From c74f75b910b7f8724b765e19e94048db2e3efcea Mon Sep 17 00:00:00 2001
From: Timothy Flynn <trflynn89@pm.me>
Date: Sat, 15 Jan 2022 16:01:20 -0500
Subject: LibJS: Implement Date.prototype.setUTCDate

---
 Userland/Libraries/LibJS/Runtime/DatePrototype.cpp | 30 ++++++++++++++++++-
 Userland/Libraries/LibJS/Runtime/DatePrototype.h   |  1 +
 .../builtins/Date/Date.prototype.setUTCDate.js     | 35 ++++++++++++++++++++++
 3 files changed, 65 insertions(+), 1 deletion(-)
 create mode 100644 Userland/Libraries/LibJS/Tests/builtins/Date/Date.prototype.setUTCDate.js

diff --git a/Userland/Libraries/LibJS/Runtime/DatePrototype.cpp b/Userland/Libraries/LibJS/Runtime/DatePrototype.cpp
index f9f8961c6e..5aedcdd71b 100644
--- a/Userland/Libraries/LibJS/Runtime/DatePrototype.cpp
+++ b/Userland/Libraries/LibJS/Runtime/DatePrototype.cpp
@@ -72,7 +72,7 @@ void DatePrototype::initialize(GlobalObject& global_object)
     define_native_function(vm.names.setMonth, set_month, 2, attr);
     define_native_function(vm.names.setSeconds, set_seconds, 2, attr);
     define_native_function(vm.names.setTime, set_time, 1, attr);
-    define_native_function(vm.names.setUTCDate, set_date, 1, attr); // FIXME: This is a hack, Serenity doesn't currently support timezones other than UTC.
+    define_native_function(vm.names.setUTCDate, set_utc_date, 1, attr);
     define_native_function(vm.names.setUTCFullYear, set_utc_full_year, 3, attr);
     define_native_function(vm.names.setUTCHours, set_utc_hours, 4, attr);
     define_native_function(vm.names.setUTCMilliseconds, set_utc_milliseconds, 1, attr);
@@ -619,6 +619,34 @@ JS_DEFINE_NATIVE_FUNCTION(DatePrototype::set_time)
     return time;
 }
 
+// 21.4.4.28 Date.prototype.setUTCDate ( date ), https://tc39.es/ecma262/#sec-date.prototype.setutcdate
+JS_DEFINE_NATIVE_FUNCTION(DatePrototype::set_utc_date)
+{
+    // 1. Let t be LocalTime(? thisTimeValue(this value)).
+    auto this_time = TRY(this_time_value(global_object, vm.this_value(global_object)));
+    auto time = local_time(this_time.as_double());
+
+    // 2. Let dt be ? ToNumber(date).
+    auto date = TRY(vm.argument(0).to_number(global_object));
+
+    // 3. Let newDate be MakeDate(MakeDay(YearFromTime(t), MonthFromTime(t), dt), TimeWithinDay(t)).
+    auto year = Value(year_from_time(time));
+    auto month = Value(month_from_time(time));
+
+    auto day = make_day(global_object, year, month, date);
+    auto new_date = make_date(day, Value(time_within_day(time)));
+
+    // 4. Let v be TimeClip(newDate).
+    new_date = time_clip(global_object, new_date);
+
+    // 5. Set the [[DateValue]] internal slot of this Date object to v.
+    auto* this_object = MUST(typed_this_object(global_object));
+    this_object->set_date_value(new_date.as_double());
+
+    // 6. Return v.
+    return new_date;
+}
+
 // 21.4.4.29 Date.prototype.setUTCFullYear ( year [ , month [ , date ] ] ), https://tc39.es/ecma262/#sec-date.prototype.setutcfullyear
 JS_DEFINE_NATIVE_FUNCTION(DatePrototype::set_utc_full_year)
 {
diff --git a/Userland/Libraries/LibJS/Runtime/DatePrototype.h b/Userland/Libraries/LibJS/Runtime/DatePrototype.h
index 87df1305fb..621a0912a5 100644
--- a/Userland/Libraries/LibJS/Runtime/DatePrototype.h
+++ b/Userland/Libraries/LibJS/Runtime/DatePrototype.h
@@ -46,6 +46,7 @@ private:
     JS_DECLARE_NATIVE_FUNCTION(set_month);
     JS_DECLARE_NATIVE_FUNCTION(set_seconds);
     JS_DECLARE_NATIVE_FUNCTION(set_time);
+    JS_DECLARE_NATIVE_FUNCTION(set_utc_date);
     JS_DECLARE_NATIVE_FUNCTION(set_utc_full_year);
     JS_DECLARE_NATIVE_FUNCTION(set_utc_hours);
     JS_DECLARE_NATIVE_FUNCTION(set_utc_milliseconds);
diff --git a/Userland/Libraries/LibJS/Tests/builtins/Date/Date.prototype.setUTCDate.js b/Userland/Libraries/LibJS/Tests/builtins/Date/Date.prototype.setUTCDate.js
new file mode 100644
index 0000000000..a6d41f7ae9
--- /dev/null
+++ b/Userland/Libraries/LibJS/Tests/builtins/Date/Date.prototype.setUTCDate.js
@@ -0,0 +1,35 @@
+describe("errors", () => {
+    test("called on non-Date object", () => {
+        expect(() => {
+            Date.prototype.setUTCDate();
+        }).toThrowWithMessage(TypeError, "Not an object of type Date");
+    });
+
+    test("called with non-numeric parameters", () => {
+        expect(() => {
+            new Date().setUTCDate(Symbol.hasInstance);
+        }).toThrowWithMessage(TypeError, "Cannot convert symbol to number");
+    });
+});
+
+describe("correct behavior", () => {
+    const d = new Date(2000, 2, 1);
+
+    test("basic functionality", () => {
+        d.setUTCDate(8);
+        expect(d.getUTCDate()).toBe(8);
+
+        d.setUTCDate("a");
+        expect(d.getUTCDate()).toBe(NaN);
+    });
+
+    test("NaN", () => {
+        d.setUTCDate(NaN);
+        expect(d.getUTCDate()).toBeNaN();
+    });
+
+    test("time clip", () => {
+        d.setUTCDate(8.65e15);
+        expect(d.getUTCDate()).toBeNaN();
+    });
+});
-- 
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