSON encoding of conditions parameter in various contexts.
conditionsJson :: T.Text -> Conditions -> [A.Pair]
conditionsJson key (Conditions op es) = b ++ a
    where
      a = if null es
          then []
          else [key .= object (map conditionJson es)]

      b = if length (take 2 es) > 1
          then ["ConditionalOperator" .= String (rendCondOp op) ]
          else []


-------------------------------------------------------------------------------
rendCondOp :: CondMerge -> T.Text
rendCondOp CondAnd = "AND"
rendCondOp CondOr = "OR"


-------------------------------------------------------------------------------
-- | How to merge multiple conditions.
data CondMerge = CondAnd | CondOr
    deriving (Eq,Show,Read,Ord,Typeable)


-- | A condition used by mutation operations ('PutItem', 'UpdateItem', etc.).
data Condition = Condition {
      condAttr :: T.Text
    -- ^ Attribute to use as the basis for this conditional
    , condOp   :: CondOp
    -- ^ Operation on the selected attribute
    } deriving (Eq,Show,Read,Ord,Typeable)


-------------------------------------------------------------------------------
-- | Conditional operation to perform on a field.
data CondOp
    = DEq DValue
    | NotEq DValue
    | DLE DValue
    | DLT DValue
    | DGE DValue
    | DGT DValue
    | NotNull
    | IsNull
    | Contains DValue
    | NotContains DValue
    | Begins DValue
    | In [DValue]
    | Between DValue DValue
    deriving (Eq,Show,Read,Ord,Typeable)


-------------------------------------------------------------------------------
getCondValues :: CondOp -> [DValue]
getCondValues c = case c of
    DEq v -> [v]
    NotEq v -> [v]
    DLE v -> [v]
    DLT v -> [v]
    DGE v -> [v]
    DGT v -> [v]
    NotNull -> []
    IsNull -> []
    Contains v -> [v]
    NotContains v -> [v]
    Begins v -> [v]
    In v -> v
    Between a b -> [a,b]


-------------------------------------------------------------------------------
renderCondOp :: CondOp -> T.Text
renderCondOp c = case c of
    DEq{} -> "EQ"
    NotEq{} -> "NE"
    DLE{} -> "LE"
    DLT{} -> "LT"
    DGE{} -> "GE"
    DGT{} -> "GT"
    NotNull -> "NOT_NULL"
    IsNull -> "NULL"
    Contains{} -> "CONTAINS"
    NotContains{} -> "NOT_CONTAINS"
    Begins{} -> "BEGINS_WITH"
    In{} -> "IN"
    Between{} -> "BETWEEN"


conditionJson :: Condition -> Pair
conditionJson Condition{..} = condAttr .= condOp


instance ToJSON CondOp where
    toJSON c = object $ ("ComparisonOperator" .= String (renderCondOp c)) : valueList
      where
        valueList =
          let vs = getCondValues c in
            if null vs
            then []
            else ["AttributeValueList" .= vs]

-------------------------------------------------------------------------------
dyApiVersion :: B.ByteString
dyApiVersion = "DynamoDB_20120810."



-------------------------------------------------------------------------------
-- | The standard response metrics on capacity consumption.
data ConsumedCapacity = ConsumedCapacity {
      capacityUnits       :: Int64
    , capacityGlobalIndex :: [(T.Text, Int64)]
    , capacityLocalIndex  :: [(T.Text, Int64)]
    , capacityTableUnits  :: Maybe Int64
    , capacityTable       :: T.Text
    } deriving (Eq,Show,Read,Ord,Typeable)


instance FromJSON ConsumedCapacity where
    parseJSON (Object v) = ConsumedCapacity
      <$> v .: "CapacityUnits"
      <*> (HM.toList <$> v .:? "GlobalSecondaryIndexes" .!= mempty)
      <*> (HM.toList <$> v .:? "LocalSecondaryIndexes" .!= mempty)
      <*> (v .:? "Table" >>= maybe (return Nothing) (.: "CapacityUnits"))
      <*> v .: "TableName"
    parseJSON _ = fail "ConsumedCapacity must be an Object."



