LibWeb: Implement Flex and FlexStyleValue types

Userland/Libraries/LibWeb/CSS/Flex.h

@@ -0,0 +1,66 @@
+/*
+ * Copyright (c) 2023, Sam Atkins <atkinssj@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Optional.h>
+#include <AK/String.h>
+#include <LibWeb/Forward.h>
+
+namespace Web::CSS {
+
+// https://drafts.csswg.org/css-grid-2/#typedef-flex
+class Flex {
+public:
+    enum class Type {
+        Fr,
+    };
+
+    static Optional<Type> unit_from_name(StringView);
+
+    Flex(double value, Type type);
+    static Flex make_fr(double);
+    Flex percentage_of(Percentage const&) const;
+
+    String to_string() const;
+    double to_fr() const;
+
+    Type type() const { return m_type; }
+    double raw_value() const { return m_value; }
+
+    bool operator==(Flex const& other) const
+    {
+        return m_type == other.m_type && m_value == other.m_value;
+    }
+
+    int operator<=>(Flex const& other) const
+    {
+        auto this_fr = to_fr();
+        auto other_fr = other.to_fr();
+
+        if (this_fr < other_fr)
+            return -1;
+        if (this_fr > other_fr)
+            return 1;
+        return 0;
+    }
+
+private:
+    StringView unit_name() const;
+
+    Type m_type;
+    double m_value { 0 };
+};
+
+}
+
+template<>
+struct AK::Formatter<Web::CSS::Flex> : Formatter<StringView> {
+    ErrorOr<void> format(FormatBuilder& builder, Web::CSS::Flex const& flex)
+    {
+        return Formatter<StringView>::format(builder, flex.to_string());
+    }
+};