import Data.List
import Data.Function

type Name = String
type Rate = Integer

data Transaction  = CreditOut Integer | CreditIn Integer
    deriving (Eq, Show)

type Customer = (Name, [Transaction])

type DB = [Customer]


testDB :: DB
testDB = [
    ("Alma", [CreditIn 3000, CreditOut 200, CreditOut 1500]),
  ("Anna", [CreditIn 5000, CreditOut 5100]),
    ("Feri", [CreditOut 1000, CreditIn 200, CreditIn 200, CreditOut 10])
    ]

testDB2 :: DB
testDB2 = [
    ("Ani", [CreditIn 3000]),
    ("Juli", [CreditOut 1000, CreditIn 200])
    ]

---

emptyDB::DB
emptyDB = []


--Benne van-e az adott ügyfél az adatbázisban?
isCust nev db = any ((==nev).fst) db


add::Name -> Integer -> DB ->DB
add nev qty db
    | (isCust nev db) && (qty>=0) = updateP nev qty db
    | (isCust nev db) && (qty<0) = updateN nev qty db
    | otherwise = db

--updateP: növeli az egyenleget

updateP _ _ [] = []
updateP nev qty (entry:db)
    | fst entry == nev = ((fst entry), (CreditIn qty):(snd entry)):db
    | otherwise = entry:(updateP nev qty db)

--updateN: csökkenti az egyenleget
updateN _ _ [] = []
updateN nev qty (entry:db)
    | fst entry == nev = ((fst entry), (CreditOut (abs qty)):(snd entry)):db
    | otherwise = entry:(updateN nev qty db)
---
sumTrans [] = 0
sumTrans ((CreditIn t):ts) = t+(sumTrans ts)
sumTrans ((CreditOut t):ts) = (sumTrans ts)-t

summarize :: DB ->[(Name,Integer)]
summarize db = map (\(a,t) -> (a,(sumTrans t))) db
---
encloseDay :: Rate -> DB -> DB
encloseDay _ [] = []
encloseDay rate (entry:db)
    | (q >= 0) = (fst entry, [(CreditIn (rate*q))]):(encloseDay rate db)
    | otherwise = (fst entry, [(CreditOut (abs q))]):(encloseDay rate db)
        where q = (sumTrans (snd entry))
---
comparing p a b = compare (p a) (p b)
maxOut db = maximumBy (comparing (sumTrans.snd)) db
maxIn db = minimumBy (comparing (sumTrans.snd)) db

maximums :: DB -> (Name,Name,Integer)
maximums db = ((fst (maxIn db)),(fst (maxOut db)),q)
    where q = (sumTrans (snd (maxOut db)))-(sumTrans (snd (maxIn db)))

---