From eb476f9f0cbd59cb4f43e3a4539ba34c31d2b492 Mon Sep 17 00:00:00 2001
From: Ninjdai <ninjdai@duck.com>
Date: Sun, 12 Nov 2023 11:17:18 +0100
Subject: [PATCH] Added warning screen for RTC and inacurrate emus

---
 include/strings.h |  2 ++
 src/main_menu.c   | 28 +++++++++++++++++++++++++++-
 src/strings.c     |  3 +++
 3 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/include/strings.h b/include/strings.h
index 845e16e9f..11e7d2f31 100644
--- a/include/strings.h
+++ b/include/strings.h
@@ -328,6 +328,8 @@ extern const u8 gText_SaveFileErased[];
 extern const u8 gText_SaveFileCorrupted[];
 extern const u8 gJPText_No1MSubCircuit[];
 extern const u8 gText_BatteryRunDry[];
+extern const u8 gText_EmuWarning[];
+extern const u8 gText_TimeWarning[];
 extern const u8 gText_MainMenuNewGame[];
 extern const u8 gText_MainMenuOption[];
 extern const u8 gText_MainMenuContinue[];
diff --git a/src/main_menu.c b/src/main_menu.c
index 53aa1228c..8d3af495a 100644
--- a/src/main_menu.c
+++ b/src/main_menu.c
@@ -179,6 +179,7 @@ static u8 sBirchSpeechMainTaskId;
 static u32 InitMainMenu(bool8);
 static void Task_MainMenuCheckSaveFile(u8);
 static void Task_MainMenuCheckBattery(u8);
+static bool8 IsAccurateGBA(void);
 static void Task_WaitForSaveFileErrorWindow(u8);
 static void CreateMainMenuErrorWindow(const u8 *);
 static void ClearMainMenuWindowTilemap(const struct WindowTemplate *);
@@ -702,8 +703,19 @@ static void Task_WaitForSaveFileErrorWindow(u8 taskId)
     }
 }
 
+static bool8 IsAccurateGBA(void) { // tests to see whether running on either an accurate emulator in >=2020, or real hardware
+  u32 code[5] = {0xFF1EE12F, 0xE1DF00B0, 0xE12FFF1E, 0xAAAABBBB, 0xCCCCDDDD}; // ARM: _;ldrh r0, [pc];bx lr
+  u32 func = (u32) &code[0];
+  if (func & 3) // not word aligned; safer to just return false here
+    return FALSE;
+  func = (func & ~3) | 0x2; // misalign PC to test PC-relative loading
+  return ((u32 (*)(void)) func)() == code[3] >> 16;
+}
+
 static void Task_MainMenuCheckBattery(u8 taskId)
 {
+    s16 *data = gTasks[taskId].data;
+
     if (!gPaletteFade.active)
     {
         SetGpuReg(REG_OFFSET_WIN0H, 0);
@@ -716,7 +728,21 @@ static void Task_MainMenuCheckBattery(u8 taskId)
 
         if (!(RtcGetErrorStatus() & RTC_ERR_FLAG_MASK))
         {
-            gTasks[taskId].func = Task_DisplayMainMenu;
+            if (tMenuType != HAS_NO_SAVED_GAME)
+                RtcCalcLocalTime();
+            if (!IsAccurateGBA()) {
+                CreateMainMenuErrorWindow(gText_EmuWarning);
+                gTasks[taskId].func = Task_WaitForBatteryDryErrorWindow;
+            // save exists and stored day count is more than a day ahead of RTC
+            } else if (tMenuType != HAS_NO_SAVED_GAME && VarGet(VAR_DAYS) > gLocalTime.days + 1) {
+                // Reset days var to today + 1
+                // Allowing daily events to happen again in a day
+                VarSet(VAR_DAYS, gLocalTime.days + 1);
+                CreateMainMenuErrorWindow(gText_TimeWarning);
+                gTasks[taskId].func = Task_WaitForBatteryDryErrorWindow;
+            } else {
+                gTasks[taskId].func = Task_DisplayMainMenu;
+            }
         }
         else
         {
diff --git a/src/strings.c b/src/strings.c
index f9137c4f1..6dcd0072c 100644
--- a/src/strings.c
+++ b/src/strings.c
@@ -36,6 +36,9 @@ const u8 gText_SaveFileCorrupted[] = _("The save file is corrupted. The\npreviou
 const u8 gText_SaveFileErased[] = _("The save file has been erased\ndue to corruption or damage.");
 const u8 gJPText_No1MSubCircuit[] = _("1Mサブきばんが ささっていません！");
 const u8 gText_BatteryRunDry[] = _("The internal battery has run dry.\nThe game can be played.\pHowever, clock-based events will\nno longer occur.");
+const u8 gText_EmuWarning[] = _("Inaccurate emulator detected.\nYou should use a recent emulator with\nsupport for RTC (Real Time Clock).\nThe game should still work, but\nyou may encouter errors");
+const u8 gText_TimeWarning[] = _("Real Time Clock is more than 1 day\nbehind saved time.\nPlease don't tamper with the RTC, as it may\nbreak some functionnality");
+
 const u8 gText_Player[] = _("PLAYER"); // Unused
 const u8 gText_Pokedex[] = _("POKéDEX"); // Unused
 const u8 gText_Time[] = _("TIME");