{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE DeriveGeneric      #-}
{-# LANGUAGE OverloadedStrings  #-}
{-# LANGUAGE RecordWildCards    #-}
{-# LANGUAGE TypeFamilies       #-}

{-# OPTIONS_GHC -fno-warn-unused-imports #-}
{-# OPTIONS_GHC -fno-warn-unused-binds   #-}
{-# OPTIONS_GHC -fno-warn-unused-matches #-}

-- Derived from AWS service descriptions, licensed under Apache 2.0.

-- |
-- Module      : Network.AWS.DynamoDB.BatchGetItem
-- Copyright   : (c) 2013-2018 Brendan Hay
-- License     : Mozilla Public License, v. 2.0.
-- Maintainer  : Brendan Hay <brendan.g.hay+amazonka@gmail.com>
-- Stability   : auto-generated
-- Portability : non-portable (GHC extensions)
--
-- The @BatchGetItem@ operation returns the attributes of one or more items from one or more tables. You identify requested items by primary key.
--
--
-- A single operation can retrieve up to 16 MB of data, which can contain as many as 100 items. @BatchGetItem@ will return a partial result if the response size limit is exceeded, the table's provisioned throughput is exceeded, or an internal processing failure occurs. If a partial result is returned, the operation returns a value for @UnprocessedKeys@ . You can use this value to retry the operation starting with the next item to get.
--
-- /Important:/ If you request more than 100 items @BatchGetItem@ will return a @ValidationException@ with the message "Too many items requested for the BatchGetItem call".
--
-- For example, if you ask to retrieve 100 items, but each individual item is 300 KB in size, the system returns 52 items (so as not to exceed the 16 MB limit). It also returns an appropriate @UnprocessedKeys@ value so you can get the next page of results. If desired, your application can include its own logic to assemble the pages of results into one data set.
--
-- If /none/ of the items can be processed due to insufficient provisioned throughput on all of the tables in the request, then @BatchGetItem@ will return a @ProvisionedThroughputExceededException@ . If /at least one/ of the items is successfully processed, then @BatchGetItem@ completes successfully, while returning the keys of the unread items in @UnprocessedKeys@ .
--
-- /Important:/ If DynamoDB returns any unprocessed items, you should retry the batch operation on those items. However, /we strongly recommend that you use an exponential backoff algorithm/ . If you retry the batch operation immediately, the underlying read or write requests can still fail due to throttling on the individual tables. If you delay the batch operation using exponential backoff, the individual requests in the batch are much more likely to succeed.
--
-- For more information, see <http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/ErrorHandling.html#BatchOperations Batch Operations and Error Handling> in the /Amazon DynamoDB Developer Guide/ .
--
-- By default, @BatchGetItem@ performs eventually consistent reads on every table in the request. If you want strongly consistent reads instead, you can set @ConsistentRead@ to @true@ for any or all tables.
--
-- In order to minimize response latency, @BatchGetItem@ retrieves items in parallel.
--
-- When designing your application, keep in mind that DynamoDB does not return items in any particular order. To help parse the response by item, include the primary key values for the items in your request in the @ProjectionExpression@ parameter.
--
-- If a requested item does not exist, it is not returned in the result. Requests for nonexistent items consume the minimum read capacity units according to the type of read. For more information, see <http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/WorkingWithTables.html#CapacityUnitCalculations Capacity Units Calculations> in the /Amazon DynamoDB Developer Guide/ .
--
module Network.AWS.DynamoDB.BatchGetItem
    (
    -- * Creating a Request
      batchGetItem
    , BatchGetItem
    -- * Request Lenses
    , bgiReturnConsumedCapacity
    , bgiRequestItems

    -- * Destructuring the Response
    , batchGetItemResponse
    , BatchGetItemResponse
    -- * Response Lenses
    , bgirsUnprocessedKeys
    , bgirsResponses
    , bgirsConsumedCapacity
    , bgirsResponseStatus
    ) where

import Network.AWS.DynamoDB.Types
import Network.AWS.DynamoDB.Types.Product
import Network.AWS.Lens
import Network.AWS.Prelude
import Network.AWS.Request
import Network.AWS.Response

