// This file is part of ICU4X. For terms of use, please see the file

// called LICENSE at the top level of the ICU4X source tree

// (online at: https://github.com/unicode-org/icu4x/blob/main/LICENSE ).

use super::components::{VarZeroSliceIter, VarZeroVecComponents};

use super::vec::VarZeroVecInner;

use super::*;

use crate::ule::*;

use core::cmp::{Ord, Ordering, PartialOrd};

use core::fmt;

use core::marker::PhantomData;

use core::mem;

use core::ops::Index;

use core::ops::Range;

/// A zero-copy "slice", that works for unsized types, i.e. the zero-copy version of `[T]`

/// where `T` is not `Sized`.

///

/// This behaves similarly to [`VarZeroVec<T>`], however [`VarZeroVec<T>`] is allowed to contain

/// owned data and as such is ideal for deserialization since most human readable

/// serialization formats cannot unconditionally deserialize zero-copy.

///

/// This type can be used inside [`VarZeroVec<T>`](crate::VarZeroVec) and [`ZeroMap`](crate::ZeroMap):

/// This essentially allows for the construction of zero-copy types isomorphic to `Vec<Vec<T>>` by instead

/// using `VarZeroVec<ZeroSlice<T>>`.

///

/// The `F` type parameter is a [`VarZeroVecFormat`] (see its docs for more details), which can be used to select the

/// precise format of the backing buffer with various size and performance tradeoffs. It defaults to [`Index16`].

///

/// This type can be nested within itself to allow for multi-level nested `Vec`s.

///

/// # Examples

///

/// ## Nested Slices

///

/// The following code constructs the conceptual zero-copy equivalent of `Vec<Vec<Vec<str>>>`

///

/// ```rust

/// use zerovec::{VarZeroSlice, VarZeroVec};

/// let strings_1: Vec<&str> = vec!["foo", "bar", "baz"];

/// let strings_2: Vec<&str> = vec!["twelve", "seventeen", "forty two"];

/// let strings_3: Vec<&str> = vec!["我", "喜歡", "烏龍茶"];

/// let strings_4: Vec<&str> = vec!["w", "ω", "文", "𑄃"];

/// let strings_12 = vec![&*strings_1, &*strings_2];

/// let strings_34 = vec![&*strings_3, &*strings_4];

/// let all_strings = vec![strings_12, strings_34];

///

/// let vzv_1: VarZeroVec<str> = VarZeroVec::from(&strings_1);

/// let vzv_2: VarZeroVec<str> = VarZeroVec::from(&strings_2);

/// let vzv_3: VarZeroVec<str> = VarZeroVec::from(&strings_3);

/// let vzv_4: VarZeroVec<str> = VarZeroVec::from(&strings_4);

/// let vzv_12 = VarZeroVec::from(&[vzv_1.as_slice(), vzv_2.as_slice()]);

/// let vzv_34 = VarZeroVec::from(&[vzv_3.as_slice(), vzv_4.as_slice()]);

/// let vzv_all = VarZeroVec::from(&[vzv_12.as_slice(), vzv_34.as_slice()]);

///

/// let reconstructed: Vec<Vec<Vec<String>>> = vzv_all

///     .iter()

///     .map(|v: &VarZeroSlice<VarZeroSlice<str>>| {

///         v.iter()

///             .map(|x: &VarZeroSlice<_>| {

///                 x.as_varzerovec()

///                     .iter()

///                     .map(|s| s.to_owned())

///                     .collect::<Vec<String>>()

///             })

///             .collect::<Vec<_>>()

///     })

///     .collect::<Vec<_>>();

/// assert_eq!(reconstructed, all_strings);

///

/// let bytes = vzv_all.as_bytes();

/// let vzv_from_bytes: VarZeroVec<VarZeroSlice<VarZeroSlice<str>>> =

///     VarZeroVec::parse_bytes(bytes).unwrap();

/// assert_eq!(vzv_from_bytes, vzv_all);

/// ```

///

/// ## Iterate over Windows

///

/// Although [`VarZeroSlice`] does not itself have a `.windows` iterator like

/// [core::slice::Windows], this behavior can be easily modeled using an iterator:

///

/// ```

/// use zerovec::VarZeroVec;

///

/// let vzv = VarZeroVec::<str>::from(&["a", "b", "c", "d"]);

/// # let mut pairs: Vec<(&str, &str)> = Vec::new();

///

/// let mut it = vzv.iter().peekable();

/// while let (Some(x), Some(y)) = (it.next(), it.peek()) {

///     // Evaluate (x, y) here.

