defmodule Moar.DateTime do
# @related [test](/test/datetime_test.exs)
@moduledoc """
DateTime-related functions. See also `Moar.NaiveDateTime`.
"""
@doc """
Adds `duration` to `date_time`.
See also `subtract/1` and `Moar.NaiveDateTime.add/2`.
> #### Note {: .info}
>
> This function is naive and intentionally doesn't account for real-world calendars and all of their complexity,
> such as leap years, leap days, daylight saving time, past and future calendar oddities, etc.
>
> As ["Falsehoods programmers believe about time"](https://gist.github.com/timvisee/fcda9bbdff88d45cc9061606b4b923ca)
> says, "If you think you understand everything about time, you're probably doing it wrong."
>
> See [`Cldr.Calendar.plus/2`](https://hexdocs.pm/ex_cldr_calendars/Cldr.Calendar.html#plus/2) for one example
> of a function that is far more likely to be correct.
```elixir
iex> start = ~U[2022-01-01T00:00:00.000Z]
iex> Moar.DateTime.add(start, {3, :minute})
~U[2022-01-01T00:03:00.000Z]
```
"""
@spec add(DateTime.t(), Moar.Duration.t()) :: DateTime.t()
def add(date_time, duration),
do: DateTime.add(date_time, Moar.Duration.convert(duration, :millisecond), :millisecond)
@doc """
Returns true if `date_time` is inclusively inside `range` which is a tuple containing a start datetime and an end
datetime.
```elixir
iex> Moar.DateTime.between?(~U[2022-01-01T02:00:00Z], {~U[2022-01-01T01:00:00Z], ~U[2022-01-01T03:00:00Z]})
true
iex> Moar.DateTime.between?(~U[2022-01-01T04:00:00Z], {~U[2022-01-01T01:00:00Z], ~U[2022-01-01T03:00:00Z]})
false
```
"""
@spec between?(DateTime.t(), {DateTime.t(), DateTime.t()}) :: boolean()
def between?(date_time, {range_start, range_end} = _range),
do: DateTime.compare(date_time, range_start) in [:eq, :gt] && DateTime.compare(date_time, range_end) in [:eq, :lt]
@doc """
Like `DateTime.from_iso8601/1` but raises if the string cannot be parsed.
```elixir
iex> Moar.DateTime.from_iso8601!("2022-01-01T00:00:00Z")
~U[2022-01-01T00:00:00Z]
iex> Moar.DateTime.from_iso8601!("2022-01-01T00:00:00+0800")
** (ArgumentError) Expected \"2022-01-01T00:00:00+0800\" to have a UTC offset of 0, but was: 28800
iex> Moar.DateTime.from_iso8601!("Next Thursday after lunch")
** (ArgumentError) Invalid ISO8601 format: "Next Thursday after lunch"
```
"""
@spec from_iso8601!(date_time_string :: String.t()) :: DateTime.t()
def from_iso8601!(date_time_string) when is_binary(date_time_string) do
case DateTime.from_iso8601(date_time_string) do
{:ok, date_time, 0} ->
date_time
{:ok, _date_time, other_offset} ->
raise ArgumentError, ~s|Expected "#{date_time_string}" to have a UTC offset of 0, but was: #{other_offset}|
{:error, :invalid_format} ->
raise ArgumentError, ~s|Invalid ISO8601 format: "#{date_time_string}"|
end
end
@doc """
Returns true if `date_time` is now or in the past and no older than `duration` ago (which defaults to 1 minute).
Returns false if `date_time` is in the future.
```elixir
iex> Moar.DateTime.recent?(Moar.DateTime.utc_now(minus: {30, :second}))
true
iex> Moar.DateTime.recent?(Moar.DateTime.utc_now(minus: {5, :minute}))
false
iex> Moar.DateTime.recent?(Moar.DateTime.utc_now(minus: {5, :minute}), {1, :hour})
true
iex> Moar.DateTime.recent?(Moar.DateTime.utc_now(plus: {5, :second}))
false
```
"""
@spec recent?(DateTime.t(), Moar.Duration.t() | nil) :: boolean()
def recent?(date_time, duration \\ {1, :minute}) do
case DateTime.diff(date_time, DateTime.utc_now(), :microsecond) do
diff when diff > 0 -> false
diff -> diff >= -1 * Moar.Duration.convert(duration, :microsecond)
end
end
@doc """
Subtracts `duration` from `date_time`.
See also `add/1` and `Moar.NaiveDateTime.subtract/2`.
> #### Note {: .info}
>
> This function is naive and intentionally doesn't account for real-world calendars and all of their complexity,
> such as leap years, leap days, daylight saving time, past and future calendar oddities, etc.
>
> As ["Falsehoods programmers believe about time"](https://gist.github.com/timvisee/fcda9bbdff88d45cc9061606b4b923ca)
> says, "If you think you understand everything about time, you're probably doing it wrong."
>
> See [`Cldr.Calendar.minus/4`](https://hexdocs.pm/ex_cldr_calendars/Cldr.Calendar.html#minus/4) for one example
> of a function that is far more likely to be correct.
```elixir
iex> start = ~U[2022-01-01T00:03:00.000Z]
iex> Moar.DateTime.subtract(start, {3, :minute})
~U[2022-01-01T00:00:00.000Z]
```
"""
@spec subtract(DateTime.t(), Moar.Duration.t()) :: DateTime.t()
def subtract(date_time, {time, unit} = _duration),
do: DateTime.add(date_time, Moar.Duration.convert({-1 * time, unit}, :millisecond), :millisecond)
@doc """
Like `DateTime.to_iso8601/1` but rounds to the nearest second first.
```elixir
iex> Moar.DateTime.to_iso8601_rounded(~U[2022-01-01T01:02:03.456789Z])
"2022-01-01T01:02:03Z"
```
"""
@spec to_iso8601_rounded(date_time :: DateTime.t()) :: String.t()
def to_iso8601_rounded(date), do: date |> DateTime.truncate(:second) |> DateTime.to_iso8601()
@doc """
Returns the current UTC time plus or minus the given duration.
```elixir
iex> Moar.DateTime.utc_now(plus: {10500, :millisecond})
...> |> Moar.Duration.format([:approx, :from_now])
"10 seconds from now"
iex> Moar.DateTime.utc_now(minus: {10, :second})
...> |> Moar.Duration.format([:approx, :ago])
"10 seconds ago"
```
"""
@spec utc_now([plus: Moar.Duration.t()] | [minus: Moar.Duration.t()]) :: DateTime.t()
def utc_now(plus: duration), do: DateTime.utc_now() |> add(duration)
def utc_now(minus: duration), do: DateTime.utc_now() |> subtract(duration)
@doc """
Returns true if `date_time` is no older than `duration` ago, and no later than `duration` from now.
```elixir
iex> Moar.DateTime.within?(Moar.DateTime.utc_now(minus: {30, :second}), {1, :minute})
true
iex> Moar.DateTime.within?(Moar.DateTime.utc_now(plus: {30, :second}), {1, :minute})
true
iex> Moar.DateTime.within?(Moar.DateTime.utc_now(minus: {5, :minute}), {1, :minute})
false
iex> Moar.DateTime.within?(Moar.DateTime.utc_now(plus: {5, :minute}), {1, :minute})
false
```
"""
@spec within?(DateTime.t(), Moar.Duration.t() | nil) :: boolean()
def within?(date_time, duration) do
now = DateTime.utc_now()
between?(date_time, {subtract(now, duration), add(now, duration)})
end
end