#![cfg(any(target_os = "linux", target_os = "dragonfly", target_os = "freebsd", target_os = "netbsd", target_os = "openbsd"))]

use std::collections::VecDeque;
use std::{env, mem, fmt};
use std::ffi::CStr;
use std::os::raw::*;
use std::sync::Arc;

use parking_lot::Mutex;
use smithay_client_toolkit::reexports::client::ConnectError;

use crate::dpi::{LogicalPosition, LogicalSize, PhysicalPosition, PhysicalSize};
use crate::icon::Icon;
use crate::error::{ExternalError, NotSupportedError, OsError as RootOsError};
use crate::event::Event;
use crate::event_loop::{EventLoopClosed, ControlFlow, EventLoopWindowTarget as RootELW};
use crate::monitor::{MonitorHandle as RootMonitorHandle, VideoMode};
use crate::window::{WindowAttributes, CursorIcon};
use self::x11::{XConnection, XError};
use self::x11::ffi::XVisualInfo;
pub use self::x11::XNotSupported;

mod dlopen;
pub mod wayland;
pub mod x11;

/// Environment variable specifying which backend should be used on unix platform.
///
/// Legal values are x11 and wayland. If this variable is set only the named backend
/// will be tried by winit. If it is not set, winit will try to connect to a wayland connection,
/// and if it fails will fallback on x11.
///
/// If this variable is set with any other value, winit will panic.
const BACKEND_PREFERENCE_ENV_VAR: &str = "WINIT_UNIX_BACKEND";

#[derive(Clone, Default)]
pub struct PlatformSpecificWindowBuilderAttributes {
    pub visual_infos: Option<XVisualInfo>,
    pub screen_id: Option<i32>,
    pub resize_increments: Option<(u32, u32)>,
    pub base_size: Option<(u32, u32)>,
    pub class: Option<(String, String)>,
    pub override_redirect: bool,
    pub x11_window_type: x11::util::WindowType,
    pub gtk_theme_variant: Option<String>,
    pub app_id: Option<String>
}

lazy_static!(
    pub static ref X11_BACKEND: Mutex<Result<Arc<XConnection>, XNotSupported>> = {
        Mutex::new(XConnection::new(Some(x_error_callback)).map(Arc::new))
    };
);

#[derive(Debug, Clone)]
pub enum OsError {
    XError(XError),
    XMisc(&'static str),
}

impl fmt::Display for OsError {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
        match self {
            OsError::XError(e) => formatter.pad(&e.description),
            OsError::XMisc(e) => formatter.pad(e),
        }
    }
}

pub enum Window {
    X(x11::Window),
    Wayland(wayland::Window),
}

#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub enum WindowId {
    X(x11::WindowId),
    Wayland(wayland::WindowId),
}

impl WindowId {
    pub unsafe fn dummy() -> Self {
        WindowId::Wayland(wayland::WindowId::dummy())
    }
}

#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub enum DeviceId {
    X(x11::DeviceId),
    Wayland(wayland::DeviceId),
}

impl DeviceId {
    pub unsafe fn dummy() -> Self {
        DeviceId::Wayland(wayland::DeviceId::dummy())
    }
}

#[derive(Debug, Clone)]
pub enum MonitorHandle {
    X(x11::MonitorHandle),
    Wayland(wayland::MonitorHandle),
}

impl MonitorHandle {
    #[inline]
    pub fn name(&self) -> Option<String> {
        match self {
            &MonitorHandle::X(ref m) => m.name(),
            &MonitorHandle::Wayland(ref m) => m.name(),
        }
    }

    #[inline]
    pub fn native_identifier(&self) -> u32 {
        match self {
            &MonitorHandle::X(ref m) => m.native_identifier(),
            &MonitorHandle::Wayland(ref m) => m.native_identifier(),
        }
    }

    #[inline]
    pub fn size(&self) -> PhysicalSize {
        match self {
            &MonitorHandle::X(ref m) => m.size(),
            &MonitorHandle::Wayland(ref m) => m.size(),
        }
    }

    #[inline]
    pub fn position(&self) -> PhysicalPosition {
        match self {
            &MonitorHandle::X(ref m) => m.position(),
            &MonitorHandle::Wayland(ref m) => m.position(),
        }
    }

    #[inline]
    pub fn hidpi_factor(&self) -> f64 {
        match self {
            &MonitorHandle::X(ref m) => m.hidpi_factor(),
            &MonitorHandle::Wayland(ref m) => m.hidpi_factor() as f64,
        }
    }

