use std::path::PathBuf;
use std::sync::Arc;

use crate::{
    point, size, Bounds, DevicePixels, Element, ElementContext, Hitbox, ImageData,
    InteractiveElement, Interactivity, IntoElement, LayoutId, Pixels, SharedUri, Size,
    StyleRefinement, Styled, UriOrPath,
};
use futures::FutureExt;
#[cfg(target_os = "macos")]
use media::core_video::CVImageBuffer;
use util::ResultExt;

/// A source of image content.
#[derive(Clone, Debug)]
pub enum ImageSource {
    /// Image content will be loaded from provided URI at render time.
    Uri(SharedUri),
    /// Image content will be loaded from the provided file at render time.
    File(Arc<PathBuf>),
    /// Cached image data
    Data(Arc<ImageData>),
    // TODO: move surface definitions into mac platform module
    /// A CoreVideo image buffer
    #[cfg(target_os = "macos")]
    Surface(CVImageBuffer),
}

impl From<SharedUri> for ImageSource {
    fn from(value: SharedUri) -> Self {
        Self::Uri(value)
    }
}

impl From<&'static str> for ImageSource {
    fn from(uri: &'static str) -> Self {
        Self::Uri(uri.into())
    }
}

impl From<String> for ImageSource {
    fn from(uri: String) -> Self {
        Self::Uri(uri.into())
    }
}

impl From<Arc<PathBuf>> for ImageSource {
    fn from(value: Arc<PathBuf>) -> Self {
        Self::File(value)
    }
}

impl From<Arc<ImageData>> for ImageSource {
    fn from(value: Arc<ImageData>) -> Self {
        Self::Data(value)
    }
}

#[cfg(target_os = "macos")]
impl From<CVImageBuffer> for ImageSource {
    fn from(value: CVImageBuffer) -> Self {
        Self::Surface(value)
    }
}

/// An image element.
pub struct Img {
    interactivity: Interactivity,
    source: ImageSource,
    grayscale: bool,
}

/// Create a new image element.
pub fn img(source: impl Into<ImageSource>) -> Img {
    Img {
        interactivity: Interactivity::default(),
        source: source.into(),
        grayscale: false,
    }
}

impl Img {
    /// Set the image to be displayed in grayscale.
    pub fn grayscale(mut self, grayscale: bool) -> Self {
        self.grayscale = grayscale;
        self
    }
}

impl Element for Img {
    type BeforeLayout = ();
    type AfterLayout = Option<Hitbox>;

    fn before_layout(&mut self, cx: &mut ElementContext) -> (LayoutId, Self::BeforeLayout) {
        let layout_id = self
            .interactivity
            .before_layout(cx, |style, cx| cx.request_layout(&style, []));
        (layout_id, ())
    }

    fn after_layout(
        &mut self,
        bounds: Bounds<Pixels>,
        _before_layout: &mut Self::BeforeLayout,
        cx: &mut ElementContext,
    ) -> Option<Hitbox> {
        self.interactivity
            .after_layout(bounds, bounds.size, cx, |_, _, hitbox, _| hitbox)
    }

    fn paint(
        &mut self,
        bounds: Bounds<Pixels>,
        _: &mut Self::BeforeLayout,
        hitbox: &mut Self::AfterLayout,
        cx: &mut ElementContext,
    ) {
        let source = self.source.clone();
        self.interactivity
            .paint(bounds, hitbox.as_ref(), cx, |style, cx| {
                let corner_radii = style.corner_radii.to_pixels(bounds.size, cx.rem_size());
                match source {
                    ImageSource::Uri(_) | ImageSource::File(_) => {
                        let uri_or_path: UriOrPath = match source {
                            ImageSource::Uri(uri) => uri.into(),
                            ImageSource::File(path) => path.into(),
                            _ => unreachable!(),
                        };

                        let image_future = cx.image_cache.get(uri_or_path.clone(), cx);
                        if let Some(data) = image_future
                            .clone()
                            .now_or_never()
                            .and_then(|result| result.ok())
                        {
                            let new_bounds = preserve_aspect_ratio(bounds, data.size());
                            cx.paint_image(new_bounds, corner_radii, data, self.grayscale)
                                .log_err();
                        } else {
                            cx.spawn(|mut cx| async move {
                                if image_future.await.ok().is_some() {
                                    cx.on_next_frame(|cx| cx.refresh());
                                }
                            })
                            .detach();
                        }
                    }

                    ImageSource::Data(data) => {
                        let new_bounds = preserve_aspect_ratio(bounds, data.size());
                        cx.paint_image(new_bounds, corner_radii, data, self.grayscale)
                            .log_err();
                    }

                    #[cfg(target_os = "macos")]
                    ImageSource::Surface(surface) => {
                        let size = size(surface.width().into(), surface.height().into());
                        let new_bounds = preserve_aspect_ratio(bounds, size);
                        // TODO: Add support for corner_radii and grayscale.
                        cx.paint_surface(new_bounds, surface);
                    }
                }
            })
    }
}

impl IntoElement for Img {
    type Element = Self;

    fn into_element(self) -> Self::Element {
        self
    }
}

impl Styled for Img {
    fn style(&mut self) -> &mut StyleRefinement {
        &mut self.interactivity.base_style
    }
}

impl InteractiveElement for Img {
    fn interactivity(&mut self) -> &mut Interactivity {
        &mut self.interactivity
    }
}

fn preserve_aspect_ratio(bounds: Bounds<Pixels>, image_size: Size<DevicePixels>) -> Bounds<Pixels> {
    let image_size = image_size.map(|dimension| Pixels::from(u32::from(dimension)));
    let image_ratio = image_size.width / image_size.height;
    let bounds_ratio = bounds.size.width / bounds.size.height;

    let new_size = if bounds_ratio > image_ratio {
        size(
            image_size.width * (bounds.size.height / image_size.height),
            bounds.size.height,
        )
    } else {
        size(
            bounds.size.width,
            image_size.height * (bounds.size.width / image_size.width),
        )
    };

    Bounds {
        origin: point(
            bounds.origin.x + (bounds.size.width - new_size.width) / 2.0,
            bounds.origin.y + (bounds.size.height - new_size.height) / 2.0,
        ),
        size: new_size,
    }
}