use std::ops::Range;

use crate::{ItemHandle, Pane};
use gpui::{
    elements::*,
    geometry::{
        rect::RectF,
        vector::{vec2f, Vector2F},
    },
    json::{json, ToJson},
    AnyElement, AnyViewHandle, Entity, LayoutContext, PaintContext, SceneBuilder, SizeConstraint,
    Subscription, View, ViewContext, ViewHandle, WindowContext,
};

pub trait StatusItemView: View {
    fn set_active_pane_item(
        &mut self,
        active_pane_item: Option<&dyn crate::ItemHandle>,
        cx: &mut ViewContext<Self>,
    );
}

trait StatusItemViewHandle {
    fn as_any(&self) -> &AnyViewHandle;
    fn set_active_pane_item(
        &self,
        active_pane_item: Option<&dyn ItemHandle>,
        cx: &mut WindowContext,
    );
    fn ui_name(&self) -> &'static str;
}

pub struct StatusBar {
    left_items: Vec<Box<dyn StatusItemViewHandle>>,
    right_items: Vec<Box<dyn StatusItemViewHandle>>,
    active_pane: ViewHandle<Pane>,
    _observe_active_pane: Subscription,
}

impl Entity for StatusBar {
    type Event = ();
}

impl View for StatusBar {
    fn ui_name() -> &'static str {
        "StatusBar"
    }

    fn render(&mut self, cx: &mut ViewContext<Self>) -> AnyElement<Self> {
        let theme = &theme::current(cx).workspace.status_bar;

        StatusBarElement {
            left: Flex::row()
                .with_children(self.left_items.iter().map(|i| {
                    ChildView::new(i.as_any(), cx)
                        .aligned()
                        .contained()
                        .with_margin_right(theme.item_spacing)
                }))
                .into_any(),
            right: Flex::row()
                .with_children(self.right_items.iter().rev().map(|i| {
                    ChildView::new(i.as_any(), cx)
                        .aligned()
                        .contained()
                        .with_margin_left(theme.item_spacing)
                }))
                .into_any(),
        }
        .contained()
        .with_style(theme.container)
        .constrained()
        .with_height(theme.height)
        .into_any()
    }
}

impl StatusBar {
    pub fn new(active_pane: &ViewHandle<Pane>, cx: &mut ViewContext<Self>) -> Self {
        let mut this = Self {
            left_items: Default::default(),
            right_items: Default::default(),
            active_pane: active_pane.clone(),
            _observe_active_pane: cx
                .observe(active_pane, |this, _, cx| this.update_active_pane_item(cx)),
        };
        this.update_active_pane_item(cx);
        this
    }

    pub fn add_left_item<T>(&mut self, item: ViewHandle<T>, cx: &mut ViewContext<Self>)
    where
        T: 'static + StatusItemView,
    {
        self.left_items.push(Box::new(item));
        cx.notify();
    }

    pub fn item_of_type<T: StatusItemView>(&self) -> Option<ViewHandle<T>> {
        self.left_items
            .iter()
            .chain(self.right_items.iter())
            .find_map(|item| item.as_any().clone().downcast())
    }

    pub fn position_of_item<T>(&self) -> Option<usize>
    where
        T: StatusItemView,
    {
        for (index, item) in self.left_items.iter().enumerate() {
            if item.as_ref().ui_name() == T::ui_name() {
                return Some(index);
            }
        }
        for (index, item) in self.right_items.iter().enumerate() {
            if item.as_ref().ui_name() == T::ui_name() {
                return Some(index + self.left_items.len());
            }
        }
        return None;
    }

    pub fn insert_item_after<T>(
        &mut self,
        position: usize,
        item: ViewHandle<T>,
        cx: &mut ViewContext<Self>,
    ) where
        T: 'static + StatusItemView,
    {
        if position < self.left_items.len() {
            self.left_items.insert(position + 1, Box::new(item))
        } else {
            self.right_items
                .insert(position + 1 - self.left_items.len(), Box::new(item))
        }
        cx.notify()
    }

