Binary match date strings

lib/ical/deserialize.ex

@@ -432,32 +432,14 @@ defmodule ICal.Deserialize do
   end
 
   @doc """
-  This function is designed to parse iCal datetime strings into erlang dates.
+  This function is designed to parse iCal datetime strings into date/times.
 
-  It should be able to handle dates from the past:
+  It respects TZID and VALUE parameters for properties, which can control the type and
+  location of the resulting date/time.
 
-      iex> {:ok, date} = ICal.Deserialize.to_date("19930407T153022Z")
-      ...> Timex.to_erl(date)
-      {{1993, 4, 7}, {15, 30, 22}}
-
-  As well as the future:
-
-      iex> {:ok, date} = ICal.Deserialize.to_date("39930407T153022Z")
-      ...> Timex.to_erl(date)
-      {{3993, 4, 7}, {15, 30, 22}}
-
-  And should return error for incorrect dates:
-
-      iex> ICal.Util.Deserialize.to_date("1993/04/07")
-      {:error, "Expected `2 digit month` at line 1, column 5."}
-
-  It should handle timezones from  the Olson Database:
-
-      iex> {:ok, date} = ICal.Deserialize.to_date("19980119T020000",
-      ...> %{"TZID" => "America/Chicago"})
-      ...> [Timex.to_erl(date), date.time_zone]
-      [{{1998, 1, 19}, {2, 0, 0}}, "America/Chicago"]
+  It returns `nil` for ill-formed dates or datetime strings.
   """
+  @spec to_date(String.t() | nil, map, ICal.t()) :: Date.t() | DateTime.t() | nil
   def to_date(nil, _params, _calendar), do: nil
 
   def to_date(date_string, %{"TZID" => timezone}, %ICal{default_timezone: default_timezone}) do
@@ -468,8 +450,14 @@ defmodule ICal.Deserialize do
   end
 
   def to_date(date_string, %{"VALUE" => "DATE"}, _calendar) do
-    case Timex.parse(date_string, "{YYYY}{0M}{0D}") do
-      {:ok, date} -> NaiveDateTime.to_date(date)
+    # of the form {YYYY}{MM}{DD}
+    with <<y::binary-size(4), m::binary-size(2), d::binary-size(2)>> <- date_string,
+         {year, ""} <- Integer.parse(y),
+         {month, ""} <- Integer.parse(m),
+         {day, ""} <- Integer.parse(d),
+         {:ok, date} <- Date.new(year, month, day) do
+      date
+    else
       _ -> nil
     end
   end
@@ -479,22 +467,54 @@ defmodule ICal.Deserialize do
   end
 
   def to_date_in_timezone(date_string, timezone) do
-    with_timezone =
-      if String.ends_with?(date_string, "Z") do
-        date_string <> timezone
-      else
-        date_string <> "Z" <> timezone
+    # datetime in the form "{YYYY}{0M}{0D}T{h24}{m}{s}Z{Zname}"
+    with <<y::binary-size(4), m::binary-size(2), d::binary-size(2), ?T, t_h::binary-size(2),
+           t_m::binary-size(2), t_s::binary-size(2), rest::binary>>
+         when rest == "" or rest == "Z" <- date_string,
+         {year, ""} <- Integer.parse(y),
+         {month, ""} <- Integer.parse(m),
+         {day, ""} <- Integer.parse(d),
+         {hour, ""} <- Integer.parse(t_h),
+         {minute, ""} <- Integer.parse(t_m),
+         {second, ""} <- Integer.parse(t_s),
+         {:ok, date} <- Date.new(year, month, day),
+         {:ok, time} <- Time.new(hour, minute, second) do
+      # RFC 5545 §3.3.5 defines how DST edge cases should be handled:
+      #
+      # Ambiguous (fall-back, clocks go back — time occurs twice): "the
+      # DATE-TIME value refers to the first occurrence of the referenced
+      # time." The first occurrence is the daylight (pre-transition) instant.
+      #
+      # Gap (spring-forward, clocks go forward — time never exists): "the
+      # DATE-TIME value is interpreted using the UTC offset before the gap."
+      # e.g. 2:30 AM in a spring-forward gap → apply pre-gap offset (EST) to
+      # get UTC, then express in the post-gap offset (EDT) → 3:30 AM EDT.
+      case DateTime.new(date, time, timezone) do
+        {:ok, dt} -> dt
+        {:ambiguous, first, _second} -> first
+        {:gap, just_before, just_after} -> adjust_to_gap(time, just_before, just_after)
+        _ -> nil
       end
-
-    case Timex.parse(with_timezone, "{YYYY}{0M}{0D}T{h24}{m}{s}Z{Zname}") do
-      {:ok, date} -> date
+    else
       _ -> nil
     end
   end
 
