use super::super::imports::*;
use std::{convert::TryFrom, mem};

/// The direction of a named pipe connection, designating who can read data and who can write it. This describes the direction of the data flow unambiguously, so that the meaning of the values is the same for the client and server – [`ClientToServer`] always means client → server, for example.
///
/// [`ClientToServer`]: enum.PipeDirection.html#variant.ClientToServer " "
// I had to type out both the link to the page and the name of the variant since the link can be clicked from module-level documentation so please don't touch it.
#[repr(u32)]
// We depend on the fact that DWORD always maps to u32, which, thankfully, will always stay true
// since the public WinAPI is supposed to be ABI-compatible. Just keep in mind that the
// #[repr(u32)] means that we can transmute this enumeration to the Windows DWORD type.
#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
pub enum PipeDirection {
    /// Represents a server ← client data flow: clients write data, the server reads it.
    ClientToServer = PIPE_ACCESS_INBOUND,
    /// Represents a server → client data flow: the server writes data, clients read it.
    ServerToClient = PIPE_ACCESS_OUTBOUND,
    /// Represents a server ⇄ client data flow: the server can write data which then is read by the client, while the client writes data which is read by the server.
    Duplex = PIPE_ACCESS_DUPLEX,
}
impl PipeDirection {
    /// Returns the role which the pipe client will have in this direction setting.
    ///
    /// # Usage
    /// ```
    /// # #[cfg(windows)] {
    /// # use interprocess::os::windows::named_pipe::{PipeDirection, PipeStreamRole};
    /// assert_eq!(
    ///     PipeDirection::ClientToServer.client_role(),
    ///     PipeStreamRole::Writer,
    /// );
    /// assert_eq!(
    ///     PipeDirection::ServerToClient.client_role(),
    ///     PipeStreamRole::Reader,
    /// );
    /// assert_eq!(
    ///     PipeDirection::Duplex.client_role(),
    ///     PipeStreamRole::ReaderAndWriter,
    /// );
    /// # }
    /// ```
    pub const fn client_role(self) -> PipeStreamRole {
        match self {
            Self::ClientToServer => PipeStreamRole::Writer,
            Self::ServerToClient => PipeStreamRole::Reader,
            Self::Duplex => PipeStreamRole::ReaderAndWriter,
        }
    }
    /// Returns the role which the pipe server will have in this direction setting.
    ///
    /// # Usage
    /// ```
    /// # #[cfg(windows)] {
    /// # use interprocess::os::windows::named_pipe::{PipeDirection, PipeStreamRole};
    /// assert_eq!(
    ///     PipeDirection::ClientToServer.server_role(),
    ///     PipeStreamRole::Reader,
    /// );
    /// assert_eq!(
    ///     PipeDirection::ServerToClient.server_role(),
    ///     PipeStreamRole::Writer,
    /// );
    /// assert_eq!(
    ///     PipeDirection::Duplex.server_role(),
    ///     PipeStreamRole::ReaderAndWriter,
    /// );
    /// # }
    /// ```
    pub const fn server_role(self) -> PipeStreamRole {
        match self {
            Self::ClientToServer => PipeStreamRole::Reader,
            Self::ServerToClient => PipeStreamRole::Writer,
            Self::Duplex => PipeStreamRole::ReaderAndWriter,
        }
    }
}
impl TryFrom<DWORD> for PipeDirection {
    type Error = ();
    /// Converts a Windows constant to a `PipeDirection` if it's in range.
    ///
    /// # Errors
    /// Returns `Err` if the value is not a valid pipe direction constant.
    fn try_from(op: DWORD) -> Result<Self, ()> {
        assert!((1..=3).contains(&op));
        // See the comment block above for why this is safe.
        unsafe { mem::transmute(op) }
    }
}
impl From<PipeDirection> for DWORD {
    fn from(op: PipeDirection) -> Self {
        unsafe { mem::transmute(op) }
    }
}
/// Describes the role of a named pipe stream. In constrast to [`PipeDirection`], the meaning of values here is relative – for example, [`Reader`] means [`ServerToClient`] if you're creating a server and [`ClientToServer`] if you're creating a client.
///
/// This enumeration is also not layout-compatible with the `PIPE_ACCESS_*` constants, in contrast to [`PipeDirection`].
