// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License in the LICENSE-APACHE file or at:
//     https://www.apache.org/licenses/LICENSE-2.0

//! Window widgets

use smallvec::SmallVec;
use std::fmt::{self, Debug};

use kas::draw::ClipRegion;
use kas::event::Callback;
use kas::prelude::*;
use kas::WindowId;

/// The main instantiation of the [`Window`] trait.
#[handler(send=noauto, generics = <> where W: Widget<Msg = VoidMsg>)]
#[widget(config=noauto)]
#[derive(Widget)]
pub struct Window<W: Widget + 'static> {
    #[widget_core]
    core: CoreData,
    restrict_dimensions: (bool, bool),
    title: CowString,
    #[widget]
    w: W,
    popups: SmallVec<[(WindowId, kas::Popup); 16]>,
    fns: Vec<(Callback, &'static dyn Fn(&mut W, &mut Manager))>,
}

impl<W: Widget> Debug for Window<W> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(
            f,
            "Window {{ core: {:?}, solver: <omitted>, w: {:?}, fns: [",
            self.core, self.w
        )?;
        let mut iter = self.fns.iter();
        if let Some(first) = iter.next() {
            write!(f, "({:?}, <Fn>)", first.0)?;
            for next in iter {
                write!(f, ", ({:?}, <Fn>)", next.0)?;
            }
        }
        write!(f, "] }}")
    }
}

impl<W: Widget + Clone> Clone for Window<W> {
    fn clone(&self) -> Self {
        Window {
            core: self.core.clone(),
            restrict_dimensions: self.restrict_dimensions.clone(),
            title: self.title.clone(),
            w: self.w.clone(),
            popups: Default::default(), // these are temporary; don't clone
            fns: self.fns.clone(),
        }
    }
}

impl<W: Widget> Window<W> {
    /// Create
    pub fn new<T: Into<CowString>>(title: T, w: W) -> Window<W> {
        Window {
            core: Default::default(),
            restrict_dimensions: (true, false),
            title: title.into(),
            w,
            popups: Default::default(),
            fns: Vec::new(),
        }
    }

    /// Configure whether min/max dimensions are forced
    ///
    /// By default, the min size is enforced but not the max.
    pub fn set_restrict_dimensions(&mut self, min: bool, max: bool) {
        self.restrict_dimensions = (min, max);
    }

    /// Add a closure to be called, with a reference to self, on the given
    /// condition. The closure must be passed by reference.
    // TODO: consider whether to keep this. The only functionality added is for
    // actions which happen on destruction.
    pub fn add_callback(&mut self, condition: Callback, f: &'static dyn Fn(&mut W, &mut Manager)) {
        self.fns.push((condition, f));
    }
}

impl<W: Widget> WidgetConfig for Window<W> {
    fn configure(&mut self, mgr: &mut Manager) {
        for (condition, f) in &self.fns {
            match condition {
                Callback::Start => f(&mut self.w, mgr),
                Callback::Close => (),
            }
        }
    }
}

impl<W: Widget> Layout for Window<W> {
    #[inline]
    fn size_rules(&mut self, size_handle: &mut dyn SizeHandle, axis: AxisInfo) -> SizeRules {
        // Note: we do not consider popups, since they are usually temporary
        self.w.size_rules(size_handle, axis)
    }

    #[inline]
    fn set_rect(&mut self, rect: Rect, align: AlignHints) {
        self.core.rect = rect;
        self.w.set_rect(rect, align);
    }

    #[inline]
    fn find_id(&self, coord: Coord) -> Option<WidgetId> {
        if !self.rect().contains(coord) {
            return None;
        }
        for popup in self.popups.iter().rev() {
            if let Some(id) = self.w.find(popup.1.id).and_then(|w| w.find_id(coord)) {
                return Some(id);
            }
        }
        self.w.find_id(coord).or(Some(self.id()))
    }