+  @doc "Parses a local date string as a NaiveDatetime, returning `nil` on failure"
+  @spec to_local_date(String.t()) :: NaiveDateTime.t() | nil
   def to_local_date(date_string) do
-    case Timex.parse(date_string, "{YYYY}{0M}{0D}T{h24}{m}{s}") do
-      {:ok, date} -> date
+    # datetime in the form "{YYYY}{0M}{0D}T{h24}{m}{s}"
+    with <<y::binary-size(4), m::binary-size(2), d::binary-size(2), ?T, t_h::binary-size(2),
+           t_m::binary-size(2), t_s::binary-size(2)>> <- date_string,
+         {year, ""} <- Integer.parse(y),
+         {month, ""} <- Integer.parse(m),
+         {day, ""} <- Integer.parse(d),
+         {hour, ""} <- Integer.parse(t_h),
+         {minute, ""} <- Integer.parse(t_m),
+         {second, ""} <- Integer.parse(t_s),
+         {:ok, datetime} <- NaiveDateTime.new(year, month, day, hour, minute, second) do
+      datetime
+    else
       _ -> nil
     end
   end
@@ -522,4 +542,28 @@ defmodule ICal.Deserialize do
   def status(%ICal.Journal{}, "FINAL"), do: :final
   def status(_, "CANCELLED"), do: :cancelled
   def status(_, _), do: nil
+
+  defp adjust_to_gap(original_time, before_gap, after_gap) do
+    before_gap =
+      before_gap
+      |> DateTime.to_time()
+      |> round_off_micros()
+
+    diff = Time.diff(original_time, before_gap)
+
+    time = Time.shift(DateTime.to_time(after_gap), second: diff)
+
+    DateTime.new!(DateTime.to_date(after_gap), time, after_gap.time_zone)
+  end
+
+  defp round_off_micros(time) do
+    # gap times are often 59.9999 seconds, the moment RIGHT before.
+    # snug those times up to the minute
+    {ms, precision} = time.microsecond
+    offset = round(ms / Integer.pow(10, precision))
+
+    time
+    |> Time.truncate(:second)
+    |> Time.shift(second: offset)
+  end
 end

mix.exs

@@ -25,7 +25,8 @@ defmodule ICal.Mixfile do
   defp deps do
     [
       {:timex, "~> 3.4"},
-      {:tzdata, "~> 1.1", optional: true},
+      {:tz, "~> 0.28", optional: true},
+      {:mint, "~>1.7", optional: true},
 
