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    use crate::fs::{asyncify, File};

    use std::io;
    use std::path::Path;

    /// Options and flags which can be used to configure how a file is opened.
    ///
    /// This builder exposes the ability to configure how a [`File`] is opened and
    /// what operations are permitted on the open file. The [`File::open`] and
    /// [`File::create`] methods are aliases for commonly used options using this
    /// builder.
    ///
    /// Generally speaking, when using `OpenOptions`, you'll first call [`new`],
    /// then chain calls to methods to set each option, then call [`open`], passing
    /// the path of the file you're trying to open. This will give you a
    /// [`io::Result`][result] with a [`File`] inside that you can further operate
    /// on.
    ///
    /// This is a specialized version of [`std::fs::OpenOptions`] for usage from
    /// the Tokio runtime.
    ///
    /// `From<std::fs::OpenOptions>` is implemented for more advanced configuration
    /// than the methods provided here.
    ///
    /// [`new`]: OpenOptions::new
    /// [`open`]: OpenOptions::open
    /// [result]: std::io::Result
    /// [`File`]: File
    /// [`File::open`]: File::open
    /// [`File::create`]: File::create
    /// [`std::fs::OpenOptions`]: std::fs::OpenOptions
    ///
    /// # Examples
    ///
    /// Opening a file to read:
    ///
    /// ```no_run
    /// use tokio::fs::OpenOptions;
    /// use std::io;
    ///
    /// #[tokio::main]
    /// async fn main() -> io::Result<()> {
    ///     let file = OpenOptions::new()
    ///         .read(true)
    ///         .open("foo.txt")
    ///         .await?;
    ///
    ///     Ok(())
    /// }
    /// ```
    ///
    /// Opening a file for both reading and writing, as well as creating it if it
    /// doesn't exist:
    ///
    /// ```no_run
    /// use tokio::fs::OpenOptions;
    /// use std::io;
    ///
    /// #[tokio::main]
    /// async fn main() -> io::Result<()> {
    ///     let file = OpenOptions::new()
    ///         .read(true)
    ///         .write(true)
    ///         .create(true)
    ///         .open("foo.txt")
    ///         .await?;
    ///
    ///     Ok(())
    /// }
    /// ```
    #[derive(Clone, Debug)]
    pub struct OpenOptions(std::fs::OpenOptions);

    impl OpenOptions {
        /// Creates a blank new set of options ready for configuration.
        ///
        /// All options are initially set to `false`.
        ///
        /// This is an async version of [`std::fs::OpenOptions::new`][std]
        ///
        /// [std]: std::fs::OpenOptions::new
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use tokio::fs::OpenOptions;
        ///
        /// let mut options = OpenOptions::new();
        /// let future = options.read(true).open("foo.txt");
        /// ```
        pub fn new() -> OpenOptions {
            OpenOptions(std::fs::OpenOptions::new())
        }

        /// Sets the option for read access.
        ///
        /// This option, when true, will indicate that the file should be
        /// `read`-able if opened.
        ///
        /// This is an async version of [`std::fs::OpenOptions::read`][std]
        ///
        /// [std]: std::fs::OpenOptions::read
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use tokio::fs::OpenOptions;
        /// use std::io;
        ///
        /// #[tokio::main]
        /// async fn main() -> io::Result<()> {
        ///     let file = OpenOptions::new()
        ///         .read(true)
        ///         .open("foo.txt")
        ///         .await?;
        ///
        ///     Ok(())
        /// }
        /// ```
        pub fn read(&mut self, read: bool) -> &mut OpenOptions {
            self.0.read(read);
            self
        }

        /// Sets the option for write access.
        ///
        /// This option, when true, will indicate that the file should be
        /// `write`-able if opened.
        ///
        /// This is an async version of [`std::fs::OpenOptions::write`][std]
        ///
        /// [std]: std::fs::OpenOptions::write
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use tokio::fs::OpenOptions;
        /// use std::io;
        ///
        /// #[tokio::main]
        /// async fn main() -> io::Result<()> {
        ///     let file = OpenOptions::new()
        ///         .write(true)
        ///         .open("foo.txt")
        ///         .await?;
        ///
        ///     Ok(())
        /// }
        /// ```
        pub fn write(&mut self, write: bool) -> &mut OpenOptions {
            self.0.write(write);
            self
        }

