Made Date constexpr so that PROPERTY getters can be constexprconstexpr-date

1 files changed, 191 insertions, 63 deletions

diff --git a/src/openvic-simulation/types/Date.hpp b/src/openvic-simulation/types/Date.hpp
index 2bf08e8..9178e6e 100644
--- a/src/openvic-simulation/types/Date.hpp
+++ b/src/openvic-simulation/types/Date.hpp
@@ -1,6 +1,6 @@
 #pragma once
 
-#include <climits>
+#include <algorithm>
 #include <cstdint>
 #include <ostream>
 #include <string>
@@ -17,32 +17,70 @@ namespace OpenVic {
 		day_t days;
 
 	public:
-		Timespan(day_t value = 0);
-
-		bool operator<(Timespan other) const;
-		bool operator>(Timespan other) const;
-		bool operator<=(Timespan other) const;
-		bool operator>=(Timespan other) const;
-		bool operator==(Timespan other) const;
-		bool operator!=(Timespan other) const;
-
-		Timespan operator+(Timespan other) const;
-		Timespan operator-(Timespan other) const;
-		Timespan operator*(day_t factor) const;
-		Timespan operator/(day_t factor) const;
-		Timespan& operator+=(Timespan other);
-		Timespan& operator-=(Timespan other);
-		Timespan& operator++();
-		Timespan operator++(int);
-
-		day_t to_int() const;
-		explicit operator day_t() const;
+		constexpr Timespan(day_t value = 0) : days { value } {}
+
+		constexpr bool operator<(Timespan other) const {
+			return days < other.days;
+		};
+		constexpr bool operator>(Timespan other) const {
+			return days > other.days;
+		};
+		constexpr bool operator<=(Timespan other) const {
+			return days <= other.days;
+		};
+		constexpr bool operator>=(Timespan other) const {
+			return days >= other.days;
+		};
+		constexpr bool operator==(Timespan other) const {
+			return days == other.days;
+		};
+		constexpr bool operator!=(Timespan other) const {
+			return days != other.days;
+		};
+
+		constexpr Timespan operator+(Timespan other) const {
+			return days + other.days;
+		}
+		constexpr Timespan operator-(Timespan other) const {
+			return days - other.days;
+		}
+		constexpr Timespan operator*(day_t factor) const {
+			return days * factor;
+		}
+		constexpr Timespan operator/(day_t factor) const {
+			return days / factor;
+		}
+		constexpr Timespan& operator+=(Timespan other) {
+			days += other.days;
+			return *this;
+		}
+		constexpr Timespan& operator-=(Timespan other) {
+			days -= other.days;
+			return *this;
+		}
+		constexpr Timespan& operator++() {
+			days++;
+			return *this;
+		}
+		constexpr Timespan operator++(int) {
+			Timespan old = *this;
+			++(*this);
+			return old;
+		}
+
+		constexpr day_t to_int() const {
+			return days;
+		}
+		explicit constexpr operator day_t() const {
+			return days;
+		}
+
 		std::string to_string() const;
 		explicit operator std::string() const;
 
-		static Timespan from_years(day_t num);
-		static Timespan from_months(day_t num);
-		static Timespan from_days(day_t num);
+		static constexpr Timespan from_years(day_t num);
+		static constexpr Timespan from_months(day_t num);
+		static constexpr Timespan from_days(day_t num);
 	};
 	std::ostream& operator<<(std::ostream& out, Timespan const& timespan);
 
