{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE ViewPatterns #-}
{-# LANGUAGE TypeApplications #-}
module Eventlog.Prune
  ( pruneBands, pruneDetailed
  ) where

import Data.List (sortBy)
import Data.Ord (comparing)
import Eventlog.Types
import Data.Map (Map, fromList, (!), toList)

import Eventlog.Args (Args(..), Sort(..))
import Data.Maybe
import Data.Word (Word64)
import Text.Read (readMaybe)
import qualified Data.Text as T

type Compare a = a -> a -> Ordering

getComparison :: Args -> Compare (Bucket, BucketInfo)
getComparison Args { sorting = Size,   reversing = False }  = cmpSizeDescending
getComparison Args { sorting = Size,   reversing = True } = cmpSizeAscending
getComparison Args { sorting = StdDev, reversing = False }  = cmpStdDevDescending
getComparison Args { sorting = StdDev, reversing = True } = cmpStdDevAscending
getComparison Args { sorting = Name,   reversing = True }  = cmpNameDescending
getComparison Args { sorting = Name,   reversing = False } = cmpNameAscending
getComparison Args { sorting = Number,   reversing = True }  = cmpNumberDescending
getComparison Args { sorting = Number,   reversing = False } = cmpNumberAscending
getComparison Args { sorting = Gradient,   reversing = True }  = cmpGradientAscending
getComparison Args { sorting = Gradient,   reversing = False } = cmpGradientDescending

cmpNameAscending, cmpNameDescending,
  cmpNumberAscending, cmpNumberDescending,
  cmpStdDevAscending, cmpStdDevDescending,
  cmpSizeAscending, cmpSizeDescending,
  cmpGradientAscending, cmpGradientDescending :: Compare (Bucket, BucketInfo)
cmpNameAscending = comparing fst
cmpNameDescending = flip cmpNameAscending
cmpNumberAscending (Bucket a, _) (Bucket b, _) = comparing (readMaybe @Word64 . T.unpack) a b <> compare a b
cmpNumberDescending = flip cmpNumberAscending
cmpStdDevAscending = comparing (bucketStddev . snd)
cmpStdDevDescending = flip cmpStdDevAscending
cmpSizeAscending = comparing (bucketTotal . snd)
cmpSizeDescending = flip cmpSizeAscending
cmpGradientAscending = comparing (fmap getGradient . bucketGradient . snd)
 where
   getGradient (_a, b, _r2) = b
cmpGradientDescending = flip cmpGradientAscending

prune :: Int
      -> Args
      -> Map Bucket BucketInfo
      -> Map Bucket (Int, BucketInfo)
prune limit args ts =
  let ccTotals = sortBy cmpSizeDescending
                  (toList ts)
      bands = take limit ccTotals
      ccs = map fst (sortBy (getComparison args) bands)
      res :: [(Bucket, (Int, BucketInfo))]
      res = zipWith (\b k -> (b, (k, ts ! b))) (reverse ccs) [1..]
  in  fromList res

pruneBands, pruneDetailed :: Args -> Map Bucket BucketInfo -> Map Bucket (Int, BucketInfo)
pruneBands as = prune (bound $ nBands as) as
pruneDetailed as = prune (fromMaybe maxBound $ detailedLimit as) as


bound :: Int -> Int
bound n
  | n <= 0 = maxBound
  | otherwise = n