        /// Sets the option for the append mode.
        ///
        /// This option, when true, means that writes will append to a file instead
        /// of overwriting previous contents.  Note that setting
        /// `.write(true).append(true)` has the same effect as setting only
        /// `.append(true)`.
        ///
        /// For most filesystems, the operating system guarantees that all writes are
        /// atomic: no writes get mangled because another process writes at the same
        /// time.
        ///
        /// One maybe obvious note when using append-mode: make sure that all data
        /// that belongs together is written to the file in one operation. This
        /// can be done by concatenating strings before passing them to [`write()`],
        /// or using a buffered writer (with a buffer of adequate size),
        /// and calling [`flush()`] when the message is complete.
        ///
        /// If a file is opened with both read and append access, beware that after
        /// opening, and after every write, the position for reading may be set at the
        /// end of the file. So, before writing, save the current position (using
        /// [`seek`]`(`[`SeekFrom`]`::`[`Current`]`(0))`), and restore it before the next read.
        ///
        /// This is an async version of [`std::fs::OpenOptions::append`][std]
        ///
        /// [std]: std::fs::OpenOptions::append
        ///
        /// ## Note
        ///
        /// This function doesn't create the file if it doesn't exist. Use the [`create`]
        /// method to do so.
        ///
        /// [`write()`]: crate::io::AsyncWriteExt::write
        /// [`flush()`]: crate::io::AsyncWriteExt::flush
        /// [`seek`]: crate::io::AsyncSeekExt::seek
        /// [`SeekFrom`]: std::io::SeekFrom
        /// [`Current`]: std::io::SeekFrom::Current
        /// [`create`]: OpenOptions::create
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use tokio::fs::OpenOptions;
        /// use std::io;
        ///
        /// #[tokio::main]
        /// async fn main() -> io::Result<()> {
        ///     let file = OpenOptions::new()
        ///         .append(true)
        ///         .open("foo.txt")
        ///         .await?;
        ///
        ///     Ok(())
        /// }
        /// ```
        pub fn append(&mut self, append: bool) -> &mut OpenOptions {
            self.0.append(append);
            self
        }

        /// Sets the option for truncating a previous file.
        ///
        /// If a file is successfully opened with this option set it will truncate
        /// the file to 0 length if it already exists.
        ///
        /// The file must be opened with write access for truncate to work.
        ///
        /// This is an async version of [`std::fs::OpenOptions::truncate`][std]
        ///
        /// [std]: std::fs::OpenOptions::truncate
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use tokio::fs::OpenOptions;
        /// use std::io;
        ///
        /// #[tokio::main]
        /// async fn main() -> io::Result<()> {
        ///     let file = OpenOptions::new()
        ///         .write(true)
        ///         .truncate(true)
        ///         .open("foo.txt")
        ///         .await?;
        ///
        ///     Ok(())
        /// }
        /// ```
        pub fn truncate(&mut self, truncate: bool) -> &mut OpenOptions {
            self.0.truncate(truncate);
            self
        }

        /// Sets the option for creating a new file.
        ///
        /// This option indicates whether a new file will be created if the file
        /// does not yet already exist.
        ///
        /// In order for the file to be created, [`write`] or [`append`] access must
        /// be used.
        ///
        /// This is an async version of [`std::fs::OpenOptions::create`][std]
        ///
        /// [std]: std::fs::OpenOptions::create
        /// [`write`]: OpenOptions::write
        /// [`append`]: OpenOptions::append
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use tokio::fs::OpenOptions;
        /// use std::io;
        ///
        /// #[tokio::main]
        /// async fn main() -> io::Result<()> {
        ///     let file = OpenOptions::new()
        ///         .write(true)
        ///         .create(true)
        ///         .open("foo.txt")
        ///         .await?;
        ///
        ///     Ok(())
        /// }
        /// ```
        pub fn create(&mut self, create: bool) -> &mut OpenOptions {
            self.0.create(create);
            self
        }