@@ -54,69 +92,159 @@ namespace OpenVic {
 		using day_t = uint8_t;
 
 		static constexpr Timespan::day_t MONTHS_IN_YEAR = 12;
-		static constexpr Timespan::day_t DAYS_IN_YEAR = 365;
-		static constexpr Timespan::day_t DAYS_IN_MONTH[MONTHS_IN_YEAR] { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
-		static Timespan::day_t const* DAYS_UP_TO_MONTH;
-		static month_t const* MONTH_FROM_DAY_IN_YEAR;
+
+		static constexpr std::array<Timespan::day_t, MONTHS_IN_YEAR> DAYS_IN_MONTH {
+			31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
+		};
+
+		static constexpr Timespan::day_t DAYS_IN_YEAR { []() {
+			Timespan::day_t days = 0;
+			for (Timespan::day_t days_in_month : DAYS_IN_MONTH) {
+				days += days_in_month;
+			}
+			return days;
+		}() };
+		static_assert(DAYS_IN_YEAR == 365);
+
+		static constexpr std::array<Timespan::day_t, MONTHS_IN_YEAR> DAYS_UP_TO_MONTH { []() {
+			std::array<Timespan::day_t, MONTHS_IN_YEAR> days_up_to_month;
+			Timespan::day_t days = 0;
+			for (Timespan::day_t month = 0; month < MONTHS_IN_YEAR; month++) {
+				days_up_to_month[month] = days;
+				days += DAYS_IN_MONTH[month];
+			}
+			return days_up_to_month;
+		}() };
+
+		static constexpr std::array<month_t, DAYS_IN_YEAR> MONTH_FROM_DAY_IN_YEAR { []() {
+			std::array<month_t, DAYS_IN_YEAR> month_from_day_in_year;
+			Timespan::day_t days_left = 0;
+			month_t month = 0;
+			for (Timespan::day_t day = 0; day < DAYS_IN_YEAR; day++) {
+				days_left = (days_left > 0 ? days_left : DAYS_IN_MONTH[month++]) - 1;
+				month_from_day_in_year[day] = month;
+			}
+			return month_from_day_in_year;
+		}() };
 
 		static constexpr char SEPARATOR_CHARACTER = '.';
-		static const std::string MONTH_NAMES[MONTHS_IN_YEAR];
+
+		static constexpr std::array<std::string_view, MONTHS_IN_YEAR> MONTH_NAMES {
+			"January", "February", "March", "April", "May", "June",
+			"July", "August", "September", "October", "November",
+			"December"
+		};
+		static constexpr std::string_view INVALID_MONTH_NAME = "Invalid Month";
 
 	private:
 		// Number of days since Jan 1st, Year 0
 		Timespan timespan;
 
-		static Timespan _date_to_timespan(year_t year, month_t month, day_t day);
-		static Timespan::day_t const* generate_days_up_to_month();
-		static month_t const* generate_month_from_day_in_year();
+		static constexpr Timespan _date_to_timespan(year_t year, month_t month, day_t day) {
+			month = std::clamp<month_t>(month, 1, MONTHS_IN_YEAR);
+			day = std::clamp<day_t>(day, 1, DAYS_IN_MONTH[month - 1]);
+			return year * DAYS_IN_YEAR + DAYS_UP_TO_MONTH[month - 1] + day - 1;
+		}
 
