zed/crates/gpui/src/image_cache.rs

use std::sync::Arc;

use crate::ImageData;
use collections::HashMap;
use futures::{
    future::{BoxFuture, Shared},
    AsyncReadExt, FutureExt,
};
use image::ImageError;
use parking_lot::Mutex;
use thiserror::Error;
use util::{
    arc_cow::ArcCow,
    defer,
    http::{self, HttpClient},
};

#[derive(Debug, Error, Clone)]
pub enum Error {
    #[error("http error: {0}")]
    Client(#[from] http::Error),
    #[error("IO error: {0}")]
    Io(Arc<std::io::Error>),
    #[error("unexpected http status: {status}, body: {body}")]
    BadStatus {
        status: http::StatusCode,
        body: String,
    },
    #[error("image error: {0}")]
    Image(Arc<ImageError>),
}

impl From<std::io::Error> for Error {
    fn from(error: std::io::Error) -> Self {
        Error::Io(Arc::new(error))
    }
}

impl From<ImageError> for Error {
    fn from(error: ImageError) -> Self {
        Error::Image(Arc::new(error))
    }
}

pub struct ImageCache {
    client: Arc<dyn HttpClient>,
    images: Arc<
        Mutex<
            HashMap<
                ArcCow<'static, str>,
                Shared<BoxFuture<'static, Result<Arc<ImageData>, Error>>>,
            >,
        >,
    >,
}

impl ImageCache {
    pub fn new(client: Arc<dyn HttpClient>) -> Self {
        ImageCache {
            client,
            images: Default::default(),
        }
    }

    pub fn get(
        &self,
        uri: ArcCow<'static, str>,
    ) -> Shared<BoxFuture<'static, Result<Arc<ImageData>, Error>>> {
        match self.images.lock().get(uri.as_ref()) {
            Some(future) => future.clone(),
            None => {
                let client = self.client.clone();
                let images = self.images.clone();
                let future = {
                    let uri = uri.clone();
                    async move {
                        // If we error, remove the cached future. Otherwise we cancel before returning.
                        let remove_cached_future = defer({
                            let uri = uri.clone();
                            move || {
                                images.lock().remove(uri.as_ref());
                            }
                        });

                        let mut response = client.get(uri.as_ref(), ().into(), true).await?;
                        let mut body = Vec::new();
                        response.body_mut().read_to_end(&mut body).await?;

                        if !response.status().is_success() {
                            return Err(Error::BadStatus {
                                status: response.status(),
                                body: String::from_utf8_lossy(&body).into_owned(),
                            });
                        }

                        let format = image::guess_format(&body)?;
                        let image =
                            image::load_from_memory_with_format(&body, format)?.into_bgra8();

                        remove_cached_future.cancel();
                        Ok(ImageData::new(image))
                    }
                }
                .boxed()
                .shared();
                self.images.lock().insert(uri.clone(), future.clone());
                future
            }
        }
    }
}