Add an extra map handler for showing lat/lon

* Split of the positioning and drawing code to the `draw_position`
  helper method
* Move the positioning and drawing code to a Tokia task

src/main.rs

@@ -58,50 +58,86 @@ async fn forecast_geo(
     Json(forecast)
 }
 
-/// Handler for showing the current map with the geocoded position for a specific metric.
+/// Handler for showing the current map with the geocoded position of an address for a specific
+/// metric.
 ///
 /// Note: This handler is mosly used for debugging purposes!
 #[get("/map?<address>&<metric>")]
-async fn show_map(
+async fn show_map_address(
     address: String,
     metric: Metric,
     maps_handle: &State<MapsHandle>,
 ) -> Option<Custom<Vec<u8>>> {
+    let position = resolve_address(address).await?;
+    let image_data = draw_position(position, metric, maps_handle).await;
+
+    image_data.map(|id| Custom(ContentType::PNG, id))
+}
+
+/// Handler for showing the current map with the geocoded position for a specific metric.
+///
+/// Note: This handler is mosly used for debugging purposes!
+#[get("/map?<lat>&<lon>&<metric>", rank = 2)]
+async fn show_map_geo(
+    lat: f64,
+    lon: f64,
+    metric: Metric,
+    maps_handle: &State<MapsHandle>,
+) -> Option<Custom<Vec<u8>>> {
+    let position = Position::new(lat, lon);
+    let image_data = draw_position(position, metric, maps_handle).await;
+
+    image_data.map(|id| Custom(ContentType::PNG, id))
+}
+
+/// Draws a crosshair on a map for the given position.
+///
+/// The map that is used is determined by the metric.
+// FIXME: Maybe move this to the `maps` module?
+async fn draw_position(
+    position: Position,
+    metric: Metric,
+    maps_handle: &MapsHandle,
+) -> Option<Vec<u8>> {
     use image::{GenericImage, Rgba};
     use std::io::Cursor;
 
-    let position = resolve_address(address).await?;
-    let now = Instant::now();
-    let maps = maps_handle.lock().expect("Maps handle lock was poisoned");
-    let (mut image, coords) = match metric {
-        Metric::PAQI => (maps.pollen_at(now)?, maps.pollen_project(position)),
-        Metric::Pollen => (maps.pollen_at(now)?, maps.pollen_project(position)),
-        Metric::UVI => (maps.uvi_at(now)?, maps.uvi_project(position)),
-        _ => return None, // Unsupported metric
-    };
-    drop(maps);
+    let maps_handle = Arc::clone(maps_handle);
+    tokio::task::spawn_blocking(move || {
+        let now = Instant::now();
+        let maps = maps_handle.lock().expect("Maps handle lock was poisoned");
+        let (mut image, coords) = match metric {
+            Metric::PAQI => (maps.pollen_at(now)?, maps.pollen_project(position)),
+            Metric::Pollen => (maps.pollen_at(now)?, maps.pollen_project(position)),
+            Metric::UVI => (maps.uvi_at(now)?, maps.uvi_project(position)),
+            _ => return None, // Unsupported metric
+        };
+        drop(maps);
 
-    if let Some((x, y)) = coords {
-        for py in 0..(image.height() - 1) {
-            image.put_pixel(x, py, Rgba::from([0x00, 0x00, 0x00, 0x70]));
+        if let Some((x, y)) = coords {
+            for py in 0..(image.height() - 1) {
+                image.put_pixel(x, py, Rgba::from([0x00, 0x00, 0x00, 0x70]));
+            }
+
+            for px in 0..(image.width() - 1) {
+                image.put_pixel(px, y, Rgba::from([0x00, 0x00, 0x00, 0x70]));
+            }
         }
 
-        for px in 0..(image.width() - 1) {
-            image.put_pixel(px, y, Rgba::from([0x00, 0x00, 0x00, 0x70]));
-        }
-    }
+        // Encode the image as PNG image data.
+        let mut image_data = Cursor::new(Vec::new());
+        image
+            .write_to(
+                &mut image_data,
+                image::ImageOutputFormat::from(image::ImageFormat::Png),
+            )
+            .ok()?;
 
-    // Encode the image as PNG image data.
-    // FIXME: This encoding call blocks the worker thread!
-    let mut image_data = Cursor::new(Vec::new());
-    image
-        .write_to(
-            &mut image_data,
-            image::ImageOutputFormat::from(image::ImageFormat::Png),
-        )
-        .ok()?;
-
-    Some(Custom(ContentType::PNG, image_data.into_inner()))
+        Some(image_data.into_inner())
+    })
+    .await
+    .ok()
+    .flatten()
 }
 
 /// Starts the main maps refresh loop and sets up and launches Rocket.
@@ -117,7 +153,15 @@ async fn main() -> Result<()> {
 
     let rocket = rocket::build()
         .manage(maps_handle)
-        .mount("/", routes![forecast_address, forecast_geo, show_map])
+        .mount(
+            "/",
+            routes![
+                forecast_address,
+                forecast_geo,
+                show_map_address,
+                show_map_geo
+            ],
+        )
         .ignite()
         .await?;
     let shutdown = rocket.shutdown();