-- | Represents the input of a @BatchGetItem@ operation.
--
--
--
-- /See:/ 'batchGetItem' smart constructor.
data BatchGetItem = BatchGetItem'
  { _bgiReturnConsumedCapacity :: !(Maybe ReturnConsumedCapacity)
  , _bgiRequestItems           :: !(Map Text KeysAndAttributes)
  } deriving (Eq, Read, Show, Data, Typeable, Generic)


-- | Creates a value of 'BatchGetItem' with the minimum fields required to make a request.
--
-- Use one of the following lenses to modify other fields as desired:
--
-- * 'bgiReturnConsumedCapacity' - Undocumented member.
--
-- * 'bgiRequestItems' - A map of one or more table names and, for each table, a map that describes one or more items to retrieve from that table. Each table name can be used only once per @BatchGetItem@ request. Each element in the map of items to retrieve consists of the following:     * @ConsistentRead@ - If @true@ , a strongly consistent read is used; if @false@ (the default), an eventually consistent read is used.     * @ExpressionAttributeNames@ - One or more substitution tokens for attribute names in the @ProjectionExpression@ parameter. The following are some use cases for using @ExpressionAttributeNames@ :     * To access an attribute whose name conflicts with a DynamoDB reserved word.     * To create a placeholder for repeating occurrences of an attribute name in an expression.     * To prevent special characters in an attribute name from being misinterpreted in an expression. Use the __#__ character in an expression to dereference an attribute name. For example, consider the following attribute name:     * @Percentile@  The name of this attribute conflicts with a reserved word, so it cannot be used directly in an expression. (For the complete list of reserved words, see <http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/ReservedWords.html Reserved Words> in the /Amazon DynamoDB Developer Guide/ ). To work around this, you could specify the following for @ExpressionAttributeNames@ :     * @{"#P":"Percentile"}@  You could then use this substitution in an expression, as in this example:     * @#P = :val@  For more information on expression attribute names, see <http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Expressions.AccessingItemAttributes.html Accessing Item Attributes> in the /Amazon DynamoDB Developer Guide/ .     * @Keys@ - An array of primary key attribute values that define specific items in the table. For each primary key, you must provide /all/ of the key attributes. For example, with a simple primary key, you only need to provide the partition key value. For a composite key, you must provide /both/ the partition key value and the sort key value.     * @ProjectionExpression@ - A string that identifies one or more attributes to retrieve from the table. These attributes can include scalars, sets, or elements of a JSON document. The attributes in the expression must be separated by commas. If no attribute names are specified, then all attributes will be returned. If any of the requested attributes are not found, they will not appear in the result. For more information, see <http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Expressions.AccessingItemAttributes.html Accessing Item Attributes> in the /Amazon DynamoDB Developer Guide/ .     * @AttributesToGet@ - This is a legacy parameter. Use @ProjectionExpression@ instead. For more information, see <http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/LegacyConditionalParameters.AttributesToGet.html AttributesToGet> in the /Amazon DynamoDB Developer Guide/ .
batchGetItem
    :: BatchGetItem
batchGetItem =
  BatchGetItem'
    {_bgiReturnConsumedCapacity = Nothing, _bgiRequestItems = mempty}


-- | Undocumented member.
bgiReturnConsumedCapacity :: Lens' BatchGetItem (Maybe ReturnConsumedCapacity)
bgiReturnConsumedCapacity = lens _bgiReturnConsumedCapacity (\ s a -> s{_bgiReturnConsumedCapacity = a})

