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use bytes::Bytes;
use dioxus::prelude::*;
use freya_elements::elements as dioxus_elements;
use freya_hooks::{
    use_applied_theme,
    use_asset_cacher,
    use_focus,
    AssetAge,
    AssetConfiguration,
    NetworkImageTheme,
    NetworkImageThemeWith,
};
use freya_node_state::dynamic_bytes;
use reqwest::Url;

use crate::Loader;

/// Properties for the [`NetworkImage`] component.
#[derive(Props, Clone, PartialEq)]
pub struct NetworkImageProps {
    /// Theme override.
    pub theme: Option<NetworkImageThemeWith>,

    /// URL of the image.
    pub url: ReadOnlySignal<Url>,

    /// Fallback element.
    pub fallback: Option<Element>,

    /// Loading element.
    pub loading: Option<Element>,

    /// Information about the image.
    pub alt: Option<String>,
}

/// Image status.
#[doc(hidden)]
#[derive(PartialEq)]
pub enum ImageState {
    /// Image is being fetched.
    Loading,

    /// Image fetching threw an error.
    Errored,

    /// Image has been fetched.
    Loaded(Signal<Bytes>),
}

/// Image component that automatically fetches and caches remote (HTTP) images.
///
/// # Example
///
/// ```rust,no_run
/// # use reqwest::Url;
/// # use freya::prelude::*;
/// fn app() -> Element {
///     rsx!(
///         NetworkImage {
///             url: "https://raw.githubusercontent.com/jigsawpieces/dog-api-images/main/greyhound/Cordelia.jpg".parse::<Url>().unwrap()
///         }
///     )
/// }
#[allow(non_snake_case)]
pub fn NetworkImage(props: NetworkImageProps) -> Element {
    let mut asset_cacher = use_asset_cacher();
    let focus = use_focus();
    let mut status = use_signal(|| ImageState::Loading);
    let mut cached_assets = use_signal::<Vec<AssetConfiguration>>(Vec::new);
    let mut assets_tasks = use_signal::<Vec<Task>>(Vec::new);

    let a11y_id = focus.attribute();
    let NetworkImageTheme { width, height } = use_applied_theme!(&props.theme, network_image);
    let alt = props.alt.as_deref();

    use_memo(move || {
        let url = props.url.read().clone();
        // Cancel previous asset fetching requests
        for asset_task in assets_tasks.write().drain(..) {
            asset_task.cancel();
        }

        // Stop using previous assets
        for cached_asset in cached_assets.write().drain(..) {
            asset_cacher.unuse_asset(cached_asset);
        }

        let asset_configuration = AssetConfiguration {
            age: AssetAge::default(),
            id: url.to_string(),
        };

        // Loading image
        status.set(ImageState::Loading);
        if let Some(asset) = asset_cacher.use_asset(&asset_configuration) {
            // Image loaded from cache
            status.set(ImageState::Loaded(asset));
            cached_assets.write().push(asset_configuration);
        } else {
            let asset_task = spawn(async move {
                let asset = fetch_image(url).await;
                if let Ok(asset_bytes) = asset {
                    let asset_signal =
                        asset_cacher.cache(asset_configuration.clone(), asset_bytes, true);
                    // Image loaded
                    status.set(ImageState::Loaded(asset_signal));
                    cached_assets.write().push(asset_configuration);
                } else if let Err(_err) = asset {
                    // Image errored
                    status.set(ImageState::Errored);
                }
            });

            assets_tasks.write().push(asset_task);
        }
    });

    if let ImageState::Loaded(bytes) = &*status.read_unchecked() {
        let image_data = dynamic_bytes(bytes.read().clone());
        rsx!(image {
            height: "{height}",
            width: "{width}",
            a11y_id,
            image_data,
            a11y_role: "image",
            a11y_alt: alt
        })
    } else if *status.read() == ImageState::Loading {
        if let Some(loading_element) = &props.loading {
            rsx!({ loading_element })
        } else {
            rsx!(
                rect {
                    height: "{height}",
                    width: "{width}",
                    main_align: "center",
                    cross_align: "center",
                    Loader {}
                }
            )
        }
    } else if let Some(fallback_element) = &props.fallback {
        rsx!({ fallback_element })
    } else {
        rsx!(
            rect {
                height: "{height}",
                width: "{width}",
                main_align: "center",
                cross_align: "center",
                label {
                    text_align: "center",
                    "Error"
                }
            }
        )
    }
}

async fn fetch_image(url: Url) -> reqwest::Result<Bytes> {
    let res = reqwest::get(url).await?;
    res.bytes().await
}