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module Model.Payers
( Payers
, ExceedingPayer
, payersDecoder
, updatePayers
, getOrderedExceedingPayers
) where
import Json.Decode as Json exposing (..)
import Dict exposing (..)
import List
import Maybe
import Model.User exposing (UserId, userIdDecoder)
type alias Payers = Dict UserId Int
payersDecoder : Decoder Payers
payersDecoder = Json.map Dict.fromList (list payerDecoder)
payerDecoder : Decoder (UserId, Int)
payerDecoder =
object2 (,)
("userId" := userIdDecoder)
("totalPayment" := int)
updatePayers : Payers -> UserId -> Int -> Payers
updatePayers payers userId amountDiff =
Dict.update
userId
(\mbAmount ->
case mbAmount of
Just amount -> Just (amount + amountDiff)
Nothing -> Nothing
)
payers
type alias ExceedingPayer =
{ userId : UserId
, amount : Int
}
getOrderedExceedingPayers : Payers -> List ExceedingPayer
getOrderedExceedingPayers payers =
let orderedPayers =
Dict.toList payers
|> List.map (\(userId, amount) -> ExceedingPayer userId amount)
|> List.sortBy .amount
maybeMinAmount =
List.head orderedPayers
|> Maybe.map .amount
in case maybeMinAmount of
Just minAmount ->
orderedPayers
|> List.map (\payer -> { payer | amount <- payer.amount - minAmount })
|> List.filter (\payer -> payer.amount /= 0)
|> List.reverse
Nothing ->
[]
|
