From 3efbe22a1becd8add86ca943b94b708abae90eb6 Mon Sep 17 00:00:00 2001
From: Bananymous <bananymousosq@gmail.com>
Date: Thu, 23 Mar 2023 11:13:51 +0200
Subject: [PATCH] Kernel: Shell now prints unix time with 'date' command

---
 kernel/kernel/Shell.cpp | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/kernel/kernel/Shell.cpp b/kernel/kernel/Shell.cpp
index a95bcee31d..71d59dfb18 100644
--- a/kernel/kernel/Shell.cpp
+++ b/kernel/kernel/Shell.cpp
@@ -217,6 +217,40 @@ argument_done:
 		0xa2f33668, 0xbcb4666d, 0xb8757bda, 0xb5365d03, 0xb1f740b4
 	};
 
+	static bool is_leap_year(uint64_t year)
+	{
+		if (year % 400 == 0)
+			return true;
+		if (year % 100 == 0)
+			return false;
+		if (year % 4 == 0)
+			return true;
+		return false;
+	}
+
+	static uint64_t leap_days_since_epoch(const BAN::Time& time)
+	{
+		uint64_t leap_years = 0;
+		for (int year = 1970; year < time.year; year++)
+			if (is_leap_year(year))
+				leap_years++;
+		if (is_leap_year(time.year))
+			if (time.month >= 3 || (time.month == 2 && time.day == 29))
+				leap_years++;
+		return leap_years;
+	}
+
+	static uint64_t unix_time(const BAN::Time& time)
+	{		
+		uint64_t month_days[] { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334 };
+
+		uint64_t years = time.year - 1970;
+		uint64_t days = years * 365 + month_days[time.month - 1] + time.day + leap_days_since_epoch(time) - 1;
+		uint64_t hours = days * 24 + time.hour;
+		uint64_t minutes = hours * 60 + time.minute;
+		uint64_t seconds = minutes * 60 + time.second;
+		return seconds;
+	}
 
 	BAN::ErrorOr<void> Shell::process_command(const BAN::Vector<BAN::String>& arguments)
 	{
@@ -230,6 +264,7 @@ argument_done:
 				return BAN::Error::from_c_string("'date' does not support command line arguments");
 			auto time = RTC::get_current_time();
 			TTY_PRINTLN("{}", time);
+			TTY_PRINTLN("{}", unix_time(time));
 		}
 		else if (arguments.front() == "echo")
 		{