       # saxy is used to generate the windows tz -> olson names code
       # see priv/generate_win32_tz_mapping.exs

mix.lock

@@ -14,13 +14,15 @@
   "file_system": {:hex, :file_system, "1.1.1", "31864f4685b0148f25bd3fbef2b1228457c0c89024ad67f7a81a3ffbc0bbad3a", [:mix], [], "hexpm", "7a15ff97dfe526aeefb090a7a9d3d03aa907e100e262a0f8f7746b78f8f87a5d"},
   "gettext": {:hex, :gettext, "0.26.2", "5978aa7b21fada6deabf1f6341ddba50bc69c999e812211903b169799208f2a8", [:mix], [{:expo, "~> 0.5.1 or ~> 1.0", [hex: :expo, repo: "hexpm", optional: false]}], "hexpm", "aa978504bcf76511efdc22d580ba08e2279caab1066b76bb9aa81c4a1e0a32a5"},
   "hackney": {:hex, :hackney, "1.25.0", "390e9b83f31e5b325b9f43b76e1a785cbdb69b5b6cd4e079aa67835ded046867", [:rebar3], [{:certifi, "~> 2.15.0", [hex: :certifi, repo: "hexpm", optional: false]}, {:idna, "~> 6.1.0", [hex: :idna, repo: "hexpm", optional: false]}, {:metrics, "~> 1.0.0", [hex: :metrics, repo: "hexpm", optional: false]}, {:mimerl, "~> 1.4", [hex: :mimerl, repo: "hexpm", optional: false]}, {:parse_trans, "3.4.1", [hex: :parse_trans, repo: "hexpm", optional: false]}, {:ssl_verify_fun, "~> 1.1.0", [hex: :ssl_verify_fun, repo: "hexpm", optional: false]}, {:unicode_util_compat, "~> 0.7.1", [hex: :unicode_util_compat, repo: "hexpm", optional: false]}], "hexpm", "7209bfd75fd1f42467211ff8f59ea74d6f2a9e81cbcee95a56711ee79fd6b1d4"},
+  "hpax": {:hex, :hpax, "1.0.3", "ed67ef51ad4df91e75cc6a1494f851850c0bd98ebc0be6e81b026e765ee535aa", [:mix], [], "hexpm", "8eab6e1cfa8d5918c2ce4ba43588e894af35dbd8e91e6e55c817bca5847df34a"},
   "idna": {:hex, :idna, "6.1.1", "8a63070e9f7d0c62eb9d9fcb360a7de382448200fbbd1b106cc96d3d8099df8d", [:rebar3], [{:unicode_util_compat, "~> 0.7.0", [hex: :unicode_util_compat, repo: "hexpm", optional: false]}], "hexpm", "92376eb7894412ed19ac475e4a86f7b413c1b9fbb5bd16dccd57934157944cea"},
   "jason": {:hex, :jason, "1.4.4", "b9226785a9aa77b6857ca22832cffa5d5011a667207eb2a0ad56adb5db443b8a", [:mix], [{:decimal, "~> 1.0 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "c5eb0cab91f094599f94d55bc63409236a8ec69a21a67814529e8d5f6cc90b3b"},
   "makeup": {:hex, :makeup, "1.2.1", "e90ac1c65589ef354378def3ba19d401e739ee7ee06fb47f94c687016e3713d1", [:mix], [{:nimble_parsec, "~> 1.4", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "d36484867b0bae0fea568d10131197a4c2e47056a6fbe84922bf6ba71c8d17ce"},
   "makeup_elixir": {:hex, :makeup_elixir, "1.0.1", "e928a4f984e795e41e3abd27bfc09f51db16ab8ba1aebdba2b3a575437efafc2", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}, {:nimble_parsec, "~> 1.2.3 or ~> 1.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "7284900d412a3e5cfd97fdaed4f5ed389b8f2b4cb49efc0eb3bd10e2febf9507"},
   "makeup_erlang": {:hex, :makeup_erlang, "1.0.3", "4252d5d4098da7415c390e847c814bad3764c94a814a0b4245176215615e1035", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}], "hexpm", "953297c02582a33411ac6208f2c6e55f0e870df7f80da724ed613f10e6706afd"},
   "metrics": {:hex, :metrics, "1.0.1", "25f094dea2cda98213cecc3aeff09e940299d950904393b2a29d191c346a8486", [:rebar3], [], "hexpm", "69b09adddc4f74a40716ae54d140f93beb0fb8978d8636eaded0c31b6f099f16"},
   "mimerl": {:hex, :mimerl, "1.4.0", "3882a5ca67fbbe7117ba8947f27643557adec38fa2307490c4c4207624cb213b", [:rebar3], [], "hexpm", "13af15f9f68c65884ecca3a3891d50a7b57d82152792f3e19d88650aa126b144"},
+  "mint": {:hex, :mint, "1.7.1", "113fdb2b2f3b59e47c7955971854641c61f378549d73e829e1768de90fc1abf1", [:mix], [{:castore, "~> 0.1.0 or ~> 1.0", [hex: :castore, repo: "hexpm", optional: true]}, {:hpax, "~> 0.1.1 or ~> 0.2.0 or ~> 1.0", [hex: :hpax, repo: "hexpm", optional: false]}], "hexpm", "fceba0a4d0f24301ddee3024ae116df1c3f4bb7a563a731f45fdfeb9d39a231b"},
   "mix_test_watch": {:hex, :mix_test_watch, "1.4.0", "d88bcc4fbe3198871266e9d2f00cd8ae350938efbb11d3fa1da091586345adbb", [:mix], [{:file_system, "~> 0.2 or ~> 1.0", [hex: :file_system, repo: "hexpm", optional: false]}], "hexpm", "2b4693e17c8ead2ef56d4f48a0329891e8c2d0d73752c0f09272a2b17dc38d1b"},
   "nimble_parsec": {:hex, :nimble_parsec, "1.4.2", "8efba0122db06df95bfaa78f791344a89352ba04baedd3849593bfce4d0dc1c6", [:mix], [], "hexpm", "4b21398942dda052b403bbe1da991ccd03a053668d147d53fb8c4e0efe09c973"},
   "parse_trans": {:hex, :parse_trans, "3.4.1", "6e6aa8167cb44cc8f39441d05193be6e6f4e7c2946cb2759f015f8c56b76e5ff", [:rebar3], [], "hexpm", "620a406ce75dada827b82e453c19cf06776be266f5a67cff34e1ef2cbb60e49a"},
@@ -29,6 +31,7 @@
   "ssl_verify_fun": {:hex, :ssl_verify_fun, "1.1.7", "354c321cf377240c7b8716899e182ce4890c5938111a1296add3ec74cf1715df", [:make, :mix, :rebar3], [], "hexpm", "fe4c190e8f37401d30167c8c405eda19469f34577987c76dde613e838bbc67f8"},
   "statistex": {:hex, :statistex, "1.1.0", "7fec1eb2f580a0d2c1a05ed27396a084ab064a40cfc84246dbfb0c72a5c761e5", [:mix], [], "hexpm", "f5950ea26ad43246ba2cce54324ac394a4e7408fdcf98b8e230f503a0cba9cf5"},
   "timex": {:hex, :timex, "3.7.13", "0688ce11950f5b65e154e42b47bf67b15d3bc0e0c3def62199991b8a8079a1e2", [:mix], [{:combine, "~> 0.10", [hex: :combine, repo: "hexpm", optional: false]}, {:gettext, "~> 0.26", [hex: :gettext, repo: "hexpm", optional: false]}, {:tzdata, "~> 1.1", [hex: :tzdata, repo: "hexpm", optional: false]}], "hexpm", "09588e0522669328e973b8b4fd8741246321b3f0d32735b589f78b136e6d4c54"},
+  "tz": {:hex, :tz, "0.28.1", "717f5ffddfd1e475e2a233e221dc0b4b76c35c4b3650b060c8e3ba29dd6632e9", [:mix], [{:castore, "~> 0.1 or ~> 1.0", [hex: :castore, repo: "hexpm", optional: true]}, {:mint, "~> 1.6", [hex: :mint, repo: "hexpm", optional: true]}], "hexpm", "bfdca1aa1902643c6c43b77c1fb0cb3d744fd2f09a8a98405468afdee0848c8a"},
   "tzdata": {:hex, :tzdata, "1.1.3", "b1cef7bb6de1de90d4ddc25d33892b32830f907e7fc2fccd1e7e22778ab7dfbc", [:mix], [{:hackney, "~> 1.17", [hex: :hackney, repo: "hexpm", optional: false]}], "hexpm", "d4ca85575a064d29d4e94253ee95912edfb165938743dbf002acdf0dcecb0c28"},
   "unicode_util_compat": {:hex, :unicode_util_compat, "0.7.1", "a48703a25c170eedadca83b11e88985af08d35f37c6f664d6dcfb106a97782fc", [:rebar3], [], "hexpm", "b3a917854ce3ae233619744ad1e0102e05673136776fb2fa76234f3e03b23642"},
 }

