//! Metadata trait definition for user-defined types that can be added to the `SharedState` ad-hoc
use std::any::Any;
use std::collections::HashMap;
use std::fmt::Debug;
use std::sync::{Arc, RwLock};
/// typedef of the `SharedState`'s `metadata` field
pub type MetadataMap = Arc<RwLock<HashMap<String, Box<dyn Metadata>>>>;
/// an implementor of this trait can be cast to [`Any`] as part of a
/// dynamic dispatch system
pub trait AsAny {
/// return the implementing type as `Any`
///
/// the normal implementation of this is to return `self`
fn as_any(&self) -> &dyn Any;
}
/// an implementor of this trait can be cast to a mutable [`Any`] as part of a
/// dynamic dispatch system
pub trait AsAnyMut {
/// return the implementing type as a mutable `Any`
///
/// the normal implementation of this is to return `&mut self`
fn as_any_mut(&mut self) -> &mut dyn Any;
}
/// an implementor of the [`Metadata`] trait will be able to store instances
/// of itself in the `metadata` field of the [`SharedState`] struct
///
/// [`SharedState`]: crate::state::SharedState
#[cfg_attr(feature = "typetag", typetag::serde(tag = "type"))]
pub trait Metadata: AsAny + AsAnyMut + Send + Sync + Debug {
/// delegates to the MetaData-implementing type, allowing for comparison
/// of two MetaData-implementing types
///
/// it's optional to implement this method, but is there if comparison
/// between two instances of the same type is needed
fn is_equal(&self, other: &dyn Any) -> bool;
}