IT WORKS!!!

src/canvas_manager.rs

@@ -42,14 +42,15 @@ impl Cell {
 
 // ================== CanvasManager ==================
 
+#[derive(Debug)]
 pub struct CanvasManager {
     canvas: HashMap<Cell, String>
 }
 
 impl CanvasManager {
     pub fn new() -> Self {
-        let x_size = 1000;
-        let y_size = 1000;
+        let x_size = 10;
+        let y_size = 10;
         let white_colour = String::from("#ffafff");
 
         let mut canvas_map: HashMap<Cell, String> = HashMap::new();
@@ -73,11 +74,15 @@ impl CanvasManager {
 
         let json_response: AppResult<Value> = serde_json::to_value(result).map_err(Into::into);
 
-        match &json_response {
-            Ok(res) => info!("JSON ok : {}", res.to_string()),
-            Err(err) => info!("JSON error: {}", err.to_string())
-        }
-
         json_response
     }
+
+    pub fn set(&mut self, x_coord: u32, y_coord: u32, colour: String) -> AppResult<Value> {
+        self.canvas.insert(Cell::new(x_coord, y_coord), colour);
+
+        let result = Response::PaintResult {
+            ok: true
+        };
+        serde_json::to_value(result).map_err(Into::into)
+    }
 }

src/lib.rs

@@ -37,6 +37,6 @@ fn do_request(req: String) -> AppResult<Value> {
 
     match request {
         Request::Get => CANVAS_MANAGER.with(|cm| cm.borrow_mut().to_response()),
-        Request::Set{x_coord, y_coord, colour} => serde_json::from_str("lala").map_err(Into::into)
+        Request::Set{x_coord, y_coord, colour} => CANVAS_MANAGER.with(|cm| cm.borrow_mut().set(x_coord, y_coord, colour))
     }
 }

src/request_response.rs

@@ -15,7 +15,7 @@ pub enum Request {
 #[serde(untagged)]
 pub enum Response {
     Matrix { state: Vec<CellStateResponse> },
-    PaintResult { error: Option<String> },
+    PaintResult { ok: bool },
     Error { message: String },
 }