```{-# LANGUAGE CPP #-}
-- |
-- Module      : Test.LeanCheck.Stats
-- Copyright   : (c) 2017-2018 Rudy Matela
-- Maintainer  : Rudy Matela <rudy@matela.com.br>
--
-- This module is part of LeanCheck,
-- a simple enumerative property-based testing library.
--
-- This module exports functions to compute statistics of Listable instances.
module Test.LeanCheck.Stats
( classStats
, classStatsT
, conditionStats
, conditionStatsT

, classify
, classifyBy
, classifyOn
, counts
, countsBy
, countsOn
)
where

import Test.LeanCheck.Core
import Data.Function (on)
#ifndef __HUGS__
import Data.List (intercalate, transpose)
#else
import Data.List (transpose)

intercalate :: [a] -> [[a]] -> [a]
intercalate xs xss = concat (intersperse xs xss)
where
intersperse             :: a -> [a] -> [a]
intersperse _   []      = []
intersperse sep (x:xs)  = x : prependToAll sep xs
where
prependToAll            :: a -> [a] -> [a]
prependToAll _   []     = []
prependToAll sep (x:xs) = sep : x : prependToAll sep xs
#endif

classStats :: (Listable a, Show b) => Int -> (a -> b) -> IO ()
classStats n f = putStrLn
. table " "
. map showCount
\$ countsOn (unquote . show . f) xs
where
xs = take n list
len = length xs
showCount (s,n) = [ s ++ ":"
, show n ++ "/" ++ show len
, show (100 * n `div` len) ++ "%"
]

classStatsT :: (Listable a, Show b) => Int -> (a -> b) -> IO ()
classStatsT n f = putStrLn
. table "  "
. ([" "]:)
. map showCounts
. prependTotal
. countsTOn (unquote . show . f)
\$ take n tiers
where
heading = "" : "tot " : map show [0..(n-1)]
showCounts (s,n,ns) = (s ++ ":") : (show n ++ " ") : map show ns
(_,n,ns) -+- (_,n',ns') = ("tot", n + n', zipWith (+) ns ns')
totalizeCounts = foldr (-+-) (undefined, 0, repeat 0)
prependTotal cs = totalizeCounts cs : cs

conditionStats :: Listable a => Int -> [(String,a->Bool)] -> IO ()
conditionStats n = putStrLn . table " " . map show1
where
xs = take n list
len = length xs
show1 (s,f) = let c = count f xs
in [ s ++ ":"
, show c ++ "/" ++ show len
, show (100 * c `div` len) ++ "%" ]
count f = length . filter f

-- TODO: implement conditionStatsT
conditionStatsT :: Listable a => Int -> [(String,a->Bool)] -> IO ()
conditionStatsT = error "conditionsStatsT: not implemented yet, use conditionStats for now"

classify :: Eq a => [a] -> [[a]]
classify = classifyBy (==)

classifyBy :: (a -> a -> Bool) -> [a] -> [[a]]
classifyBy (==) []     = []
classifyBy (==) (x:xs) = (x:filter (== x) xs)
: classifyBy (==) (filter (/= x) xs)
where
x /= y = not (x == y)

classifyOn :: Eq b => (a -> b) -> [a] -> [[a]]
classifyOn f xs = map (map fst)
. classifyBy ((==) `on` snd)
\$ map (\x -> (x,f x)) xs

counts :: Eq a => [a] -> [(a,Int)]
counts = map headLength . classify

countsBy :: (a -> a -> Bool) -> [a] -> [(a,Int)]
countsBy (==) = map headLength . classifyBy (==)

countsOn :: Eq b => (a -> b) -> [a] -> [(b,Int)]
countsOn f = map (\xs -> (f \$ head xs, length xs)) . classifyOn f

countsT :: Eq a => [[a]] -> [(a,Int,[Int])]
countsT xss = [(x,n,map (count x) xss) | (x,n) <- counts (concat xss)]
where
count x = length . filter (== x)

countsTOn :: Eq b => (a -> b) -> [[a]] -> [(b,Int,[Int])]
countsTOn f = countsT . mapT f

unquote :: String -> String
unquote ('"':s) | last s == '"' = init s
unquote s = s

table :: String -> [[String]] -> String
table s []  = ""
table s sss = unlines
. map (removeTrailing ' ')
. map (intercalate s)
. transpose
. map (normalize ' ')
. foldr1 (zipWith (++))
. map (normalize "" . map lines)
. normalize ""
\$ sss

-- | Fits a list to a certain width by appending a certain value
--
-- > fit ' ' 6 "str" == "str   "
--
-- > fit 0 6 [1,2,3] == [1,2,3,0,0,0]
fit :: a -> Int -> [a] -> [a]
fit x n xs = replicate (n - length xs) x ++ xs

-- | normalize makes all list the same length by adding a value
--
-- > normalize ["asdf","qw","er"] == normalize ["asdf","qw  ","er  "]
normalize :: a -> [[a]] -> [[a]]
normalize x xs = map (x `fit` maxLength xs) xs

-- | Given a list of lists returns the maximum length
maxLength :: [[a]] -> Int
maxLength = maximum . (0:) . map length

removeTrailing :: Eq a => a -> [a] -> [a]
removeTrailing x = reverse
. dropWhile (==x)
. reverse
```