add Duration.from_iso8601/1

lib/elixir/lib/calendar/duration.ex

@@ -197,4 +197,52 @@ defmodule Duration do
       microsecond: {-ms, p}
     }
   end
+
+  @doc """
+  Parses an ISO 8601 formatted duration string to a `Duration` struct.
+
+  A decimal fraction may be specified for seconds only, using either a comma or a full stop.
+
+  ## Examples
+
+      iex> Duration.from_iso8601("P1Y2M3DT4H5M6S")
+      {:ok, %Duration{year: 1, month: 2, day: 3, hour: 4, minute: 5, second: 6}}
+      iex> Duration.from_iso8601("PT10H30M")
+      {:ok, %Duration{hour: 10, minute: 30, second: 0}}
+      iex> Duration.from_iso8601("P3Y-2MT3H")
+      {:ok, %Duration{year: 3, month: -2, hour: 3}}
+      iex> Duration.from_iso8601("P1YT4.650S")
+      {:ok, %Duration{year: 1, second: 4, microsecond: {650000, 3}}}
+
+  """
+  @spec from_iso8601(String.t()) :: {:ok, t} | {:error, atom}
+  def from_iso8601(string) when is_binary(string) do
+    case Calendar.ISO.parse_duration(string) do
+      {:ok, duration} ->
+        {:ok, new!(duration)}
+
+      error ->
+        error
+    end
+  end
+
+  @doc """
+  Same as `from_iso8601/1` but raises an ArgumentError.
+
+  ## Examples
+
+      iex> Duration.from_iso8601!("P1Y2M3DT4H5M6S")
+      %Duration{year: 1, month: 2, day: 3, hour: 4, minute: 5, second: 6}
+
+  """
+  @spec from_iso8601!(String.t()) :: t
+  def from_iso8601!(string) when is_binary(string) do
+    case from_iso8601(string) do
+      {:ok, duration} ->
+        duration
+
+      {:error, reason} ->
+        raise ArgumentError, ~s/failed to parse duration "#{string}". reason: #{inspect(reason)}/
+    end
+  end
 end

lib/elixir/lib/calendar/iso.ex

@@ -18,7 +18,8 @@ defmodule Calendar.ISO do
 
   The standard library supports a minimal set of possible ISO 8601 features.
   Specifically, the parser only supports calendar dates and does not support
-  ordinal and week formats.
+  ordinal and week formats. Additionally, it supports parsing ISO 8601
+  formatted durations, including negative time units and fractional seconds.
 
   By default Elixir only parses extended-formatted date/times. You can opt-in
   to parse basic-formatted date/times.
@@ -29,7 +30,7 @@ defmodule Calendar.ISO do
 
   Elixir does not support reduced accuracy formats (for example, a date without
   the day component) nor decimal precisions in the lowest component (such as
-  `10:01:25,5`). No functions exist to parse ISO 8601 durations or time intervals.
+  `10:01:25,5`).
 
   #### Examples
 
@@ -663,6 +664,65 @@ defmodule Calendar.ISO do
     end
   end
 
+  @doc """
+  Parses an ISO 8601 formatted duration string to a list of `Duration` compabitble unit pairs.
+
+  See `Duration.from_iso8601/1`.
+  """
+  @doc since: "1.17.0"
+  @spec parse_duration(String.t()) :: {:ok, [Duration.unit_pair()]} | {:error, atom()}
+  def parse_duration("P" <> string) when byte_size(string) > 0 do
+    parse_duration_date(string, [], year: ?Y, month: ?M, week: ?W, day: ?D)
+  end
+
+  def parse_duration(_) do
+    {:error, :invalid_duration}
+  end
+
+  defp parse_duration_date("", acc, _allowed), do: {:ok, acc}
+
+  defp parse_duration_date("T" <> string, acc, _allowed) when byte_size(string) > 0 do
+    parse_duration_time(string, acc, hour: ?H, minute: ?M, second: ?S)
+  end
+
+  defp parse_duration_date(string, acc, allowed) do
+    with {integer, <<next, rest::binary>>} <- Integer.parse(string),
+         {key, allowed} <- find_unit(allowed, next) do
+      parse_duration_date(rest, [{key, integer} | acc], allowed)
+    else
+      _ -> {:error, :invalid_date_component}
+    end
+  end
+
+  defp parse_duration_time("", acc, _allowed), do: {:ok, acc}
+
+  defp parse_duration_time(string, acc, allowed) do
+    case Integer.parse(string) do
+      {second, <<delimiter, _::binary>> = rest} when delimiter in [?., ?,] ->
+        case parse_microsecond(rest) do
+          {{ms, precision}, "S"} ->
+            ms = if second > 0, do: ms, else: -ms
+            {:ok, [second: second, microsecond: {ms, precision}] ++ acc}
+
+          _ ->
+            {:error, :invalid_time_component}
+        end
+
+      {integer, <<next, rest::binary>>} ->
+        case find_unit(allowed, next) do
+          {key, allowed} -> parse_duration_time(rest, [{key, integer} | acc], allowed)
+          false -> {:error, :invalid_time_component}
+        end
+
+      _ ->
+        {:error, :invalid_time_component}
+    end
+  end
+
+  defp find_unit([{key, unit} | rest], unit), do: {key, rest}
+  defp find_unit([_ | rest], unit), do: find_unit(rest, unit)
+  defp find_unit([], _unit), do: false
+
   @doc """
   Returns the `t:Calendar.iso_days/0` format of the specified date.
 

