//! This module defines backends for WebAssembly execution.
//!
//! Canary is designed to support multiple WebAssembly runtimes for different
//! purposes. Currently, [wasmtime](https://wasmtime.dev) is the only one
//! implemented, but in the future, [wasm3](https://github.com/wasm3/wasm3)
//! will also be provided.

use super::*;

/// A WebAssembly runtime backend.
pub trait Backend {
    fn load_module(&self, module: &[u8]) -> Arc<dyn Instance>;
}

/// An instance of a WebAssembly module.
///
/// All self parameters to this trait's functions are immutable, so the
/// implementation must provide interior mutability. This allows instances
/// to intelligently optimize the execution of their scripts, for example, by
/// allowing the execution of multiple ABI calls from multiple threads when
/// a script supports the WebAssembly multithreading extension.
pub trait Instance {
    fn bind_panel(&self, panel: PanelId, msg: Vec<u8>) -> u32;
    fn update(&self, panel: PanelId, dt: f32);
    fn draw(&self, panel: PanelId) -> Vec<DrawCommand>;
    fn on_cursor_event(&self, panel: PanelId, kind: CursorEventKind, at: Vec2);
    fn on_message(&self, panel: PanelId, msg: Vec<u8>);
}