From 0c8b8b251d642c1a22bf4eda8d2214d680b67faf Mon Sep 17 00:00:00 2001
From: William Brawner <me@wbrawner.com>
Date: Mon, 18 Nov 2024 17:55:01 -0700
Subject: [PATCH] Add find and delete operations for doubly-linked list

---
 include/doubly-linked-list.h | 13 ++++++++++++-
 src/doubly-linked-list.c     | 33 +++++++++++++++++++++++++++++++++
 test/dll.c                   | 29 +++++++++++++++++++++++++++++
 3 files changed, 74 insertions(+), 1 deletion(-)

diff --git a/include/doubly-linked-list.h b/include/doubly-linked-list.h
index c26204c..325a94f 100644
--- a/include/doubly-linked-list.h
+++ b/include/doubly-linked-list.h
@@ -6,6 +6,7 @@ struct dll_node {
 
 typedef struct dll_node dll_node;
 
+// TODO: I probably don't need a separate "list" type
 typedef struct {
   struct dll_node *head;
 } dll_list;
@@ -33,7 +34,17 @@ void dll_list_append(dll_list *list, dll_node *node) {
   dll_list_insert(list, node, -1);
 }
 
-// TODO: find and delete operations on list
+/**
+ * Searches the given list for a node with a given value
+ * @returns a pointer to the node with the value or NULL if no nodes match the value
+ */
+dll_node *dll_list_find(dll_list *list, char *value);
+
+/**
+ * Removes the first node with the matching value in the given list
+ * @returns a pointer to the node with the value or NULL if no nodes match the value
+ */
+dll_node *dll_list_delete(dll_list *list, char *value);
 
 dll_node *dll_node_new(char *value);
 
diff --git a/src/doubly-linked-list.c b/src/doubly-linked-list.c
index 691e25f..4177f50 100644
--- a/src/doubly-linked-list.c
+++ b/src/doubly-linked-list.c
@@ -50,6 +50,39 @@ void dll_list_insert(dll_list *list, dll_node *node, int index) {
   current_node->next = node;
 }
 
+dll_node *dll_list_find(dll_list *list, char *value) {
+  if (list == NULL) {
+    return NULL;
+  }
+
+  dll_node *current_node = list->head;
+  while (current_node != NULL) {
+    if (strcmp(current_node->value, value) == 0) {
+      return current_node;
+    }
+    current_node = current_node->next;
+  }
+
+  return NULL;
+}
+
+dll_node *dll_list_delete(dll_list *list, char *value) {
+  dll_node *target_node = dll_list_find(list, value);
+  if (target_node == NULL) {
+    return NULL;
+  }
+
+  if (target_node->previous != NULL) {
+    target_node->previous->next = target_node->next;
+  } else {
+    list->head = target_node->next;
+  }
+  if (target_node->next != NULL) {
+    target_node->next->previous = target_node->previous;
+  }
+  return target_node;
+}
+
 dll_node *dll_node_new(char *value) {
   dll_node *node = malloc(sizeof(dll_node));
   node->previous = NULL;
diff --git a/test/dll.c b/test/dll.c
index 64f4aa7..1f862e5 100644
--- a/test/dll.c
+++ b/test/dll.c
@@ -8,6 +8,17 @@ dll_list *list = NULL;
 dll_node *head = NULL;
 char *list_string = NULL;
 
+#define ASSERT_PTR_EQ(expected, actual)                                        \
+  {                                                                            \
+    if (expected != actual) {                                       \
+      fprintf(stderr,                                                          \
+              "pointers don't match. expected: \"%p\", actual: \"%p\"\n",       \
+              (void*)expected, (void*)actual);                                               \
+      cleanup();                                                               \
+      return 1;                                                                \
+    }                                                                          \
+  }
+
 #define ASSERT_STR_EQ(expected, actual)                                        \
   {                                                                            \
     if (strcmp(expected, actual) != 0) {                                       \
@@ -71,6 +82,7 @@ int main(int argc, char **argv) {
   dll_list_append(list, head);
   head = NULL;
   // TODO: Extract test utilities to shared file
+  // TODO: Maybe break these out into separate files?
   list_string = list_to_string(list);
   ASSERT_STR_EQ("0", list_string);
 
@@ -88,6 +100,23 @@ int main(int argc, char **argv) {
   list_string = list_to_string(list);
   ASSERT_STR_EQ("0, 1, 2", list_string);
 
+  ASSERT_PTR_EQ(second, dll_list_find(list, "1"));
+
+  ASSERT_PTR_EQ(third, dll_list_delete(list, "2"));
+  dll_node_free(third);
+
+  free(list_string);
+  list_string = list_to_string(list);
+  ASSERT_STR_EQ("0, 1", list_string);
+
+  head = list->head;
+  ASSERT_PTR_EQ(head, dll_list_delete(list, "0"));
+  dll_node_free(head);
+
+  free(list_string);
+  list_string = list_to_string(list);
+  ASSERT_STR_EQ("1", list_string);
+
   cleanup();
   return 0;
 }