use crate::{
    executor,
    geometry::vector::Vector2F,
    platform::{self, Event, WindowContext},
    Scene,
};
use anyhow::{anyhow, Result};
use cocoa::{
    appkit::{
        NSBackingStoreBuffered, NSScreen, NSView, NSViewHeightSizable, NSViewWidthSizable,
        NSWindow, NSWindowStyleMask,
    },
    base::{id, nil},
    foundation::{NSAutoreleasePool, NSInteger, NSSize, NSString},
    quartzcore::AutoresizingMask,
};
use ctor::ctor;
use foreign_types::ForeignType as _;
use metal::{MTLClearColor, MTLLoadAction, MTLStoreAction};
use objc::{
    class,
    declare::ClassDecl,
    msg_send,
    runtime::{Class, Object, Protocol, Sel, BOOL, NO, YES},
    sel, sel_impl,
};
use pathfinder_geometry::vector::vec2f;
use smol::Timer;
use std::{
    cell::RefCell,
    ffi::c_void,
    mem, ptr,
    rc::{Rc, Weak},
    time::Duration,
};

use super::{geometry::RectFExt, renderer::Renderer};

const WINDOW_STATE_IVAR: &'static str = "windowState";

static mut WINDOW_CLASS: *const Class = ptr::null();
static mut VIEW_CLASS: *const Class = ptr::null();

#[allow(non_upper_case_globals)]
const NSViewLayerContentsRedrawDuringViewResize: NSInteger = 2;

#[ctor]
unsafe fn build_classes() {
    WINDOW_CLASS = {
        let mut decl = ClassDecl::new("GPUIWindow", class!(NSWindow)).unwrap();
        decl.add_ivar::<*mut c_void>(WINDOW_STATE_IVAR);
        decl.add_method(sel!(dealloc), dealloc_window as extern "C" fn(&Object, Sel));
        decl.add_method(
            sel!(canBecomeMainWindow),
            yes as extern "C" fn(&Object, Sel) -> BOOL,
        );
        decl.add_method(
            sel!(canBecomeKeyWindow),
            yes as extern "C" fn(&Object, Sel) -> BOOL,
        );
        decl.add_method(
            sel!(sendEvent:),
            send_event as extern "C" fn(&Object, Sel, id),
        );
        decl.register()
    };

    VIEW_CLASS = {
        let mut decl = ClassDecl::new("GPUIView", class!(NSView)).unwrap();
        decl.add_ivar::<*mut c_void>(WINDOW_STATE_IVAR);

        decl.add_method(sel!(dealloc), dealloc_view as extern "C" fn(&Object, Sel));

        decl.add_method(
            sel!(keyDown:),
            handle_view_event as extern "C" fn(&Object, Sel, id),
        );
        decl.add_method(
            sel!(mouseDown:),
            handle_view_event as extern "C" fn(&Object, Sel, id),
        );
        decl.add_method(
            sel!(mouseUp:),
            handle_view_event as extern "C" fn(&Object, Sel, id),
        );
        decl.add_method(
            sel!(mouseDragged:),
            handle_view_event as extern "C" fn(&Object, Sel, id),
        );
        decl.add_method(
            sel!(scrollWheel:),
            handle_view_event as extern "C" fn(&Object, Sel, id),
        );

        decl.add_method(
            sel!(makeBackingLayer),
            make_backing_layer as extern "C" fn(&Object, Sel) -> id,
        );

        decl.add_protocol(Protocol::get("CALayerDelegate").unwrap());
        decl.add_method(
            sel!(viewDidChangeBackingProperties),
            view_did_change_backing_properties as extern "C" fn(&Object, Sel),
        );
        decl.add_method(
            sel!(setFrameSize:),
            set_frame_size as extern "C" fn(&Object, Sel, NSSize),
        );
        decl.add_method(
            sel!(displayLayer:),
            display_layer as extern "C" fn(&Object, Sel, id),
        );

        decl.register()
    };
}

pub struct Window(Rc<RefCell<WindowState>>);

