use std::ffi::OsStr;
use std::iter::FusedIterator;

use crate::path::{Component, Path};

/// An iterator over the [`Component`]s of a [`Path`].
///
/// This `struct` is created by the [`components`] method on [`Path`].
/// See its documentation for more.
///
/// # Examples
///
/// ```
/// use async_std::path::Path;
///
/// let path = Path::new("/tmp/foo/bar.txt");
///
/// for component in path.components() {
///     println!("{:?}", component);
/// }
/// ```
///
/// [`Component`]: enum.Component.html
/// [`components`]: struct.Path.html#method.components
/// [`Path`]: struct.Path.html
#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
pub struct Components<'a> {
    pub(crate) inner: std::path::Components<'a>,
}

impl<'a> Components<'a> {
    /// Extracts a slice corresponding to the portion of the path remaining for iteration.
    ///
    /// # Examples
    ///
    /// ```
    /// use async_std::path::Path;
    ///
    /// let mut components = Path::new("/tmp/foo/bar.txt").components();
    /// components.next();
    /// components.next();
    ///
    /// assert_eq!(Path::new("foo/bar.txt"), components.as_path());
    /// ```
    pub fn as_path(&self) -> &'a Path {
        self.inner.as_path().into()
    }
}

impl AsRef<Path> for Components<'_> {
    fn as_ref(&self) -> &Path {
        self.as_path()
    }
}

impl AsRef<OsStr> for Components<'_> {
    fn as_ref(&self) -> &OsStr {
        self.as_path().as_os_str()
    }
}

impl<'a> Iterator for Components<'a> {
    type Item = Component<'a>;

    fn next(&mut self) -> Option<Component<'a>> {
        self.inner.next()
    }
}

impl<'a> DoubleEndedIterator for Components<'a> {
    fn next_back(&mut self) -> Option<Component<'a>> {
        self.inner.next_back()
    }
}

impl FusedIterator for Components<'_> {}

impl AsRef<Path> for Component<'_> {
    fn as_ref(&self) -> &Path {
        self.as_os_str().as_ref()
    }
}