defmodule Tarearbol.Calendar do
@moduledoc """
Handy functions to work with dates.
"""
use Boundary
@days_in_week 7
@doc """
Returns a `DateTime` instance of the beginning of the period given as third
parameters, related to the `DateTime` instance given as the first parameter
(defaulted to `DateTime.utc_now/0`).
The number of periods to shift might be given as the second parameter
(defaults to `0`.)
_Examples:_
iex> dt = DateTime.from_unix!(1567091960)
~U[2019-08-29 15:19:20Z]
iex> Tarearbol.Calendar.beginning_of(dt, :year)
~U[2019-01-01 00:00:00Z]
iex> Tarearbol.Calendar.beginning_of(dt, -2, :year)
~U[2017-01-01 00:00:00Z]
iex> Tarearbol.Calendar.beginning_of(dt, :month)
~U[2019-08-01 00:00:00Z]
iex> Tarearbol.Calendar.beginning_of(dt, 6, :month)
~U[2020-02-01 00:00:00Z]
iex> Tarearbol.Calendar.beginning_of(dt, 4, :day)
~U[2019-09-02 00:00:00Z]
iex> Tarearbol.Calendar.beginning_of(dt, :week)
~U[2019-08-26 00:00:00Z]
iex> Tarearbol.Calendar.beginning_of(dt, -34, :week)
~U[2018-12-31 00:00:00Z]
iex> Tarearbol.Calendar.beginning_of(dt, :hour)
~U[2019-08-29 15:00:00Z]
iex> Tarearbol.Calendar.beginning_of(dt, -28*24-16, :hour)
~U[2019-07-31 23:00:00Z]
iex> Tarearbol.Calendar.end_of(dt, :hour)
~U[2019-08-29 15:59:59Z]
iex> Tarearbol.Calendar.end_of(dt, 5, :month)
~U[2020-01-31 23:59:59Z]
iex> Tarearbol.Calendar.end_of(dt, -1, :year)
~U[2018-12-31 23:59:59Z]
"""
@spec beginning_of(dt :: DateTime.t() | nil, count :: integer(), atom()) :: DateTime.t()
def beginning_of(dt \\ nil, count \\ 0, what)
################################### YEAR ###################################
def beginning_of(dt, count, :year) do
dt = if is_nil(dt), do: DateTime.utc_now(), else: dt
%DateTime{nullify(dt) | year: dt.year + count, month: 1, day: 1}
end
################################### MONTH ##################################
def beginning_of(dt, 0, :month) do
dt = if is_nil(dt), do: DateTime.utc_now(), else: dt
%DateTime{nullify(dt) | year: dt.year, month: dt.month, day: 1}
end
def beginning_of(dt, 1, :month) do
dt = if is_nil(dt), do: DateTime.utc_now(), else: dt
{year, month} =
if dt.month == dt.calendar.months_in_year(dt.year),
do: {dt.year + 1, 1},
else: {dt.year, dt.month + 1}
%DateTime{nullify(dt) | year: year, month: month, day: 1}
end
def beginning_of(dt, -1, :month) do
dt = if is_nil(dt), do: DateTime.utc_now(), else: dt
{year, month} =
if dt.month == 1,
do: {dt.year - 1, dt.calendar.months_in_year(dt.year - 1)},
else: {dt.year, dt.month - 1}
%DateTime{nullify(dt) | year: year, month: month, day: 1}
end
################################### WEEK ###################################
def beginning_of(dt, 0, :week) do
dt = if is_nil(dt), do: DateTime.utc_now(), else: dt
beginning_of(dt, 1 - dt.calendar.day_of_week(dt.year, dt.month, dt.day), :day)
end
def beginning_of(dt, n, :week) when is_integer(n) do
dt = if is_nil(dt), do: DateTime.utc_now(), else: dt
dt
|> beginning_of(0, :week)
|> beginning_of(n * @days_in_week, :day)
end
################################ DAY OF WEEK ###############################
def beginning_of(dt, dow, :day_of_week) when is_integer(dow) and dow > 0 and dow < 8 do
dt = if is_nil(dt), do: DateTime.utc_now(), else: dt
diff = dow - dt.calendar.day_of_week(dt.year, dt.month, dt.day)
beginning_of(dt, if(diff > 0, do: diff, else: 7 + diff), :day)
end
################################### DAY ####################################
def beginning_of(dt, 0, :day) do
dt = if is_nil(dt), do: DateTime.utc_now(), else: dt
%DateTime{nullify(dt) | year: dt.year, month: dt.month, day: dt.day}
end
def beginning_of(dt, 1, :day) do
dt = if is_nil(dt), do: DateTime.utc_now(), else: dt
days_in_this_month = dt.calendar.days_in_month(dt.year, dt.month)
months_in_this_year = dt.calendar.months_in_year(dt.year)
