path: root/src/entity.rs

use core::{
	alloc::Layout,
	marker::PhantomData,
	ops::{Deref, DerefMut},
};

use alloc::{
	alloc::{alloc, dealloc},
	borrow::Cow,
	string::String,
};
use serde::{Deserialize, Serialize};

use crate::ScriptContext;

mod tortuise {
	#[link(wasm_import_module = "tortuise")]
	unsafe extern "C" {
		pub unsafe fn entity_size(context: u64, name: *const u8, name_len: usize) -> usize;
		pub unsafe fn load_entity(context: u64, name: *const u8, name_len: usize, offset: *mut u8);
		pub unsafe fn save_entity(
			context: u64,
			name: *const u8,
			name_len: usize,
			offset: *const u8,
			size: usize,
		);
	}
}

fn load_entity<'de, T: Deserialize<'de>>(context: u64, name: &str) -> Option<T> {
	unsafe {
		let size = tortuise::entity_size(context, name.as_ptr(), name.len());
		let Ok(layout) = Layout::array::<u8>(size) else {
			log::error!("Failed to create layout for size: {size}");
			panic!();
		};
		let ptr = alloc(layout);
		tortuise::load_entity(context, name.as_ptr(), name.len(), ptr);
		let data = core::slice::from_raw_parts(ptr, size);
		let data = messagepack_serde::from_slice(data).ok()?;
		dealloc(ptr, layout);
		Some(data)
	}
}

fn save_entity<T: Serialize>(context: u64, name: &str, state: &T) {
	unsafe {
		let data = messagepack_serde::to_vec(state).unwrap();
		tortuise::save_entity(
			context,
			name.as_ptr(),
			name.len(),
			data.as_ptr(),
			data.len(),
		);
	}
}

pub struct Entity<T> {
	name: Cow<'static, str>,
	default: fn() -> T,
}

pub struct EntityRef<'entity, T> {
	entity: PhantomData<&'entity Entity<T>>,
	data: T,
}

pub struct EntityMut<'entity, T: Serialize> {
	context: u64,
	entity: &'entity Entity<T>,
	data: T,
}

impl<'de, T: Serialize + Deserialize<'de>> Entity<T> {
	pub const fn new(name: &'static str, default: fn() -> T) -> Self {
		Self {
			name: Cow::Borrowed(name),
			default,
		}
	}

	pub const fn from_string(name: String, default: fn() -> T) -> Self {
		Self {
			name: Cow::Owned(name),
			default,
		}
	}

	pub fn get(&self, context: &ScriptContext) -> EntityRef<'_, T> {
		EntityRef {
			entity: PhantomData,
			data: load_entity(context.0, &self.name).unwrap_or_else(self.default),
		}
	}

	pub fn get_mut(&mut self, context: &ScriptContext) -> EntityMut<'_, T> {
		EntityMut {
			context: context.0,
			entity: self,
			data: load_entity(context.0, &self.name).unwrap_or_else(self.default),
		}
	}
}

impl<T> Deref for EntityRef<'_, T> {
	type Target = T;

	fn deref(&self) -> &Self::Target {
		&self.data
	}
}

impl<T: Serialize> Deref for EntityMut<'_, T> {
	type Target = T;

	fn deref(&self) -> &Self::Target {
		&self.data
	}
}

impl<T: Serialize> DerefMut for EntityMut<'_, T> {
	fn deref_mut(&mut self) -> &mut Self::Target {
		&mut self.data
	}
}

impl<T: Serialize> Drop for EntityMut<'_, T> {
	fn drop(&mut self) {
		save_entity(self.context, &self.entity.name, &self.data);
	}
}