/// #   pairs.push((x, y));

/// }

/// # assert_eq!(pairs, &[("a", "b"), ("b", "c"), ("c", "d")]);

/// ```

//

// safety invariant: The slice MUST be one which parses to

// a valid VarZeroVecComponents<T>

#[repr(transparent)]

pub struct VarZeroSlice<T: ?Sized, F = Index16> {

    marker: PhantomData<(F, T)>,

    /// The original slice this was constructed from

    entire_slice: [u8],

}

impl<T: VarULE + ?Sized, F: VarZeroVecFormat> VarZeroSlice<T, F> {

    /// Construct a new empty VarZeroSlice

    pub const fn new_empty() -> &'static Self {

        // The empty VZV is special-cased to the empty slice

        unsafe { mem::transmute(&[] as &[u8]) }

    }

    /// Obtain a [`VarZeroVecComponents`] borrowing from the internal buffer

    #[inline]

    pub(crate) fn as_components<'a>(&'a self) -> VarZeroVecComponents<'a, T, F> {

        unsafe {

            // safety: VarZeroSlice is guaranteed to parse here

            VarZeroVecComponents::from_bytes_unchecked(&self.entire_slice)

        }

    }

Unexecuted instantiation: <zerovec::varzerovec::slice::VarZeroSlice<zerovec::zerovec::slice::ZeroSlice<icu_properties::props::Script>>>::as_components

Unexecuted instantiation: <zerovec::varzerovec::slice::VarZeroSlice<str>>::as_components

Unexecuted instantiation: <zerovec::varzerovec::slice::VarZeroSlice<_, _>>::as_components

    /// Uses a `&[u8]` buffer as a `VarZeroSlice<T>` without any verification.

    ///

    /// # Safety

    ///

    /// `bytes` need to be an output from [`VarZeroSlice::as_bytes()`].

    pub const unsafe fn from_bytes_unchecked(bytes: &[u8]) -> &Self {

        // self is really just a wrapper around a byte slice

        mem::transmute(bytes)

    }

    /// Get the number of elements in this slice

    ///

    /// # Example

    ///

    /// ```rust

    /// # use zerovec::VarZeroVec;

    ///

    /// let strings = vec!["foo", "bar", "baz", "quux"];

    /// let vec = VarZeroVec::<str>::from(&strings);

    ///

    /// assert_eq!(vec.len(), 4);

    /// ```

    pub fn len(&self) -> usize {

        self.as_components().len()

    }

Unexecuted instantiation: <zerovec::varzerovec::slice::VarZeroSlice<str>>::len

Unexecuted instantiation: <zerovec::varzerovec::slice::VarZeroSlice<_, _>>::len

    /// Returns `true` if the slice contains no elements.

    ///

    /// # Examples

    ///

    /// ```

    /// # use zerovec::VarZeroVec;

    ///

    /// let strings: Vec<String> = vec![];

    /// let vec = VarZeroVec::<str>::from(&strings);

    ///

    /// assert!(vec.is_empty());

    /// ```

    pub fn is_empty(&self) -> bool {

        self.as_components().is_empty()

    }

Unexecuted instantiation: <zerovec::varzerovec::slice::VarZeroSlice<str>>::is_empty

Unexecuted instantiation: <zerovec::varzerovec::slice::VarZeroSlice<_, _>>::is_empty

    /// Obtain an iterator over this slice's elements

    ///

    /// # Example

    ///

    /// ```rust

    /// # use zerovec::VarZeroVec;