 	public:
 		// The Timespan is considered to be the number of days since Jan 1st, Year 0
-		Date(Timespan total_days);
+		constexpr Date(Timespan total_days) : timespan { total_days >= 0 ? total_days : 0 } {}
 		// Year month day specification
-		Date(year_t year = 0, month_t month = 1, day_t day = 1);
-
-		year_t get_year() const;
-		month_t get_month() const;
-		day_t get_day() const;
-
-		bool operator<(Date other) const;
-		bool operator>(Date other) const;
-		bool operator<=(Date other) const;
-		bool operator>=(Date other) const;
-		bool operator==(Date other) const;
-		bool operator!=(Date other) const;
-
-		Date operator+(Timespan other) const;
-		Timespan operator-(Date other) const;
-		Date& operator+=(Timespan other);
-		Date& operator-=(Timespan other);
-		Date& operator++();
-		Date operator++(int);
-
-		bool in_range(Date start, Date end) const;
-
-		/* This returns a std::string const&, rather than a std::string_view, as it needs to be converted to a
-		 * godot::StringName in order to be localised, and std::string_view to a godot::StringName conversion requires an
-		 * intermediary std::string. */
-		std::string const& get_month_name() const;
+		constexpr Date(year_t year = 0, month_t month = 1, day_t day = 1) : timespan { _date_to_timespan(year, month, day) } {}
+
+		constexpr year_t get_year() const {
+			return static_cast<Timespan::day_t>(timespan) / DAYS_IN_YEAR;
+		}
+		constexpr month_t get_month() const {
+			return MONTH_FROM_DAY_IN_YEAR[static_cast<Timespan::day_t>(timespan) % DAYS_IN_YEAR];
+		}
+		constexpr day_t get_day() const {
+			return (static_cast<Timespan::day_t>(timespan) % DAYS_IN_YEAR) - DAYS_UP_TO_MONTH[get_month() - 1] + 1;
+		}
+
+		constexpr bool operator<(Date other) const {
+			return timespan < other.timespan;
+		};
+		constexpr bool operator>(Date other) const {
+			return timespan > other.timespan;
+		};
+		constexpr bool operator<=(Date other) const {
+			return timespan <= other.timespan;
+		};
+		constexpr bool operator>=(Date other) const {
+			return timespan >= other.timespan;
+		};
+		constexpr bool operator==(Date other) const {
+			return timespan == other.timespan;
+		};
+		constexpr bool operator!=(Date other) const {
+			return timespan != other.timespan;
+		};
+
+		constexpr Date operator+(Timespan other) const {
+			return timespan + other;
+		}
+		constexpr Timespan operator-(Date other) const {
+			return timespan - other.timespan;
+		}
+		constexpr Date& operator+=(Timespan other) {
+			timespan += other;
+			return *this;
+		}
+		constexpr Date& operator-=(Timespan other) {
+			timespan -= other;
+			return *this;
+		}
+		constexpr Date& operator++() {
+			timespan++;
+			return *this;
+		}
+		constexpr Date operator++(int) {
+			Date old = *this;
+			++(*this);
+			return old;
+		}
+
+		constexpr bool in_range(Date start, Date end) const {
+			return start <= *this && *this <= end;
+		}
+
+		constexpr std::string_view get_month_name() const {
+			const month_t month = get_month();
+			if (1 <= month && month <= MONTHS_IN_YEAR) {
+				return MONTH_NAMES[month - 1];
+			}
+			return INVALID_MONTH_NAME;
+		}
+
 		std::string to_string() const;
 		explicit operator std::string() const;
+
 		// Parsed from string of the form YYYY.MM.DD
 		static Date from_string(char const* str, char const* end, bool* successful = nullptr, bool quiet = false);
-		static Date from_string(char const* str, size_t length, bool* successful = nullptr, bool quiet = false);
+		static Date from_string(char const* str, std::size_t length, bool* successful = nullptr, bool quiet = false);
 		static Date from_string(std::string_view str, bool* successful = nullptr, bool quiet = false);
 	};
 	std::ostream& operator<<(std::ostream& out, Date date);
+
+	constexpr Timespan Timespan::from_years(day_t num) {
+		return num * Date::DAYS_IN_YEAR;
+	}
+	constexpr Timespan Timespan::from_months(day_t num) {
+		return (num / Date::MONTHS_IN_YEAR) * Date::DAYS_IN_YEAR + Date::DAYS_UP_TO_MONTH[num % Date::MONTHS_IN_YEAR];
+	}
+	constexpr Timespan Timespan::from_days(day_t num) {
+		return num;
+	}
 }
 
 namespace std {
 	template<>
 	struct hash<OpenVic::Date> {
-		[[nodiscard]] size_t operator()(OpenVic::Date date) const {
-			size_t result = 0;
+		[[nodiscard]] std::size_t operator()(OpenVic::Date date) const {
+			std::size_t result = 0;
 			OpenVic::utility::perfect_hash(result, date.get_day(), date.get_month(), date.get_year());
 			return result;
 		}
 	};
-}
\ No newline at end of file
+}