// utils module

//

// Copyright 2019 Raphaël Gomès <rgomes@octobus.net>

//

// This software may be used and distributed according to the terms of the

// GNU General Public License version 2 or any later version.

//! Contains useful functions, traits, structs, etc. for use in core.

pub mod files;

pub mod hg_path;

/// Useful until rust/issues/56345 is stable

///

/// # Examples

///

/// ```

/// use crate::hg::utils::find_slice_in_slice;

///

/// let haystack = b"This is the haystack".to_vec();

/// assert_eq!(find_slice_in_slice(&haystack, b"the"), Some(8));

/// assert_eq!(find_slice_in_slice(&haystack, b"not here"), None);

/// ```

pub fn find_slice_in_slice<T>(slice: &[T], needle: &[T]) -> Option<usize>

where

    for<'a> &'a [T]: PartialEq,

{

    slice

        .windows(needle.len())

        .position(|window| window == needle)

}

/// Replaces the `from` slice with the `to` slice inside the `buf` slice.

///

/// # Examples

///

/// ```

/// use crate::hg::utils::replace_slice;

/// let mut line = b"I hate writing tests!".to_vec();

/// replace_slice(&mut line, b"hate", b"love");

/// assert_eq!(

///     line,

///     b"I love writing tests!".to_vec()

/// );

/// ```

pub fn replace_slice<T>(buf: &mut [T], from: &[T], to: &[T])

where

    T: Clone + PartialEq,

{

    if buf.len() < from.len() || from.len() != to.len() {

        return;

    }

    for i in 0..=buf.len() - from.len() {

        if buf[i..].starts_with(from) {

            buf[i..(i + from.len())].clone_from_slice(to);

        }

    }

}

pub trait SliceExt {

    fn trim_end(&self) -> &Self;

    fn trim_start(&self) -> &Self;

    fn trim(&self) -> &Self;

    fn drop_prefix(&self, needle: &Self) -> Option<&Self>;

}

fn is_not_whitespace(c: &u8) -> bool {

    !(*c as char).is_whitespace()

}

impl SliceExt for [u8] {

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

        if let Some(last) = self.iter().rposition(is_not_whitespace) {

            &self[..last + 1]

        } else {

            &[]

        }

    }

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

        if let Some(first) = self.iter().position(is_not_whitespace) {

            &self[first..]

        } else {

            &[]

        }

    }

    /// ```

    /// use hg::utils::SliceExt;

    /// assert_eq!(

    ///     b"  to trim  ".trim(),

    ///     b"to trim"

    /// );

    /// assert_eq!(

    ///     b"to trim  ".trim(),

    ///     b"to trim"

    /// );

    /// assert_eq!(

    ///     b"  to trim".trim(),

    ///     b"to trim"

    /// );

    /// ```

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

        self.trim_start().trim_end()

    }

    fn drop_prefix(&self, needle: &Self) -> Option<&Self> {

        if self.starts_with(needle) {

            Some(&self[needle.len()..])

        } else {

            None

        }

    }

}