struct WindowState {
    native_window: id,
    event_callback: Option<Box<dyn FnMut(Event)>>,
    resize_callback: Option<Box<dyn FnMut(&mut dyn platform::WindowContext)>>,
    synthetic_drag_counter: usize,
    executor: Rc<executor::Foreground>,
    scene_to_render: Option<Scene>,
    renderer: Renderer,
    command_queue: metal::CommandQueue,
    device: metal::Device,
    layer: id,
}

pub struct RenderContext<'a> {
    pub drawable_size: Vector2F,
    pub device: &'a metal::Device,
    pub command_encoder: &'a metal::RenderCommandEncoderRef,
}

impl Window {
    pub fn open(
        options: platform::WindowOptions,
        executor: Rc<executor::Foreground>,
    ) -> Result<Self> {
        const PIXEL_FORMAT: metal::MTLPixelFormat = metal::MTLPixelFormat::BGRA8Unorm;

        unsafe {
            let pool = NSAutoreleasePool::new(nil);

            let frame = options.bounds.to_ns_rect();
            let style_mask = NSWindowStyleMask::NSClosableWindowMask
                | NSWindowStyleMask::NSMiniaturizableWindowMask
                | NSWindowStyleMask::NSResizableWindowMask
                | NSWindowStyleMask::NSTitledWindowMask;

            let native_window: id = msg_send![WINDOW_CLASS, alloc];
            let native_window = native_window.initWithContentRect_styleMask_backing_defer_(
                frame,
                style_mask,
                NSBackingStoreBuffered,
                NO,
            );

            if native_window == nil {
                return Err(anyhow!("window returned nil from initializer"));
            }

            let device = metal::Device::system_default()
                .ok_or_else(|| anyhow!("could not find default metal device"))?;

            let layer: id = msg_send![class!(CAMetalLayer), layer];
            let _: () = msg_send![layer, setDevice: device.as_ptr()];
            let _: () = msg_send![layer, setPixelFormat: PIXEL_FORMAT];
            let _: () = msg_send![layer, setAllowsNextDrawableTimeout: NO];
            let _: () = msg_send![layer, setNeedsDisplayOnBoundsChange: YES];
            let _: () = msg_send![layer, setPresentsWithTransaction: YES];
            let _: () = msg_send![
                layer,
                setAutoresizingMask: AutoresizingMask::WIDTH_SIZABLE
                    | AutoresizingMask::HEIGHT_SIZABLE
            ];

            let native_view: id = msg_send![VIEW_CLASS, alloc];
            let native_view = NSView::init(native_view);
            if native_view == nil {
                return Err(anyhow!("view return nil from initializer"));
            }

            let window = Self(Rc::new(RefCell::new(WindowState {
                native_window,
                event_callback: None,
                resize_callback: None,
                synthetic_drag_counter: 0,
                executor,
                scene_to_render: Default::default(),
                renderer: Renderer::new(&device, PIXEL_FORMAT)?,
                command_queue: device.new_command_queue(),
                device,
                layer,
            })));

            (*native_window).set_ivar(
                WINDOW_STATE_IVAR,
                Rc::into_raw(window.0.clone()) as *const c_void,
            );
            (*native_view).set_ivar(
                WINDOW_STATE_IVAR,
                Rc::into_raw(window.0.clone()) as *const c_void,
            );

            if let Some(title) = options.title.as_ref() {
                native_window.setTitle_(NSString::alloc(nil).init_str(title));
            }
            native_window.setAcceptsMouseMovedEvents_(YES);

            native_view.setAutoresizingMask_(NSViewWidthSizable | NSViewHeightSizable);
            native_view.setWantsBestResolutionOpenGLSurface_(YES);

