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use std::mem;

pub mod pchannel;
pub mod pdeque;
pub mod ttlcell;
pub mod time;

/// Delivery policies
#[derive(Debug, Copy, Clone, Eq, PartialEq, Default)]
pub enum DeliveryPolicy {
    #[default]
    /// always deliver, fail if no room (default)
    Always,
    /// skip delivery if no room
    Optional,
    /// always deliver the message but always in a single copy (latest)
    Single,
    /// deliver a single latest copy, skip if no room
    SingleOptional,
}

/// Specify delivery policy for own data
pub trait MessageDeliveryPolicy
where
    Self: Sized,
{
    /// Delivery policy
    fn delivery_policy(&self) -> DeliveryPolicy {
        DeliveryPolicy::Always
    }
    /// Priority, for ordered
    fn priority(&self) -> usize {
        0
    }
    /// Has equal kind with other
    ///
    /// (default: check enum discriminant)
    fn eq_kind(&self, other: &Self) -> bool {
        mem::discriminant(self) == mem::discriminant(other)
    }
    /// Used to clean up expired values if no room
    fn is_expired(&self) -> bool {
        false
    }
    #[doc(hidden)]
    fn is_delivery_policy_single(&self) -> bool {
        let dp = self.delivery_policy();
        dp == DeliveryPolicy::Single || dp == DeliveryPolicy::SingleOptional
    }
    #[doc(hidden)]
    fn is_delivery_policy_optional(&self) -> bool {
        let dp = self.delivery_policy();
        dp == DeliveryPolicy::Optional || dp == DeliveryPolicy::SingleOptional
    }
}