exercism/elixir/library-fees/lib/library_fees.ex

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Elixir
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2023-12-20 02:32:19 +00:00
defmodule LibraryFees do
def datetime_from_string(string) do
case NaiveDateTime.from_iso8601(string) do
{:ok, naive_date_time} -> naive_date_time
_ -> :error
end
end
def before_noon?(datetime) do
datetime.hour < 12
end
defp days_to_return(checkout_datetime) do
if(before_noon?(checkout_datetime), do: 28, else: 29)
end
def return_date(checkout_datetime) do
checkout_datetime
|> NaiveDateTime.add(days_to_return(checkout_datetime), :day)
|> NaiveDateTime.to_date()
end
def days_late(planned_return_date, actual_return_datetime) do
actual_return_datetime
|> NaiveDateTime.to_date()
|> Date.diff(planned_return_date)
|> case do
late_in_days when late_in_days > 0 -> late_in_days
_late_in_days -> 0
end
end
def monday?(datetime) do
datetime
|> NaiveDateTime.to_date()
|> Date.day_of_week(:monday)
|> case do
1 -> true
_ -> false
end
end
def calculate_late_fee(checkout, return, rate) do
checkout_date_time = datetime_from_string(checkout)
actual_return_date_time = datetime_from_string(return)
planed_return_date_time = return_date(checkout_date_time)
fee = days_late(planed_return_date_time, actual_return_date_time) * rate
case monday?(actual_return_date_time) do
true -> floor(fee * 0.5)
_ -> fee
end
end
end