            // From winit crate: On Mojave, views automatically become layer-backed shortly after
            // being added to a native_window. Changing the layer-backedness of a view breaks the
            // association between the view and its associated OpenGL context. To work around this,
            // on we explicitly make the view layer-backed up front so that AppKit doesn't do it
            // itself and break the association with its context.
            native_view.setWantsLayer(YES);
            let _: () = msg_send![
                native_view,
                setLayerContentsRedrawPolicy: NSViewLayerContentsRedrawDuringViewResize
            ];

            native_window.setContentView_(native_view.autorelease());
            native_window.makeFirstResponder_(native_view);

            native_window.center();
            native_window.makeKeyAndOrderFront_(nil);

            pool.drain();

            Ok(window)
        }
    }

    pub fn zoom(&self) {
        unsafe {
            self.0.as_ref().borrow().native_window.performZoom_(nil);
        }
    }
}

impl Drop for Window {
    fn drop(&mut self) {
        unsafe {
            self.0.as_ref().borrow().native_window.close();
        }
    }
}

impl platform::Window for Window {
    fn on_event(&mut self, callback: Box<dyn FnMut(Event)>) {
        self.0.as_ref().borrow_mut().event_callback = Some(callback);
    }

    fn on_resize(&mut self, callback: Box<dyn FnMut(&mut dyn platform::WindowContext)>) {
        self.0.as_ref().borrow_mut().resize_callback = Some(callback);
    }
}

impl platform::WindowContext for Window {
    fn size(&self) -> Vector2F {
        self.0.as_ref().borrow().size()
    }

    fn scale_factor(&self) -> f32 {
        self.0.as_ref().borrow().scale_factor()
    }

    fn present_scene(&mut self, scene: Scene) {
        self.0.as_ref().borrow_mut().present_scene(scene);
    }
}

impl platform::WindowContext for WindowState {
    fn size(&self) -> Vector2F {
        let NSSize { width, height, .. } =
            unsafe { NSView::frame(self.native_window.contentView()) }.size;
        vec2f(width as f32, height as f32)
    }

    fn scale_factor(&self) -> f32 {
        unsafe {
            let screen: id = msg_send![self.native_window, screen];
            NSScreen::backingScaleFactor(screen) as f32
        }
    }

    fn present_scene(&mut self, scene: Scene) {
        self.scene_to_render = Some(scene);
        unsafe {
            let _: () = msg_send![self.native_window.contentView(), setNeedsDisplay: YES];
        }
    }
}

unsafe fn get_window_state(object: &Object) -> Rc<RefCell<WindowState>> {
    let raw: *mut c_void = *object.get_ivar(WINDOW_STATE_IVAR);
    let rc1 = Rc::from_raw(raw as *mut RefCell<WindowState>);
    let rc2 = rc1.clone();
    mem::forget(rc1);
    rc2
}

unsafe fn drop_window_state(object: &Object) {
    let raw: *mut c_void = *object.get_ivar(WINDOW_STATE_IVAR);
    Rc::from_raw(raw as *mut WindowState);
}

extern "C" fn yes(_: &Object, _: Sel) -> BOOL {
    YES
}

extern "C" fn dealloc_window(this: &Object, _: Sel) {
    unsafe {
        drop_window_state(this);
        let () = msg_send![super(this, class!(NSWindow)), dealloc];
    }
}

extern "C" fn dealloc_view(this: &Object, _: Sel) {
    unsafe {
        drop_window_state(this);
        let () = msg_send![super(this, class!(NSView)), dealloc];
    }
}

extern "C" fn handle_view_event(this: &Object, _: Sel, native_event: id) {
    let window_state = unsafe { get_window_state(this) };
    let weak_window_state = Rc::downgrade(&window_state);
    let mut window_state_borrow = window_state.as_ref().borrow_mut();

    let event = unsafe { Event::from_native(native_event, Some(window_state_borrow.size().y())) };

    if let Some(event) = event {
        match event {
            Event::LeftMouseDragged { position } => {
                window_state_borrow.synthetic_drag_counter += 1;
                window_state_borrow
                    .executor
                    .spawn(synthetic_drag(
                        weak_window_state,
                        window_state_borrow.synthetic_drag_counter,
                        position,
                    ))
                    .detach();
            }
            Event::LeftMouseUp { .. } => {
                window_state_borrow.synthetic_drag_counter += 1;
            }
            _ => {}
        }