data ReturnConsumption = RCIndexes | RCTotal | RCNone
    deriving (Eq,Show,Read,Ord,Typeable)

instance ToJSON ReturnConsumption where
    toJSON RCIndexes = String "INDEXES"
    toJSON RCTotal = String "TOTAL"
    toJSON RCNone = String "NONE"

instance Default ReturnConsumption where
    def = RCNone

data ReturnItemCollectionMetrics = RICMSize | RICMNone
    deriving (Eq,Show,Read,Ord,Typeable)

instance ToJSON ReturnItemCollectionMetrics where
    toJSON RICMSize = String "SIZE"
    toJSON RICMNone = String "NONE"

instance Default ReturnItemCollectionMetrics where
    def = RICMNone


data ItemCollectionMetrics = ItemCollectionMetrics {
      icmKey      :: (T.Text, DValue)
    , icmEstimate :: [Double]
    } deriving (Eq,Show,Read,Ord,Typeable)


instance FromJSON ItemCollectionMetrics where
    parseJSON (Object v) = ItemCollectionMetrics
      <$> (do m <- v .: "ItemCollectionKey"
              return $ head $ HM.toList m)
      <*> v .: "SizeEstimateRangeGB"
    parseJSON _ = fail "ItemCollectionMetrics must be an Object."


-------------------------------------------------------------------------------
-- | What to return from the current update operation
data UpdateReturn
    = URNone                    -- ^ Return nothing
    | URAllOld                  -- ^ Return old values
    | URUpdatedOld              -- ^ Return old values with a newer replacement
    | URAllNew                  -- ^ Return new values
    | URUpdatedNew              -- ^ Return new values that were replacements
    deriving (Eq,Show,Read,Ord,Typeable)


instance ToJSON UpdateReturn where
    toJSON URNone = toJSON (String "NONE")
    toJSON URAllOld = toJSON (String "ALL_OLD")
    toJSON URUpdatedOld = toJSON (String "UPDATED_OLD")
    toJSON URAllNew = toJSON (String "ALL_NEW")
    toJSON URUpdatedNew = toJSON (String "UPDATED_NEW")


instance Default UpdateReturn where
    def = URNone



-------------------------------------------------------------------------------
-- | What to return from a 'Query' or 'Scan' query.
data QuerySelect
    = SelectSpecific [T.Text]
    -- ^ Only return selected attributes
    | SelectCount
    -- ^ Return counts instead of attributes
    | SelectProjected
    -- ^ Return index-projected attributes
    | SelectAll
    -- ^ Default. Return everything.
    deriving (Eq,Show,Read,Ord,Typeable)


instance Default QuerySelect where def = SelectAll

-------------------------------------------------------------------------------
querySelectJson (SelectSpecific as) =
    [ "Select" .= String "SPECIFIC_ATTRIBUTES"
    , "AttributesToGet" .= as]
querySelectJson SelectCount = ["Select" .= String "COUNT"]
querySelectJson SelectProjected = ["Select" .= String "ALL_PROJECTED_ATTRIBUTES"]
querySelectJson SelectAll = ["Select" .= String "ALL_ATTRIBUTES"]


-------------------------------------------------------------------------------
-- | A class to help predict DynamoDb size of values, attributes and
-- entire items. The result is given in number of bytes.
class DynSize a where
    dynSize :: a -> Int

instance DynSize DValue where
    dynSize (DNum _) = 8
    dynSize (DString a) = T.length a
    dynSize (DBinary bs) = T.length . T.decodeUtf8 $ Base64.encode bs
    dynSize (DNumSet s) = 8 * S.size s
    dynSize (DStringSet s) = sum $ map (dynSize . DString) $ S.toList s
    dynSize (DBinSet s) = sum $ map (dynSize . DBinary) $ S.toList s

instance DynSize Attribute where
    dynSize (Attribute k v) = T.length k + dynSize v

instance DynSize Item where
    dynSize m = sum $ map dynSize $ attributes m

instance DynSize a => DynSize [a] where
    dynSize as = sum $ map dynSize as

instance DynSize a => DynSize (Maybe a) where
    dynSize = maybe 0 dynSize

instance (DynSize a, DynSize b) => DynSize (Either a b) where
    dynSize = either dynSize dynSize


-------------------------------------------------------------------------------
-- | Will an attribute be considered empty by DynamoDb?
--
-- A 'PutItem' (or similar) with empty attributes will be rejected
-- with a 'ValidationException'.
nullAttr :: Attribute -> Bool
nullAttr (Attribute _ val) =
    case val of
      DString "" -> True
      DBinary "" -> True
      DNumSet s | S.null s -> True
      DStringSet s | S.null s -> True
      DBinSet s | S.null s -> True
      _ -> False




-------------------------------------------------------------------------------
--
-- | Item Parsing
--
-------------------------------------------------------------------------------