        /// Sets the option to always create a new file.
        ///
        /// This option indicates whether a new file will be created.  No file is
        /// allowed to exist at the target location, also no (dangling) symlink.
        ///
        /// This option is useful because it is atomic. Otherwise between checking
        /// whether a file exists and creating a new one, the file may have been
        /// created by another process (a TOCTOU race condition / attack).
        ///
        /// If `.create_new(true)` is set, [`.create()`] and [`.truncate()`] are
        /// ignored.
        ///
        /// The file must be opened with write or append access in order to create a
        /// new file.
        ///
        /// This is an async version of [`std::fs::OpenOptions::create_new`][std]
        ///
        /// [std]: std::fs::OpenOptions::create_new
        /// [`.create()`]: OpenOptions::create
        /// [`.truncate()`]: OpenOptions::truncate
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use tokio::fs::OpenOptions;
        /// use std::io;
        ///
        /// #[tokio::main]
        /// async fn main() -> io::Result<()> {
        ///     let file = OpenOptions::new()
        ///         .write(true)
        ///         .create_new(true)
        ///         .open("foo.txt")
        ///         .await?;
        ///
        ///     Ok(())
        /// }
        /// ```
        pub fn create_new(&mut self, create_new: bool) -> &mut OpenOptions {
            self.0.create_new(create_new);
            self
        }

        /// Opens a file at `path` with the options specified by `self`.
        ///
        /// This is an async version of [`std::fs::OpenOptions::open`][std]
        ///
        /// [std]: std::fs::OpenOptions::open
        ///
        /// # Errors
        ///
        /// This function will return an error under a number of different
        /// circumstances. Some of these error conditions are listed here, together
        /// with their [`ErrorKind`]. The mapping to [`ErrorKind`]s is not part of
        /// the compatibility contract of the function, especially the `Other` kind
        /// might change to more specific kinds in the future.
        ///
        /// * [`NotFound`]: The specified file does not exist and neither `create`
        ///   or `create_new` is set.
        /// * [`NotFound`]: One of the directory components of the file path does
        ///   not exist.
        /// * [`PermissionDenied`]: The user lacks permission to get the specified
        ///   access rights for the file.
        /// * [`PermissionDenied`]: The user lacks permission to open one of the
        ///   directory components of the specified path.
        /// * [`AlreadyExists`]: `create_new` was specified and the file already
        ///   exists.
        /// * [`InvalidInput`]: Invalid combinations of open options (truncate
        ///   without write access, no access mode set, etc.).
        /// * [`Other`]: One of the directory components of the specified file path
        ///   was not, in fact, a directory.
        /// * [`Other`]: Filesystem-level errors: full disk, write permission
        ///   requested on a read-only file system, exceeded disk quota, too many
        ///   open files, too long filename, too many symbolic links in the
        ///   specified path (Unix-like systems only), etc.
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use tokio::fs::OpenOptions;
        /// use std::io;
        ///
        /// #[tokio::main]
        /// async fn main() -> io::Result<()> {
        ///     let file = OpenOptions::new().open("foo.txt").await?;
        ///     Ok(())
        /// }
        /// ```
        ///
        /// [`ErrorKind`]: std::io::ErrorKind
        /// [`AlreadyExists`]: std::io::ErrorKind::AlreadyExists
        /// [`InvalidInput`]: std::io::ErrorKind::InvalidInput
        /// [`NotFound`]: std::io::ErrorKind::NotFound
        /// [`Other`]: std::io::ErrorKind::Other
        /// [`PermissionDenied`]: std::io::ErrorKind::PermissionDenied
        pub async fn open(&self, path: impl AsRef<Path>) -> io::Result<File> {
            let path = path.as_ref().to_owned();
            let opts = self.0.clone();

            let std = asyncify(move || opts.open(path)).await?;
            Ok(File::from_std(std))
        }

        /// Returns a mutable reference to the underlying `std::fs::OpenOptions`
        pub(super) fn as_inner_mut(&mut self) -> &mut std::fs::OpenOptions {
            &mut self.0
        }
    }

    feature! {
        #![unix]

        use std::os::unix::fs::OpenOptionsExt;

        impl OpenOptions {
            /// Sets the mode bits that a new file will be created with.
            ///
            /// If a new file is created as part of an `OpenOptions::open` call then this
            /// specified `mode` will be used as the permission bits for the new file.
            /// If no `mode` is set, the default of `0o666` will be used.
            /// The operating system masks out bits with the system's `umask`, to produce
            /// the final permissions.
            ///
            /// # Examples
            ///
            /// ```no_run
            /// use tokio::fs::OpenOptions;
            /// use std::io;
            ///
            /// #[tokio::main]
            /// async fn main() -> io::Result<()> {
            ///     let mut options = OpenOptions::new();
            ///     options.mode(0o644); // Give read/write for owner and read for others.
            ///     let file = options.open("foo.txt").await?;
            ///
            ///     Ok(())
            /// }
            /// ```
            pub fn mode(&mut self, mode: u32) -> &mut OpenOptions {
                self.as_inner_mut().mode(mode);
                self
            }

