From 87bf7654d2c65dbd44f9cb1354d1a302138d9386 Mon Sep 17 00:00:00 2001
From: Jady Wright <iamjwright159@gmail.com>
Date: Fri, 20 Sep 2024 00:24:01 -0400
Subject: [PATCH] Start to figure out modding

Currently this doesn't work. The TypeIds of things in different binaries are different, so all the bevy reflecty things break.

Depends on:
- https://github.com/bevyengine/bevy/pull/13080
- https://github.com/bevyengine/bevy/discussions/8390
- https://github.com/bevyengine/bevy/issues/32
---
 Cargo.toml          |  2 +-
 mod_bin/Cargo.toml  | 11 ++++++++++
 mod_bin/src/main.rs | 50 +++++++++++++++++++++++++++++++++++++++++++++
 mod_lib/Cargo.toml  | 11 ++++++++++
 mod_lib/src/lib.rs  | 31 ++++++++++++++++++++++++++++
 5 files changed, 104 insertions(+), 1 deletion(-)
 create mode 100644 mod_bin/Cargo.toml
 create mode 100644 mod_bin/src/main.rs
 create mode 100644 mod_lib/Cargo.toml
 create mode 100644 mod_lib/src/lib.rs

diff --git a/Cargo.toml b/Cargo.toml
index 5df15bb0..007de59f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,5 +1,5 @@
 [workspace]
-members = ["sbepis", "marching_cubes", "jack_noir"]
+members = ["sbepis", "marching_cubes", "jack_noir", "mod_lib", "mod_bin"]
 default-members = ["sbepis"]
 resolver = "2"
 
diff --git a/mod_bin/Cargo.toml b/mod_bin/Cargo.toml
new file mode 100644
index 00000000..641c843f
--- /dev/null
+++ b/mod_bin/Cargo.toml
@@ -0,0 +1,11 @@
+[package]
+name = "mod_bin"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+bevy_dylib = "0.14.2"
+bevy = { version = "0.14.2", features = ["dynamic_linking"] }
+bevy-inspector-egui = "0.26.0"
+bevy_mod_debugdump = "0.11.1"
+libloading = "0.8.5"
diff --git a/mod_bin/src/main.rs b/mod_bin/src/main.rs
new file mode 100644
index 00000000..e4e9f20a
--- /dev/null
+++ b/mod_bin/src/main.rs
@@ -0,0 +1,50 @@
+#![allow(deprecated)]
+
+use std::any::TypeId;
+use std::ffi::OsStr;
+
+use bevy::prelude::*;
+use libloading::{Library, Symbol};
+
+fn main() {
+	let mut app = App::new();
+	app.add_plugins((
+		DefaultPlugins,
+		bevy_inspector_egui::quick::WorldInspectorPlugin::new(),
+	));
+	unsafe {
+		// app.load_plugin("./target/debug/libmod_lib.so");
+
+		match dynamically_load_plugin("./target/debug/libmod_lib.so") {
+			Ok((lib, plugin)) => {
+				info!(
+					"Plugin loaded! {:?} {:?}",
+					app.world(),
+					TypeId::of::<Schedules>()
+				);
+				std::mem::forget(lib);
+				plugin.build(&mut app);
+			}
+			Err(e) => error!("Failed to load plugin: {:?}", e),
+		}
+	}
+	bevy_mod_debugdump::print_schedule_graph(&mut app, Update);
+	app.run();
+}
+
+pub unsafe fn dynamically_load_plugin<P: AsRef<OsStr>>(
+	path: P,
+) -> Result<(Library, Box<dyn Plugin>), libloading::Error> {
+	// SAFETY: Caller must follow the safety requirements of Library::new.
+	let lib = unsafe { Library::new(path)? };
+
+	// SAFETY: Loaded plugins are not allowed to specify `_bevy_create_plugin` symbol manually, but
+	// must instead automatically generate it through `DynamicPlugin`.
+	let func: Symbol<unsafe fn() -> *mut dyn Plugin> = unsafe { lib.get(b"_bevy_create_plugin")? };
+
+	// SAFETY: `func` is automatically generated and is guaranteed to return a pointer created using
+	// `Box::into_raw`.
+	let plugin = unsafe { Box::from_raw(func()) };
+
+	Ok((lib, plugin))
+}
diff --git a/mod_lib/Cargo.toml b/mod_lib/Cargo.toml
new file mode 100644
index 00000000..1e95fe07
--- /dev/null
+++ b/mod_lib/Cargo.toml
@@ -0,0 +1,11 @@
+[package]
+name = "mod_lib"
+version = "0.1.0"
+edition = "2021"
+
+[lib]
+crate-type = ["dylib"]
+
+[dependencies]
+bevy_dylib = "0.14.2"
+bevy = { version = "0.14.2", features = ["dynamic_linking"] }
diff --git a/mod_lib/src/lib.rs b/mod_lib/src/lib.rs
new file mode 100644
index 00000000..e9ef2cdb
--- /dev/null
+++ b/mod_lib/src/lib.rs
@@ -0,0 +1,31 @@
+#![allow(deprecated)]
+
+use bevy::prelude::*;
+use std::any::TypeId;
+
+#[no_mangle]
+pub fn _bevy_create_plugin() -> *mut dyn Plugin {
+	// make sure the constructor is the correct type.
+	let object = ModLib {};
+	let boxed = Box::new(object);
+	Box::into_raw(boxed)
+}
+
+pub struct ModLib;
+
+impl Plugin for ModLib {
+	fn build(&self, app: &mut App) {
+		println!(
+			"ModLib loaded! {:?} {:?}",
+			app.world(),
+			TypeId::of::<Schedules>()
+		);
+		app.add_systems(Update, setup);
+		println!("ModLib system added!");
+	}
+}
+
+fn setup(mut commands: Commands) {
+	println!("Hello from mod_lib!");
+	commands.spawn(Name::new("Sample modded entity"));
+}