From d8f8e4a1d6632be0b61ad73711bea2775df1c4b9 Mon Sep 17 00:00:00 2001
From: Isaac Freund <mail@isaacfreund.com>
Date: Sun, 26 Feb 2023 12:06:48 +0100
Subject: [PATCH] Add more list.Link Functions

- Add Link.replaceWith()
- Add Link.swapWith()
- Rename Link.insertAfter() -> Link.insert() as the status quo reads
  very poorly in practice.
---
 example/list.zig            | 10 ++++------
 src/wayland_server_core.zig | 30 ++++++++++++++++++++++++++----
 2 files changed, 30 insertions(+), 10 deletions(-)

diff --git a/example/list.zig b/example/list.zig
index 88cbdbc..6208bb8 100644
--- a/example/list.zig
+++ b/example/list.zig
@@ -46,11 +46,10 @@ pub fn main() void {
             while (it.next()) |b| std.debug.print("{}\n", .{b.data});
         }
 
-        three.link.remove();
-        a.prepend(&three);
+        three.link.swapWith(&four.link);
 
         {
-            std.debug.print("reverse moved three\n", .{});
+            std.debug.print("reverse swapped 3/4\n", .{});
             var it = a.iterator(.reverse);
             while (it.next()) |b| std.debug.print("{}\n", .{b.data});
         }
@@ -81,11 +80,10 @@ pub fn main() void {
             while (it.next()) |b| std.debug.print("{}\n", .{b.data});
         }
 
-        three.link.remove();
-        a.prepend(&three);
+        two.link.swapWith(&five.link);
 
         {
-            std.debug.print("reverse moved three\n", .{});
+            std.debug.print("reverse swapped 2/5\n", .{});
             var it = a.iterator(.reverse);
             while (it.next()) |b| std.debug.print("{}\n", .{b.data});
         }
diff --git a/src/wayland_server_core.zig b/src/wayland_server_core.zig
index 6eac6d3..a256083 100644
--- a/src/wayland_server_core.zig
+++ b/src/wayland_server_core.zig
@@ -372,7 +372,7 @@ pub const list = struct {
             link.* = .{ .prev = link, .next = link };
         }
 
-        pub fn insertAfter(link: *Link, other: *Link) void {
+        pub fn insert(link: *Link, other: *Link) void {
             other.prev = link;
             other.next = link.next;
             link.next = other;
@@ -384,6 +384,28 @@ pub const list = struct {
             link.next.?.prev = link.prev;
             link.* = .{ .prev = null, .next = null };
         }
+
+        pub fn replaceWith(link: *Link, other: *Link) void {
+            other.next = link.next;
+            other.next.?.prev = other;
+            other.prev = link.prev;
+            other.prev.?.next = other;
+
+            link.* = .{ .prev = null, .next = null };
+        }
+
+        pub fn swapWith(link: *Link, other: *Link) void {
+            const old_other_prev = other.prev.?;
+            other.remove();
+
+            link.replaceWith(other);
+
+            if (old_other_prev == link) {
+                other.insert(link);
+            } else {
+                old_other_prev.insert(link);
+            }
+        }
     };
 
     pub const Direction = enum {
@@ -406,12 +428,12 @@ pub const list = struct {
 
             pub fn prepend(head: *Self, elem: *T) void {
                 const link = if (link_field) |f| &@field(elem, f) else elem.getLink();
-                head.link.insertAfter(link);
+                head.link.insert(link);
             }
 
             pub fn append(head: *Self, elem: *T) void {
                 const link = if (link_field) |f| &@field(elem, f) else elem.getLink();
-                head.link.prev.?.insertAfter(link);
+                head.link.prev.?.insert(link);
             }
 
             pub fn length(head: *const Self) usize {
@@ -577,7 +599,7 @@ pub fn Signal(comptime T: type) type {
                 const listener = @fieldParentPtr(Listener(T), "link", pos);
 
                 cursor.link.remove();
-                pos.insertAfter(&cursor.link);
+                pos.insert(&cursor.link);
 
                 listener.notify(listener, data);
             }