-- | A map of one or more table names and, for each table, a map that describes one or more items to retrieve from that table. Each table name can be used only once per @BatchGetItem@ request. Each element in the map of items to retrieve consists of the following:     * @ConsistentRead@ - If @true@ , a strongly consistent read is used; if @false@ (the default), an eventually consistent read is used.     * @ExpressionAttributeNames@ - One or more substitution tokens for attribute names in the @ProjectionExpression@ parameter. The following are some use cases for using @ExpressionAttributeNames@ :     * To access an attribute whose name conflicts with a DynamoDB reserved word.     * To create a placeholder for repeating occurrences of an attribute name in an expression.     * To prevent special characters in an attribute name from being misinterpreted in an expression. Use the __#__ character in an expression to dereference an attribute name. For example, consider the following attribute name:     * @Percentile@  The name of this attribute conflicts with a reserved word, so it cannot be used directly in an expression. (For the complete list of reserved words, see <http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/ReservedWords.html Reserved Words> in the /Amazon DynamoDB Developer Guide/ ). To work around this, you could specify the following for @ExpressionAttributeNames@ :     * @{"#P":"Percentile"}@  You could then use this substitution in an expression, as in this example:     * @#P = :val@  For more information on expression attribute names, see <http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Expressions.AccessingItemAttributes.html Accessing Item Attributes> in the /Amazon DynamoDB Developer Guide/ .     * @Keys@ - An array of primary key attribute values that define specific items in the table. For each primary key, you must provide /all/ of the key attributes. For example, with a simple primary key, you only need to provide the partition key value. For a composite key, you must provide /both/ the partition key value and the sort key value.     * @ProjectionExpression@ - A string that identifies one or more attributes to retrieve from the table. These attributes can include scalars, sets, or elements of a JSON document. The attributes in the expression must be separated by commas. If no attribute names are specified, then all attributes will be returned. If any of the requested attributes are not found, they will not appear in the result. For more information, see <http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Expressions.AccessingItemAttributes.html Accessing Item Attributes> in the /Amazon DynamoDB Developer Guide/ .     * @AttributesToGet@ - This is a legacy parameter. Use @ProjectionExpression@ instead. For more information, see <http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/LegacyConditionalParameters.AttributesToGet.html AttributesToGet> in the /Amazon DynamoDB Developer Guide/ .
bgiRequestItems :: Lens' BatchGetItem (HashMap Text KeysAndAttributes)
bgiRequestItems = lens _bgiRequestItems (\ s a -> s{_bgiRequestItems = a}) . _Map

instance AWSRequest BatchGetItem where
        type Rs BatchGetItem = BatchGetItemResponse
        request = postJSON dynamoDB
        response
          = receiveJSON
              (\ s h x ->
                 BatchGetItemResponse' <$>
                   (x .?> "UnprocessedKeys" .!@ mempty) <*>
                     (x .?> "Responses" .!@ mempty)
                     <*> (x .?> "ConsumedCapacity" .!@ mempty)
                     <*> (pure (fromEnum s)))

instance Hashable BatchGetItem where

instance NFData BatchGetItem where

instance ToHeaders BatchGetItem where
        toHeaders
          = const
              (mconcat
                 ["X-Amz-Target" =#
                    ("DynamoDB_20120810.BatchGetItem" :: ByteString),
                  "Content-Type" =#
                    ("application/x-amz-json-1.0" :: ByteString)])

instance ToJSON BatchGetItem where
        toJSON BatchGetItem'{..}
          = object
              (catMaybes
                 [("ReturnConsumedCapacity" .=) <$>
                    _bgiReturnConsumedCapacity,
                  Just ("RequestItems" .= _bgiRequestItems)])

instance ToPath BatchGetItem where
        toPath = const "/"

instance ToQuery BatchGetItem where
        toQuery = const mempty

-- | Represents the output of a @BatchGetItem@ operation.
--
--
--
-- /See:/ 'batchGetItemResponse' smart constructor.
data BatchGetItemResponse = BatchGetItemResponse'
  { _bgirsUnprocessedKeys  :: !(Maybe (Map Text KeysAndAttributes))
  , _bgirsResponses        :: !(Maybe (Map Text [Map Text AttributeValue]))
  , _bgirsConsumedCapacity :: !(Maybe [ConsumedCapacity])
  , _bgirsResponseStatus   :: !Int
  } deriving (Eq, Read, Show, Data, Typeable, Generic)


