//! Arbitrary object store
use std::any::{
    TypeId,
    Any,
};
use std::collections::HashMap;

/// Arbitrarily typed singleton store.
///
/// Stores one object per type.
#[derive(Debug)]
pub struct SingletonStore
{
    objects: HashMap<TypeId, Box<dyn Any + 'static>>,
}

#[inline] fn unbox_to<T: Any>(b: Box<dyn Any + 'static>) -> Option<T>
{
    b.downcast().map(|ok| *ok).ok()
}

impl SingletonStore
{
    pub fn has<T: Any>(&self) -> bool
    {
	self.objects.contains_key(&TypeId::of::<T>())
    }
    
    pub fn remove<T: Any>(&mut self) -> Option<T>
    {
	self.objects.remove(&TypeId::of::<T>())
	    .and_then(|x| x.downcast().ok())
	    .map(|x| *x)
    }
    pub fn insert<T: Any>(&mut self, value: T) -> Option<T>
    {
	self.objects.insert(TypeId::of::<T>(), Box::new(value))
	    .and_then(unbox_to)
    }

    pub fn get_mut<T: Any>(&mut self) -> Option<&mut T>
    {
	self.objects.get_mut(&TypeId::of::<T>())
	    .and_then(|x| x.downcast_mut())
    }
    pub fn get<T: Any>(&self) -> Option<&T>
    {
	self.objects.get(&TypeId::of::<T>())
	    .and_then(|x| x.downcast_ref())
    }

    pub fn new() -> Self
    {
	Self {
	    objects: HashMap::new(),
	}
    }
}