Properly send errors in api

Cargo.toml

@@ -12,6 +12,8 @@ members = [
 ]
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+[features]
+default = []
 
 [dependencies]
 s2 = {version="0.0.12", default-features=false}

web/src/main.rs

@@ -1,6 +1,6 @@
 use std::str::FromStr;
 
-use rocket::{get, routes, serde::json::Json};
+use rocket::{get, routes, serde::json::Json, Responder};
 use serde::{Deserialize, Serialize};
 use this_algorithm::Address;
 
@@ -18,20 +18,30 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
 }
 
 #[get("/address?<lat>&<lon>")]
-async fn get_address(lat: f64, lon: f64) -> Result<String, String> {
-    Address::from_lat_lon(lat, lon)
-        .map(|a| a.to_string())
-        .map_err(|e| e.to_string())
+async fn get_address(lat: Option<String>, lon: Option<String>) -> Result<String, ApiError> {
+    let (lat, lon) = lat.zip(lon).ok_or(ApiError::InvalidRequest(
+        "lat and lon parameters are required",
+    ))?;
+    let lat = lat
+        .parse::<f64>()
+        .map_err(|_| ApiError::InvalidRequest("Invalid lat parameter"))?;
+    let lon = lon
+        .parse::<f64>()
+        .map_err(|_| ApiError::InvalidRequest("Invalid lon parameter"))?;
+
+    Ok(Address::from_lat_lon(lat, lon)?.to_string())
 }
 
 #[get("/coords?<address>")]
-async fn get_coords(address: String) -> Result<Json<Coords>, String> {
+async fn get_coords(address: Option<String>) -> Result<Json<Coords>, ApiError> {
+    let address = address.ok_or(ApiError::InvalidRequest("address parameter required"))?;
+
     Address::from_str(&address)
         .as_ref()
+        .map_err(Into::into)
         .map(Address::to_lat_lon)
         .map(Coords::from)
         .map(Json)
-        .map_err(|e| e.to_string())
 }
 
 #[derive(Serialize, Deserialize)]
@@ -45,3 +55,24 @@ impl From<(f64, f64)> for Coords {
         Self { lat, lon }
     }
 }
+
+#[derive(Responder)]
+#[response(status = 400)]
+enum ApiError {
+    #[response(status = 400)]
+    AlgorithmError(String),
+    #[response(status = 400)]
+    InvalidRequest(&'static str),
+}
+
+impl From<&this_algorithm::Error> for ApiError {
+    fn from(e: &this_algorithm::Error) -> Self {
+        Self::AlgorithmError(e.to_string())
+    }
+}
+
+impl From<this_algorithm::Error> for ApiError {
+    fn from(e: this_algorithm::Error) -> Self {
+        Self::from(&e)
+    }
+}