    ///

    /// let strings = vec!["foo", "bar", "baz", "quux"];

    /// let vec = VarZeroVec::<str>::from(&strings);

    ///

    /// let mut iter_results: Vec<&str> = vec.iter().collect();

    /// assert_eq!(iter_results[0], "foo");

    /// assert_eq!(iter_results[1], "bar");

    /// assert_eq!(iter_results[2], "baz");

    /// assert_eq!(iter_results[3], "quux");

    /// ```

    pub fn iter<'b>(&'b self) -> VarZeroSliceIter<'b, T, F> {

        self.as_components().iter()

    }

Unexecuted instantiation: <zerovec::varzerovec::slice::VarZeroSlice<str>>::iter

Unexecuted instantiation: <zerovec::varzerovec::slice::VarZeroSlice<_, _>>::iter

    /// Get one of this slice's elements, returning `None` if the index is out of bounds

    ///

    /// # Example

    ///

    /// ```rust

    /// # use zerovec::VarZeroVec;

    ///

    /// let strings = vec!["foo", "bar", "baz", "quux"];

    /// let vec = VarZeroVec::<str>::from(&strings);

    ///

    /// let mut iter_results: Vec<&str> = vec.iter().collect();

    /// assert_eq!(vec.get(0), Some("foo"));

    /// assert_eq!(vec.get(1), Some("bar"));

    /// assert_eq!(vec.get(2), Some("baz"));

    /// assert_eq!(vec.get(3), Some("quux"));

    /// assert_eq!(vec.get(4), None);

    /// ```

    pub fn get(&self, idx: usize) -> Option<&T> {

        self.as_components().get(idx)

    }

Unexecuted instantiation: <zerovec::varzerovec::slice::VarZeroSlice<zerovec::zerovec::slice::ZeroSlice<icu_properties::props::Script>>>::get

Unexecuted instantiation: <zerovec::varzerovec::slice::VarZeroSlice<str>>::get

Unexecuted instantiation: <zerovec::varzerovec::slice::VarZeroSlice<_, _>>::get

    /// Get one of this slice's elements

    ///

    /// # Safety

    ///

    /// `index` must be in range

    ///

    /// # Example

    ///

    /// ```rust

    /// # use zerovec::VarZeroVec;

    ///

    /// let strings = vec!["foo", "bar", "baz", "quux"];

    /// let vec = VarZeroVec::<str>::from(&strings);

    ///

    /// let mut iter_results: Vec<&str> = vec.iter().collect();

    /// unsafe {

    ///     assert_eq!(vec.get_unchecked(0), "foo");

    ///     assert_eq!(vec.get_unchecked(1), "bar");

    ///     assert_eq!(vec.get_unchecked(2), "baz");

    ///     assert_eq!(vec.get_unchecked(3), "quux");

    /// }

    /// ```

    pub unsafe fn get_unchecked(&self, idx: usize) -> &T {

        self.as_components().get_unchecked(idx)

    }

    /// Obtain an owned `Vec<Box<T>>` out of this

    ///

    /// ✨ *Enabled with the `alloc` Cargo feature.*

    #[cfg(feature = "alloc")]

    pub fn to_vec(&self) -> alloc::vec::Vec<alloc::boxed::Box<T>> {

        self.as_components().to_vec()

    }

    /// Get a reference to the entire encoded backing buffer of this slice

    ///

    /// The bytes can be passed back to [`Self::parse_bytes()`].

    ///

    /// To take the bytes as a vector, see [`VarZeroVec::into_bytes()`].

