feat: prevent reversing directly into snake neck and play denied sound effect

source/game_input.cpp

@@ -4,6 +4,8 @@
 #include <cstdint>
 #include <cstdio>
 
+#include "consts.h"
+
 bool handle_input_frame(InputContext &ctx) {
     scanKeys();
     const uint32_t keys = keysDown();
@@ -69,25 +71,76 @@ bool handle_input_frame(InputContext &ctx) {
 
     if (!ctx.state->paused && !ctx.state->gameOver) {
         const bool cursed = ctx.state->curseTicksRemaining > 0;
+        uint16_t requested_dir = 0;
+        bool has_dir_input = false;
 
         if ((keys != 0U) && ((keys & KEY_UP) != 0U)) {
-            ctx.state->snakeDirection = cursed ? 2 : 0;
-            draw_game(*ctx.state, *ctx.renderAssets);
+            requested_dir = cursed ? 2 : 0;
+            has_dir_input = true;
+        } else if ((keys != 0U) && ((keys & KEY_RIGHT) != 0U)) {
+            requested_dir = cursed ? 3 : 1;
+            has_dir_input = true;
+        } else if ((keys != 0U) && ((keys & KEY_DOWN) != 0U)) {
+            requested_dir = cursed ? 0 : 2;
+            has_dir_input = true;
+        } else if ((keys != 0U) && ((keys & KEY_LEFT) != 0U)) {
+            requested_dir = cursed ? 1 : 3;
+            has_dir_input = true;
         }
 
-        if ((keys != 0U) && ((keys & KEY_RIGHT) != 0U)) {
-            ctx.state->snakeDirection = cursed ? 3 : 1;
-            draw_game(*ctx.state, *ctx.renderAssets);
-        }
+        if (has_dir_input) {
+            bool is_reversing = false;
 
-        if ((keys != 0U) && ((keys & KEY_DOWN) != 0U)) {
-            ctx.state->snakeDirection = cursed ? 0 : 2;
-            draw_game(*ctx.state, *ctx.renderAssets);
-        }
+            if (ctx.state->snake.size() >= 2) {
+                const auto &head = ctx.state->snake.front();
+                const auto &neck = ctx.state->snake.at(1);
+                int next_x = head[0];
+                int next_y = head[1];
 
-        if ((keys != 0U) && ((keys & KEY_LEFT) != 0U)) {
-            ctx.state->snakeDirection = cursed ? 1 : 3;
-            draw_game(*ctx.state, *ctx.renderAssets);
+                switch (requested_dir) {
+                case 0:
+                    next_y--;
+                    break;
+                case 1:
+                    next_x++;
+                    break;
+                case 2:
+                    next_y++;
+                    break;
+                case 3:
+                    next_x--;
+                    break;
+                default:
+                    break;
+                }
+
+                if (next_x > X_MAX) {
+                    next_x = 0;
+                } else if (next_x < 0) {
+                    next_x = X_MAX;
+                }
+
+                if (next_y > Y_MAX) {
+                    next_y = 0;
+                } else if (next_y < 0) {
+                    next_y = Y_MAX;
+                }
+
+                if (next_x == neck[0] && next_y == neck[1]) {
+                    is_reversing = true;
+                }
+            } else {
+                if ((ctx.state->snakeDirection + 2) % 4 == requested_dir) {
+                    is_reversing = true;
+                }
+            }
+
+            if (is_reversing) {
+                audio_play_denied(*ctx.audio);
+            } else if (ctx.state->snakeDirection != requested_dir) {
+                ctx.state->snakeDirection = requested_dir;
+                draw_game(*ctx.state, *ctx.renderAssets);
+            }
         }
     }