diff --git a/app/src/api.rs b/app/src/api.rs
index 894d1e2..dd9c618 100644
--- a/app/src/api.rs
+++ b/app/src/api.rs
@@ -39,103 +39,138 @@ where
     })
 }
 
+struct RequestBody<T>(T);
+
+impl<'a, R> From<&'a R> for RequestBody<Json<&'a R>>
+where
+    R: serde::ser::Serialize,
+{
+    fn from(request: &'a R) -> Self {
+        Self(Json(&request))
+    }
+}
+
+impl From<yew::format::Nothing> for RequestBody<yew::format::Nothing> {
+    fn from(request: yew::format::Nothing) -> Self {
+        Self(request)
+    }
+}
+
+fn call_server<Req, CallbackResult, Resp, F, RB>(
+    url: &str,
+    request: RB,
+    callback: Callback<Result<CallbackResult>>,
+    handler: F,
+) -> Result<FetchTask>
+where
+    F: Fn(http::StatusCode, Resp) -> Result<CallbackResult> + 'static,
+    CallbackResult: 'static,
+    RB: Into<RequestBody<Req>>,
+    Req: Into<yew::format::Text>,
+    Result<Resp>: From<Result<String>> + 'static,
+{
+    let request = Request::post(url)
+        .header("Content-Type", "application/json")
+        .body(request.into().0)?;
+    let handler = create_handler(callback, handler);
+    FetchService::fetch_with_options(request, get_default_options(), handler)
+}
+
 impl HostService {
     pub fn list_users(
         request: ListUsersRequest,
         callback: Callback<Result<Vec<User>>>,
     ) -> Result<FetchTask> {
-        let url = "/api/users";
-        let request = Request::post(url)
-            .header("Content-Type", "application/json")
-            .body(Json(&request))?;
-        let handler = create_handler(callback, |status, data: String| {
+        call_server("/api/users", &request, callback, |status, data: String| {
             if status.is_success() {
                 serde_json::from_str(&data).map_err(|e| anyhow!("Could not parse response: {}", e))
             } else {
                 Err(anyhow!("[{}]: {}", status, data))
             }
-        });
-        FetchService::fetch_with_options(request, get_default_options(), handler)
+        })
     }
 
     pub fn login_start(
         request: login::ClientLoginStartRequest,
         callback: Callback<Result<login::ServerLoginStartResponse>>,
     ) -> Result<FetchTask> {
-        let url = "/auth/opaque/login/start";
-        let request = Request::post(url)
-            .header("Content-Type", "application/json")
-            .body(Json(&request))?;
-        let handler = create_handler(callback, |status, data: String| {
-            if status.is_success() {
-                serde_json::from_str(&data).map_err(|e| anyhow!("Could not parse response: {}", e))
-            } else {
-                Err(anyhow!(
-                    "Could not start authentication: [{}]: {}",
-                    status,
-                    data
-                ))
-            }
-        });
-        FetchService::fetch_with_options(request, get_default_options(), handler)
+        call_server(
+            "/auth/opaque/login/start",
+            &request,
+            callback,
+            |status, data: String| {
+                if status.is_success() {
+                    serde_json::from_str(&data)
+                        .map_err(|e| anyhow!("Could not parse response: {}", e))
+                } else {
+                    Err(anyhow!(
+                        "Could not start authentication: [{}]: {}",
+                        status,
+                        data
+                    ))
+                }
+            },
+        )
     }
 
     pub fn login_finish(
         request: login::ClientLoginFinishRequest,
         callback: Callback<Result<String>>,
     ) -> Result<FetchTask> {
-        let url = "/auth/opaque/login/finish";
-        let request = Request::post(url)
-            .header("Content-Type", "application/json")
-            .body(Json(&request))?;
-        let handler = create_handler(callback, |status, data: String| {
-            if status.is_success() {
-                get_claims_from_jwt(&data)
-                    .map_err(|e| anyhow!("Could not parse response: {}", e))
-                    .and_then(|jwt_claims| {
-                        set_cookie("user_id", &jwt_claims.user, &jwt_claims.exp)
-                            .map(|_| jwt_claims.user.clone())
-                            .map_err(|e| anyhow!("Error clearing cookie: {}", e))
-                    })
-            } else {
-                Err(anyhow!(
-                    "Could not finish authentication: [{}]: {}",
-                    status,
-                    data
-                ))
-            }
-        });
-        FetchService::fetch_with_options(request, get_default_options(), handler)
+        call_server(
+            "/auth/opaque/login/finish",
+            &request,
+            callback,
+            |status, data: String| {
+                if status.is_success() {
+                    get_claims_from_jwt(&data)
+                        .map_err(|e| anyhow!("Could not parse response: {}", e))
+                        .and_then(|jwt_claims| {
+                            set_cookie("user_id", &jwt_claims.user, &jwt_claims.exp)
+                                .map(|_| jwt_claims.user.clone())
+                                .map_err(|e| anyhow!("Error clearing cookie: {}", e))
+                        })
+                } else {
+                    Err(anyhow!(
+                        "Could not finish authentication: [{}]: {}",
+                        status,
+                        data
+                    ))
+                }
+            },
+        )
     }
 
     pub fn logout(callback: Callback<Result<()>>) -> Result<FetchTask> {
-        let url = "/auth/logout";
-        let request = Request::post(url).body(yew::format::Nothing)?;
-        let handler = create_handler(callback, |status, data: String| {
-            if status.is_success() {
-                Ok(())
-            } else {
-                Err(anyhow!("Could not logout: [{}]: {}", status, data))
-            }
-        });
-        FetchService::fetch_with_options(request, get_default_options(), handler)
+        call_server(
+            "/auth/logout",
+            yew::format::Nothing,
+            callback,
+            |status, data: String| {
+                if status.is_success() {
+                    Ok(())
+                } else {
+                    Err(anyhow!("Could not logout: [{}]: {}", status, data))
+                }
+            },
+        )
     }
 
     pub fn create_user(
         request: CreateUserRequest,
         callback: Callback<Result<()>>,
     ) -> Result<FetchTask> {
-        let url = "/api/users/create";
-        let request = Request::post(url)
-            .header("Content-Type", "application/json")
-            .body(Json(&request))?;
-        let handler = create_handler(callback, |status, data: String| {
-            if status.is_success() {
-                Ok(())
-            } else {
-                Err(anyhow!("Could not create a user: [{}]: {}", status, data))
-            }
-        });
-        FetchService::fetch_with_options(request, get_default_options(), handler)
+        call_server(
+            "/api/users/create",
+            &request,
+            callback,
+            |status, data: String| {
+                if status.is_success() {
+                    Ok(())
+                } else {
+                    Err(anyhow!("Could not create a user: [{}]: {}", status, data))
+                }
+            },
+        )
     }
 }