Statum/src/ActionRegistry.vala

using Invercargill.DataStructures;
using InvercargillJson;
using Inversion;

namespace Statum {

    /**
     * Resolves Statum actions to/from their auto-assigned GUID endpoints; the
     * design follows the old Spry 0.1 `PathProvider`, removed in Spry 0.2.
     *
     * Every action registered via {@link StatumConfigurator.action} is assigned a
     * random GUID and served at `/_statum/action/{guid}` by a single
     * {@link ActionEndpoint}. The same GUID (looked up by type) is used when an
     * {@link Statum.Model.ActionDto} reference is authored for embedding in state.
     *
     * GUIDs are random per process start; this is fine because action references
     * are re-embedded into state on every entrypoint load, so a stale GUID never
     * survives a page render.
     */
    public class ActionRegistry : Object {

        private Cryptography.EncryptionProvider encryption_provider = inject<Cryptography.EncryptionProvider>();

        private Dictionary<string, Type> guid_to_type = new Dictionary<string, Type>();
        private Dictionary<string, string> type_to_guid = new Dictionary<string, string>();

        /** Registers an action type and assigns it a GUID (idempotent). */
        public void register<TAction>() {
            register_type(typeof(TAction));
        }

        /** Registers an action type and assigns it a GUID (idempotent). */
        public void register_type(Type type) {
            var name = type.name();
            if (type_to_guid.has(name)) {
                return;
            }
            var guid = Uuid.string_random();
            guid_to_type[guid] = type;
            type_to_guid[name] = guid;
        }

        /** The GUID assigned to `TAction` (registering it first if needed). */
        public string guid_for<TAction>() {
            return guid_for_type(typeof(TAction));
        }

        /** The GUID assigned to `type` (registering it first if needed). */
        public string guid_for_type(Type type) {
            var name = type.name();
            string guid;
            if (type_to_guid.try_get(name, out guid)) {
                return guid;
            }
            register_type(type);
            type_to_guid.try_get(name, out guid);
            return guid;
        }

        /** Resolves a GUID back to its action type for dispatch, or `null`. */
        public Type? resolve(string guid) {
            Type type;
            if (guid_to_type.try_get(guid, out type)) {
                return type;
            }
            return null;
        }

        /** The seal namespace for `TAction`'s private data (its type name). */
        public string namespace_for<TAction>() {
            return typeof(TAction).name();
        }

        /** The seal namespace for `type`'s private data (its type name). */
        public string namespace_for_type(Type type) {
            return type.name();
        }

        /**
         * Authors an {@link Model.ActionDto} reference for `TAction` (no private
         * data) that the client can invoke via `stm-action`.
         */
        public Model.ActionDto author<TAction>(string method = "POST") {
            return new Model.ActionDto() {
                uri = @"/_statum/action/$(guid_for<TAction>())",
                method = method
            };
        }

        /**
         * Authors an {@link Model.ActionDto} reference for `TAction` carrying
         * `model` as sealed private data. The blob is sealed under
         * {@link namespace_for}'s namespace, which the matching
         * `TypedStatumAction<TPrivate>` handler decrypts with its per-type
         * namespace.
         *
         * (Named distinctly from {@link author} because Vala does not permit
         * methods that overload on generic arity.)
         */
        public Model.ActionDto author_private<TAction, TPrivate>(TPrivate model, string method = "POST") throws GLib.Error {
            var blob = encryption_provider.author_properties(
                namespace_for<TAction>(),
                GObjectMapping.to_properties((Object) model));
            return new Model.ActionDto() {
                uri = @"/_statum/action/$(guid_for<TAction>())",
                method = method,
                @private = blob
            };
        }
    }
}