Fix as_date()'s std::bad_cast with decimal value (#240)

Signed-off-by: Dominik Thalhammer <dominik@thalhammer.it>
Co-authored-by: Prosperoh <prosperoh@protonmail.com>
Co-authored-by: Dominik Thalhammer <dominik@thalhammer.it>

Author: 3 people

include/jwt-cpp/jwt.h

@@ -23,6 +23,7 @@
 
 #include <algorithm>
 #include <chrono>
+#include <cmath>
 #include <codecvt>
 #include <functional>
 #include <iterator>
@@ -2253,11 +2254,18 @@ namespace jwt {
 		typename json_traits::string_type as_string() const { return json_traits::as_string(val); }
 
 		/**
-		 * Get the contained JSON value as a date
+		 * \brief Get the contained JSON value as a date
+		 *
+		 * If the value is a decimal, it is rounded up to the closest integer
+		 *
 		 * \return content as date
 		 * \throw std::bad_cast Content was not a date
 		 */
-		date as_date() const { return std::chrono::system_clock::from_time_t(as_int()); }
+		date as_date() const {
+			using std::chrono::system_clock;
+			if (get_type() == json::type::number) return system_clock::from_time_t(std::round(as_number()));
+			return system_clock::from_time_t(as_int());
+		}
 
 		/**
 		 * Get the contained JSON value as an array