//! [iced](https://github.com/iced-rs/iced) editor support for NIH plug.
//!
//! TODO: Proper usage example, for now check out the gain_gui example

use baseview::{Size, WindowOpenOptions, WindowScalePolicy};
use crossbeam::atomic::AtomicCell;
use nih_plug::prelude::{Editor, GuiContext, ParamSetter, ParentWindowHandle};
use std::marker::PhantomData;
use std::sync::atomic::{AtomicBool, Ordering};
use std::sync::Arc;

/// Re-export for convenience.
pub use iced_baseview::*;

/// FIXME: Document how this works once everything actually works. The below comment is from the
///        egui version.
///
/// Create an [`Editor`] instance using an [`iced`][::iced] GUI. Using the user state parameter is
/// optional, but it can be useful for keeping track of some temporary GUI-only settings. See the
/// `gui_gain` example for more information on how to use this. The [`IcedState`] passed to this
/// function contains the GUI's intitial size, and this is kept in sync whenever the GUI gets
/// resized. You can also use this to know if the GUI is open, so you can avoid performing
/// potentially expensive calculations while the GUI is not open. If you want this size to be
/// persisted when restoring a plugin instance, then you can store it in a `#[persist = "key"]`
/// field on your parameters struct.
///
/// See [`IcedState::from_size()`].
pub fn create_iced_editor<A>(
    iced_state: Arc<IcedState>,
    initialization_flags: A::Flags,
) -> Option<Box<dyn Editor>>
where
    A: Application + 'static + Send + Sync,
    A::Flags: Clone + Sync,
{
    Some(Box::new(IcedEditor::<A> {
        iced_state,
        initialization_flags,

        scaling_factor: AtomicCell::new(None),

        _phantom: PhantomData,
    }))
}

// TODO: Once we add resizing, we may want to be able to remember the GUI size. In that case we need
//       to make this serializable (only restoring the size of course) so it can be persisted.
pub struct IcedState {
    size: AtomicCell<(u32, u32)>,
    open: AtomicBool,
}

impl IcedState {
    /// Initialize the GUI's state. This value can be passed to [`create_iced_editor()`]. The window
    /// size is in logical pixels, so before it is multiplied by the DPI scaling factor.
    pub fn from_size(width: u32, height: u32) -> Arc<IcedState> {
        Arc::new(IcedState {
            size: AtomicCell::new((width, height)),
            open: AtomicBool::new(false),
        })
    }

    /// Return a `(width, height)` pair for the current size of the GUI in logical pixels.
    pub fn size(&self) -> (u32, u32) {
        self.size.load()
    }

    /// Whether the GUI is currently visible.
    // Called `is_open()` instead of `open()` to avoid the ambiguity.
    pub fn is_open(&self) -> bool {
        self.open.load(Ordering::Acquire)
    }
}

/// An [`Editor`] implementation that renders an iced [`Application`].
struct IcedEditor<A>
where
    A: Application + 'static + Send + Sync,
    A::Flags: Clone + Sync,
{
    iced_state: Arc<IcedState>,
    initialization_flags: A::Flags,

    // FIXME:
    // /// The plugin's state. This is kept in between editor openenings.
    // user_state: Arc<RwLock<T>>,
    // update: Arc<dyn Fn(&Context, &ParamSetter, &mut T) + 'static + Send + Sync>,
    //
    /// The scaling factor reported by the host, if any. On macOS this will never be set and we
    /// should use the system scaling factor instead.
    scaling_factor: AtomicCell<Option<f32>>,

    _phantom: PhantomData<A>,
}

impl<A> Editor for IcedEditor<A>
where
    A: Application + 'static + Send + Sync,
    A::Flags: Clone + Sync,
{
    fn spawn(
        &self,
        parent: ParentWindowHandle,
        context: Arc<dyn GuiContext>,
    ) -> Box<dyn std::any::Any + Send + Sync> {
        // FIXME: Somehow get the context/parametersetter to the GUI. Another trait that adds a
        //        `set_context()` would be the easiest way but perhaps not the cleanest.

        let (unscaled_width, unscaled_height) = self.iced_state.size();
        let scaling_factor = self.scaling_factor.load();
        // TODO: iced_baseview does not have gracefuly error handling for context creation failures.
        //       This will panic if the context could not be created.
        let window = IcedWindow::<A>::open_parented(
            &parent,
            Settings {
                window: WindowOpenOptions {
                    title: String::from("iced window"),
                    // Baseview should be doing the DPI scaling for us
                    size: Size::new(unscaled_width as f64, unscaled_height as f64),
                    // NOTE: For some reason passing 1.0 here causes the UI to be scaled on macOS but
                    //       not the mouse events.
                    scale: scaling_factor
                        .map(|factor| WindowScalePolicy::ScaleFactor(factor as f64))
                        .unwrap_or(WindowScalePolicy::SystemScaleFactor),

                    #[cfg(feature = "opengl")]
                    gl_config: Some(baseview::gl::GlConfig {
                        // FIXME: glow_glyph forgot to add an `#extension`, so this won't work under
                        //        OpenGL 3.2 at the moment. With that change applied this should work on
                        //        OpenGL 3.2/macOS.
                        version: (3, 3),
                        red_bits: 8,
                        blue_bits: 8,
                        green_bits: 8,
                        alpha_bits: 8,
                        depth_bits: 24,
                        stencil_bits: 8,
                        samples: None,
                        srgb: true,
                        double_buffer: true,
                        vsync: true,
                        ..Default::default()
                    }),
                    // FIXME: Rust analyzer always thinks baseview/opengl is enabled even if we
                    //        don't explicitly enable it, so you'd get a compile error if this line
                    //        is missing
                    #[cfg(not(feature = "opengl"))]
                    gl_config: None,
                },
                flags: self.initialization_flags.clone(),
            },
        );

        self.iced_state.open.store(true, Ordering::Release);
        Box::new(IcedEditorHandle {
            iced_state: self.iced_state.clone(),
            window,
        })
    }

    fn size(&self) -> (u32, u32) {
        self.iced_state.size()
    }

    fn set_scale_factor(&self, factor: f32) -> bool {
        self.scaling_factor.store(Some(factor));
        true
    }
}

/// The window handle used for [`IcedEditor`].
struct IcedEditorHandle<Message: 'static + Send> {
    iced_state: Arc<IcedState>,
    window: iced_baseview::WindowHandle<Message>,
}

/// The window handle enum stored within 'WindowHandle' contains raw pointers. Is there a way around
/// having this requirement?
unsafe impl<Message: Send> Send for IcedEditorHandle<Message> {}
unsafe impl<Message: Send> Sync for IcedEditorHandle<Message> {}

impl<Message: Send> Drop for IcedEditorHandle<Message> {
    fn drop(&mut self) {
        self.iced_state.open.store(false, Ordering::Release);
        self.window.close_window();
    }
}