//! The underlying OsString/OsStr implementation on Unix and many other
//! systems: just a `Vec<u8>`/`[u8]`.

use crate::borrow::Cow;
use crate::ffi::{OsStr, OsString};
use crate::fmt;
use crate::mem;
use crate::rc::Rc;
use crate::sealed::Sealed;
use crate::str;
use crate::sync::Arc;
use crate::sys_common::bytestring::debug_fmt_bytestring;
use crate::sys_common::{AsInner, FromInner, IntoInner};

use core::str::lossy::Utf8Lossy;

#[derive(Clone, Hash)]
pub(crate) struct Buf {
    pub inner: Vec<u8>,
}

// FIXME:
// `Buf::as_slice` current implementation relies
// on `Slice` being layout-compatible with `[u8]`.
// When attribute privacy is implemented, `Slice` should be annotated as `#[repr(transparent)]`.
// Anyway, `Slice` representation and layout are considered implementation detail, are
// not documented and must not be relied upon.
pub(crate) struct Slice {
    pub inner: [u8],
}

impl fmt::Debug for Slice {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        debug_fmt_bytestring(&self.inner, formatter)
    }
}

impl fmt::Display for Slice {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt::Display::fmt(&Utf8Lossy::from_bytes(&self.inner), formatter)
    }
}

impl fmt::Debug for Buf {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt::Debug::fmt(self.as_slice(), formatter)
    }
}

impl fmt::Display for Buf {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt::Display::fmt(self.as_slice(), formatter)
    }
}

impl IntoInner<Vec<u8>> for Buf {
    fn into_inner(self) -> Vec<u8> {
        self.inner
    }
}

impl AsInner<[u8]> for Buf {
    fn as_inner(&self) -> &[u8] {
        &self.inner
    }
}

impl Buf {
    pub fn from_string(s: String) -> Buf {
        Buf { inner: s.into_bytes() }
    }

    #[inline]
    pub fn with_capacity(capacity: usize) -> Buf {
        Buf { inner: Vec::with_capacity(capacity) }
    }

    #[inline]
    pub fn clear(&mut self) {
        self.inner.clear()
    }

    #[inline]
    pub fn capacity(&self) -> usize {
        self.inner.capacity()
    }

    #[inline]
    pub fn reserve(&mut self, additional: usize) {
        self.inner.reserve(additional)
    }

    #[inline]
    pub fn reserve_exact(&mut self, additional: usize) {
        self.inner.reserve_exact(additional)
    }

    #[inline]
    pub fn shrink_to_fit(&mut self) {
        self.inner.shrink_to_fit()
    }

    #[inline]
    pub fn shrink_to(&mut self, min_capacity: usize) {
        self.inner.shrink_to(min_capacity)
    }

    #[inline]
    pub fn as_slice(&self) -> &Slice {
        // SAFETY: Slice just wraps [u8],
        // and &*self.inner is &[u8], therefore
        // transmuting &[u8] to &Slice is safe.
        unsafe { mem::transmute(&*self.inner) }
    }

    #[inline]
    pub fn as_mut_slice(&mut self) -> &mut Slice {
        // SAFETY: Slice just wraps [u8],
        // and &mut *self.inner is &mut [u8], therefore
        // transmuting &mut [u8] to &mut Slice is safe.
        unsafe { mem::transmute(&mut *self.inner) }
    }

    pub fn into_string(self) -> Result<String, Buf> {
        String::from_utf8(self.inner).map_err(|p| Buf { inner: p.into_bytes() })
    }

    pub fn push_slice(&mut self, s: &Slice) {
        self.inner.extend_from_slice(&s.inner)
    }

    #[inline]
    pub fn into_box(self) -> Box<Slice> {
        unsafe { mem::transmute(self.inner.into_boxed_slice()) }
    }

    #[inline]
    pub fn from_box(boxed: Box<Slice>) -> Buf {
        let inner: Box<[u8]> = unsafe { mem::transmute(boxed) };
        Buf { inner: inner.into_vec() }
    }

    #[inline]
    pub fn into_arc(&self) -> Arc<Slice> {
        self.as_slice().into_arc()
    }

    #[inline]
    pub fn into_rc(&self) -> Rc<Slice> {
        self.as_slice().into_rc()
    }
}

impl Slice {
    #[inline]
    fn from_u8_slice(s: &[u8]) -> &Slice {
        unsafe { mem::transmute(s) }
    }

