Statum/src/SlotPostEndpoint.vala

using Invercargill;
using Invercargill.DataStructures;
using InvercargillJson;
using Inversion;
using Astralis;

namespace Statum {

    /**
     * `POST /_statum/slots` — refreshes snapshots whose `transmit_after` window
     * has elapsed, and is also the target of a `transmit(retry)` directive.
     *
     * The client POSTs a JSON array of Statum frames it holds. For each frame
     * this endpoint verifies the signature: on success it
     * {@link StateService.restore_slot}s the slot into the cache, re-signs it
     * (issuing a fresh `as_at`/`transmit_after`), and returns a `set` directive
     * so the client refreshes its local snapshot; on failure it returns an
     * `invalidate` for that frame's signature so the client drops the slot whose
     * frame the server could not trust.
     */
    public class SlotPostEndpoint : Object, Endpoint {

        private StateService state_service = inject<StateService>();
        private Cryptography.SigningProvider signing_provider = inject<Cryptography.SigningProvider>();

        public async HttpResult handle_request(HttpContext http_context, RouteContext route_context) throws GLib.Error {
            var body = yield http_context.request.request_body.read_all();
            var body_str = body.to_raw_string();

            var directives = new Series<Model.DirectiveDto>();
            var invalid_signatures = new Series<string>();

            if (body_str.strip().length > 0) {
                var body_element = new JsonElement.from_string(body_str);
                var array = body_element.as<JsonArray>();
                foreach (var item in array) {
                    var frame = Model.FrameDto.get_mapper().materialise(item.as<JsonObject>());

                    try {
                        signing_provider.verify_frame(frame);
                    } catch (GLib.Error e) {
                        // Signature did not verify: tell the client to drop the
                        // slot holding this frame, identified by signature.
                        if (frame.signature != null && frame.signature.length > 0) {
                            invalid_signatures.add(frame.signature);
                        }
                        continue;
                    }

                    var content_element = new JsonElement.from_string(frame.content);
                    var content_object = content_element.as<JsonObject>();
                    var snapshot = Model.SnapshotDto.get_mapper().materialise(content_object);

                    state_service.restore_slot(frame);

                    var refreshed = state_service.sign_slot(snapshot.slot.key);
                    if (refreshed != null) {
                        directives.add(new Model.SetDirectiveDto.with_frame((!)refreshed));
                    }
                }
            }

            return StatumDirectives.to_result(directives, invalid_signatures);
        }

    }

}