    #[inline]
    fn draw(&self, draw_handle: &mut dyn DrawHandle, mgr: &event::ManagerState, disabled: bool) {
        let disabled = disabled || self.is_disabled();
        self.w.draw(draw_handle, mgr, disabled);
        for popup in &self.popups {
            let class = ClipRegion::Popup;
            draw_handle.clip_region(self.core.rect, Coord::ZERO, class, &mut |draw_handle| {
                self.find(popup.1.id)
                    .map(|w| w.draw(draw_handle, mgr, disabled));
            });
        }
    }
}

impl<W: Widget<Msg = VoidMsg> + 'static> event::SendEvent for Window<W> {
    fn send(&mut self, mgr: &mut Manager, id: WidgetId, event: Event) -> Response<Self::Msg> {
        if !self.is_disabled() && id <= self.w.id() {
            return self.w.send(mgr, id, event);
        }
        Response::Unhandled(event)
    }
}

impl<W: Widget<Msg = VoidMsg> + 'static> kas::Window for Window<W> {
    fn title(&self) -> &str {
        &self.title
    }

    fn restrict_dimensions(&self) -> (bool, bool) {
        self.restrict_dimensions
    }

    fn add_popup(
        &mut self,
        size_handle: &mut dyn SizeHandle,
        mgr: &mut Manager,
        id: WindowId,
        popup: kas::Popup,
    ) {
        let index = self.popups.len();
        self.popups.push((id, popup));
        self.resize_popup(size_handle, index);
        mgr.send_action(TkAction::Redraw);
    }

    fn remove_popup(&mut self, mgr: &mut Manager, id: WindowId) {
        for i in 0..self.popups.len() {
            if id == self.popups[i].0 {
                self.popups.remove(i);
                mgr.send_action(TkAction::RegionMoved);
                return;
            }
        }
    }

    fn resize_popups(&mut self, size_handle: &mut dyn SizeHandle) {
        for i in 0..self.popups.len() {
            self.resize_popup(size_handle, i);
        }
    }

    fn handle_closure(&mut self, mgr: &mut Manager) {
        for (condition, f) in &self.fns {
            match condition {
                Callback::Close => f(&mut self.w, mgr),
                Callback::Start => (),
            }
        }
    }
}

// This is like WidgetChildren::find, but returns a translated Rect.
fn find_rect(widget: &dyn WidgetConfig, id: WidgetId) -> Option<Rect> {
    if id == widget.id() {
        return Some(widget.rect());
    } else if id > widget.id() {
        return None;
    }

    for i in 0..widget.len() {
        if let Some(w) = widget.get(i) {
            if id > w.id() {
                continue;
            }
            return find_rect(w, id).map(|rect| rect - widget.translation(i));
        }
        break;
    }
    None
}

impl<W: Widget> Window<W> {
    fn resize_popup(&mut self, size_handle: &mut dyn SizeHandle, index: usize) {
        // Notation: p=point/coord, s=size, m=margin
        // r=window/root rect, c=anchor rect
        let r = self.core.rect;
        let popup = &mut self.popups[index].1;

        let c = find_rect(self.w.as_widget(), popup.parent).unwrap();
        let widget = self.w.find_mut(popup.id).unwrap();
        let mut cache = layout::SolveCache::find_constraints(widget, size_handle);
        let ideal = cache.ideal(false);
        let m = cache.margins();

        let is_reversed = popup.direction.is_reversed();
        let place_in = |rp, rs: u32, cp: i32, cs, ideal, m: (u16, u16)| -> (i32, u32) {
            let before: i32 = cp - (rp + m.1 as i32);
            let before = before.max(0) as u32;
            let after = rs.saturating_sub(cs + before + m.0 as u32);
            if after >= ideal {
                if is_reversed && before >= ideal {
                    (cp - ideal as i32 - m.1 as i32, ideal)
                } else {
                    (cp + cs as i32 + m.0 as i32, ideal)
                }
            } else if before >= ideal {
                (cp - ideal as i32 - m.1 as i32, ideal)
            } else if before > after {
                (rp, before)
            } else {
                (cp + cs as i32 + m.0 as i32, after)
            }
        };
        let place_out = |rp, rs, cp: i32, cs, ideal: u32| -> (i32, u32) {
            let pos = cp.min(rp + rs as i32 - ideal as i32).max(rp);
            let size = ideal.max(cs).min(rs);
            (pos, size)
        };
        let rect = if popup.direction.is_horizontal() {
            let (x, w) = place_in(r.pos.0, r.size.0, c.pos.0, c.size.0, ideal.0, m.horiz);
            let (y, h) = place_out(r.pos.1, r.size.1, c.pos.1, c.size.1, ideal.1);
            Rect::new(Coord(x, y), Size(w, h))
        } else {
            let (x, w) = place_out(r.pos.0, r.size.0, c.pos.0, c.size.0, ideal.0);
            let (y, h) = place_in(r.pos.1, r.size.1, c.pos.1, c.size.1, ideal.1, m.vert);
            Rect::new(Coord(x, y), Size(w, h))
        };

        cache.apply_rect(widget, size_handle, rect, false);
    }
}