    ///

    /// # Example

    ///

    /// ```rust

    /// # use zerovec::VarZeroVec;

    ///

    /// let strings = vec!["foo", "bar", "baz"];

    /// let vzv = VarZeroVec::<str>::from(&strings);

    ///

    /// assert_eq!(vzv, VarZeroVec::parse_bytes(vzv.as_bytes()).unwrap());

    /// ```

    #[inline]

    pub const fn as_bytes(&self) -> &[u8] {

        &self.entire_slice

    }

    /// Get this [`VarZeroSlice`] as a borrowed [`VarZeroVec`]

    ///

    /// If you wish to repeatedly call methods on this [`VarZeroSlice`],

    /// it is more efficient to perform this conversion first

    pub const fn as_varzerovec<'a>(&'a self) -> VarZeroVec<'a, T, F> {

        VarZeroVec(VarZeroVecInner::Borrowed(self))

    }

    /// Parse a VarZeroSlice from a slice of the appropriate format

    ///

    /// Slices of the right format can be obtained via [`VarZeroSlice::as_bytes()`]

    pub fn parse_bytes<'a>(slice: &'a [u8]) -> Result<&'a Self, UleError> {

        <Self as VarULE>::parse_bytes(slice)

    }

}

impl<T, F> VarZeroSlice<T, F>

where

    T: VarULE,

    T: ?Sized,

    T: Ord,

    F: VarZeroVecFormat,

{

    /// Binary searches a sorted `VarZeroVec<T>` for the given element. For more information, see

    /// the standard library function [`binary_search`].

    ///

    /// # Example

    ///

    /// ```

    /// # use zerovec::VarZeroVec;

    ///

    /// let strings = vec!["a", "b", "f", "g"];

    /// let vec = VarZeroVec::<str>::from(&strings);

    ///

    /// assert_eq!(vec.binary_search("f"), Ok(2));

    /// assert_eq!(vec.binary_search("e"), Err(2));

    /// ```

    ///

    /// [`binary_search`]: https://doc.rust-lang.org/std/primitive.slice.html#method.binary_search

    #[inline]

    pub fn binary_search(&self, x: &T) -> Result<usize, usize> {

        self.as_components().binary_search(x)

    }

Unexecuted instantiation: <zerovec::varzerovec::slice::VarZeroSlice<str>>::binary_search

Unexecuted instantiation: <zerovec::varzerovec::slice::VarZeroSlice<_, _>>::binary_search

    /// Binary searches a `VarZeroVec<T>` for the given element within a certain sorted range.

    ///

    /// If the range is out of bounds, returns `None`. Otherwise, returns a `Result` according

    /// to the behavior of the standard library function [`binary_search`].

    ///

    /// The index is returned relative to the start of the range.

    ///

    /// # Example

    ///

    /// ```

    /// # use zerovec::VarZeroVec;

    /// let strings = vec!["a", "b", "f", "g", "m", "n", "q"];

    /// let vec = VarZeroVec::<str>::from(&strings);

    ///

    /// // Same behavior as binary_search when the range covers the whole slice:

    /// assert_eq!(vec.binary_search_in_range("g", 0..7), Some(Ok(3)));

    /// assert_eq!(vec.binary_search_in_range("h", 0..7), Some(Err(4)));

    ///

    /// // Will not look outside of the range:

    /// assert_eq!(vec.binary_search_in_range("g", 0..1), Some(Err(1)));

    /// assert_eq!(vec.binary_search_in_range("g", 6..7), Some(Err(0)));

    ///

    /// // Will return indices relative to the start of the range:

    /// assert_eq!(vec.binary_search_in_range("g", 1..6), Some(Ok(2)));

    /// assert_eq!(vec.binary_search_in_range("h", 1..6), Some(Err(3)));

    ///

    /// // Will return `None` if the range is out of bounds:

    /// assert_eq!(vec.binary_search_in_range("x", 100..200), None);

    /// assert_eq!(vec.binary_search_in_range("x", 0..200), None);

    /// ```

    ///

    /// [`binary_search`]: https://doc.rust-lang.org/std/primitive.slice.html#method.binary_search

    #[inline]

    pub fn binary_search_in_range(

        &self,

        x: &T,

        range: Range<usize>,

    ) -> Option<Result<usize, usize>> {

        self.as_components().binary_search_in_range(x, range)

    }

}

impl<T, F> VarZeroSlice<T, F>

where

    T: VarULE,

    T: ?Sized,

    F: VarZeroVecFormat,

{

    /// Binary searches a sorted `VarZeroVec<T>` for the given predicate. For more information, see

    /// the standard library function [`binary_search_by`].

