LibTimeZone: Add method to convert a time zone to a string

Author: https://github.com/trflynn89
Commit: https://github.com/SerenityOS/serenity/commit/1c2c98ac5d0
Pull-request: https://github.com/SerenityOS/serenity/pull/11799
Reviewed-by: https://github.com/linusg ✅

Meta/Lagom/Tools/CodeGenerators/LibTimeZone/GenerateTimeZoneData.cpp

@@ -231,7 +231,7 @@ static void generate_time_zone_data_implementation(Core::File& file, TimeZoneDat
 namespace TimeZone {
 )~~~");
 
-    auto append_from_string = [&](StringView enum_title, StringView enum_snake, auto const& values, auto const& aliases) {
+    auto append_string_conversions = [&](StringView enum_title, StringView enum_snake, auto const& values, auto const& aliases) {
         HashValueMap<String> hashes;
         hashes.ensure_capacity(values.size());
 
@@ -248,9 +248,10 @@ namespace TimeZone {
         options.sensitivity = CaseSensitivity::CaseInsensitive;
 
         generate_value_from_string(generator, "{}_from_string"sv, enum_title, enum_snake, move(hashes), options);
+        generate_value_to_string(generator, "{}_to_string"sv, enum_title, enum_snake, format_identifier, values);
     };
 
-    append_from_string("TimeZone"sv, "time_zone"sv, time_zone_data.time_zone_names, time_zone_data.time_zone_aliases);
+    append_string_conversions("TimeZone"sv, "time_zone"sv, time_zone_data.time_zone_names, time_zone_data.time_zone_aliases);
 
     generator.append(R"~~~(
 }

Meta/Lagom/Tools/CodeGenerators/LibUnicode/GeneratorUtil.h

@@ -363,6 +363,36 @@ Optional<@return_type@> @method_name@(StringView key)
 )~~~");
 }
 
+template<typename IdentifierFormatter>
+void generate_value_to_string(SourceGenerator& generator, StringView method_name_format, StringView value_type, StringView value_name, IdentifierFormatter&& format_identifier, Span<String const> values)
+{
+    generator.set("method_name", String::formatted(method_name_format, value_name));
+    generator.set("value_type", value_type);
+    generator.set("value_name", value_name);
+
+    generator.append(R"~~~(
+StringView @method_name@(@value_type@ @value_name@)
+{
+    using enum @value_type@;
+
+    switch (@value_name@) {)~~~");
+
+    for (auto const& value : values) {
+        generator.set("enum_value", format_identifier(value_type, value));
+        generator.set("string_value", value);
+        generator.append(R"~~~(
+    case @enum_value@:
+        return "@string_value@"sv;)~~~");
+    }
+
+    generator.append(R"~~~(
+    }
+
+    VERIFY_NOT_REACHED();
+}
+)~~~");
+}
+
 template<typename IdentifierFormatter>
 void generate_enum(SourceGenerator& generator, IdentifierFormatter&& format_identifier, StringView name, StringView default_, Vector<String>& values, Vector<Alias> aliases = {})
 {

Tests/LibTimeZone/TestTimeZone.cpp

@@ -53,4 +53,20 @@ TEST_CASE(case_insensitive_time_zone_from_string)
     EXPECT_EQ(TimeZone::time_zone_from_string("uTc"sv), TimeZone::TimeZone::UTC);
 }
 
+TEST_CASE(time_zone_to_string)
+{
+    EXPECT_EQ(TimeZone::time_zone_to_string(TimeZone::TimeZone::America_New_York), "America/New_York"sv);
+    EXPECT_EQ(TimeZone::time_zone_to_string(TimeZone::TimeZone::Europe_Paris), "Europe/Paris"sv);
+    EXPECT_EQ(TimeZone::time_zone_to_string(TimeZone::TimeZone::Etc_GMT_Ahead_2), "Etc/GMT+2"sv);
+    EXPECT_EQ(TimeZone::time_zone_to_string(TimeZone::TimeZone::Etc_GMT_Behind_5), "Etc/GMT-5"sv);
+}
+
+TEST_CASE(time_zone_to_string_link)
+{
+    EXPECT_EQ(TimeZone::time_zone_to_string(TimeZone::TimeZone::Etc_UTC), "Etc/UTC"sv);
+    EXPECT_EQ(TimeZone::time_zone_to_string(TimeZone::TimeZone::UTC), "Etc/UTC"sv);
+    EXPECT_EQ(TimeZone::time_zone_to_string(TimeZone::TimeZone::Universal), "Etc/UTC"sv);
+    EXPECT_EQ(TimeZone::time_zone_to_string(TimeZone::TimeZone::Etc_Universal), "Etc/UTC"sv);
+}
+
 #endif

Userland/Libraries/LibTimeZone/TimeZone.cpp

@@ -9,5 +9,6 @@
 namespace TimeZone {
 
 Optional<TimeZone> __attribute__((weak)) time_zone_from_string(StringView) { return {}; }
+StringView __attribute__((weak)) time_zone_to_string(TimeZone) { return {}; }
 
 }

Userland/Libraries/LibTimeZone/TimeZone.h

@@ -13,5 +13,6 @@
 namespace TimeZone {
 
 Optional<TimeZone> time_zone_from_string(StringView time_zone);
+StringView time_zone_to_string(TimeZone time_zone);
 
 }