ParkingMeterKata.fs

module ParkingMeterKata
open System

type Coin =
    | TenCents = 10
    | TwentyCents = 20
    | FiftyCents = 50
    | OneEuro = 100
    | TwoEuro = 200

let amountOfCoin (coin: Coin) =
    Convert.ToDecimal (coin |> int) / 100m

let amountOfCoins (coins: seq<Coin>) =
    coins |> Seq.map amountOfCoin |> Seq.sum

let priceTable =
    [ 8.M, 600M
      5.M, 300M
      3.M, 120M
      2.M, 60M
      1.M, 20M ]

let getMinutesBought (amount: Decimal) =
    let priceRange = priceTable |> Seq.tryFind (fun (price, time) -> amount >= price)
    match priceRange with
    | Some (price, time) -> (amount /  price) * time 
    | None -> failwith "Not enough"

let isExcludeDay (date: DateTime) =
    date.DayOfWeek = DayOfWeek.Sunday
    || date.Month = 8
    // TODO public holidates

let minutesInADay = 600M

let payingDays (startDate: DateTime) = 
    let allDates = Seq.initInfinite (fun x -> startDate.AddDays( x |> float)) 
    allDates |> Seq.filter (fun x -> not (isExcludeDay x))

let startPayingNextDay (startDate: DateTime) =
    startDate.Hour > 19

let addTime (startDate: DateTime) (minutes: Decimal) =
    let days = 
        (Math.Floor (minutes / minutesInADay)|> int) +
        (if startPayingNextDay startDate then 1 else 0)
    let remainingMinutes = minutes % minutesInADay |> float
    let date = if days > 0 then Seq.nth days (payingDays startDate) else startDate
    let dateWithAllMinsAdded = date.AddMinutes(remainingMinutes)
    if dateWithAllMinsAdded.Hour > 19 then
        let nextDay = Seq.nth 1 (payingDays date)
        let nextDayAt9 = nextDay.Date.AddHours(9.)
        let remainingMins = 
            dateWithAllMinsAdded - date.Date.AddHours(19.)
        nextDayAt9.Add( remainingMins)
    else
        dateWithAllMinsAdded

let calcuateEndDateFromAmount (time: DateTime) (amount: Decimal) =
    let minutes = getMinutesBought amount
    addTime time minutes

let calcumateEndDateFromCoins (time: DateTime) (coins: seq<Coin>) =
    calcuateEndDateFromAmount time (coins |> amountOfCoins)

//[<EntryPoint>]
//let main argv = 
//    printfn "%A" argv
//    0 // return an integer exit code