/// Represents the result of a non-blocking read from a [DashMap](crate::DashMap).

#[derive(Debug)]

pub enum TryResult<R> {

    /// The value was present in the map, and the lock for the shard was successfully obtained.

    Present(R),

    /// The shard wasn't locked, and the value wasn't present in the map.

    Absent,

    /// The shard was locked.

    Locked,

}

impl<R> TryResult<R> {

    /// Returns `true` if the value was present in the map, and the lock for the shard was successfully obtained.

    pub fn is_present(&self) -> bool {

        matches!(self, TryResult::Present(_))

    }

    /// Returns `true` if the shard wasn't locked, and the value wasn't present in the map.

    pub fn is_absent(&self) -> bool {

        matches!(self, TryResult::Absent)

    }

    /// Returns `true` if the shard was locked.

    pub fn is_locked(&self) -> bool {

        matches!(self, TryResult::Locked)

    }

    /// If `self` is [Present](TryResult::Present), returns the reference to the value in the map.

    /// Panics if `self` is not [Present](TryResult::Present).

    pub fn unwrap(self) -> R {

        match self {

            TryResult::Present(r) => r,

            TryResult::Locked => panic!("Called unwrap() on TryResult::Locked"),

            TryResult::Absent => panic!("Called unwrap() on TryResult::Absent"),

        }

    }

    /// If `self` is [Present](TryResult::Present), returns the reference to the value in the map.

    /// If `self` is not [Present](TryResult::Present), returns `None`.

    pub fn try_unwrap(self) -> Option<R> {

        match self {

            TryResult::Present(r) => Some(r),

            _ => None,

        }

    }

}