{year, month, day} =
case {dt.day, dt.month} do
{^days_in_this_month, ^months_in_this_year} ->
{dt.year + 1, 1, 1}
{^days_in_this_month, month} ->
{dt.year, month + 1, 1}
{day, month} ->
{dt.year, month, day + 1}
end
%DateTime{nullify(dt) | year: year, month: month, day: day}
end
def beginning_of(dt, -1, :day) do
dt = if is_nil(dt), do: DateTime.utc_now(), else: dt
{year, month, day} =
case {dt.day, dt.month} do
{1, 1} ->
month = dt.calendar.months_in_year(dt.year - 1)
{dt.year - 1, month, dt.calendar.days_in_month(dt.year, month)}
{1, month} ->
{dt.year, month - 1, dt.calendar.days_in_month(dt.year, month - 1)}
{day, month} ->
{dt.year, month, day - 1}
end
%DateTime{nullify(dt) | year: year, month: month, day: day}
end
################################### HOUR ###################################
def beginning_of(dt, 0, :hour) do
dt = if is_nil(dt), do: DateTime.utc_now(), else: dt
%DateTime{nullify(dt) | year: dt.year, month: dt.month, day: dt.day, hour: dt.hour}
end
def beginning_of(dt, -1, :hour) do
dt = if is_nil(dt), do: DateTime.utc_now(), else: dt
{year, month, day, hour} =
case {dt.hour, dt.day, dt.month} do
{0, 1, 1} ->
month = dt.calendar.months_in_year(dt.year - 1)
{dt.year - 1, month, dt.calendar.days_in_month(dt.year, month), 23}
{0, 1, month} ->
{dt.year, month - 1, dt.calendar.days_in_month(dt.year, month - 1), 23}
{0, day, month} ->
{dt.year, month, day - 1, 23}
{hour, day, month} ->
{dt.year, month, day, hour - 1}
end
%DateTime{nullify(dt) | year: year, month: month, day: day, hour: hour}
end
def beginning_of(dt, 1, :hour) do
dt = if is_nil(dt), do: DateTime.utc_now(), else: dt
days_in_this_month = dt.calendar.days_in_month(dt.year, dt.month)
months_in_this_year = dt.calendar.months_in_year(dt.year)
{year, month, day, hour} =
case {dt.hour, dt.day, dt.month} do
{23, ^days_in_this_month, ^months_in_this_year} ->
{dt.year + 1, 1, 1, 0}
{23, ^days_in_this_month, month} ->
{dt.year, month + 1, 1, 0}
{23, day, month} ->
{dt.year, month, day + 1, 0}
{hour, day, month} ->
{dt.year, month, day, hour + 1}
end
%DateTime{nullify(dt) | year: year, month: month, day: day, hour: hour}
end
################################## GENERICS ################################
def beginning_of(_dt, count, period)
when period not in [:year, :month, :week, :day, :hour, :minute],
do: {:error, {period, count}}
def beginning_of(dt, count, period) when count > 1 do
dt = if is_nil(dt), do: DateTime.utc_now(), else: dt
Enum.reduce(1..count, dt, fn _, acc -> beginning_of(acc, 1, period) end)
end
def beginning_of(dt, count, period) when count < 1 do
dt = if is_nil(dt), do: DateTime.utc_now(), else: dt
Enum.reduce(1..-count, dt, fn _, acc -> beginning_of(acc, -1, period) end)
end
################################### END_OF #################################
@spec end_of(dt :: DateTime.t() | nil, count :: integer(), atom()) :: DateTime.t()
def end_of(dt \\ nil, n \\ 0, period)
def end_of(dt, n, period) do
dt
|> beginning_of(n, period)
|> DateTime.add(period_in_seconds(dt, period) - 1)
end
################################## INTERNALS ###############################
defp period_in_seconds(dt \\ nil, period)
defp period_in_seconds(_, :minute), do: 60
defp period_in_seconds(_, :hour), do: 60 * 60
defp period_in_seconds(_, :day), do: 60 * 60 * 24
defp period_in_seconds(dt, :month),
do: dt.calendar.days_in_month(dt.year, dt.month) * period_in_seconds(:day)
defp period_in_seconds(dt, :year) do
Enum.reduce(1..dt.calendar.months_in_year(dt.year), 0, fn month, acc ->
acc + dt.calendar.days_in_month(dt.year, month) * period_in_seconds(:day)
end)
end
defp nullify(%DateTime{} = dt) do
%DateTime{
dt
| year: 0,
month: 0,
day: 0,
hour: 0,
minute: 0,
second: 0,
microsecond: {0, 0}
}
end
end
