added timezone support

CMakeLists.txt

@@ -1,6 +1,39 @@
 cmake_minimum_required(VERSION 3.6)
 
 project(top)
+
+option(LIBCRON_BUILD_TZ_CLOCK "Build timezone clock" OFF)
+option(LIBCRON_MANUAL_TZ_DB "User will set TZ DB manually by invoking date::set_install in their code" OFF)
+
+if(LIBCRON_BUILD_TZ_CLOCK)
+    add_library(date-tz)
+    target_sources(date-tz
+      PUBLIC
+        ${CMAKE_CURRENT_SOURCE_DIR}/libcron/externals/date/include/date/tz.h
+      PRIVATE
+        ${CMAKE_CURRENT_SOURCE_DIR}/libcron/externals/date/include/date/tz_private.h
+        ${CMAKE_CURRENT_LIST_DIR}/libcron/externals/date/src/tz.cpp
+    )
+    target_include_directories(date-tz PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/libcron/externals/date/include)
+
+    if (LIBCRON_MANUAL_TZ_DB)
+        target_compile_definitions(date-tz PRIVATE AUTO_DOWNLOAD=0 HAS_REMOTE_API=0)
+    else()
+        find_package(CURL REQUIRED)
+        target_link_libraries(date-tz PRIVATE CURL::libcurl)
+        target_compile_definitions(date-tz PRIVATE AUTO_DOWNLOAD=1 HAS_REMOTE_API=1)
+    endif()
+
+    if (WIN32 AND BUILD_SHARED_LIBS)
+        target_compile_definitions(date-tz PUBLIC DATE_BUILD_DLL=1)
+    endif()
+
+    if(NOT MSVC)
+        find_package(Threads)
+        target_link_libraries(date-tz PUBLIC Threads::Threads)
+    endif()
+endif()
+
 add_subdirectory(libcron)
 add_subdirectory(test)
 
@@ -9,4 +42,3 @@ add_dependencies(cron_test libcron)
 install(TARGETS libcron DESTINATION lib)
 install(DIRECTORY libcron/include/libcron DESTINATION include)
 install(DIRECTORY libcron/externals/date/include/date DESTINATION include)
-

README.md

@@ -131,6 +131,34 @@ This library uses `std::chrono::system_clock::timepoint` as its time unit. While
 uses a `LocalClock` by default which offsets `system_clock::now()` by the current UTC-offset. If you wish to work in
 UTC, then construct the Cron instance, passing it a `libcron::UTCClock`.  
 
+## TzClock
+
+This library also offers a `libcron::TzClock` as its time unit. Which makes use of the timezone support of date's library.
+With `libcron::TzClock` you can set one of available regions from the iana Timezone database: 
+
+```
+Cron<TzClock> cron;
+if(cron.get_clock().set_time_zone("Africa/Maputo"))
+  std::cout << "Successfully set timezone to: Africa/Maputo \n";
+else
+  std::cout << "Failed to set timezone to:  Africa/Maputo \n";
+```
+
+`libcron::TzClock` behaves like `libcron::UTCClock` if no timezone is set.
+
+If you want to use TzClock you have to set -DLIBCRON_BUILD_TZ_CLOCK=ON when building libcron. TzClock is a fully optional feature
+if you don't enable it, it won't be build at all.
+
+By default when setting the time zone with `TzClock::set_time_zone`, date-tz will automatically download the neweset database version from [Time Zones](https://www.iana.org/time-zones).
+This can be disabled with `-DLIBCRON_MANUAL_TZ_DB=ON`. If this is set user will be responsible of downloading timezone database.
+
+Setting database path / install path can be done with `date::set_install`. If not set path will default to: "~/Downloads/tzdata" ("%homedrive%\%homepath%\downloads\tzdata" on Windows).
+Using TzClock without LIBCRON_MANUAL_TZ_DB requires liburl installed in your system. On Windows it will also require 7-Zip installed into the default location.
+TzClock by default protects it's time_zone with a `std::mutex` this can be disabled by setting LockType to libcron::NullLock.
+
+[More Info about date-tz](https://howardhinnant.github.io/date/tz.html)
+[Available Regions](https://en.wikipedia.org/wiki/List_of_tz_database_time_zones)
+
 # Supported formatting
 
 This implementation supports cron format, as specified below.  

