From e4277701506cbbcf133c0bb744078f7db79d1f39 Mon Sep 17 00:00:00 2001
From: Illia Korpan <illia.korpan@student.tuke.sk>
Date: Wed, 15 Apr 2026 08:48:27 +0200
Subject: [PATCH] 123

---
 du4/snake.c | 101 ++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 95 insertions(+), 6 deletions(-)

diff --git a/du4/snake.c b/du4/snake.c
index 7038cdb..e8052cd 100644
--- a/du4/snake.c
+++ b/du4/snake.c
@@ -1,23 +1,112 @@
 #include "snake.h"
 #include <stdlib.h>
 
-struct snake* add_snake(struct snake* snake,int x,int y){
-    return NULL;
+struct snake* add_snake(struct snake* snake, int x, int y){
+    struct snake* new_head = (struct snake*)malloc(sizeof(struct snake));
+    if (new_head == NULL) {
+        return snake;
+    }
+    new_head->x = x;
+    new_head->y = y;
+    new_head->next = snake;
+    return new_head;
 }
 
 struct snake* remove_snake(struct snake* snake){
-    return NULL;
+    if (snake == NULL) {
+        return NULL;
+    }
+    
+    // If snake has only one part
+    if (snake->next == NULL) {
+        free(snake);
+        return NULL;
+    }
+    
+    // Find the second-to-last part
+    struct snake* current = snake;
+    while (current->next->next != NULL) {
+        current = current->next;
+    }
+    
+    // Free the last part
+    free(current->next);
+    current->next = NULL;
+    
+    return snake;
 }
 
 void free_snake(struct snake* sn){
+    while (sn != NULL) {
+        struct snake* temp = sn;
+        sn = sn->next;
+        free(temp);
+    }
 }
 
-int is_snake(struct snake* snake,int x,int y){
+int is_snake(struct snake* snake, int x, int y){
+    struct snake* current = snake;
+    while (current != NULL) {
+        if (current->x == x && current->y == y) {
+            return 1;
+        }
+        current = current->next;
+    }
     return 0;
 }
 
 int step_state(struct state* st){
-	int nx = (st->snake->x + st->sx);
+    int nx = (st->snake->x + st->sx);
     int ny = (st->snake->y + st->sy);
+    
+    // Check if new position is on the wall
+    if (nx < 0 || nx >= st->width || ny < 0 || ny >= st->height) {
+        return END_WALL;
+    }
+    
+    // Check if new position is on the snake (excluding the head)
+    struct snake* current = st->snake->next;
+    while (current != NULL) {
+        if (current->x == nx && current->y == ny) {
+            return END_SNAKE;
+        }
+        current = current->next;
+    }
+    
+    // Check if new position is on food
+    int food_index = -1;
+    for (int i = 0; i < FOOD_COUNT; i++) {
+        if (st->foodx[i] == nx && st->foody[i] == ny) {
+            food_index = i;
+            break;
+        }
+    }
+    
+    if (food_index != -1) {
+        // Mark food as eaten
+        st->foodx[food_index] = -1;
+        st->foody[food_index] = -1;
+        // Add new snake part at food position
+        st->snake = add_snake(st->snake, nx, ny);
+        
+        // Check if there is any food left
+        int food_left = 0;
+        for (int i = 0; i < FOOD_COUNT; i++) {
+            if (st->foodx[i] >= 0) {
+                food_left = 1;
+                break;
+            }
+        }
+        
+        if (!food_left) {
+            return END_FOOD;
+        }
+        return END_CONTINUE;
+    }
+    
+    // Normal move: add new head and remove tail
+    st->snake = add_snake(st->snake, nx, ny);
+    st->snake = remove_snake(st->snake);
+    
     return END_CONTINUE;
-}
+}
\ No newline at end of file