test/ical/deserialize_test.exs

@@ -148,10 +148,6 @@ defmodule ICal.DeserializeTest do
       assert nil == ICal.Deserialize.to_date_in_timezone("garbage", "America/Chicago")
     end
 
-    @tag skip: """
-         implementation returns the second (EST) occurrence instead of the first (EDT);
-         RFC 5545 §3.3.5 requires the first occurrence for ambiguous fall-back times
-         """
     test "to_date_in_timezone/2 handles ambiguous wall clock time during DST fall-back" do
       # RFC 5545 §3.3.5: when a local time occurs more than once (clocks fall
       # back), "the DATE-TIME value refers to the first occurrence of the
@@ -162,6 +158,7 @@ defmodule ICal.DeserializeTest do
       # America/New_York falls back on 2023-11-05; 1:30 AM occurs twice.
       # The first occurrence is EDT (std_offset: 3600, total offset -04:00).
       result = ICal.Deserialize.to_date_in_timezone("20231105T013000", "America/New_York")
+      #       result = ICal.Deserialize.to_date_in_timezone("20070311T023000", "America/New_York")
 
       assert %DateTime{
                year: 2023,
@@ -176,11 +173,6 @@ defmodule ICal.DeserializeTest do
              } = result
     end
 
-    @tag skip: """
-         implementation returns just_after (3:00 AM EDT) instead of applying the pre-gap
-         offset (3:30 AM EDT); RFC 5545 §3.3.5 requires interpreting the wall clock time
-         using the UTC offset before the gap
-         """
     test "to_date_in_timezone/2 handles non-existent wall clock time during DST spring-forward" do
       # RFC 5545 §3.3.5: when a local time does not occur (clocks spring
       # forward), "the DATE-TIME value is interpreted using the UTC offset

test/test_helper.exs

@@ -52,4 +52,5 @@ defmodule ICal.Test.Helper do
   end
 end
 
+Calendar.put_time_zone_database(Tz.TimeZoneDatabase)
 ExUnit.start()