            /// Pass custom flags to the `flags` argument of `open`.
            ///
            /// The bits that define the access mode are masked out with `O_ACCMODE`, to
            /// ensure they do not interfere with the access mode set by Rusts options.
            ///
            /// Custom flags can only set flags, not remove flags set by Rusts options.
            /// This options overwrites any previously set custom flags.
            ///
            /// # Examples
            ///
            /// ```no_run
            /// use libc;
            /// use tokio::fs::OpenOptions;
            /// use std::io;
            ///
            /// #[tokio::main]
            /// async fn main() -> io::Result<()> {
            ///     let mut options = OpenOptions::new();
            ///     options.write(true);
            ///     if cfg!(unix) {
            ///         options.custom_flags(libc::O_NOFOLLOW);
            ///     }
            ///     let file = options.open("foo.txt").await?;
            ///
            ///     Ok(())
            /// }
            /// ```
            pub fn custom_flags(&mut self, flags: i32) -> &mut OpenOptions {
                self.as_inner_mut().custom_flags(flags);
                self
            }
        }
    }

    feature! {
        #![windows]

        use std::os::windows::fs::OpenOptionsExt;

        impl OpenOptions {
            /// Overrides the `dwDesiredAccess` argument to the call to [`CreateFile`]
            /// with the specified value.
            ///
            /// This will override the `read`, `write`, and `append` flags on the
            /// `OpenOptions` structure. This method provides fine-grained control over
            /// the permissions to read, write and append data, attributes (like hidden
            /// and system), and extended attributes.
            ///
            /// # Examples
            ///
            /// ```no_run
            /// use tokio::fs::OpenOptions;
            ///
            /// # #[tokio::main]
            /// # async fn main() -> std::io::Result<()> {
            /// // Open without read and write permission, for example if you only need
            /// // to call `stat` on the file
            /// let file = OpenOptions::new().access_mode(0).open("foo.txt").await?;
            /// # Ok(())
            /// # }
            /// ```
            ///
            /// [`CreateFile`]: https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea
            pub fn access_mode(&mut self, access: u32) -> &mut OpenOptions {
                self.as_inner_mut().access_mode(access);
                self
            }

            /// Overrides the `dwShareMode` argument to the call to [`CreateFile`] with
            /// the specified value.
            ///
            /// By default `share_mode` is set to
            /// `FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE`. This allows
            /// other processes to read, write, and delete/rename the same file
            /// while it is open. Removing any of the flags will prevent other
            /// processes from performing the corresponding operation until the file
            /// handle is closed.
            ///
            /// # Examples
            ///
            /// ```no_run
            /// use tokio::fs::OpenOptions;
            ///
            /// # #[tokio::main]
            /// # async fn main() -> std::io::Result<()> {
            /// // Do not allow others to read or modify this file while we have it open
            /// // for writing.
            /// let file = OpenOptions::new()
            ///     .write(true)
            ///     .share_mode(0)
            ///     .open("foo.txt").await?;
            /// # Ok(())
            /// # }
            /// ```
            ///
            /// [`CreateFile`]: https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea
            pub fn share_mode(&mut self, share: u32) -> &mut OpenOptions {
                self.as_inner_mut().share_mode(share);
                self
            }

            /// Sets extra flags for the `dwFileFlags` argument to the call to
            /// [`CreateFile2`] to the specified value (or combines it with
            /// `attributes` and `security_qos_flags` to set the `dwFlagsAndAttributes`
            /// for [`CreateFile`]).
            ///
            /// Custom flags can only set flags, not remove flags set by Rust's options.
            /// This option overwrites any previously set custom flags.
            ///
            /// # Examples
            ///
            /// ```no_run
            /// use winapi::um::winbase::FILE_FLAG_DELETE_ON_CLOSE;
            /// use tokio::fs::OpenOptions;
            ///
            /// # #[tokio::main]
            /// # async fn main() -> std::io::Result<()> {
            /// let file = OpenOptions::new()
            ///     .create(true)
            ///     .write(true)
            ///     .custom_flags(FILE_FLAG_DELETE_ON_CLOSE)
            ///     .open("foo.txt").await?;
            /// # Ok(())
            /// # }
            /// ```
            ///
            /// [`CreateFile`]: https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea
            /// [`CreateFile2`]: https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfile2
            pub fn custom_flags(&mut self, flags: u32) -> &mut OpenOptions {
                self.as_inner_mut().custom_flags(flags);
                self
            }