        if let Some(mut callback) = window_state_borrow.event_callback.take() {
            drop(window_state_borrow);
            callback(event);
            window_state.borrow_mut().event_callback = Some(callback);
        }
    }
}

extern "C" fn send_event(this: &Object, _: Sel, native_event: id) {
    unsafe {
        let () = msg_send![super(this, class!(NSWindow)), sendEvent: native_event];
    }
}

extern "C" fn make_backing_layer(this: &Object, _: Sel) -> id {
    let window_state = unsafe { get_window_state(this) };
    let window_state = window_state.as_ref().borrow();
    window_state.layer
}

extern "C" fn view_did_change_backing_properties(this: &Object, _: Sel) {
    let window_state = unsafe { get_window_state(this) };
    let mut window_state = window_state.as_ref().borrow_mut();

    unsafe {
        let _: () =
            msg_send![window_state.layer, setContentsScale: window_state.scale_factor() as f64];
    }

    if let Some(mut callback) = window_state.resize_callback.take() {
        callback(&mut *window_state);
        window_state.resize_callback = Some(callback);
    };
}

extern "C" fn set_frame_size(this: &Object, _: Sel, size: NSSize) {
    let window_state = unsafe { get_window_state(this) };
    let mut window_state = window_state.as_ref().borrow_mut();

    if window_state.size() == vec2f(size.width as f32, size.height as f32) {
        return;
    }

    unsafe {
        let _: () = msg_send![super(this, class!(NSView)), setFrameSize: size];
    }

    let scale_factor = window_state.scale_factor() as f64;
    let drawable_size: NSSize = NSSize {
        width: size.width * scale_factor,
        height: size.height * scale_factor,
    };

    unsafe {
        let _: () = msg_send![window_state.layer, setDrawableSize: drawable_size];
    }

    if let Some(mut callback) = window_state.resize_callback.take() {
        callback(&mut *window_state);
        window_state.resize_callback = Some(callback);
    };
}

extern "C" fn display_layer(this: &Object, _: Sel, _: id) {
    unsafe {
        let window_state = get_window_state(this);
        let mut window_state = window_state.as_ref().borrow_mut();

        if let Some(scene) = window_state.scene_to_render.take() {
            let drawable: &metal::MetalDrawableRef = msg_send![window_state.layer, nextDrawable];

            let render_pass_descriptor = metal::RenderPassDescriptor::new();
            let color_attachment = render_pass_descriptor
                .color_attachments()
                .object_at(0)
                .unwrap();
            color_attachment.set_texture(Some(drawable.texture()));
            color_attachment.set_load_action(MTLLoadAction::Clear);
            color_attachment.set_store_action(MTLStoreAction::Store);
            color_attachment.set_clear_color(MTLClearColor::new(0., 0., 0., 1.));

            let command_queue = window_state.command_queue.clone();
            let command_buffer = command_queue.new_command_buffer();
            let command_encoder = command_buffer.new_render_command_encoder(render_pass_descriptor);

            let size = window_state.size();
            let scale_factor = window_state.scale_factor();
            let device = window_state.device.clone();

            window_state.renderer.render(
                &scene,
                &RenderContext {
                    drawable_size: size * scale_factor,
                    device: &device,
                    command_encoder,
                },
            );

            command_encoder.end_encoding();
            command_buffer.commit();
            command_buffer.wait_until_completed();
            drawable.present();
        };
    }
}

async fn synthetic_drag(
    window_state: Weak<RefCell<WindowState>>,
    drag_id: usize,
    position: Vector2F,
) {
    loop {
        Timer::after(Duration::from_millis(16)).await;
        if let Some(window_state) = window_state.upgrade() {
            let mut window_state = window_state.borrow_mut();
            if window_state.synthetic_drag_counter == drag_id {
                if let Some(mut callback) = window_state.event_callback.take() {
                    callback(Event::LeftMouseDragged { position });
                    window_state.event_callback = Some(callback);
                }
            } else {
                break;
            }
        }
    }
}