    pub fn remove_item_at(&mut self, position: usize, cx: &mut ViewContext<Self>) {
        if position < self.left_items.len() {
            self.left_items.remove(position);
        } else {
            self.right_items.remove(position - self.left_items.len());
        }
        cx.notify();
    }

    pub fn add_right_item<T>(&mut self, item: ViewHandle<T>, cx: &mut ViewContext<Self>)
    where
        T: 'static + StatusItemView,
    {
        self.right_items.push(Box::new(item));
        cx.notify();
    }

    pub fn set_active_pane(&mut self, active_pane: &ViewHandle<Pane>, cx: &mut ViewContext<Self>) {
        self.active_pane = active_pane.clone();
        self._observe_active_pane =
            cx.observe(active_pane, |this, _, cx| this.update_active_pane_item(cx));
        self.update_active_pane_item(cx);
    }

    fn update_active_pane_item(&mut self, cx: &mut ViewContext<Self>) {
        let active_pane_item = self.active_pane.read(cx).active_item();
        for item in self.left_items.iter().chain(&self.right_items) {
            item.set_active_pane_item(active_pane_item.as_deref(), cx);
        }
    }
}

impl<T: StatusItemView> StatusItemViewHandle for ViewHandle<T> {
    fn as_any(&self) -> &AnyViewHandle {
        self
    }

    fn set_active_pane_item(
        &self,
        active_pane_item: Option<&dyn ItemHandle>,
        cx: &mut WindowContext,
    ) {
        self.update(cx, |this, cx| {
            this.set_active_pane_item(active_pane_item, cx)
        });
    }

    fn ui_name(&self) -> &'static str {
        T::ui_name()
    }
}

impl From<&dyn StatusItemViewHandle> for AnyViewHandle {
    fn from(val: &dyn StatusItemViewHandle) -> Self {
        val.as_any().clone()
    }
}

struct StatusBarElement {
    left: AnyElement<StatusBar>,
    right: AnyElement<StatusBar>,
}

impl Element<StatusBar> for StatusBarElement {
    type LayoutState = ();
    type PaintState = ();

    fn layout(
        &mut self,
        mut constraint: SizeConstraint,
        view: &mut StatusBar,
        cx: &mut LayoutContext<StatusBar>,
    ) -> (Vector2F, Self::LayoutState) {
        let max_width = constraint.max.x();
        constraint.min = vec2f(0., constraint.min.y());

        let right_size = self.right.layout(constraint, view, cx);
        let constraint = SizeConstraint::new(
            vec2f(0., constraint.min.y()),
            vec2f(max_width - right_size.x(), constraint.max.y()),
        );

        self.left.layout(constraint, view, cx);

        (vec2f(max_width, right_size.y()), ())
    }

    fn paint(
        &mut self,
        scene: &mut SceneBuilder,
        bounds: RectF,
        visible_bounds: RectF,
        _: &mut Self::LayoutState,
        view: &mut StatusBar,
        cx: &mut PaintContext<StatusBar>,
    ) -> Self::PaintState {
        let origin_y = bounds.upper_right().y();
        let visible_bounds = bounds.intersection(visible_bounds).unwrap_or_default();

        let left_origin = vec2f(bounds.lower_left().x(), origin_y);
        self.left
            .paint(scene, left_origin, visible_bounds, view, cx);

        let right_origin = vec2f(bounds.upper_right().x() - self.right.size().x(), origin_y);
        self.right
            .paint(scene, right_origin, visible_bounds, view, cx);
    }

    fn rect_for_text_range(
        &self,
        _: Range<usize>,
        _: RectF,
        _: RectF,
        _: &Self::LayoutState,
        _: &Self::PaintState,
        _: &StatusBar,
        _: &ViewContext<StatusBar>,
    ) -> Option<RectF> {
        None
    }

    fn debug(
        &self,
        bounds: RectF,
        _: &Self::LayoutState,
        _: &Self::PaintState,
        _: &StatusBar,
        _: &ViewContext<StatusBar>,
    ) -> serde_json::Value {
        json!({
            "type": "StatusBarElement",
            "bounds": bounds.to_json()
        })
    }
}