Automatic save backup system (#260)

* Made errors print to console as well

---------

Co-authored-by: Mr-Wiseguy <mrwiseguyromhacking@gmail.com>

src/recomp/pi.cpp

@@ -96,20 +96,36 @@ struct {
 
 const std::u8string save_folder = u8"saves";
 const std::u8string save_filename = std::u8string{recomp::mm_game_id} + u8".bin";
+const std::u8string save_filename_temp = std::u8string{recomp::mm_game_id} + u8".bin.temp";
+const std::u8string save_filename_backup = std::u8string{recomp::mm_game_id} + u8".bin.bak";
 
 std::filesystem::path get_save_file_path() {
     return recomp::get_app_folder_path() / save_folder / save_filename;
 }
 
+std::filesystem::path get_save_file_path_temp() {
+    return recomp::get_app_folder_path() / save_folder / save_filename_temp;
+}
+
+std::filesystem::path get_save_file_path_backup() {
+    return recomp::get_app_folder_path() / save_folder / save_filename_backup;
+}
+
 void update_save_file() {
-    std::ofstream save_file{ get_save_file_path(), std::ios_base::binary };
+    std::ofstream save_file{ get_save_file_path_temp(), std::ios_base::binary };
 
     if (save_file.good()) {
         std::lock_guard lock{ save_context.save_buffer_mutex };
         save_file.write(save_context.save_buffer.data(), save_context.save_buffer.size());
+        if (std::filesystem::exists(get_save_file_path())) {
+            std::filesystem::rename(get_save_file_path(),get_save_file_path_backup());
         } else {
-        fprintf(stderr, "Failed to save!\n");
+            printf("\nSavefile doesn't exist. Skip renaming.");
-        std::exit(EXIT_FAILURE);
+        }
+        std::filesystem::rename(get_save_file_path_temp(),get_save_file_path());
+    } else {
+        recomp::message_box("Failed to write to the save file. Check your file permissions. If you have moved your appdata folder to Dropbox or similar, this can cause issues.");
+        //std::exit(EXIT_FAILURE);
     }
 }
 
@@ -176,6 +192,7 @@ void save_clear(uint32_t start, uint32_t size, char value) {
 
 void ultramodern::init_saving(RDRAM_ARG1) {
     std::filesystem::path save_file_path = get_save_file_path();
+    std::filesystem::path save_file_path_backup = get_save_file_path_backup();
 
     // Ensure the save file directory exists.
     std::filesystem::create_directories(save_file_path.parent_path());
@@ -184,10 +201,16 @@ void ultramodern::init_saving(RDRAM_ARG1) {
     std::ifstream save_file{ save_file_path, std::ios_base::binary };
     if (save_file.good()) {
         save_file.read(save_context.save_buffer.data(), save_context.save_buffer.size());
+    } else {
+        // Reading the save file faield, so try to read the backup save file.
+        std::ifstream save_file_backup{ save_file_path_backup, std::ios_base::binary };
+        if (save_file_backup.good()) {
+            save_file_backup.read(save_context.save_buffer.data(), save_context.save_buffer.size());
         } else {
             // Otherwise clear the save file to all zeroes.
             save_context.save_buffer.fill(0);
         }
+    }
 
     save_context.saving_thread = std::thread{saving_thread_func, PASS_RDRAM};
 }

src/ui/ui_renderer.cpp

@@ -1477,4 +1477,5 @@ recomp::Menu recomp::get_current_menu() {
 
 void recomp::message_box(const char* msg) {
     SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR, recomp::program_name.data(), msg, nullptr);
+    printf("[ERROR] %s\n", msg);
 }