use std::ffi::OsStr;
use std::path::Path;

/// Returns true if and only if this file path is considered to be hidden.
#[cfg(unix)]
pub fn is_hidden<P: AsRef<Path>>(path: P) -> bool {
    use std::os::unix::ffi::OsStrExt;

    if let Some(name) = file_name(path.as_ref()) {
        name.as_bytes().get(0) == Some(&b'.')
    } else {
        false
    }
}

/// Returns true if and only if this file path is considered to be hidden.
#[cfg(not(unix))]
pub fn is_hidden<P: AsRef<Path>>(path: P) -> bool {
    if let Some(name) = file_name(path.as_ref()) {
        name.to_str().map(|s| s.starts_with(".")).unwrap_or(false)
    } else {
        false
    }
}

/// Strip `prefix` from the `path` and return the remainder.
///
/// If `path` doesn't have a prefix `prefix`, then return `None`.
#[cfg(unix)]
pub fn strip_prefix<'a, P: AsRef<Path> + ?Sized>(
    prefix: &'a P,
    path: &'a Path,
) -> Option<&'a Path> {
    use std::os::unix::ffi::OsStrExt;

    let prefix = prefix.as_ref().as_os_str().as_bytes();
    let path = path.as_os_str().as_bytes();
    if prefix.len() > path.len() || prefix != &path[0..prefix.len()] {
        None
    } else {
        Some(&Path::new(OsStr::from_bytes(&path[prefix.len()..])))
    }
}

/// Strip `prefix` from the `path` and return the remainder.
///
/// If `path` doesn't have a prefix `prefix`, then return `None`.
#[cfg(not(unix))]
pub fn strip_prefix<'a, P: AsRef<Path> + ?Sized>(
    prefix: &'a P,
    path: &'a Path,
) -> Option<&'a Path> {
    path.strip_prefix(prefix).ok()
}

/// Returns true if this file path is just a file name. i.e., Its parent is
/// the empty string.
#[cfg(unix)]
pub fn is_file_name<P: AsRef<Path>>(path: P) -> bool {
    use std::os::unix::ffi::OsStrExt;
    use memchr::memchr;

    let path = path.as_ref().as_os_str().as_bytes();
    memchr(b'/', path).is_none()
}

/// Returns true if this file path is just a file name. i.e., Its parent is
/// the empty string.
#[cfg(not(unix))]
pub fn is_file_name<P: AsRef<Path>>(path: P) -> bool {
    path.as_ref().parent().map(|p| p.as_os_str().is_empty()).unwrap_or(false)
}

/// The final component of the path, if it is a normal file.
///
/// If the path terminates in ., .., or consists solely of a root of prefix,
/// file_name will return None.
#[cfg(unix)]
pub fn file_name<'a, P: AsRef<Path> + ?Sized>(
    path: &'a P,
) -> Option<&'a OsStr> {
    use std::os::unix::ffi::OsStrExt;
    use memchr::memrchr;

    let path = path.as_ref().as_os_str().as_bytes();
    if path.is_empty() {
        return None;
    } else if path.len() == 1 && path[0] == b'.' {
        return None;
    } else if path.last() == Some(&b'.') {
        return None;
    } else if path.len() >= 2 && &path[path.len() - 2..] == &b".."[..] {
        return None;
    }
    let last_slash = memrchr(b'/', path).map(|i| i + 1).unwrap_or(0);
    Some(OsStr::from_bytes(&path[last_slash..]))
}

/// The final component of the path, if it is a normal file.
///
/// If the path terminates in ., .., or consists solely of a root of prefix,
/// file_name will return None.
#[cfg(not(unix))]
pub fn file_name<'a, P: AsRef<Path> + ?Sized>(
    path: &'a P,
) -> Option<&'a OsStr> {
    path.as_ref().file_name()
}