use std::borrow::Cow;
use std::env::current_dir;
use std::ffi::OsStr;
use std::fs;
use std::io;
#[cfg(any(unix, target_os = "redox"))]
use std::os::unix::fs::PermissionsExt;
use std::path::{Component, Path, PathBuf};

use crate::walk;

pub fn path_absolute_form(path: &Path) -> io::Result<PathBuf> {
    if path.is_absolute() {
        return Ok(path.to_path_buf());
    }

    let path = path.strip_prefix(".").unwrap_or(path);
    current_dir().map(|path_buf| path_buf.join(path))
}

pub fn absolute_path(path: &Path) -> io::Result<PathBuf> {
    let path_buf = path_absolute_form(path)?;

    #[cfg(windows)]
    let path_buf = Path::new(
        path_buf
            .as_path()
            .to_string_lossy()
            .trim_start_matches(r"\\?\"),
    )
    .to_path_buf();

    Ok(path_buf)
}

// Path::is_dir() is not guaranteed to be intuitively correct for "." and ".."
// See: https://github.com/rust-lang/rust/issues/45302
pub fn is_dir(path: &Path) -> bool {
    path.is_dir() && (path.file_name().is_some() || path.canonicalize().is_ok())
}

#[cfg(any(unix, target_os = "redox"))]
pub fn is_executable(md: &fs::Metadata) -> bool {
    md.permissions().mode() & 0o111 != 0
}

#[cfg(windows)]
pub fn is_executable(_: &fs::Metadata) -> bool {
    false
}

pub fn is_empty(entry: &walk::DirEntry) -> bool {
    if let Some(file_type) = entry.file_type() {
        if file_type.is_dir() {
            if let Ok(mut entries) = fs::read_dir(entry.path()) {
                entries.next().is_none()
            } else {
                false
            }
        } else if file_type.is_file() {
            entry.metadata().map(|m| m.len() == 0).unwrap_or(false)
        } else {
            false
        }
    } else {
        false
    }
}

#[cfg(any(unix, target_os = "redox"))]
pub fn osstr_to_bytes(input: &OsStr) -> Cow<[u8]> {
    use std::os::unix::ffi::OsStrExt;
    Cow::Borrowed(input.as_bytes())
}

#[cfg(windows)]
pub fn osstr_to_bytes(input: &OsStr) -> Cow<[u8]> {
    let string = input.to_string_lossy();

    match string {
        Cow::Owned(string) => Cow::Owned(string.into_bytes()),
        Cow::Borrowed(string) => Cow::Borrowed(string.as_bytes()),
    }
}

/// Remove the `./` prefix from a path.
pub fn strip_current_dir(pathbuf: &PathBuf) -> &Path {
    let mut iter = pathbuf.components();
    let mut iter_next = iter.clone();
    if iter_next.next() == Some(Component::CurDir) {
        iter.next();
    }
    iter.as_path()
}

#[cfg(test)]
mod tests {
    use super::strip_current_dir;
    use std::path::{Path, PathBuf};

    #[test]
    fn strip_current_dir_basic() {
        assert_eq!(strip_current_dir(&PathBuf::from("./foo")), Path::new("foo"));
        assert_eq!(strip_current_dir(&PathBuf::from("foo")), Path::new("foo"));
        assert_eq!(
            strip_current_dir(&PathBuf::from("./foo/bar/baz")),
            Path::new("foo/bar/baz")
        );
        assert_eq!(
            strip_current_dir(&PathBuf::from("foo/bar/baz")),
            Path::new("foo/bar/baz")
        );
    }
}