LibTimeZone: Parse and generate a list of time zones used by region

The zone1970.tab file in the TZDB contains regional time zone data, some
of which we already parse for the system time zone settings map.

This parses the region names from that file and generates a list of time
zones which are used in each of those regions.

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

@@ -18,8 +18,8 @@
 
 namespace {
 
-using StringIndexType = u8;
-constexpr auto s_string_index_type = "u8"sv;
+using StringIndexType = u16;
+constexpr auto s_string_index_type = "u16"sv;
 
 struct DateTime {
     u16 year { 0 };
@@ -67,6 +67,9 @@ struct TimeZoneData {
     Vector<String> dst_offset_names;
 
     HashMap<String, TimeZone::Location> time_zone_coordinates;
+
+    HashMap<String, Vector<StringIndexType>> time_zone_regions;
+    Vector<String> time_zone_region_names;
 };
 
 }
@@ -379,6 +382,7 @@ static ErrorOr<void> parse_time_zone_coordinates(Core::Stream::BufferedFile& fil
             continue;
 
         auto segments = line.split_view('\t');
+        auto regions = segments[0];
         auto coordinates = segments[1];
         auto zone = segments[2];
 
@@ -389,6 +393,14 @@ static ErrorOr<void> parse_time_zone_coordinates(Core::Stream::BufferedFile& fil
         auto longitude = parse_coordinate(coordinates.substring_view(index));
 
         time_zone_data.time_zone_coordinates.set(zone, { latitude, longitude });
+
+        regions.for_each_split_view(',', false, [&](auto region) {
+            auto index = time_zone_data.unique_strings.ensure(zone);
+            time_zone_data.time_zone_regions.ensure(region).append(index);
+
+            if (!time_zone_data.time_zone_region_names.contains_slow(region))
+                time_zone_data.time_zone_region_names.append(region);
+        });
     }
 
     return {};
@@ -447,6 +459,7 @@ namespace TimeZone {
 
     generate_enum(generator, format_identifier, "TimeZone"sv, {}, time_zone_data.time_zone_names, time_zone_data.time_zone_aliases);
     generate_enum(generator, format_identifier, "DaylightSavingsRule"sv, {}, time_zone_data.dst_offset_names);
+    generate_enum(generator, format_identifier, "Region"sv, {}, time_zone_data.time_zone_region_names);
 
     generator.append(R"~~~(
 }
@@ -556,6 +569,26 @@ static constexpr Array<@type@, @size@> @name@ { {
             append_offsets(name, "DaylightSavingsOffset"sv, dst_offsets);
         });
 
+    generate_mapping(generator, time_zone_data.time_zone_region_names, s_string_index_type, "s_regional_time_zones"sv, "s_regional_time_zones_{}", format_identifier,
+        [&](auto const& name, auto const& value) {
+            auto const& time_zones = time_zone_data.time_zone_regions.find(value)->value;
+
+            generator.set("name", name);
+            generator.set("size", String::number(time_zones.size()));
+
+            generator.append(R"~~~(
+static constexpr Array<@string_index_type@, @size@> @name@ { {)~~~");
+
+            bool first = true;
+            for (auto const& time_zone : time_zones) {
+                generator.append(first ? " " : ", ");
+                generator.append(String::number(time_zone));
+                first = false;
+            }
+
+            generator.append(" } };");
+        });
+
     generator.set("size", String::number(time_zone_data.time_zone_names.size()));
     generator.append(R"~~~(
 static constexpr Array<Location, @size@> s_time_zone_locations { {
@@ -590,6 +623,7 @@ static constexpr Array<Location, @size@> s_time_zone_locations { {
 
     append_string_conversions("TimeZone"sv, "time_zone"sv, time_zone_data.time_zone_names, time_zone_data.time_zone_aliases);
     append_string_conversions("DaylightSavingsRule"sv, "daylight_savings_rule"sv, time_zone_data.dst_offset_names);
+    append_string_conversions("Region"sv, "region"sv, time_zone_data.time_zone_region_names);
 
     generator.append(R"~~~(
 static Array<DaylightSavingsOffset const*, 2> find_dst_offsets(TimeZoneOffset const& time_zone_offset, AK::Time time)
@@ -727,6 +761,25 @@ Optional<Location> get_time_zone_location(TimeZone time_zone)
         return location;
     return {};
 }
+
+Vector<StringView> time_zones_in_region(StringView region)
+{
+    auto region_value = region_from_string(region);
+    if (!region_value.has_value())
+        return {};
+
+    auto region_index = to_underlying(*region_value);
+
+    auto const& regional_time_zones = s_regional_time_zones[region_index];
+
+    Vector<StringView> time_zones;
+    time_zones.ensure_capacity(regional_time_zones.size());
+
+    for (auto time_zone : regional_time_zones)
+        time_zones.unchecked_append(s_string_list[time_zone]);
+
+    return time_zones;
+}
 )~~~");
 
     generate_available_values(generator, "all_time_zones"sv, time_zone_data.time_zone_names);

Userland/Libraries/LibTimeZone/Forward.h

@@ -11,6 +11,7 @@
 namespace TimeZone {
 
 enum class DaylightSavingsRule : u8;
+enum class Region : u8;
 enum class TimeZone : u16;
 
 }

Userland/Libraries/LibTimeZone/TimeZone.cpp

@@ -192,4 +192,8 @@ Optional<Location> get_time_zone_location(StringView time_zone)
     return {};
 }
 
+Optional<Region> __attribute__((weak)) region_from_string(StringView) { return {}; }
+StringView __attribute__((weak)) region_to_string(Region) { return {}; }
+Vector<StringView> __attribute__((weak)) time_zones_in_region(StringView) { return {}; }
+
 }

Userland/Libraries/LibTimeZone/TimeZone.h

@@ -13,6 +13,7 @@
 #include <AK/StringView.h>
 #include <AK/Time.h>
 #include <AK/Types.h>
+#include <AK/Vector.h>
 #include <LibTimeZone/Forward.h>
 
 namespace TimeZone {
@@ -68,4 +69,8 @@ Optional<Array<NamedOffset, 2>> get_named_time_zone_offsets(StringView time_zone
 Optional<Location> get_time_zone_location(TimeZone time_zone);
 Optional<Location> get_time_zone_location(StringView time_zone);
 
+Optional<Region> region_from_string(StringView region);
+StringView region_to_string(Region region);
+Vector<StringView> time_zones_in_region(StringView region);
+
 }