///
/// [`PipeDirection`]: enum.PipeDirection.html " "
/// [`Reader`]: #variant.Reader " "
/// [`ServerToClient`]: enum.PipeDirection.html#variant.ServerToClient " "
/// [`ClientToServer`]: enum.PipeDirection.html#variant.ClientToServer " "
#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
#[repr(u32)]
pub enum PipeStreamRole {
    /// The stream only reads data.
    Reader,
    /// The stream only writes data.
    Writer,
    /// The stream both reads and writes data.
    ReaderAndWriter,
}
impl PipeStreamRole {
    /// Returns the data flow direction of the data stream, assuming that the value describes the role of the server.
    ///
    /// # Usage
    /// ```
    /// # #[cfg(windows)] {
    /// # use interprocess::os::windows::named_pipe::{PipeDirection, PipeStreamRole};
    /// assert_eq!(
    ///     PipeStreamRole::Reader.direction_as_server(),
    ///     PipeDirection::ClientToServer,
    /// );
    /// assert_eq!(
    ///     PipeStreamRole::Writer.direction_as_server(),
    ///     PipeDirection::ServerToClient,
    /// );
    /// assert_eq!(
    ///     PipeStreamRole::ReaderAndWriter.direction_as_server(),
    ///     PipeDirection::Duplex,
    /// );
    /// # }
    /// ```
    pub const fn direction_as_server(self) -> PipeDirection {
        match self {
            Self::Reader => PipeDirection::ClientToServer,
            Self::Writer => PipeDirection::ServerToClient,
            Self::ReaderAndWriter => PipeDirection::Duplex,
        }
    }
    /// Returns the data flow direction of the data stream, assuming that the value describes the role of the client.
    ///
    /// # Usage
    /// ```
    /// # #[cfg(windows)] {
    /// # use interprocess::os::windows::named_pipe::{PipeDirection, PipeStreamRole};
    /// assert_eq!(
    ///     PipeStreamRole::Reader.direction_as_client(),
    ///     PipeDirection::ServerToClient,
    /// );
    /// assert_eq!(
    ///     PipeStreamRole::Writer.direction_as_client(),
    ///     PipeDirection::ClientToServer,
    /// );
    /// assert_eq!(
    ///     PipeStreamRole::ReaderAndWriter.direction_as_client(),
    ///     PipeDirection::Duplex,
    /// );
    /// # }
    /// ```
    pub const fn direction_as_client(self) -> PipeDirection {
        match self {
            Self::Reader => PipeDirection::ServerToClient,
            Self::Writer => PipeDirection::ClientToServer,
            Self::ReaderAndWriter => PipeDirection::Duplex,
        }
    }
}

/// Specifies the mode for a pipe stream.
#[repr(u32)]
#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
pub enum PipeMode {
    /// Designates that the pipe stream works in byte stream mode, erasing the boundaries of separate messages.
    Bytes = PIPE_TYPE_BYTE,
    /// Designates that the pipe stream works in message stream mode, preserving the boundaries of separate messages yet still allowing to read them in byte stream mode.
    Messages = PIPE_TYPE_MESSAGE,
}
impl PipeMode {
    /// Converts the value into a raw `DWORD`-typed constant, either `PIPE_TYPE_BYTE` or `PIPE_TYPE_MESSAGE` depending on the value.
    pub const fn to_pipe_type(self) -> DWORD {
        self as _
    }
    /// Converts the value into a raw `DWORD`-typed constant, either `PIPE_READMODE_BYTE` or `PIPE_READMODE_MESSAGE` depending on the value.
    pub const fn to_readmode(self) -> DWORD {
        match self {
            Self::Bytes => PIPE_READMODE_BYTE,
            Self::Messages => PIPE_READMODE_MESSAGE,
        }
    }
}
impl TryFrom<DWORD> for PipeMode {
    type Error = ();
    /// Converts a Windows constant to a `PipeMode` if it's in range. Both `PIPE_TYPE_*` and `PIPE_READMODE_*` are supported.
    ///
    /// # Errors
    /// Returns `Err` if the value is not a valid pipe stream mode constant.
    fn try_from(op: DWORD) -> Result<Self, ()> {
        // It's nicer to only match than to check and transmute
        #[allow(unreachable_patterns)] // PIPE_READMODE_BYTE and PIPE_TYPE_BYTE are equal
        match op {
            PIPE_TYPE_BYTE | PIPE_READMODE_BYTE => Ok(Self::Bytes),
            PIPE_READMODE_MESSAGE | PIPE_TYPE_MESSAGE => Ok(Self::Messages),
            _ => Err(()),
        }
    }
}