use crate::{
    element::{Element, IntoElement, Layout},
    layout_context::LayoutContext,
    paint_context::PaintContext,
};
use anyhow::Result;
use gpui::{geometry::Size, text_layout::LineLayout, LayoutId, RenderContext};
use parking_lot::Mutex;
use std::sync::Arc;

impl<V: 'static, S: Into<ArcCow<'static, str>>> IntoElement<V> for S {
    type Element = Text;

    fn into_element(self) -> Self::Element {
        Text { text: self.into() }
    }
}

pub struct Text {
    text: ArcCow<'static, str>,
}

impl<V: 'static> Element<V> for Text {
    type PaintState = Arc<Mutex<Option<TextLayout>>>;

    fn layout(
        &mut self,
        _view: &mut V,
        cx: &mut LayoutContext<V>,
    ) -> Result<(LayoutId, Self::PaintState)> {
        let fonts = cx.platform().fonts();
        let text_style = cx.text_style();
        let line_height = cx.font_cache().line_height(text_style.font_size);
        let text = self.text.clone();
        let paint_state = Arc::new(Mutex::new(None));

        let layout_id = cx.add_measured_layout_node(Default::default(), {
            let paint_state = paint_state.clone();
            move |_params| {
                let line_layout = fonts.layout_line(
                    text.as_ref(),
                    text_style.font_size,
                    &[(text.len(), text_style.to_run())],
                );

                let size = Size {
                    width: line_layout.width,
                    height: line_height,
                };

                paint_state.lock().replace(TextLayout {
                    line_layout: Arc::new(line_layout),
                    line_height,
                });

                size
            }
        });

        Ok((layout_id?, paint_state))
    }

    fn paint<'a>(
        &mut self,
        _view: &mut V,
        layout: &Layout,
        paint_state: &mut Self::PaintState,
        cx: &mut PaintContext<V>,
    ) {
        let line_layout;
        let line_height;
        {
            let paint_state = paint_state.lock();
            let paint_state = paint_state
                .as_ref()
                .expect("measurement has not been performed");
            line_layout = paint_state.line_layout.clone();
            line_height = paint_state.line_height;
        }

        let text_style = cx.text_style();
        let line =
            gpui::text_layout::Line::new(line_layout, &[(self.text.len(), text_style.to_run())]);

        let origin = layout.bounds.origin();
        // TODO: We haven't added visible bounds to the new element system yet, so this is a placeholder.
        let visible_bounds = layout.bounds;
        line.paint(cx.scene, origin, visible_bounds, line_height, cx.legacy_cx);
    }
}

pub struct TextLayout {
    line_layout: Arc<LineLayout>,
    line_height: f32,
}

pub enum ArcCow<'a, T: ?Sized> {
    Borrowed(&'a T),
    Owned(Arc<T>),
}

impl<'a, T: ?Sized> Clone for ArcCow<'a, T> {
    fn clone(&self) -> Self {
        match self {
            Self::Borrowed(borrowed) => Self::Borrowed(borrowed),
            Self::Owned(owned) => Self::Owned(owned.clone()),
        }
    }
}

impl<'a, T: ?Sized> From<&'a T> for ArcCow<'a, T> {
    fn from(s: &'a T) -> Self {
        Self::Borrowed(s)
    }
}

impl<T> From<Arc<T>> for ArcCow<'_, T> {
    fn from(s: Arc<T>) -> Self {
        Self::Owned(s)
    }
}

impl From<String> for ArcCow<'_, str> {
    fn from(value: String) -> Self {
        Self::Owned(value.into())
    }
}

impl<T: ?Sized> std::ops::Deref for ArcCow<'_, T> {
    type Target = T;

    fn deref(&self) -> &Self::Target {
        match self {
            ArcCow::Borrowed(s) => s,
            ArcCow::Owned(s) => s.as_ref(),
        }
    }
}

impl<T: ?Sized> AsRef<T> for ArcCow<'_, T> {
    fn as_ref(&self) -> &T {
        match self {
            ArcCow::Borrowed(borrowed) => borrowed,
            ArcCow::Owned(owned) => owned.as_ref(),
        }
    }
}