LibWeb/HTML: Implement <input> element valueAsNumber for 'week'

One point to note is that I am not entirely sure what the result
of the pre-existing valueAsNumber test should be for this strange
case which does not lie exactly on a week/day boundary. Chrome
gives a negative timestamp, which seems more wrong than the result
we give, and neither gecko or WebKit appear to support the 'week'
type. So I'm considering this result acceptable for now, and this
may be something that will need more WPT tests added in the future.

Libraries/LibWeb/HTML/Dates.cpp

@@ -308,4 +308,59 @@ i32 number_of_months_since_unix_epoch(YearAndMonth year_and_month)
     return (year_and_month.year - 1970) * 12 + year_and_month.month - 1;
 }
 
+// https://html.spec.whatwg.org/multipage/common-microsyntaxes.html#parse-a-week-string
+Optional<WeekYearAndWeek> parse_a_week_string(StringView input_view)
+{
+    // 1. Let input be the string being parsed.
+    // 2. Let position be a pointer into input, initially pointing at the start of the string.
+    GenericLexer input { input_view };
+
+    // 3. Collect a sequence of code points that are ASCII digits from input given position. If the collected sequence is
+    //    not at least four characters long, then fail. Otherwise, interpret the resulting sequence as a base-ten integer.
+    //    Let that number be the year.
+    auto year_string = input.consume_while(is_ascii_digit);
+    if (year_string.length() < 4)
+        return {};
+    auto maybe_year = year_string.to_number<u32>();
+    if (!maybe_year.has_value())
+        return {};
+    auto year = maybe_year.value();
+
+    // 4. If year is not a number greater than zero, then fail.
+    if (year < 1)
+        return {};
+
+    // 5. If position is beyond the end of input or if the character at position is not a U+002D HYPHEN-MINUS character, then
+    //    fail. Otherwise, move position forwards one character.
+    if (!input.consume_specific('-'))
+        return {};
+
+    // 6. If position is beyond the end of input or if the character at position is not a U+0057 LATIN CAPITAL LETTER W character
+    //    (W), then fail. Otherwise, move position forwards one character.
+    if (!input.consume_specific('W'))
+        return {};
+
+    // 7. Collect a sequence of code points that are ASCII digits from input given position. If the collected sequence is not
+    //    exactly two characters long, then fail. Otherwise, interpret the resulting sequence as a base-ten integer. Let that
+    //    number be the week.
+    auto week_string = input.consume_while(is_ascii_digit);
+    if (week_string.length() != 2)
+        return {};
+    auto week = week_string.to_number<u32>().value();
+
+    // 8. Let maxweek be the week number of the last day of year year.
+    auto maxweek = week_number_of_the_last_day(year);
+
+    // 9. If week is not a number in the range 1 ≤ week ≤ maxweek, then fail.
+    if (week < 1 || week > maxweek)
+        return {};
+
+    // 10. If position is not beyond the end of input, then fail.
+    if (!input.is_eof())
+        return {};
+
+    // 11. Return the week-year number year and the week number week.
+    return WeekYearAndWeek { year, week };
+}
+
 }

Libraries/LibWeb/HTML/Dates.h

@@ -28,6 +28,13 @@ struct YearAndMonth {
     u32 month;
 };
 Optional<YearAndMonth> parse_a_month_string(StringView);
+
+struct WeekYearAndWeek {
+    u32 week_year;
+    u32 week;
+};
+Optional<WeekYearAndWeek> parse_a_week_string(StringView);
+
 i32 number_of_months_since_unix_epoch(YearAndMonth);
 
 }

Libraries/LibWeb/HTML/HTMLInputElement.cpp

@@ -2079,6 +2079,20 @@ static Optional<double> convert_month_string_to_number(StringView input)
     return number_of_months_since_unix_epoch(maybe_year_and_month.value());
 }
 
+// https://html.spec.whatwg.org/multipage/input.html#week-state-(type=week):concept-input-value-string-number
+static Optional<double> convert_week_string_to_number(StringView input)
+{
+    // The algorithm to convert a string to a number, given a string input, is as follows: If parsing a week
+    // string from input results in an error, then return an error; otherwise, return the number of
+    // milliseconds elapsed from midnight UTC on the morning of 1970-01-01 (the time represented by the value
+    // "1970-01-01T00:00:00.0Z") to midnight UTC on the morning of the Monday of the parsed week, ignoring
+    // leap seconds.
+    auto parsed_week = parse_a_week_string(input);
+    if (!parsed_week.has_value())
+        return {};
+    return UnixDateTime::from_iso8601_week(parsed_week->week_year, parsed_week->week).milliseconds_since_epoch();
+}
+
 // https://html.spec.whatwg.org/multipage/input.html#concept-input-value-string-number
 Optional<double> HTMLInputElement::convert_string_to_number(StringView input) const
 {
@@ -2093,6 +2107,9 @@ Optional<double> HTMLInputElement::convert_string_to_number(StringView input) co
     if (type_state() == TypeAttributeState::Month)
         return convert_month_string_to_number(input);
 