    #[inline]
    pub fn video_modes(&self) -> Box<dyn Iterator<Item = VideoMode>> {
        match self {
            MonitorHandle::X(m) => Box::new(m.video_modes()),
            MonitorHandle::Wayland(m) => Box::new(m.video_modes()),
        }
    }
}

impl Window {
    #[inline]
    pub fn new<T>(
        window_target: &EventLoopWindowTarget<T>,
        attribs: WindowAttributes,
        pl_attribs: PlatformSpecificWindowBuilderAttributes,
    ) -> Result<Self, RootOsError> {
        match *window_target {
            EventLoopWindowTarget::Wayland(ref window_target) => {
                wayland::Window::new(window_target, attribs, pl_attribs).map(Window::Wayland)
            },
            EventLoopWindowTarget::X(ref window_target) => {
                x11::Window::new(window_target, attribs, pl_attribs).map(Window::X)
            },
        }
    }

    #[inline]
    pub fn id(&self) -> WindowId {
        match self {
            &Window::X(ref w) => WindowId::X(w.id()),
            &Window::Wayland(ref w) => WindowId::Wayland(w.id()),
        }
    }

    #[inline]
    pub fn set_title(&self, title: &str) {
        match self {
            &Window::X(ref w) => w.set_title(title),
            &Window::Wayland(ref w) => w.set_title(title),
        }
    }

    #[inline]
    pub fn set_visible(&self, visible: bool) {
        match self {
            &Window::X(ref w) => w.set_visible(visible),
            &Window::Wayland(ref w) => w.set_visible(visible),
        }
    }

    #[inline]
    pub fn outer_position(&self) -> Result<LogicalPosition, NotSupportedError> {
        match self {
            &Window::X(ref w) => w.outer_position(),
            &Window::Wayland(ref w) => w.outer_position(),
        }
    }

    #[inline]
    pub fn inner_position(&self) -> Result<LogicalPosition, NotSupportedError> {
        match self {
            &Window::X(ref m) => m.inner_position(),
            &Window::Wayland(ref m) => m.inner_position(),
        }
    }

    #[inline]
    pub fn set_outer_position(&self, position: LogicalPosition) {
        match self {
            &Window::X(ref w) => w.set_outer_position(position),
            &Window::Wayland(ref w) => w.set_outer_position(position),
        }
    }

    #[inline]
    pub fn inner_size(&self) -> LogicalSize {
        match self {
            &Window::X(ref w) => w.inner_size(),
            &Window::Wayland(ref w) => w.inner_size(),
        }
    }

    #[inline]
    pub fn outer_size(&self) -> LogicalSize {
        match self {
            &Window::X(ref w) => w.outer_size(),
            &Window::Wayland(ref w) => w.outer_size(),
        }
    }

    #[inline]
    pub fn set_inner_size(&self, size: LogicalSize) {
        match self {
            &Window::X(ref w) => w.set_inner_size(size),
            &Window::Wayland(ref w) => w.set_inner_size(size),
        }
    }

    #[inline]
    pub fn set_min_inner_size(&self, dimensions: Option<LogicalSize>) {
        match self {
            &Window::X(ref w) => w.set_min_inner_size(dimensions),
            &Window::Wayland(ref w) => w.set_min_inner_size(dimensions),
        }
    }

    #[inline]
    pub fn set_max_inner_size(&self, dimensions: Option<LogicalSize>) {
        match self {
            &Window::X(ref w) => w.set_max_inner_size(dimensions),
            &Window::Wayland(ref w) => w.set_max_inner_size(dimensions),
        }
    }

    #[inline]
    pub fn set_resizable(&self, resizable: bool) {
        match self {
            &Window::X(ref w) => w.set_resizable(resizable),
            &Window::Wayland(ref w) => w.set_resizable(resizable),
        }
    }

    #[inline]
    pub fn set_cursor_icon(&self, cursor: CursorIcon) {
        match self {
            &Window::X(ref w) => w.set_cursor_icon(cursor),
            &Window::Wayland(ref w) => w.set_cursor_icon(cursor)
        }
    }

    #[inline]
    pub fn set_cursor_grab(&self, grab: bool) -> Result<(), ExternalError> {
        match self {
            &Window::X(ref window) => window.set_cursor_grab(grab),
            &Window::Wayland(ref window) => window.set_cursor_grab(grab),
        }
    }

    #[inline]
    pub fn set_cursor_visible(&self, visible: bool) {
        match self {
            &Window::X(ref window) => window.set_cursor_visible(visible),
            &Window::Wayland(ref window) => window.set_cursor_visible(visible),
        }
    }

    #[inline]
    pub fn hidpi_factor(&self) -> f64 {
       match self {
            &Window::X(ref w) => w.hidpi_factor(),
            &Window::Wayland(ref w) => w.hidpi_factor() as f64,
        }
    }

