/* LICENSE BEGIN
    This file is part of the SixtyFPS Project -- https://sixtyfps.io
    Copyright (c) 2020 Olivier Goffart <olivier.goffart@sixtyfps.io>
    Copyright (c) 2020 Simon Hausmann <simon.hausmann@sixtyfps.io>

    SPDX-License-Identifier: GPL-3.0-only
    This file is also available under commercial licensing terms.
    Please contact info@sixtyfps.io for more information.
LICENSE END */
/*! Module handling mouse events

TODO: Keyboard events
*/

use crate::component::ComponentRefPin;
use crate::graphics::Point;
use crate::item_tree::{ItemVisitorResult, VisitChildrenResult};
use euclid::default::Vector2D;

/// The type of a MouseEvent
#[repr(C)]
#[derive(Debug, Clone, Copy)]
pub enum MouseEventType {
    /// The mouse was pressed
    MousePressed,
    /// The mouse was relased
    MouseReleased,
    /// The mouse position has changed
    MouseMoved,
    /// The mouse exited the item or component
    MouseExit,
}

/// Structur representing a mouse event
#[repr(C)]
#[derive(Debug, Clone, Copy)]
pub struct MouseEvent {
    /// The position of the cursor
    pub pos: Point,
    /// The action performed (pressed/released/moced)
    pub what: MouseEventType,
}

/// This value is returned by the input handler of a component
/// to notify the run-time about how the event was handled and
/// what the next steps are.
#[repr(C)]
#[derive(Debug, Copy, Clone, Eq, PartialEq)]
pub enum InputEventResult {
    /// The event was accepted. This may result in additional events, for example
    /// accepting a mouse move will result in a MouseExit event later.
    EventAccepted,
    EventIgnored,
    /* /// Same as grab, but continue forwarding the event to children.
    /// If a child grab the mouse, the grabber will be stored in the item itself.
    /// Only item that have grabbed storage can return this.
    /// The new_grabber is a reference to a usize to store thenext grabber
    TentativeGrab {
        new_grabber: &'a Cell<usize>,
    },
    /// While we have a TentaztiveGrab
    Forward {
        to: usize,
    },*/
    /// All further mouse event need to be sent to this item or component
    GrabMouse,
}

pub fn process_ungrabbed_mouse_event(
    component: ComponentRefPin,
    event: MouseEvent,
) -> (InputEventResult, VisitChildrenResult) {
    let offset = Vector2D::new(0., 0.);

    let mut result = InputEventResult::EventIgnored;
    let item_index = crate::item_tree::visit_items(
        component,
        crate::item_tree::TraversalOrder::FrontToBack,
        |_, item, offset| -> ItemVisitorResult<Vector2D<f32>> {
            let geom = item.as_ref().geometry();
            let geom = geom.translate(*offset);

            if geom.contains(event.pos) {
                let mut event2 = event.clone();
                event2.pos -= geom.origin.to_vector();
                match item.as_ref().input_event(event2) {
                    InputEventResult::EventAccepted => {
                        result = InputEventResult::EventAccepted;
                        return ItemVisitorResult::Abort;
                    }
                    InputEventResult::EventIgnored => (),
                    InputEventResult::GrabMouse => {
                        result = InputEventResult::GrabMouse;
                        return ItemVisitorResult::Abort;
                    }
                };
            }

            ItemVisitorResult::Continue(geom.origin.to_vector())
        },
        offset,
    );

    (
        result,
        if result == InputEventResult::GrabMouse {
            item_index
        } else {
            VisitChildrenResult::CONTINUE
        },
    )
}
/*
/// The event must be in the component coordinate
/// Returns the new grabber.
pub fn process_grabbed_mouse_event(
    component: ComponentRefPin,
    item: core::pin::Pin<ItemRef>,
    offset: Point,
    event: MouseEvent,
    old_grab: VisitChildrenResult,
) -> (InputEventResult, VisitChildrenResult) {
    let mut event2 = event.clone();
    event2.pos -= offset.to_vector();

    let res = item.as_ref().input_event(event2);
    match res {
        InputEventResult::EventIgnored => {
            // We need then to forward to another event
            process_ungrabbed_mouse_event(component, event)
        }
        InputEventResult::GrabMouse => (res, old_grab),
        InputEventResult::EventAccepted => (res, VisitChildrenResult::CONTINUE),
    }
}*/

pub(crate) mod ffi {
    use super::*;

    #[no_mangle]
    pub extern "C" fn sixtyfps_process_ungrabbed_mouse_event(
        component: core::pin::Pin<crate::component::ComponentRef>,
        event: MouseEvent,
        new_mouse_grabber: &mut crate::item_tree::VisitChildrenResult,
    ) -> InputEventResult {
        let (res, grab) = process_ungrabbed_mouse_event(component, event);
        *new_mouse_grabber = grab;
        res
    }
    /*
    #[no_mangle]
    pub extern "C" fn sixtyfps_process_grabbed_mouse_event(
        component: ComponentRefPin,
        item: core::pin::Pin<ItemRef>,
        offset: Point,
        event: MouseEvent,
        old_grab: VisitChildrenResult,
    ) -> (InputEventResult, crate::item_tree::VisitChildrenResult) {
        process_grabbed_mouse_event(component, item, offset, event, old_grab)
    }*/
}