add custom message for failed to signup due to username being taken

Cargo.toml

@@ -14,4 +14,4 @@ serde_json = "1.0"
 tracing = "0.1"
 tracing-subscriber = { version = "0.3", features = ["env-filter"] }
 sha256 = "1.1"
-
+jsonwebtoken = "8.3"

src/main.rs

@@ -16,6 +16,8 @@ async fn main() {
     // initialize tracing
     tracing_subscriber::fmt::init();
 
+    // Ex.
+    // export DATABASE_URL="postgres://school_app_api_user:school_app_api_pass@localhost/school_app_api"
     let db_url = std::env::var("DATABASE_URL")
         .expect("Set `DATABASE_URL` to the url of the postgres database.");
 
@@ -49,7 +51,6 @@ async fn root() -> &'static str {
 }
 
 async fn signup(State(pool): State<PgPool>, Json(signup): Json<Signup>) -> impl IntoResponse {
-    println!("{:?}", signup);
     // insert your application logic here
     let pass_hash = sha256::digest(&*signup.password);
 
@@ -67,10 +68,27 @@ RETURNING id;
 
     match result {
         Ok(record) => (StatusCode::CREATED, Json(json!({"id": record.id}))),
-        Err(err) => (
+        Err(err) => {
+            // See if we get an error for a duplicate usename
+            if let sqlx::Error::Database(database_err) = &err {
+                if let Some(err_code) = database_err.code() {
+                    if err_code == "23505" {
+                        return (
+                            StatusCode::BAD_REQUEST,
+                            Json(json!({
+                                "error": format!("username '{}' is taken.", signup.username)
+                            })),
+                        );
+                    }
+                }
+            }
+            (
                 StatusCode::INTERNAL_SERVER_ERROR,
-            Json(json!({ "error": format!("Error signing up: {}", err) })),
-        ),
+                Json(json!({
+                    "error": format!("Unknown error signing up: {}", err)
+                })),
+            )
+        }
     }
 }