Refactor HTTP implementation of API methods

sync-server/src/api/get_child_version.rs

@@ -1,7 +1,17 @@
-use crate::api::ServerState;
+use crate::api::{
+    ServerState, HISTORY_SEGMENT_CONTENT_TYPE, PARENT_VERSION_ID_HEADER, VERSION_ID_HEADER,
+};
 use crate::types::{ClientId, VersionId};
 use actix_web::{error, get, http::StatusCode, web, HttpResponse, Result};
 
+/// Get a child version.
+///
+/// On succcess, the response is the same sequence of bytes originally sent to the server,
+/// with content-type `application/vnd.taskchampion.history-segment`.  The `X-Version-Id` and
+/// `X-Parent-Version-Id` headers contain the corresponding values.
+///
+/// If no such child exists, returns a 404 with no content.
+/// Returns other 4xx or 5xx responses on other errors.
 #[get("/client/{client_id}/get-child-version/{parent_version_id}")]
 pub(crate) async fn service(
     data: web::Data<ServerState>,
@@ -11,7 +21,14 @@ pub(crate) async fn service(
         .get_child_version(client_id, parent_version_id)
         .map_err(|e| error::InternalError::new(e, StatusCode::INTERNAL_SERVER_ERROR))?;
     if let Some(result) = result {
-        Ok(HttpResponse::Ok().json(result))
+        Ok(HttpResponse::Ok()
+            .content_type(HISTORY_SEGMENT_CONTENT_TYPE)
+            .header(VERSION_ID_HEADER, result.version_id.to_string())
+            .header(
+                PARENT_VERSION_ID_HEADER,
+                result.parent_version_id.to_string(),
+            )
+            .body(result.history_segment))
     } else {
         Err(error::ErrorNotFound("no such version"))
     }