    ///

    /// # Example

    ///

    /// ```

    /// # use zerovec::VarZeroVec;

    /// let strings = vec!["a", "b", "f", "g"];

    /// let vec = VarZeroVec::<str>::from(&strings);

    ///

    /// assert_eq!(vec.binary_search_by(|probe| probe.cmp("f")), Ok(2));

    /// assert_eq!(vec.binary_search_by(|probe| probe.cmp("e")), Err(2));

    /// ```

    ///

    /// [`binary_search_by`]: https://doc.rust-lang.org/std/primitive.slice.html#method.binary_search_by

    #[inline]

    pub fn binary_search_by(&self, predicate: impl FnMut(&T) -> Ordering) -> Result<usize, usize> {

        self.as_components().binary_search_by(predicate)

    }

    /// Binary searches a `VarZeroVec<T>` for the given predicate within a certain sorted range.

    ///

    /// If the range is out of bounds, returns `None`. Otherwise, returns a `Result` according

    /// to the behavior of the standard library function [`binary_search`].

    ///

    /// The index is returned relative to the start of the range.

    ///

    /// # Example

    ///

    /// ```

    /// # use zerovec::VarZeroVec;

    /// let strings = vec!["a", "b", "f", "g", "m", "n", "q"];

    /// let vec = VarZeroVec::<str>::from(&strings);

    ///

    /// // Same behavior as binary_search when the range covers the whole slice:

    /// assert_eq!(

    ///     vec.binary_search_in_range_by(|v| v.cmp("g"), 0..7),

    ///     Some(Ok(3))

    /// );

    /// assert_eq!(

    ///     vec.binary_search_in_range_by(|v| v.cmp("h"), 0..7),

    ///     Some(Err(4))

    /// );

    ///

    /// // Will not look outside of the range:

    /// assert_eq!(

    ///     vec.binary_search_in_range_by(|v| v.cmp("g"), 0..1),

    ///     Some(Err(1))

    /// );

    /// assert_eq!(

    ///     vec.binary_search_in_range_by(|v| v.cmp("g"), 6..7),

    ///     Some(Err(0))

    /// );

    ///

    /// // Will return indices relative to the start of the range:

    /// assert_eq!(

    ///     vec.binary_search_in_range_by(|v| v.cmp("g"), 1..6),

    ///     Some(Ok(2))

    /// );

    /// assert_eq!(

    ///     vec.binary_search_in_range_by(|v| v.cmp("h"), 1..6),

    ///     Some(Err(3))

    /// );

    ///

    /// // Will return `None` if the range is out of bounds:

    /// assert_eq!(

    ///     vec.binary_search_in_range_by(|v| v.cmp("x"), 100..200),

    ///     None

    /// );

    /// assert_eq!(vec.binary_search_in_range_by(|v| v.cmp("x"), 0..200), None);

    /// ```

    ///

    /// [`binary_search`]: https://doc.rust-lang.org/std/primitive.slice.html#method.binary_search

    pub fn binary_search_in_range_by(

        &self,

        predicate: impl FnMut(&T) -> Ordering,

        range: Range<usize>,

    ) -> Option<Result<usize, usize>> {

        self.as_components()

            .binary_search_in_range_by(predicate, range)

    }

}

// Safety (based on the safety checklist on the VarULE trait):

//  1. VarZeroSlice does not include any uninitialized or padding bytes (achieved by `#[repr(transparent)]` on a

//     `[u8]` slice which satisfies this invariant)

//  2. VarZeroSlice is aligned to 1 byte (achieved by `#[repr(transparent)]` on a

//     `[u8]` slice which satisfies this invariant)

//  3. The impl of `validate_bytes()` returns an error if any byte is not valid.

