From b969e85412c8a616bbbf99cdd7406d205cb653fd Mon Sep 17 00:00:00 2001
From: Mineplay <tristanfranssen@strawhats.nl>
Date: Tue, 29 Apr 2025 16:02:11 -0500
Subject: [PATCH] feat(doubly linked list): implemented insert at index

---
 Include/Fledasty/Core/DoublyLinkedList.h |  2 +
 Src/Core/DoublyLinkedList.c              | 51 ++++++++++++++++++++++++
 Src/Core/LinkedList.c                    |  1 +
 Tests/Main.c                             |  9 +++++
 4 files changed, 63 insertions(+)

diff --git a/Include/Fledasty/Core/DoublyLinkedList.h b/Include/Fledasty/Core/DoublyLinkedList.h
index b5b55d9..0b754fa 100644
--- a/Include/Fledasty/Core/DoublyLinkedList.h
+++ b/Include/Fledasty/Core/DoublyLinkedList.h
@@ -44,4 +44,6 @@ FledastyError fledasty_doubly_list_destroy(FledastyDoublyLinkedList *current_dou
 
 FledastyError fledasty_doubly_linked_list_append(FledastyDoublyLinkedList *current_doubly_linked_list, void *value);
 
+FledastyError fledasty_doubly_linked_list_insert_at_index(FledastyDoublyLinkedList *current_doubly_linked_list, const size_t index, void *value);
+
 #endif
\ No newline at end of file
diff --git a/Src/Core/DoublyLinkedList.c b/Src/Core/DoublyLinkedList.c
index 50e7bf6..db9bd1d 100644
--- a/Src/Core/DoublyLinkedList.c
+++ b/Src/Core/DoublyLinkedList.c
@@ -113,3 +113,54 @@ FledastyError fledasty_doubly_linked_list_append(FledastyDoublyLinkedList *curre
 
     return FLEDASTY_ERROR_NONE;
 }
+
+FledastyError fledasty_doubly_linked_list_insert_at_index(FledastyDoublyLinkedList *current_doubly_linked_list, const size_t index, void *value) {
+    if (current_doubly_linked_list == NULL || value == NULL) {
+        return FLEDASTY_ERROR_INVALID_POINTER;
+    }
+
+    if (index > current_doubly_linked_list->size) {
+        return FLEDASTY_ERROR_INDEX_OUT_OF_RANGE;
+    }
+
+    FledastyDoublyLinkedListNode *new_node = (FledastyDoublyLinkedListNode*)hallocy_malloc(sizeof(FledastyDoublyLinkedListNode));
+    
+    new_node->value = hallocy_malloc(current_doubly_linked_list->element_byte_size);
+    hallocy_copy_memory(new_node->value, value, current_doubly_linked_list->element_byte_size);
+
+    if (index == 0) {
+        new_node->previous = NULL;
+        new_node->next = current_doubly_linked_list->start;
+
+        current_doubly_linked_list->start->previous = new_node;
+        current_doubly_linked_list->start = new_node;
+    } else if (index == current_doubly_linked_list->size) {
+        new_node->previous = current_doubly_linked_list->end;
+        new_node->next = NULL;
+        
+        current_doubly_linked_list->end->next = new_node;
+        current_doubly_linked_list->end = new_node;
+    } else {
+        FledastyDoublyLinkedListNode *current_node = NULL;
+        if (index < current_doubly_linked_list->size / 2) {
+            current_node = current_doubly_linked_list->start;
+            for (size_t node = 0; node < index - 1; node += 1) {
+                current_node = current_node->next;
+            }
+        } else {
+            current_node = current_doubly_linked_list->end;
+            for (size_t node = current_doubly_linked_list->size - 1; node > index - 1; node -= 1) {
+                current_node = current_node->previous;
+            }
+        }
+    
+        new_node->previous = current_node;
+        new_node->next = current_node->next;
+
+        current_node->next->previous = new_node;
+        current_node->next = new_node;
+    }
+
+    current_doubly_linked_list->size += 1;
+    return FLEDASTY_ERROR_NONE;
+}
diff --git a/Src/Core/LinkedList.c b/Src/Core/LinkedList.c
index 5b415e1..2e3a32f 100644
--- a/Src/Core/LinkedList.c
+++ b/Src/Core/LinkedList.c
@@ -123,6 +123,7 @@ FledastyError fledasty_linked_list_insert_at_index(FledastyLinkedList *current_l
         new_node->next = current_linked_list->start;
         current_linked_list->start = new_node;
     } else if (index == current_linked_list->size) {
+        new_node->next = NULL;
         current_linked_list->end->next = new_node;
         current_linked_list->end = new_node;
     } else {
diff --git a/Tests/Main.c b/Tests/Main.c
index dead7ab..679cbb6 100644
--- a/Tests/Main.c
+++ b/Tests/Main.c
@@ -146,12 +146,21 @@ int main() {
         fledasty_doubly_linked_list_append(&test_doubly_linked_list, &i);
     }
 
+    insert_value = 35;
+    fledasty_doubly_linked_list_insert_at_index(&test_doubly_linked_list, test_doubly_linked_list.size - 1, &insert_value);
+
     FledastyDoublyLinkedListNode *test_doubly_linked_list_node = test_doubly_linked_list.start;
     for (int i = 0; i < test_doubly_linked_list.size; i += 1) {
         printf("Doubly linked list get: %d\n", *(int*)test_doubly_linked_list_node->value);
         test_doubly_linked_list_node = test_doubly_linked_list_node->next;
     }
 
+    test_doubly_linked_list_node = test_doubly_linked_list.end;
+    for (int i = 0; i < test_doubly_linked_list.size; i += 1) {
+        printf("Doubly linked list get backwards: %d\n", *(int*)test_doubly_linked_list_node->value);
+        test_doubly_linked_list_node = test_doubly_linked_list_node->previous;
+    }
+
     fledasty_doubly_list_destroy(&test_doubly_linked_list);
     printf("Done\n");
     return 0;