    #[inline]
    pub fn set_cursor_position(&self, position: LogicalPosition) -> Result<(), ExternalError> {
        match self {
            &Window::X(ref w) => w.set_cursor_position(position),
            &Window::Wayland(ref w) => w.set_cursor_position(position),
        }
    }

    #[inline]
    pub fn set_maximized(&self, maximized: bool) {
        match self {
            &Window::X(ref w) => w.set_maximized(maximized),
            &Window::Wayland(ref w) => w.set_maximized(maximized),
        }
    }

    #[inline]
    pub fn fullscreen(&self) -> Option<RootMonitorHandle> {
        match self {
            &Window::X(ref w) => w.fullscreen(),
            &Window::Wayland(ref w) => w.fullscreen()
                .map(|monitor_id| RootMonitorHandle { inner: MonitorHandle::Wayland(monitor_id) })
        }
    }

    #[inline]
    pub fn set_fullscreen(&self, monitor: Option<RootMonitorHandle>) {
        match self {
            &Window::X(ref w) => w.set_fullscreen(monitor),
            &Window::Wayland(ref w) => w.set_fullscreen(monitor)
        }
    }

    #[inline]
    pub fn set_decorations(&self, decorations: bool) {
        match self {
            &Window::X(ref w) => w.set_decorations(decorations),
            &Window::Wayland(ref w) => w.set_decorations(decorations)
        }
    }

    #[inline]
    pub fn set_always_on_top(&self, always_on_top: bool) {
        match self {
            &Window::X(ref w) => w.set_always_on_top(always_on_top),
            &Window::Wayland(_) => (),
        }
    }

    #[inline]
    pub fn set_window_icon(&self, window_icon: Option<Icon>) {
        match self {
            &Window::X(ref w) => w.set_window_icon(window_icon),
            &Window::Wayland(_) => (),
        }
    }

    #[inline]
    pub fn set_ime_position(&self, position: LogicalPosition) {
        match self {
            &Window::X(ref w) => w.set_ime_position(position),
            &Window::Wayland(_) => (),
        }
    }

    #[inline]
    pub fn request_redraw(&self) {
        match self {
            &Window::X(ref w) => w.request_redraw(),
            &Window::Wayland(ref w) => w.request_redraw(),
        }
    }

    #[inline]
    pub fn current_monitor(&self) -> RootMonitorHandle {
        match self {
            &Window::X(ref window) => RootMonitorHandle { inner: MonitorHandle::X(window.current_monitor()) },
            &Window::Wayland(ref window) => RootMonitorHandle { inner: MonitorHandle::Wayland(window.current_monitor()) },
        }
    }

    #[inline]
    pub fn available_monitors(&self) -> VecDeque<MonitorHandle> {
        match self {
            &Window::X(ref window) => window.available_monitors()
                .into_iter()
                .map(MonitorHandle::X)
                .collect(),
            &Window::Wayland(ref window) => window.available_monitors()
                .into_iter()
                .map(MonitorHandle::Wayland)
                .collect(),
        }
    }

    #[inline]
    pub fn primary_monitor(&self) -> MonitorHandle {
        match self {
            &Window::X(ref window) => MonitorHandle::X(window.primary_monitor()),
            &Window::Wayland(ref window) => MonitorHandle::Wayland(window.primary_monitor()),
        }
    }
}


unsafe extern "C" fn x_error_callback(
    display: *mut x11::ffi::Display,
    event: *mut x11::ffi::XErrorEvent,
) -> c_int {
    let xconn_lock = X11_BACKEND.lock();
    if let Ok(ref xconn) = *xconn_lock {
        let mut buf: [c_char; 1024] = mem::uninitialized();
        (xconn.xlib.XGetErrorText)(
            display,
            (*event).error_code as c_int,
            buf.as_mut_ptr(),
            buf.len() as c_int,
        );
        let description = CStr::from_ptr(buf.as_ptr()).to_string_lossy();

        let error = XError {
            description: description.into_owned(),
            error_code: (*event).error_code,
            request_code: (*event).request_code,
            minor_code: (*event).minor_code,
        };

        error!("X11 error: {:#?}", error);

        *xconn.latest_error.lock() = Some(error);
    }
    // Fun fact: this return value is completely ignored.
    0
}


pub enum EventLoop<T: 'static> {
    Wayland(wayland::EventLoop<T>),
    X(x11::EventLoop<T>)
}