//  4. The impl of `validate_bytes()` returns an error if the slice cannot be used in its entirety

//  5. The impl of `from_bytes_unchecked()` returns a reference to the same data.

//  6. `as_bytes()` is equivalent to a regular transmute of the underlying data

//  7. VarZeroSlice byte equality is semantic equality (relying on the guideline of the underlying VarULE type)

unsafe impl<T: VarULE + ?Sized + 'static, F: VarZeroVecFormat> VarULE for VarZeroSlice<T, F> {

    fn validate_bytes(bytes: &[u8]) -> Result<(), UleError> {

        let _: VarZeroVecComponents<T, F> =

            VarZeroVecComponents::parse_bytes(bytes).map_err(|_| UleError::parse::<Self>())?;

        Ok(())

    }

    unsafe fn from_bytes_unchecked(bytes: &[u8]) -> &Self {

        // self is really just a wrapper around a byte slice

        mem::transmute(bytes)

    }

Unexecuted instantiation: <zerovec::varzerovec::slice::VarZeroSlice<str> as zerovec::ule::VarULE>::from_bytes_unchecked

Unexecuted instantiation: <zerovec::varzerovec::slice::VarZeroSlice<_, _> as zerovec::ule::VarULE>::from_bytes_unchecked

    fn as_bytes(&self) -> &[u8] {

        &self.entire_slice

    }

Unexecuted instantiation: <zerovec::varzerovec::slice::VarZeroSlice<str> as zerovec::ule::VarULE>::as_bytes

Unexecuted instantiation: <zerovec::varzerovec::slice::VarZeroSlice<_, _> as zerovec::ule::VarULE>::as_bytes

}

impl<T: VarULE + ?Sized, F: VarZeroVecFormat> Index<usize> for VarZeroSlice<T, F> {

    type Output = T;

    fn index(&self, index: usize) -> &Self::Output {

        #[expect(clippy::panic)] // documented

        match self.get(index) {

            Some(x) => x,

            None => panic!(

                "index out of bounds: the len is {} but the index is {index}",

                self.len()

            ),

        }

    }

}

impl<T, F> PartialEq<VarZeroSlice<T, F>> for VarZeroSlice<T, F>

where

    T: VarULE,

    T: ?Sized,

    T: PartialEq,

    F: VarZeroVecFormat,

{

    #[inline]

    fn eq(&self, other: &VarZeroSlice<T, F>) -> bool {

        // VarULE has an API guarantee that this is equivalent

        // to `T::VarULE::eq()`

        self.entire_slice.eq(&other.entire_slice)

    }

}

impl<T, F> Eq for VarZeroSlice<T, F>

where

    T: VarULE,

    T: ?Sized,

    T: Eq,

    F: VarZeroVecFormat,

{

}

impl<T: VarULE + ?Sized + PartialOrd, F: VarZeroVecFormat> PartialOrd for VarZeroSlice<T, F> {

    #[inline]

    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {

        self.iter().partial_cmp(other.iter())

    }

}

impl<T: VarULE + ?Sized + Ord, F: VarZeroVecFormat> Ord for VarZeroSlice<T, F> {

    #[inline]

    fn cmp(&self, other: &Self) -> Ordering {

        self.iter().cmp(other.iter())

    }

}

impl<T: VarULE + ?Sized, F: VarZeroVecFormat> fmt::Debug for VarZeroSlice<T, F>

where

    T: fmt::Debug,

{

    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {

        f.debug_list().entries(self.iter()).finish()

    }

Unexecuted instantiation: <zerovec::varzerovec::slice::VarZeroSlice<str> as core::fmt::Debug>::fmt

Unexecuted instantiation: <zerovec::varzerovec::slice::VarZeroSlice<_, _> as core::fmt::Debug>::fmt

}

impl<T: ?Sized, F: VarZeroVecFormat> AsRef<VarZeroSlice<T, F>> for VarZeroSlice<T, F> {

    fn as_ref(&self) -> &VarZeroSlice<T, F> {

        self

    }

}