From aaaae38fa1e3399a1b9bf0468edaf6d5e3bd9edc Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Tue, 25 Oct 2022 20:55:41 -0700
Subject: [PATCH] pkg/objc: more message send stuff

---
 pkg/objc/class.zig    | 11 +++++++++++
 pkg/objc/main.zig     |  1 +
 pkg/objc/msg_send.zig | 19 ++++++++++++++++++-
 pkg/objc/object.zig   | 10 ++++++++++
 pkg/objc/sel.zig      |  9 +++++++--
 5 files changed, 47 insertions(+), 3 deletions(-)
 create mode 100644 pkg/objc/object.zig

diff --git a/pkg/objc/class.zig b/pkg/objc/class.zig
index 95dddb5af..f655c82eb 100644
--- a/pkg/objc/class.zig
+++ b/pkg/objc/class.zig
@@ -26,6 +26,17 @@ test "getClass" {
 test "msgSend" {
     const testing = std.testing;
     const NSObject = Class.getClass("NSObject").?;
+
+    // Should work with primitives
     const id = NSObject.msgSend(c.id, objc.Sel.registerName("alloc"), .{});
     try testing.expect(id != null);
+    {
+        const obj: objc.Object = .{ .value = id };
+        obj.msgSend(void, objc.sel("dealloc"), .{});
+    }
+
+    // Should work with our wrappers
+    const obj = NSObject.msgSend(objc.Object, objc.Sel.registerName("alloc"), .{});
+    try testing.expect(obj.value != null);
+    obj.msgSend(void, objc.sel("dealloc"), .{});
 }
diff --git a/pkg/objc/main.zig b/pkg/objc/main.zig
index 6c6270d4c..6eefc51fe 100644
--- a/pkg/objc/main.zig
+++ b/pkg/objc/main.zig
@@ -1,5 +1,6 @@
 pub const c = @import("c.zig");
 pub usingnamespace @import("class.zig");
+pub usingnamespace @import("object.zig");
 pub usingnamespace @import("sel.zig");
 
 test {
diff --git a/pkg/objc/msg_send.zig b/pkg/objc/msg_send.zig
index 6f276b593..4f2eaf699 100644
--- a/pkg/objc/msg_send.zig
+++ b/pkg/objc/msg_send.zig
@@ -19,9 +19,26 @@ pub fn MsgSend(comptime T: type) type {
             sel: objc.Sel,
             args: anytype,
         ) Return {
+            // Build our function type and call it
             const Fn = MsgSendFn(Return, @TypeOf(target.value), @TypeOf(args));
             const msg_send_ptr = @ptrCast(std.meta.FnPtr(Fn), &c.objc_msgSend);
-            return @call(.{}, msg_send_ptr, .{ target.value, sel } ++ args);
+            const result = @call(.{}, msg_send_ptr, .{ target.value, sel } ++ args);
+
+            // This is a special nicety: if the return type is one of our
+            // public structs then we wrap the msgSend id result with it.
+            // This lets msgSend magically work with Object and so on.
+            const is_pkg_struct = comptime is_pkg_struct: {
+                for (@typeInfo(objc).Struct.decls) |decl| {
+                    if (decl.is_pub and Return == @field(objc, decl.name)) {
+                        break :is_pkg_struct true;
+                    }
+                }
+
+                break :is_pkg_struct false;
+            };
+
+            if (!is_pkg_struct) return result;
+            return .{ .value = result };
         }
     };
 }
diff --git a/pkg/objc/object.zig b/pkg/objc/object.zig
new file mode 100644
index 000000000..41c779eeb
--- /dev/null
+++ b/pkg/objc/object.zig
@@ -0,0 +1,10 @@
+const std = @import("std");
+const c = @import("c.zig");
+const objc = @import("main.zig");
+const MsgSend = @import("msg_send.zig").MsgSend;
+
+pub const Object = struct {
+    value: c.id,
+
+    pub usingnamespace MsgSend(Object);
+};
diff --git a/pkg/objc/sel.zig b/pkg/objc/sel.zig
index 4c4c62f7a..23c629f48 100644
--- a/pkg/objc/sel.zig
+++ b/pkg/objc/sel.zig
@@ -1,6 +1,11 @@
 const std = @import("std");
 const c = @import("c.zig");
 
+// Shorthand, equivalent to Sel.registerName
+pub inline fn sel(name: [:0]const u8) Sel {
+    return Sel.registerName(name);
+}
+
 pub const Sel = struct {
     value: c.SEL,
 
@@ -20,6 +25,6 @@ pub const Sel = struct {
 
 test {
     const testing = std.testing;
-    const sel = Sel.registerName("yo");
-    try testing.expectEqualStrings("yo", sel.getName());
+    const s = Sel.registerName("yo");
+    try testing.expectEqualStrings("yo", s.getName());
 }