#[derive(Clone)]
pub enum EventLoopProxy<T: 'static> {
    X(x11::EventLoopProxy<T>),
    Wayland(wayland::EventLoopProxy<T>),
}

impl<T:'static> EventLoop<T> {
    pub fn new() -> EventLoop<T> {
        if let Ok(env_var) = env::var(BACKEND_PREFERENCE_ENV_VAR) {
            match env_var.as_str() {
                "x11" => {
                    // TODO: propagate
                    return EventLoop::new_x11().expect("Failed to initialize X11 backend");
                },
                "wayland" => {
                    return EventLoop::new_wayland()
                        .expect("Failed to initialize Wayland backend");
                },
                _ => panic!(
                    "Unknown environment variable value for {}, try one of `x11`,`wayland`",
                    BACKEND_PREFERENCE_ENV_VAR,
                ),
            }
        }

        let wayland_err = match EventLoop::new_wayland() {
            Ok(event_loop) => return event_loop,
            Err(err) => err,
        };

        let x11_err = match EventLoop::new_x11() {
            Ok(event_loop) => return event_loop,
            Err(err) => err,
        };

        let err_string = format!(
            "Failed to initialize any backend! Wayland status: {:?} X11 status: {:?}",
            wayland_err,
            x11_err,
        );
        panic!(err_string);
    }

    pub fn new_wayland() -> Result<EventLoop<T>, ConnectError> {
        wayland::EventLoop::new()
            .map(EventLoop::Wayland)
    }

    pub fn new_x11() -> Result<EventLoop<T>, XNotSupported> {
        X11_BACKEND
            .lock()
            .as_ref()
            .map(Arc::clone)
            .map(x11::EventLoop::new)
            .map(EventLoop::X)
            .map_err(|err| err.clone())
    }

    #[inline]
    pub fn available_monitors(&self) -> VecDeque<MonitorHandle> {
        match *self {
            EventLoop::Wayland(ref evlp) => evlp
                .available_monitors()
                .into_iter()
                .map(MonitorHandle::Wayland)
                .collect(),
            EventLoop::X(ref evlp) => evlp
                .x_connection()
                .available_monitors()
                .into_iter()
                .map(MonitorHandle::X)
                .collect(),
        }
    }

    #[inline]
    pub fn primary_monitor(&self) -> MonitorHandle {
        match *self {
            EventLoop::Wayland(ref evlp) => MonitorHandle::Wayland(evlp.primary_monitor()),
            EventLoop::X(ref evlp) => MonitorHandle::X(evlp.x_connection().primary_monitor()),
        }
    }

    pub fn create_proxy(&self) -> EventLoopProxy<T> {
        match *self {
            EventLoop::Wayland(ref evlp) => EventLoopProxy::Wayland(evlp.create_proxy()),
            EventLoop::X(ref evlp) => EventLoopProxy::X(evlp.create_proxy()),
        }
    }

    pub fn run_return<F>(&mut self, callback: F)
        where F: FnMut(crate::event::Event<T>, &RootELW<T>, &mut ControlFlow)
    {
        match *self {
            EventLoop::Wayland(ref mut evlp) => evlp.run_return(callback),
            EventLoop::X(ref mut evlp) => evlp.run_return(callback)
        }
    }

    pub fn run<F>(self, callback: F) -> !
        where F: 'static + FnMut(crate::event::Event<T>, &RootELW<T>, &mut ControlFlow)
    {
        match self {
            EventLoop::Wayland(evlp) => evlp.run(callback),
            EventLoop::X(evlp) => evlp.run(callback)
        }
    }

    #[inline]
    pub fn is_wayland(&self) -> bool {
        match *self {
            EventLoop::Wayland(_) => true,
            EventLoop::X(_) => false,
        }
    }

    pub fn window_target(&self) -> &crate::event_loop::EventLoopWindowTarget<T> {
        match *self {
            EventLoop::Wayland(ref evl) => evl.window_target(),
            EventLoop::X(ref evl) => evl.window_target()
        }
    }
}

impl<T: 'static> EventLoopProxy<T> {
    pub fn send_event(&self, event: T) -> Result<(), EventLoopClosed> {
        match *self {
            EventLoopProxy::Wayland(ref proxy) => proxy.send_event(event),
            EventLoopProxy::X(ref proxy) => proxy.send_event(event),
        }
    }
}

pub enum EventLoopWindowTarget<T> {
    Wayland(wayland::EventLoopWindowTarget<T>),
    X(x11::EventLoopWindowTarget<T>)
}

fn sticky_exit_callback<T, F>(
    evt: Event<T>, target: &RootELW<T>, control_flow: &mut ControlFlow, callback: &mut F
) where F: FnMut(Event<T>, &RootELW<T>, &mut ControlFlow)
{
    // make ControlFlow::Exit sticky by providing a dummy
    // control flow reference if it is already Exit.
    let mut dummy = ControlFlow::Exit;
    let cf = if *control_flow == ControlFlow::Exit {
        &mut dummy
    } else {
        control_flow
    };
    // user callback
    callback(evt, target, cf)
}