-- | Creates a value of 'BatchGetItemResponse' with the minimum fields required to make a request.
--
-- Use one of the following lenses to modify other fields as desired:
--
-- * 'bgirsUnprocessedKeys' - A map of tables and their respective keys that were not processed with the current response. The @UnprocessedKeys@ value is in the same form as @RequestItems@ , so the value can be provided directly to a subsequent @BatchGetItem@ operation. For more information, see @RequestItems@ in the Request Parameters section. Each element consists of:     * @Keys@ - An array of primary key attribute values that define specific items in the table.     * @ProjectionExpression@ - One or more attributes to be retrieved from the table or index. By default, all attributes are returned. If a requested attribute is not found, it does not appear in the result.     * @ConsistentRead@ - The consistency of a read operation. If set to @true@ , then a strongly consistent read is used; otherwise, an eventually consistent read is used. If there are no unprocessed keys remaining, the response contains an empty @UnprocessedKeys@ map.
--
-- * 'bgirsResponses' - A map of table name to a list of items. Each object in @Responses@ consists of a table name, along with a map of attribute data consisting of the data type and attribute value.
--
-- * 'bgirsConsumedCapacity' - The read capacity units consumed by the entire @BatchGetItem@ operation. Each element consists of:     * @TableName@ - The table that consumed the provisioned throughput.     * @CapacityUnits@ - The total number of capacity units consumed.
--
-- * 'bgirsResponseStatus' - -- | The response status code.
batchGetItemResponse
    :: Int -- ^ 'bgirsResponseStatus'
    -> BatchGetItemResponse
batchGetItemResponse pResponseStatus_ =
  BatchGetItemResponse'
    { _bgirsUnprocessedKeys = Nothing
    , _bgirsResponses = Nothing
    , _bgirsConsumedCapacity = Nothing
    , _bgirsResponseStatus = pResponseStatus_
    }


-- | A map of tables and their respective keys that were not processed with the current response. The @UnprocessedKeys@ value is in the same form as @RequestItems@ , so the value can be provided directly to a subsequent @BatchGetItem@ operation. For more information, see @RequestItems@ in the Request Parameters section. Each element consists of:     * @Keys@ - An array of primary key attribute values that define specific items in the table.     * @ProjectionExpression@ - One or more attributes to be retrieved from the table or index. By default, all attributes are returned. If a requested attribute is not found, it does not appear in the result.     * @ConsistentRead@ - The consistency of a read operation. If set to @true@ , then a strongly consistent read is used; otherwise, an eventually consistent read is used. If there are no unprocessed keys remaining, the response contains an empty @UnprocessedKeys@ map.
bgirsUnprocessedKeys :: Lens' BatchGetItemResponse (HashMap Text KeysAndAttributes)
bgirsUnprocessedKeys = lens _bgirsUnprocessedKeys (\ s a -> s{_bgirsUnprocessedKeys = a}) . _Default . _Map

-- | A map of table name to a list of items. Each object in @Responses@ consists of a table name, along with a map of attribute data consisting of the data type and attribute value.
bgirsResponses :: Lens' BatchGetItemResponse (HashMap Text [HashMap Text AttributeValue])
bgirsResponses = lens _bgirsResponses (\ s a -> s{_bgirsResponses = a}) . _Default . _Map

-- | The read capacity units consumed by the entire @BatchGetItem@ operation. Each element consists of:     * @TableName@ - The table that consumed the provisioned throughput.     * @CapacityUnits@ - The total number of capacity units consumed.
bgirsConsumedCapacity :: Lens' BatchGetItemResponse [ConsumedCapacity]
bgirsConsumedCapacity = lens _bgirsConsumedCapacity (\ s a -> s{_bgirsConsumedCapacity = a}) . _Default . _Coerce

-- | -- | The response status code.
bgirsResponseStatus :: Lens' BatchGetItemResponse Int
bgirsResponseStatus = lens _bgirsResponseStatus (\ s a -> s{_bgirsResponseStatus = a})

instance NFData BatchGetItemResponse where