use std::error::Error;

/// Standard result type.
pub type Usually<T> = Result<T, Box<dyn Error>>;

/// Standard optional result type.
pub type Perhaps<T> = Result<Option<T>, Box<dyn Error>>;

/// Implement the `From` trait.
#[macro_export] macro_rules! from {
    ($(<$($lt:lifetime),+>)?|$state:ident:$Source:ty|$Target:ty=$cb:expr) => {
        impl $(<$($lt),+>)? From<$Source> for $Target {
            fn from ($state:$Source) -> Self { $cb }
        }
    };
}

pub trait Has<T>: Send + Sync {
    fn get     (&self)     -> &T;
    fn get_mut (&mut self) -> &mut T;
}

#[macro_export] macro_rules! has {
    ($T:ty: |$self:ident : $S:ty| $x:expr) => {
        impl Has<$T> for $S {
            fn get     (&$self)     -> &$T     { &$x }
            fn get_mut (&mut $self) -> &mut $T { &mut $x }
        }
    };
}

pub trait MaybeHas<T>: Send + Sync {
    fn get     (&self)     -> Option<&T>;
    fn get_mut (&mut self) -> Option<&mut T>;
}

#[macro_export] macro_rules! maybe_has {
    ($T:ty: |$self:ident : $S:ty| $x:block; $y:block $(;)?) => {
        impl MaybeHas<$T> for $S {
            fn get     (&$self)     -> Option<&$T>     $x
            fn get_mut (&mut $self) -> Option<&mut $T> $y
        }
    };
}