+    if (type_state() == TypeAttributeState::Week)
+        return convert_week_string_to_number(input);
+
     dbgln("HTMLInputElement::convert_string_to_number() not implemented for input type {}", type());
     return {};
 }
@@ -2108,6 +2125,36 @@ static String convert_number_to_month_string(double input)
     return MUST(String::formatted("{:04d}-{:02d}", static_cast<int>(year), static_cast<int>(months) + 1));
 }
 
+// https://html.spec.whatwg.org/multipage/input.html#week-state-(type=week):concept-input-value-string-number
+static String convert_number_to_week_string(double input)
+{
+    // The algorithm to convert a number to a string, given a number input, is as follows: Return a valid week string that
+    // that represents the week that, in UTC, is current input milliseconds after midnight UTC on the morning of 1970-01-01
+    // (the time represented by the value "1970-01-01T00:00:00.0Z").
+
+    int days_since_epoch = static_cast<int>(input / AK::ms_per_day);
+    int year = 1970;
+
+    while (true) {
+        auto days = days_in_year(year);
+        if (days_since_epoch < days)
+            break;
+        days_since_epoch -= days;
+        ++year;
+    }
+
+    auto january_1_weekday = day_of_week(year, 1, 1);
+    int offset_to_week_start = (january_1_weekday <= 3) ? january_1_weekday : january_1_weekday - 7;
+    int week = (days_since_epoch + offset_to_week_start) / 7 + 1;
+
+    if (week < 0) {
+        --year;
+        week = weeks_in_year(year) + week;
+    }
+
+    return MUST(String::formatted("{:04d}-W{:02d}", year, week));
+}
+
 // https://html.spec.whatwg.org/multipage/input.html#concept-input-value-string-number
 String HTMLInputElement::convert_number_to_string(double input) const
 {
@@ -2122,6 +2169,9 @@ String HTMLInputElement::convert_number_to_string(double input) const
     if (type_state() == TypeAttributeState::Month)
         return convert_number_to_month_string(input);
 
+    if (type_state() == TypeAttributeState::Week)
+        return convert_number_to_week_string(input);
+
     dbgln("HTMLInputElement::convert_number_to_string() not implemented for input type {}", type());
     return {};
 }

Tests/LibWeb/Text/expected/HTML/HTMLInputElement-valueAsNumber.txt

@@ -33,7 +33,7 @@ email threw exception: InvalidStateError: valueAsNumber: Invalid input type used
 password threw exception: InvalidStateError: valueAsNumber: Invalid input type used
 date did not throw: NaN
 month did not throw: 100
-week did not throw: NaN
+week did not throw: 345600000
 time did not throw: NaN
 datetime-local did not throw: NaN
 color threw exception: InvalidStateError: valueAsNumber: Invalid input type used

Tests/LibWeb/Text/expected/wpt-import/html/semantics/forms/the-input-element/input-valueasnumber.txt

@@ -2,8 +2,8 @@ Harness status: OK
 
 Found 60 tests
 
-38 Pass
-22 Fail
+43 Pass
+17 Fail
 Pass	valueAsNumber getter on type date (actual value: , expected valueAsNumber: NaN)
 Pass	valueAsNumber getter on type date (actual value: 0000-12-10, expected valueAsNumber: NaN)
 Pass	valueAsNumber getter on type date (actual value: 2019-00-12, expected valueAsNumber: NaN)
@@ -26,11 +26,11 @@ Pass	valueAsNumber getter on type week (actual value: , expected valueAsNumber:
 Pass	valueAsNumber getter on type week (actual value: 0000-W50, expected valueAsNumber: NaN)
 Pass	valueAsNumber getter on type week (actual value: 2019-W00, expected valueAsNumber: NaN)
 Pass	valueAsNumber getter on type week (actual value: 2019-W60, expected valueAsNumber: NaN)
-Fail	valueAsNumber getter on type week (actual value: 2019-W50, expected valueAsNumber: 1575849600000)
-Fail	valueAsNumber getter on type week (actual value: 1969-W20, expected valueAsNumber: -20217600000)
-Fail	valueAsNumber setter on type week (actual valueAsNumber: 0, expected value: 1970-W01)
-Fail	valueAsNumber setter on type week (actual valueAsNumber: 1575849600000, expected value: 2019-W50)
-Fail	valueAsNumber setter on type week (actual valueAsNumber: -20217600000, expected value: 1969-W20)
+Pass	valueAsNumber getter on type week (actual value: 2019-W50, expected valueAsNumber: 1575849600000)
+Pass	valueAsNumber getter on type week (actual value: 1969-W20, expected valueAsNumber: -20217600000)
+Pass	valueAsNumber setter on type week (actual valueAsNumber: 0, expected value: 1970-W01)
+Pass	valueAsNumber setter on type week (actual valueAsNumber: 1575849600000, expected value: 2019-W50)
+Pass	valueAsNumber setter on type week (actual valueAsNumber: -20217600000, expected value: 1969-W20)
 Pass	valueAsNumber getter on type time (actual value: , expected valueAsNumber: NaN)
 Pass	valueAsNumber getter on type time (actual value: 24:00, expected valueAsNumber: NaN)
 Pass	valueAsNumber getter on type time (actual value: 00:60, expected valueAsNumber: NaN)