use std::panic::Location;

use gpui::prelude::FluentBuilder;
use gpui::{
    App, Div, Element, ElementId, InteractiveElement, IntoElement, ParentElement, RenderOnce,
    ScrollHandle, StatefulInteractiveElement, StyleRefinement, Styled, Window, div,
};
use gpui_base::{Scrollbar, ScrollbarAxis};

use crate::StyledExt as _;

/// A trait for elements that can be made scrollable with scrollbars.
pub trait ScrollableElement: InteractiveElement + Styled + ParentElement + Element {
    /// Almost equivalent to [`StatefulInteractiveElement::overflow_y_scroll`], but adds Vertical scrollbar.
    #[track_caller]
    fn overflow_y_scrollbar(self) -> Scrollable<Self> {
        Scrollable::new(self, ScrollbarAxis::Vertical)
    }
}

/// A scrollable element wrapper that adds scrollbars to an interactive element.
#[derive(IntoElement)]
pub struct Scrollable<E: InteractiveElement + Styled + ParentElement + Element> {
    id: ElementId,
    element: E,
    axis: ScrollbarAxis,
}

impl<E> Scrollable<E>
where
    E: InteractiveElement + Styled + ParentElement + Element,
{
    #[track_caller]
    fn new(element: E, axis: impl Into<ScrollbarAxis>) -> Self {
        let caller = Location::caller();
        Self {
            id: ElementId::CodeLocation(*caller),
            element,
            axis: axis.into(),
        }
    }
}

impl<E> ParentElement for Scrollable<E>
where
    E: InteractiveElement + Styled + ParentElement + Element,
{
    fn extend(&mut self, elements: impl IntoIterator<Item = gpui::AnyElement>) {
        self.element.extend(elements)
    }
}

impl<E> RenderOnce for Scrollable<E>
where
    E: InteractiveElement + Styled + ParentElement + Element + 'static,
{
    fn render(mut self, window: &mut Window, cx: &mut App) -> impl IntoElement {
        let scroll_handle = window
            .use_keyed_state(self.id.clone(), cx, |_, _| ScrollHandle::default())
            .read(cx)
            .clone();
        let style = StyleRefinement {
            size: self.element.style().size.clone(),
            ..Default::default()
        };

        div()
            .id(self.id)
            .size_full()
            .refine_style(&style)
            .relative()
            .child(
                div()
                    .id("scroll-area")
                    .flex()
                    .size_full()
                    .track_scroll(&scroll_handle)
                    .map(|this| match self.axis {
                        ScrollbarAxis::Vertical => this.flex_col().overflow_y_scroll(),
                        ScrollbarAxis::Horizontal => this.flex_row().overflow_x_scroll(),
                        ScrollbarAxis::Both => this.overflow_scroll(),
                    })
                    .child(self.element.size_auto().flex_1()),
            )
            .child(
                Scrollbar::new(&scroll_handle)
                    .axis(self.axis)
                    .id("scrollbar"),
            )
    }
}

impl ScrollableElement for Div {}