//! Extension traits implemented by several HTTP types.

use smallvec::{Array, SmallVec};

// TODO: It would be nice if we could somehow have one trait that could give us
// either SmallVec or Vec.
/// Trait implemented by types that can be converted into a collection.
pub trait IntoCollection<T> {
    /// Converts `self` into a collection.
    fn into_collection<A: Array<Item=T>>(self) -> SmallVec<A>;

    #[doc(hidden)]
    fn mapped<U, F: FnMut(T) -> U, A: Array<Item=U>>(self, f: F) -> SmallVec<A>;
}

impl<T> IntoCollection<T> for T {
    #[inline]
    fn into_collection<A: Array<Item=T>>(self) -> SmallVec<A> {
        let mut vec = SmallVec::new();
        vec.push(self);
        vec
    }

    #[inline(always)]
    fn mapped<U, F: FnMut(T) -> U, A: Array<Item=U>>(self, mut f: F) -> SmallVec<A> {
        f(self).into_collection()
    }
}

impl<T> IntoCollection<T> for Vec<T> {
    #[inline(always)]
    fn into_collection<A: Array<Item=T>>(self) -> SmallVec<A> {
        SmallVec::from_vec(self)
    }

    #[inline]
    fn mapped<U, F: FnMut(T) -> U, A: Array<Item=U>>(self, f: F) -> SmallVec<A> {
        self.into_iter().map(f).collect()
    }
}

macro_rules! impl_for_slice {
    ($($size:tt)*) => (
        impl<'a, T: Clone> IntoCollection<T> for &'a [T $($size)*] {
            #[inline(always)]
            fn into_collection<A: Array<Item=T>>(self) -> SmallVec<A> {
                self.iter().cloned().collect()
            }

            #[inline]
            fn mapped<U, F, A: Array<Item=U>>(self, f: F) -> SmallVec<A>
                where F: FnMut(T) -> U
            {
                self.iter().cloned().map(f).collect()
            }
        }
    )
}

impl_for_slice!();
impl_for_slice!(; 1);
impl_for_slice!(; 2);
impl_for_slice!(; 3);
impl_for_slice!(; 4);
impl_for_slice!(; 5);
impl_for_slice!(; 6);
impl_for_slice!(; 7);
impl_for_slice!(; 8);
impl_for_slice!(; 9);
impl_for_slice!(; 10);

use std::borrow::Cow;

/// Trait implemented by types that can be converted into owned versions of
/// themselves.
pub trait IntoOwned {
    /// The owned version of the type.
    type Owned: 'static;

    /// Converts `self` into an owned version of itself.
    fn into_owned(self) -> Self::Owned;
}

impl<T: IntoOwned> IntoOwned for Option<T> {
    type Owned = Option<T::Owned>;

    #[inline(always)]
    fn into_owned(self) -> Self::Owned {
        self.map(|inner| inner.into_owned())
    }
}

impl<'a, B: 'static + ToOwned + ?Sized> IntoOwned for Cow<'a, B> {
    type Owned = Cow<'static, B>;

    #[inline(always)]
    fn into_owned(self) -> Self::Owned {
        Cow::Owned(self.into_owned())
    }
}