use super::oshandle::RawOsHandle;
use crate::handle::{HandleRights, Rights, RightsExt};
use std::cell::Cell;
use std::convert::TryFrom;
use std::fs::File;
use std::io;
use std::os::windows::prelude::{AsRawHandle, FromRawHandle, IntoRawHandle};

#[derive(Debug)]
/// A directory in the operating system's file system. Its impl of `Handle` is
/// in `sys::osdir`. This type is exposed to all other modules as
/// `sys::osdir::OsDir` when configured.
///
/// # Constructing `OsDir`
///
/// `OsDir` can currently only be constructed from `std::fs::File` using
/// the `std::convert::TryFrom` trait:
///
/// ```rust,no_run
/// use std::fs::OpenOptions;
/// use std::convert::TryFrom;
/// use std::os::windows::fs::OpenOptionsExt;
/// use wasi_common::OsDir;
/// use winapi::um::winbase::FILE_FLAG_BACKUP_SEMANTICS;
///
/// let dir = OpenOptions::new().read(true).attributes(FILE_FLAG_BACKUP_SEMANTICS).open("some_dir").unwrap();
/// let os_dir = OsDir::try_from(dir).unwrap();
/// ```
pub struct OsDir {
    pub(crate) rights: Cell<HandleRights>,
    pub(crate) handle: RawOsHandle,
}

impl OsDir {
    pub(crate) fn new(rights: HandleRights, handle: RawOsHandle) -> io::Result<Self> {
        let rights = Cell::new(rights);
        Ok(Self { rights, handle })
    }
}

impl TryFrom<File> for OsDir {
    type Error = io::Error;

    fn try_from(file: File) -> io::Result<Self> {
        let ft = file.metadata()?.file_type();
        if !ft.is_dir() {
            return Err(io::Error::from_raw_os_error(libc::EINVAL));
        }
        let rights = get_rights(&file)?;
        let handle = unsafe { RawOsHandle::from_raw_handle(file.into_raw_handle()) };
        Self::new(rights, handle)
    }
}

fn get_rights(file: &File) -> io::Result<HandleRights> {
    use winx::file::{query_access_information, AccessMode};
    let mut rights = HandleRights::new(Rights::directory_base(), Rights::directory_inheriting());
    let mode = query_access_information(file.as_raw_handle())?;
    if mode.contains(AccessMode::FILE_GENERIC_READ) {
        rights.base |= Rights::FD_READ;
    }
    if mode.contains(AccessMode::FILE_GENERIC_WRITE) {
        rights.base |= Rights::FD_WRITE;
    }
    Ok(rights)
}