libcron/CMakeLists.txt

@@ -35,6 +35,13 @@ target_include_directories(${PROJECT_NAME}
 		PRIVATE ${CMAKE_CURRENT_LIST_DIR}/externals/date/include
 		PUBLIC include)
 
+if(LIBCRON_BUILD_TZ_CLOCK)
+	target_link_libraries(${PROJECT_NAME} PUBLIC
+		date-tz
+	)
+	target_compile_definitions(${PROJECT_NAME} PUBLIC -DBUILD_TZ_CLOCK)
+endif()
+
 if(NOT MSVC)
 	# Assume a modern compiler (gcc 9.3)
 	target_compile_definitions (${PROJECT_NAME} PRIVATE -DHAS_UNCAUGHT_EXCEPTIONS)

libcron/include/libcron/CronClock.h

@@ -1,6 +1,10 @@
 #pragma once
 
 #include <chrono>
+#ifdef BUILD_TZ_CLOCK
+#include <date/tz.h>
+#include <mutex>
+#endif
 
 namespace libcron
 {
@@ -39,4 +43,47 @@ namespace libcron
 
 			std::chrono::seconds utc_offset(std::chrono::system_clock::time_point now) const override;
     };
+
+#ifdef BUILD_TZ_CLOCK
+    template<typename LockType = std::mutex>
+    class TzClock : public ICronClock
+    {
+        public:
+            std::chrono::system_clock::time_point now() const override
+            {
+                auto now = std::chrono::system_clock::now();
+                return now + utc_offset(now);
+            }
+
+            std::chrono::seconds utc_offset(std::chrono::system_clock::time_point now) const override
+            {
+                // If we don't have a timezone we use utc
+                using namespace std::chrono;
+                std::lock_guard<LockType> lock(time_zone_mtx);
+                if (time_zone)
+                    return time_zone->get_info(now).offset;
+                else
+                    return 0s;
+            }
+
+            bool set_time_zone(std::string_view tz_name)
+            {
+                const date::time_zone *new_zone{nullptr};
+                try
+                {
+                    new_zone = date::locate_zone(tz_name);
+                }
+                catch (std::runtime_error &err)
+                {
+                    return false;
+                }
+                std::lock_guard<LockType> lock(time_zone_mtx);
+                time_zone = new_zone;
+                return true;
+            }
+        private:
+            mutable LockType time_zone_mtx{};
+            const date::time_zone* time_zone{nullptr};
+    };
+#endif
 }

test/CMakeLists.txt

@@ -38,6 +38,13 @@ else()
 	target_link_libraries(${PROJECT_NAME} libcron)
 endif()
 
+if(LIBCRON_BUILD_TZ_CLOCK)
+	target_link_libraries(${PROJECT_NAME}
+		date-tz
+	)
+	target_compile_definitions(${PROJECT_NAME} PUBLIC -DBUILD_TZ_CLOCK)
+endif()
+
 set_target_properties(${PROJECT_NAME} PROPERTIES
         ARCHIVE_OUTPUT_DIRECTORY "${CMAKE_CURRENT_LIST_DIR}/out"
         LIBRARY_OUTPUT_DIRECTORY "${CMAKE_CURRENT_LIST_DIR}/out"

test/CronTest.cpp

@@ -448,3 +448,36 @@ SCENARIO("Tasks can be added and removed from the scheduler")
         }
     }
 }
+
+#ifdef BUILD_TZ_CLOCK
+
+SCENARIO("TzClock: Timezone is not set fallback to utc")
+{
+    GIVEN("No timezone")
+    {
+        TzClock tz_clock{};
+        auto now = std::chrono::system_clock::now();
+        REQUIRE(tz_clock.utc_offset(now) == 0s);
+    }
+    GIVEN("A wrong timezone")
+    {
+        TzClock tz_clock{};
+        auto now = std::chrono::system_clock::now();
+        tz_clock.set_time_zone("404Not/Found");
+        REQUIRE(tz_clock.utc_offset(now) == 0s);
+    }
+}
+
+SCENARIO("TzClock: Setting time zone")
+{
+    TzClock tz_clock;
+    GIVEN("Valid time zone")
+    {
+        REQUIRE(tz_clock.set_time_zone("Europe/Berlin"));
+    }
+    GIVEN("Invalid time zone")
+    {
+        REQUIRE_FALSE(tz_clock.set_time_zone("404Not/Found"));
+    }
+}
+#endif