    #[inline]
    pub fn from_str(s: &str) -> &Slice {
        Slice::from_u8_slice(s.as_bytes())
    }

    pub fn to_str(&self) -> Option<&str> {
        str::from_utf8(&self.inner).ok()
    }

    pub fn to_string_lossy(&self) -> Cow<'_, str> {
        String::from_utf8_lossy(&self.inner)
    }

    pub fn to_owned(&self) -> Buf {
        Buf { inner: self.inner.to_vec() }
    }

    pub fn clone_into(&self, buf: &mut Buf) {
        self.inner.clone_into(&mut buf.inner)
    }

    #[inline]
    pub fn into_box(&self) -> Box<Slice> {
        let boxed: Box<[u8]> = self.inner.into();
        unsafe { mem::transmute(boxed) }
    }

    pub fn empty_box() -> Box<Slice> {
        let boxed: Box<[u8]> = Default::default();
        unsafe { mem::transmute(boxed) }
    }

    #[inline]
    pub fn into_arc(&self) -> Arc<Slice> {
        let arc: Arc<[u8]> = Arc::from(&self.inner);
        unsafe { Arc::from_raw(Arc::into_raw(arc) as *const Slice) }
    }

    #[inline]
    pub fn into_rc(&self) -> Rc<Slice> {
        let rc: Rc<[u8]> = Rc::from(&self.inner);
        unsafe { Rc::from_raw(Rc::into_raw(rc) as *const Slice) }
    }

    #[inline]
    pub fn make_ascii_lowercase(&mut self) {
        self.inner.make_ascii_lowercase()
    }

    #[inline]
    pub fn make_ascii_uppercase(&mut self) {
        self.inner.make_ascii_uppercase()
    }

    #[inline]
    pub fn to_ascii_lowercase(&self) -> Buf {
        Buf { inner: self.inner.to_ascii_lowercase() }
    }

    #[inline]
    pub fn to_ascii_uppercase(&self) -> Buf {
        Buf { inner: self.inner.to_ascii_uppercase() }
    }

    #[inline]
    pub fn is_ascii(&self) -> bool {
        self.inner.is_ascii()
    }

    #[inline]
    pub fn eq_ignore_ascii_case(&self, other: &Self) -> bool {
        self.inner.eq_ignore_ascii_case(&other.inner)
    }
}

/// Platform-specific extensions to [`OsString`].
///
/// This trait is sealed: it cannot be implemented outside the standard library.
/// This is so that future additional methods are not breaking changes.
#[stable(feature = "rust1", since = "1.0.0")]
pub trait OsStringExt: Sealed {
    /// Creates an [`OsString`] from a byte vector.
    ///
    /// See the module documentation for an example.
    #[stable(feature = "rust1", since = "1.0.0")]
    fn from_vec(vec: Vec<u8>) -> Self;

    /// Yields the underlying byte vector of this [`OsString`].
    ///
    /// See the module documentation for an example.
    #[stable(feature = "rust1", since = "1.0.0")]
    fn into_vec(self) -> Vec<u8>;
}

#[stable(feature = "rust1", since = "1.0.0")]
impl OsStringExt for OsString {
    fn from_vec(vec: Vec<u8>) -> OsString {
        FromInner::from_inner(Buf { inner: vec })
    }
    fn into_vec(self) -> Vec<u8> {
        self.into_inner().inner
    }
}

/// Platform-specific extensions to [`OsStr`].
///
/// This trait is sealed: it cannot be implemented outside the standard library.
/// This is so that future additional methods are not breaking changes.
#[stable(feature = "rust1", since = "1.0.0")]
pub trait OsStrExt: Sealed {
    #[stable(feature = "rust1", since = "1.0.0")]
    /// Creates an [`OsStr`] from a byte slice.
    ///
    /// See the module documentation for an example.
    fn from_bytes(slice: &[u8]) -> &Self;

    /// Gets the underlying byte view of the [`OsStr`] slice.
    ///
    /// See the module documentation for an example.
    #[stable(feature = "rust1", since = "1.0.0")]
    fn as_bytes(&self) -> &[u8];
}

#[stable(feature = "rust1", since = "1.0.0")]
impl OsStrExt for OsStr {
    #[inline]
    fn from_bytes(slice: &[u8]) -> &OsStr {
        unsafe { mem::transmute(slice) }
    }
    #[inline]
    fn as_bytes(&self) -> &[u8] {
        &self.as_inner().inner
    }
}