Created
August 6, 2016 09:16
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| defmodule ExclusiveDateRange do | |
| defstruct first: nil, last: nil | |
| def new(first, last) do | |
| %ExclusiveDateRange{first: first, last: last} | |
| end | |
| defimpl Enumerable, for: ExclusiveDateRange do | |
| def reduce _dr, {:halt, acc}, _fun do | |
| {:halted, acc} | |
| end | |
| def reduce(dr, {:suspend, acc}, fun) do | |
| {:suspended, acc, &reduce(dr, &1, fun)} | |
| end | |
| def reduce(%ExclusiveDateRange{first: d, last: d}, {:cont, acc}, _fun) do | |
| {:done, acc} | |
| end | |
| def reduce(%ExclusiveDateRange{first: d1, last: d2}, {:cont, acc}, fun) do | |
| reduce(%ExclusiveDateRange{first: next(d1), last: d2}, fun.(d1, acc), fun) | |
| end | |
| defp next %Date{year: y, month: m, day: d} do | |
| case Date.new(y, m, d + 1) do | |
| {:ok, nd} -> nd | |
| {:error, :invalid_date} -> | |
| case Date.new(y, m + 1, 1) do | |
| {:ok, nd} -> nd | |
| {:error, :invalid_date} -> | |
| {:ok, nd} = Date.new(y + 1, 1, 1) | |
| nd | |
| end | |
| end | |
| end | |
| def member?(%ExclusiveDateRange{first: d1, last: d2}, value) do | |
| days1 = date_to_gregorian_days d1 | |
| days2 = date_to_gregorian_days(d2) - 1 | |
| days3 = date_to_gregorian_days value | |
| {:ok, Enum.member?(days1..days2, days3)} | |
| end | |
| def count(%ExclusiveDateRange{first: d1, last: d2}) do | |
| days1 = date_to_gregorian_days d1 | |
| days2 = date_to_gregorian_days d2 | |
| {:ok, days2 - days1} | |
| end | |
| defp date_to_gregorian_days date do | |
| date |> Date.to_erl |> :calendar.date_to_gregorian_days | |
| end | |
| end | |
| end |
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