From 9cfa84b1bfd63a3a50db6b6517d15152f00ddc0f Mon Sep 17 00:00:00 2001
From: Max VelDink <mveldink@justworks.com>
Date: Thu, 11 Jul 2024 15:40:10 -0400
Subject: [PATCH] feat: add coercion support for DateTime

---
 lib/typed/coercion/coercer_registry.rb        |  1 +
 lib/typed/coercion/date_time_coercer.rb       | 29 ++++++++++++++++
 test/typed/coercion/date_coercer_test.rb      |  2 ++
 test/typed/coercion/date_time_coercer_test.rb | 33 +++++++++++++++++++
 4 files changed, 65 insertions(+)
 create mode 100644 lib/typed/coercion/date_time_coercer.rb
 create mode 100644 test/typed/coercion/date_time_coercer_test.rb

diff --git a/lib/typed/coercion/coercer_registry.rb b/lib/typed/coercion/coercer_registry.rb
index 402cc3a..6c70825 100644
--- a/lib/typed/coercion/coercer_registry.rb
+++ b/lib/typed/coercion/coercer_registry.rb
@@ -19,6 +19,7 @@ class CoercerRegistry
           IntegerCoercer,
           FloatCoercer,
           DateCoercer,
+          DateTimeCoercer,
           EnumCoercer,
           StructCoercer,
           TypedArrayCoercer,
diff --git a/lib/typed/coercion/date_time_coercer.rb b/lib/typed/coercion/date_time_coercer.rb
new file mode 100644
index 0000000..d400dd9
--- /dev/null
+++ b/lib/typed/coercion/date_time_coercer.rb
@@ -0,0 +1,29 @@
+# typed: strict
+
+require "date"
+
+module Typed
+  module Coercion
+    class DateTimeCoercer < Coercer
+      extend T::Generic
+
+      Target = type_member { {fixed: DateTime} }
+
+      sig { override.params(type: T::Types::Base).returns(T::Boolean) }
+      def used_for_type?(type)
+        T::Utils.coerce(type) == T::Utils.coerce(DateTime)
+      end
+
+      sig { override.params(type: T::Types::Base, value: Value).returns(Result[Target, CoercionError]) }
+      def coerce(type:, value:)
+        return Failure.new(CoercionError.new("Type must be a DateTime.")) unless used_for_type?(type)
+
+        return Success.new(value) if value.is_a?(DateTime)
+
+        Success.new(DateTime.parse(value))
+      rescue Date::Error, TypeError
+        Failure.new(CoercionError.new("'#{value}' cannot be coerced into DateTime."))
+      end
+    end
+  end
+end
diff --git a/test/typed/coercion/date_coercer_test.rb b/test/typed/coercion/date_coercer_test.rb
index 8bb5976..9643fb4 100644
--- a/test/typed/coercion/date_coercer_test.rb
+++ b/test/typed/coercion/date_coercer_test.rb
@@ -1,5 +1,7 @@
 # typed: true
 
+require "test_helper"
+
 class DateCoercerTest < Minitest::Test
   def setup
     @coercer = Typed::Coercion::DateCoercer.new
diff --git a/test/typed/coercion/date_time_coercer_test.rb b/test/typed/coercion/date_time_coercer_test.rb
new file mode 100644
index 0000000..2983c40
--- /dev/null
+++ b/test/typed/coercion/date_time_coercer_test.rb
@@ -0,0 +1,33 @@
+# typed: true
+
+require "test_helper"
+
+class DateTimeCoercerTest < Minitest::Test
+  def setup
+    @coercer = Typed::Coercion::DateTimeCoercer.new
+    @type = T::Utils.coerce(DateTime)
+  end
+
+  def test_used_for_type_works
+    assert(@coercer.used_for_type?(@type))
+    refute(@coercer.used_for_type?(T::Utils.coerce(Integer)))
+  end
+
+  def test_when_non_date_type_given_returns_failure
+    result = @coercer.coerce(type: T::Utils.coerce(Integer), value: DateTime.now)
+
+    assert_failure(result)
+    assert_error(Typed::Coercion::CoercionError.new("Type must be a DateTime."), result)
+  end
+
+  def test_when_coercable_returns_success
+    assert_payload(DateTime.new(2024, 7, 11, 19, 31, 30), @coercer.coerce(type: @type, value: "2024-07-11T19:31:30Z"))
+    assert_payload(DateTime.new(2024, 7, 11, 19, 31, 30), @coercer.coerce(type: @type, value: "2024-07-11T19:31:30"))
+    assert_payload(DateTime.new(2024, 7, 11), @coercer.coerce(type: @type, value: "2024-07-11"))
+  end
+
+  def test_when_not_coercable_returns_failure
+    assert_error(Typed::Coercion::CoercionError.new("'a' cannot be coerced into DateTime."), @coercer.coerce(type: @type, value: "a"))
+    assert_error(Typed::Coercion::CoercionError.new("'1' cannot be coerced into DateTime."), @coercer.coerce(type: @type, value: 1))
+  end
+end