{-# LANGUAGE DeriveDataTypeable        #-}
{-# LANGUAGE FlexibleContexts          #-}
{-# LANGUAGE FlexibleInstances         #-}
{-# LANGUAGE MultiParamTypeClasses     #-}
{-# LANGUAGE NoMonomorphismRestriction #-}
{-# LANGUAGE OverloadedStrings         #-}
{-# LANGUAGE RecordWildCards           #-}
{-# LANGUAGE ScopedTypeVariables       #-}
{-# LANGUAGE TypeFamilies              #-}
-----------------------------------------------------------------------------
-- |
-- Module      :  Aws.DynamoDb.Commands.UpdateItem
-- Copyright   :  Soostone Inc
-- License     :  BSD3
--
-- Maintainer  :  Ozgun Ataman <ozgun.ataman@soostone.com>
-- Stability   :  experimental
--
--
----------------------------------------------------------------------------

module Aws.DynamoDb.Commands.UpdateItem
    ( UpdateItem(..)
    , updateItem
    , AttributeUpdate(..)
    , au
    , UpdateAction(..)
    , UpdateItemResponse(..)
    ) where

-------------------------------------------------------------------------------
import           Control.Applicative
import           Data.Aeson
import           Data.Default
import qualified Data.Text           as T
import           Prelude
-------------------------------------------------------------------------------
import           Aws.Core
import           Aws.DynamoDb.Core
-------------------------------------------------------------------------------


-- | An @UpdateItem@ request.
data UpdateItem = UpdateItem {
      uiTable   :: T.Text
    , uiKey     :: PrimaryKey
    , uiUpdates :: [AttributeUpdate]
    , uiExpect  :: Conditions
    -- ^ Conditional update - see DynamoDb documentation
    , uiReturn  :: UpdateReturn
    , uiRetCons :: ReturnConsumption
    , uiRetMet  :: ReturnItemCollectionMetrics
    } deriving (Eq,Show,Read,Ord)


-------------------------------------------------------------------------------
-- | Construct a minimal 'UpdateItem' request.
updateItem
    :: T.Text                   -- ^ Table name
    -> PrimaryKey               -- ^ Primary key for item
    -> [AttributeUpdate]        -- ^ Updates for this item
    -> UpdateItem
updateItem tn key ups = UpdateItem tn key ups def def def def


-- | A helper to avoid overlapping instances for 'ToJSON'.
newtype AttributeUpdates = AttributeUpdates {
    getAttributeUpdates :: [AttributeUpdate]
    }


data AttributeUpdate = AttributeUpdate {
      auAttr   :: Attribute
    -- ^ Attribute key-value
    , auAction :: UpdateAction
    -- ^ Type of update operation.
    } deriving (Eq,Show,Read,Ord)


instance DynSize AttributeUpdate where
    dynSize (AttributeUpdate a _) = dynSize a

-------------------------------------------------------------------------------
-- | Shorthand for the 'AttributeUpdate' constructor. Defaults to PUT
-- for the update action.
au :: Attribute -> AttributeUpdate
au a = AttributeUpdate a def


instance ToJSON AttributeUpdates where
    toJSON = object . map mk . getAttributeUpdates
        where
          mk AttributeUpdate { auAction = UDelete, auAttr = auAttr } =
            (attrName auAttr) .= object
            ["Action" .= UDelete]
          mk AttributeUpdate { .. } = (attrName auAttr) .= object
            ["Value" .= (attrVal auAttr), "Action" .= auAction]


-------------------------------------------------------------------------------
-- | Type of attribute update to perform.
--
-- See AWS docs at:
--
-- @http:\/\/docs.aws.amazon.com\/amazondynamodb\/latest\/APIReference\/API_UpdateItem.html@
data UpdateAction
    = UPut                      -- ^ Simpley write, overwriting any previous value
    | UAdd                      -- ^ Numerical add or add to set.
    | UDelete                   -- ^ Empty value: remove; Set value: Subtract from set.
    deriving (Eq,Show,Read,Ord)


instance ToJSON UpdateAction where
    toJSON UPut = String "PUT"
    toJSON UAdd = String "ADD"
    toJSON UDelete = String "DELETE"


instance Default UpdateAction where
    def = UPut


instance ToJSON UpdateItem where
    toJSON UpdateItem{..} =
        object $ expectsJson uiExpect ++
          [ "TableName" .= uiTable
          , "Key" .= uiKey
          , "AttributeUpdates" .= AttributeUpdates uiUpdates
          , "ReturnValues" .= uiReturn
          , "ReturnConsumedCapacity" .= uiRetCons
          , "ReturnItemCollectionMetrics" .= uiRetMet
          ]


data UpdateItemResponse = UpdateItemResponse {
      uirAttrs    :: Maybe Item
    -- ^ Old attributes, if requested
    , uirConsumed :: Maybe ConsumedCapacity
    -- ^ Amount of capacity consumed
    } deriving (Eq,Show,Read,Ord)



instance Transaction UpdateItem UpdateItemResponse


instance SignQuery UpdateItem where
    type ServiceConfiguration UpdateItem = DdbConfiguration
    signQuery gi = ddbSignQuery "UpdateItem" gi


instance FromJSON UpdateItemResponse where
    parseJSON (Object v) = UpdateItemResponse
        <$> v .:? "Attributes"
        <*> v .:? "ConsumedCapacity"
    parseJSON _ = fail "UpdateItemResponse expected a JSON object"


instance ResponseConsumer r UpdateItemResponse where
    type ResponseMetadata UpdateItemResponse = DdbResponse
    responseConsumer _ _ ref resp = ddbResponseConsumer ref resp


instance AsMemoryResponse UpdateItemResponse where
    type MemoryResponse UpdateItemResponse = UpdateItemResponse
    loadToMemory = return