            /// Sets the `dwFileAttributes` argument to the call to [`CreateFile2`] to
            /// the specified value (or combines it with `custom_flags` and
            /// `security_qos_flags` to set the `dwFlagsAndAttributes` for
            /// [`CreateFile`]).
            ///
            /// If a _new_ file is created because it does not yet exist and
            /// `.create(true)` or `.create_new(true)` are specified, the new file is
            /// given the attributes declared with `.attributes()`.
            ///
            /// If an _existing_ file is opened with `.create(true).truncate(true)`, its
            /// existing attributes are preserved and combined with the ones declared
            /// with `.attributes()`.
            ///
            /// In all other cases the attributes get ignored.
            ///
            /// # Examples
            ///
            /// ```no_run
            /// use winapi::um::winnt::FILE_ATTRIBUTE_HIDDEN;
            /// use tokio::fs::OpenOptions;
            ///
            /// # #[tokio::main]
            /// # async fn main() -> std::io::Result<()> {
            /// let file = OpenOptions::new()
            ///     .write(true)
            ///     .create(true)
            ///     .attributes(FILE_ATTRIBUTE_HIDDEN)
            ///     .open("foo.txt").await?;
            /// # Ok(())
            /// # }
            /// ```
            ///
            /// [`CreateFile`]: https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea
            /// [`CreateFile2`]: https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfile2
            pub fn attributes(&mut self, attributes: u32) -> &mut OpenOptions {
                self.as_inner_mut().attributes(attributes);
                self
            }

            /// Sets the `dwSecurityQosFlags` argument to the call to [`CreateFile2`] to
            /// the specified value (or combines it with `custom_flags` and `attributes`
            /// to set the `dwFlagsAndAttributes` for [`CreateFile`]).
            ///
            /// By default `security_qos_flags` is not set. It should be specified when
            /// opening a named pipe, to control to which degree a server process can
            /// act on behalf of a client process (security impersonation level).
            ///
            /// When `security_qos_flags` is not set, a malicious program can gain the
            /// elevated privileges of a privileged Rust process when it allows opening
            /// user-specified paths, by tricking it into opening a named pipe. So
            /// arguably `security_qos_flags` should also be set when opening arbitrary
            /// paths. However the bits can then conflict with other flags, specifically
            /// `FILE_FLAG_OPEN_NO_RECALL`.
            ///
            /// For information about possible values, see [Impersonation Levels] on the
            /// Windows Dev Center site. The `SECURITY_SQOS_PRESENT` flag is set
            /// automatically when using this method.
            ///
            /// # Examples
            ///
            /// ```no_run
            /// use winapi::um::winbase::SECURITY_IDENTIFICATION;
            /// use tokio::fs::OpenOptions;
            ///
            /// # #[tokio::main]
            /// # async fn main() -> std::io::Result<()> {
            /// let file = OpenOptions::new()
            ///     .write(true)
            ///     .create(true)
            ///
            ///     // Sets the flag value to `SecurityIdentification`.
            ///     .security_qos_flags(SECURITY_IDENTIFICATION)
            ///
            ///     .open(r"\\.\pipe\MyPipe").await?;
            /// # Ok(())
            /// # }
            /// ```
            ///
            /// [`CreateFile`]: https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea
            /// [`CreateFile2`]: https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfile2
            /// [Impersonation Levels]:
            ///     https://docs.microsoft.com/en-us/windows/win32/api/winnt/ne-winnt-security_impersonation_level
            pub fn security_qos_flags(&mut self, flags: u32) -> &mut OpenOptions {
                self.as_inner_mut().security_qos_flags(flags);
                self
            }
        }
    }

    impl From<std::fs::OpenOptions> for OpenOptions {
        fn from(options: std::fs::OpenOptions) -> OpenOptions {
            OpenOptions(options)
        }
    }

    impl Default for OpenOptions {
        fn default() -> Self {
            Self::new()
        }
    }