pi-frame-server/src/api.rs

use crate::imageproc::{DiffusionMatrix, Ditherer, EInkImage, ErrorDiffusionDither};
use axum::extract::Multipart;
use axum::http::StatusCode;
use axum::response::IntoResponse;
use axum::{extract::State, response::Response, routing::post, Router};
use image::ImageReader;
use std::io::Cursor;
use std::time::Duration;
use tracing::{debug, error, info, instrument};

use crate::display::EInkPanel;
use std::sync::Arc;
use tokio::sync::mpsc::{self, Receiver, Sender};
use tokio::task::JoinHandle;

pub enum ImageFormFields {
    DitherType,
    ImageFile,
}

#[derive(Clone)]
pub struct Context {
    display_channel: Sender<DisplaySetCommand>,
    display_task: Arc<JoinHandle<()>>,
}

impl Context {
    #[must_use]
    pub fn new(disp: Box<dyn EInkPanel + Send>) -> Self {
        let (tx, rx) = mpsc::channel(2);
        let task = tokio::spawn(display_task(rx, disp));
        Self {
            display_channel: tx,
            display_task: Arc::new(task),
        }
    }
}

#[derive(Debug)]
pub struct DisplaySetCommand {
    img: Box<EInkImage>,
}
#[instrument(skip_all)]
pub async fn display_task(
    mut rx: Receiver<DisplaySetCommand>,
    mut display: Box<dyn EInkPanel + Send>,
) {
    while let Some(cmd) = rx.recv().await {
        info!("Got a display set command");
        let raw_buf = cmd.img.into_display_buffer();
        if let Err(e) = display.display(&raw_buf) {
            error!("Error displaying command {e}");
        }
        info!("Done setting display");
    }
}

// Make our own error that wraps `anyhow::Error`.
struct AppError(anyhow::Error);

// Tell axum how to convert `AppError` into a response.
impl IntoResponse for AppError {
    fn into_response(self) -> Response {
        (
            StatusCode::INTERNAL_SERVER_ERROR,
            format!("Something went wrong: {}", self.0),
        )
            .into_response()
    }
}

// This enables using `?` on functions that return `Result<_, anyhow::Error>` to turn them into
// `Result<_, AppError>`. That way you don't need to do that manually.
impl<E> From<E> for AppError
where
    E: Into<anyhow::Error>,
{
    fn from(err: E) -> Self {
        Self(err.into())
    }
}

/// API routes for axum
/// Start with the basics: Send an image, crop it, dither, and upload.
/// we defer the upload to a separate task.
pub fn router() -> Router<Context> {
    Router::new().route("/setimage", post(set_image))
}

#[instrument(skip(ctx))]
async fn set_image(
    State(ctx): State<Context>,
    mut parts: Multipart,
) -> Result<impl IntoResponse, AppError> {
    while let Some(field) = parts.next_field().await? {
        let name = field.name().expect("fields always have names").to_string();
        let data = field.bytes().await?;
        debug!("Length of `{}` is {} bytes", name, data.len());
        if &name == "image" {
            let reader = ImageReader::new(Cursor::new(data))
                .with_guessed_format()
                .expect("Cursor io never fails");
            debug!("Guessed format: {:?}", reader.format());

            let image = reader.decode()?;
            let mut buf = EInkImage::new(800, 480);
            let dither = ErrorDiffusionDither::new(DiffusionMatrix::Atkinson);
            dither.dither(&image.into(), &mut buf);
            let cmd = DisplaySetCommand { img: Box::new(buf) };
            ctx.display_channel
                .send_timeout(cmd, Duration::from_secs(10))
                .await?;
        }
    }
    Ok(())
}