lib/elixir/test/elixir/calendar/duration_test.exs

@@ -217,4 +217,90 @@ defmodule DurationTest do
                microsecond: {0, 0}
              }
   end
+
+  test "from_iso8601/1" do
+    assert Duration.from_iso8601("P1Y2M3DT4H5M6S") ==
+             {:ok, %Duration{year: 1, month: 2, day: 3, hour: 4, minute: 5, second: 6}}
+
+    assert Duration.from_iso8601("P3WT5H3M") == {:ok, %Duration{week: 3, hour: 5, minute: 3}}
+    assert Duration.from_iso8601("PT5H3M") == {:ok, %Duration{hour: 5, minute: 3}}
+    assert Duration.from_iso8601("P1Y2M3D") == {:ok, %Duration{year: 1, month: 2, day: 3}}
+    assert Duration.from_iso8601("PT4H5M6S") == {:ok, %Duration{hour: 4, minute: 5, second: 6}}
+    assert Duration.from_iso8601("P1Y2M") == {:ok, %Duration{year: 1, month: 2}}
+    assert Duration.from_iso8601("P3D") == {:ok, %Duration{day: 3}}
+    assert Duration.from_iso8601("PT4H5M") == {:ok, %Duration{hour: 4, minute: 5}}
+    assert Duration.from_iso8601("PT6S") == {:ok, %Duration{second: 6}}
+    assert Duration.from_iso8601("P2M4Y") == {:error, :invalid_date_component}
+    assert Duration.from_iso8601("P4Y2W3Y") == {:error, :invalid_date_component}
+    assert Duration.from_iso8601("P5HT4MT3S") == {:error, :invalid_date_component}
+    assert Duration.from_iso8601("P5H3HT4M") == {:error, :invalid_date_component}
+    assert Duration.from_iso8601("PT1D") == {:error, :invalid_time_component}
+    assert Duration.from_iso8601("PT.6S") == {:error, :invalid_time_component}
+    assert Duration.from_iso8601("invalid") == {:error, :invalid_duration}
+  end
+
+  test "from_iso8601!/1" do
+    assert Duration.from_iso8601!("P1Y2M3DT4H5M6S") == %Duration{
+             year: 1,
+             month: 2,
+             day: 3,
+             hour: 4,
+             minute: 5,
+             second: 6
+           }
+
+    assert Duration.from_iso8601!("P3WT5H3M") == %Duration{week: 3, hour: 5, minute: 3}
+    assert Duration.from_iso8601!("PT5H3M") == %Duration{hour: 5, minute: 3}
+    assert Duration.from_iso8601!("P1Y2M3D") == %Duration{year: 1, month: 2, day: 3}
+    assert Duration.from_iso8601!("PT4H5M6S") == %Duration{hour: 4, minute: 5, second: 6}
+    assert Duration.from_iso8601!("P1Y2M") == %Duration{year: 1, month: 2}
+    assert Duration.from_iso8601!("P3D") == %Duration{day: 3}
+    assert Duration.from_iso8601!("PT4H5M") == %Duration{hour: 4, minute: 5}
+    assert Duration.from_iso8601!("PT6S") == %Duration{second: 6}
+    assert Duration.from_iso8601!("PT1,6S") == %Duration{second: 1, microsecond: {600_000, 1}}
+    assert Duration.from_iso8601!("PT-1.6S") == %Duration{second: -1, microsecond: {-600_000, 1}}
+
+    assert Duration.from_iso8601!("PT-1.234567S") == %Duration{
+             second: -1,
+             microsecond: {-234_567, 6}
+           }
+
+    assert Duration.from_iso8601!("PT1.12345678S") == %Duration{
+             second: 1,
+             microsecond: {123_456, 6}
+           }
+
+    assert Duration.from_iso8601!("P3Y4W-3DT-6S") == %Duration{
+             year: 3,
+             week: 4,
+             day: -3,
+             second: -6
+           }
+
+    assert Duration.from_iso8601!("PT-4.23S") == %Duration{second: -4, microsecond: {-230_000, 2}}
+
+    assert_raise ArgumentError,
+                 ~s/failed to parse duration "P5H3HT4M". reason: :invalid_date_component/,
+                 fn ->
+                   Duration.from_iso8601!("P5H3HT4M")
+                 end
+
+    assert_raise ArgumentError,
+                 ~s/failed to parse duration "P4Y2W3Y". reason: :invalid_date_component/,
+                 fn ->
+                   Duration.from_iso8601!("P4Y2W3Y")
+                 end
+
+    assert_raise ArgumentError,
+                 ~s/failed to parse duration "invalid". reason: :invalid_duration/,
+                 fn ->
+                   Duration.from_iso8601!("invalid")
+                 end
+
+    assert_raise ArgumentError,
+                 ~s/failed to parse duration "P4.5YT6S". reason: :invalid_date_component/,
+                 fn ->
+                   Duration.from_iso8601!("P4.5YT6S")
+                 end
+  end
 end