From 3b401e770eb33c6b02dfc90637cf2eb8c89999c1 Mon Sep 17 00:00:00 2001
From: Kyle Isom <kyle@imap.cc>
Date: Sat, 29 Nov 2025 13:05:12 -0800
Subject: [PATCH] working on undo

---
 abuf.c | 17 +++++++++++++++
 undo.c | 66 +++++++++++++++++++++++++++++++++++++++++++++++++++-------
 undo.h | 12 +++++++----
 3 files changed, 83 insertions(+), 12 deletions(-)

diff --git a/abuf.c b/abuf.c
index c302cb0..b877c6a 100644
--- a/abuf.c
+++ b/abuf.c
@@ -74,6 +74,11 @@ ab_append(abuf *buf, const char *s, size_t len)
 void
 ab_append_ab(abuf *buf, const abuf *other)
 {
+	assert(buf != NULL);
+	if (other == NULL) {
+		return;
+	}
+
 	ab_append(buf, other->b, other->size);
 }
 
@@ -104,6 +109,18 @@ ab_prepend(abuf *buf, const char *s, const size_t len)
 }
 
 
+void
+ab_prepend_ab(abuf *buf, const abuf *other)
+{
+	assert(buf != NULL);
+	if (other == NULL) {
+		return;
+	}
+
+	ab_prepend(buf, other->b, other->size);
+}
+
+
 void
 ab_free(abuf *buf)
 {
diff --git a/undo.c b/undo.c
index fa07057..f5bea5a 100644
--- a/undo.c
+++ b/undo.c
@@ -1,6 +1,7 @@
 #include <assert.h>
 #include <stdlib.h>
 #include "abuf.h"
+#include "buffer.h"
 #include "undo.h"
 
 
@@ -18,7 +19,7 @@ undo_node_new(undo_kind kind)
 	ab_init(&node->text);
 	
 	node->next = NULL;
-	node->parent = NULL;
+	node->next = NULL;
 
 	return node;
 }
@@ -101,7 +102,7 @@ undo_prepend(undo_tree *tree, abuf *buf)
 	assert(tree != NULL);
 	assert(tree->pending != NULL);
 
-	ab_prepend_ab(tree->pending->text, buf);
+	ab_prepend_ab(&tree->pending->text, buf);
 }
 
 
@@ -111,7 +112,7 @@ undo_append(undo_tree *tree, abuf *buf)
 	assert(tree != NULL);
 	assert(tree->pending != NULL);
 
-	ab_append_ab(tree->pending->text, buf);
+	ab_append_ab(&tree->pending->text, buf);
 }
 
 
@@ -121,7 +122,7 @@ undo_prependch(undo_tree *tree, char c)
 	assert(tree != NULL);
 	assert(tree->pending != NULL);
 
-	ab_prependch(tree->pending->text, c);
+	ab_prependch(&tree->pending->text, c);
 }
 
 
@@ -131,7 +132,7 @@ undo_appendch(undo_tree *tree, char c)
 	assert(tree != NULL);
 	assert(tree->pending != NULL);
 
-	ab_appendch(tree->pending->text, c);
+	ab_appendch(&tree->pending->text, c);
 }
 
 
@@ -144,10 +145,59 @@ undo_commit(undo_tree *tree)
 		return;
 	}
 
+	if (tree->root == NULL) {
+		assert(tree->current == NULL);
 
+		tree->root    = tree->pending;
+		tree->current = tree->pending;
+		tree->pending = NULL;
+
+		return;
+	}
+
+	assert(tree->current != NULL);
+	if (tree->current->next != NULL) {
+		undo_node_free_all(tree->current->next);
+	}
+
+	tree->pending->prev = tree->current;
+	tree->current->next = tree->pending;
+	tree->current       = tree->pending;
+	tree->pending       = NULL;
 }
 
 
-void		 undo_apply(struct buffer *buf);
-void		 editor_undo(struct buffer *buf);
-void		 editor_redo(struct buffer *buf);
+int
+undo_apply(struct buffer *buf, int direction)
+{
+	(void)buf;
+	(void)direction;
+
+	return 0;
+}
+
+
+int
+editor_undo(struct buffer *buf)
+{
+	if (buf == NULL) {
+		return 0;
+	}
+
+	undo_commit(&buf->tree);
+	return undo_apply(buf, UNDO_DIR_UNDO);
+	
+}
+
+
+int
+editor_redo(struct buffer *buf)
+{
+	if (buf == NULL) {
+		return 0;
+	}
+
+	undo_commit(&buf->tree);
+	return undo_apply(buf, UNDO_DIR_REDO);
+}
+
diff --git a/undo.h b/undo.h
index 198e47e..d0a1e7a 100644
--- a/undo.h
+++ b/undo.h
@@ -10,6 +10,10 @@
 struct	 buffer;
 
 
+#define		UNDO_DIR_UNDO		-1
+#define		UNDO_DIR_REDO		 1
+
+
 typedef enum undo_kind {
 	UNDO_INSERT  = 1 << 0,
 	UNDO_UNKNOWN = 1 << 1,
@@ -22,7 +26,7 @@ typedef struct undo_node {
 	abuf			 text;
 
 	struct undo_node	*next;
-	struct undo_node	*parent;
+	struct undo_node	*prev;
 
 } undo_node;
 
@@ -44,9 +48,9 @@ void		 undo_append(undo_tree *tree, abuf *buf);
 void		 undo_prependch(undo_tree *tree, char c);
 void		 undo_appendch(undo_tree *tree, char c);
 void		 undo_commit(undo_tree *tree);
-void		 undo_apply(struct buffer *buf);
-void		 editor_undo(struct buffer *buf);
-void		 editor_redo(struct buffer *buf);
+int		 undo_apply(struct buffer *buf, int direction);
+int		 editor_undo(struct buffer *buf);
+int		 editor_redo(struct buffer *buf);
 
 
 #endif