-- | Failure continuation.
type Failure f r   = String -> f r

-- | Success continuation.
type Success a f r = a -> f r


-- | A continuation-based parser type.
newtype Parser a = Parser {
      runParser :: forall f r.
                   Failure f r
                -> Success a f r
                -> f r
    }

instance Monad Parser where
    m >>= g = Parser $ \kf ks -> let ks' a = runParser (g a) kf ks
                                 in runParser m kf ks'
    {-# INLINE (>>=) #-}
    return a = Parser $ \_kf ks -> ks a
    {-# INLINE return #-}
    fail msg = Parser $ \kf _ks -> kf msg
    {-# INLINE fail #-}

instance Functor Parser where
    fmap f m = Parser $ \kf ks -> let ks' a = ks (f a)
                                  in runParser m kf ks'
    {-# INLINE fmap #-}

instance Applicative Parser where
    pure  = return
    {-# INLINE pure #-}
    (<*>) = apP
    {-# INLINE (<*>) #-}

instance Alternative Parser where
    empty = fail "empty"
    {-# INLINE empty #-}
    (<|>) = mplus
    {-# INLINE (<|>) #-}

instance MonadPlus Parser where
    mzero = fail "mzero"
    {-# INLINE mzero #-}
    mplus a b = Parser $ \kf ks -> let kf' _ = runParser b kf ks
                                   in runParser a kf' ks
    {-# INLINE mplus #-}

instance Monoid (Parser a) where
    mempty  = fail "mempty"
    {-# INLINE mempty #-}
    mappend = mplus
    {-# INLINE mappend #-}

apP :: Parser (a -> b) -> Parser a -> Parser b
apP d e = do
  b <- d
  a <- e
  return (b a)
{-# INLINE apP #-}


-------------------------------------------------------------------------------
-- | Types convertible to DynamoDb 'Item' collections.
--
-- Use 'attr' and 'attrAs' combinators to conveniently define instances.
class ToDynItem a where
    toItem :: a -> Item


-------------------------------------------------------------------------------
-- | Types parseable from DynamoDb 'Item' collections.
--
-- User 'getAttr' family of functions to applicatively or monadically
-- parse into your custom types.
class FromDynItem a where
    parseItem :: Item -> Parser a


instance ToDynItem Item where toItem = id

instance FromDynItem Item where parseItem = return


instance DynVal a => ToDynItem [(T.Text, a)] where
    toItem as = item $ map (uncurry attr) as

instance (Typeable a, DynVal a) => FromDynItem [(T.Text, a)] where
    parseItem i = mapM f $ M.toList i
        where
          f (k,v) = do
              v' <- maybe (fail (valErr (Tagged v :: Tagged a DValue))) return $
                    fromValue v
              return (k, v')


instance DynVal a => ToDynItem (M.Map T.Text a) where
    toItem m = toItem $ M.toList m


instance (Typeable a, DynVal a) => FromDynItem (M.Map T.Text a) where
    parseItem i = M.fromList <$> parseItem i


valErr :: forall a. Typeable a => Tagged a DValue -> String
valErr (Tagged dv) = "Can't convert DynamoDb value " <> show dv <>
              " into type " <> (show (typeOf (undefined :: a)))


-- | Convenience combinator for parsing fields from an 'Item' returned
-- by DynamoDb.
getAttr
    :: forall a. (Typeable a, DynVal a)
    => T.Text
    -- ^ Attribute name
    -> Item
    -- ^ Item from DynamoDb
    -> Parser a
getAttr k m = do
    case M.lookup k m of
      Nothing -> fail ("Key " <> T.unpack k <> " not found")
      Just dv -> maybe (fail (valErr (Tagged dv :: Tagged a DValue))) return $ fromValue dv


-- | Parse attribute if it's present in the 'Item'. Fail if attribute
-- is present but conversion fails.
getAttr'
    :: forall a. (Typeable a, DynVal a)
    => T.Text
    -- ^ Attribute name
    -> Item
    -- ^ Item from DynamoDb
    -> Parser (Maybe a)
getAttr' k m = do
    case M.lookup k m of
      Nothing -> return Nothing
      Just dv -> return $ fromValue dv


-------------------------------------------------------------------------------
-- | Parse an 'Item' into target type using the 'FromDynItem'
-- instance.
fromItem :: FromDynItem a => Item -> Either String a
fromItem i = runParser (parseItem i) Left Right






