-- Copyright (c) 2013-2014 PivotCloud, Inc.
--
-- Aws.Kinesis.Reshard.Analysis
--
-- Please feel free to contact us at licensing@pivotmail.com with any
-- contributions, additions, or other feedback; we would love to hear from
-- you.
--
-- Licensed under the Apache License, Version 2.0 (the "License"); you may
-- not use this file except in compliance with the License. You may obtain a
-- copy of the License at http://www.apache.org/licenses/LICENSE-2.0
--
-- Unless required by applicable law or agreed to in writing, software
-- distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
-- WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
-- License for the specific language governing permissions and limitations
-- under the License.
--

{-# LANGUAGE ConstraintKinds #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE MultiWayIf #-}
{-# LANGUAGE UnicodeSyntax #-}

module Aws.Kinesis.Reshard.Analysis
( analyzeStream
) where

import Aws.Kinesis.Reshard.Shards
import Aws.Kinesis.Reshard.Metrics
import Aws.Kinesis.Reshard.Monad
import Control.Concurrent.Async.Lifted
import Control.Lens
import Prelude.Unicode

analyzeStream
  ∷ MonadReshard m
  ⇒ m (Maybe ReshardingAction)
analyzeStream = do
  (totalBps, shardCount) ← getBytesPerSecond `concurrently` countOpenShards
  threshold ← view oShardCapacityThreshold
  maximumShardCount ← view oMaximumShardCount
  let percentCapacity = shardlyBps / maximumBps
      maximumBps = 1000000
      shardlyBps = totalBps / fromIntegral shardCount
  return $
    if | shardCount > maximumShardCount → Just MergeShardsAction
       | percentCapacity < threshold * 0.5 ∧ shardCount > 1 → Just MergeShardsAction
       | percentCapacity ≥ threshold ∧ shardCount < maximumShardCount → Just SplitShardsAction
       | otherwise → Nothing