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library seaside.continuation;
import 'package:shelf/shelf.dart';
import 'component.dart';
import 'has_state.dart';
import 'keys.dart';
/// Type of an action callback function.
typedef Action = void Function();
/// Part of the flow of pages within a session.
class Continuation {
final String sessionKey;
final String continuationKey;
final Map<HasState, dynamic> snapshots = Map.identity();
final Map<String, Action> callbacks = {};
Continuation(this.sessionKey, this.continuationKey, Component component) {
.expand((child) => child.states)
.forEach((state) => snapshots[state] = state.snapshot());
/// Restores the state and executes the callbacks of the request.
void call(Request request) {
final queryParameters = request.requestedUri.queryParameters;
snapshots.forEach((key, value) => key.restore(value));
.forEach((key) => callbacks[key]());
/// Registers a [callback] and returns the corresponding URL.
Uri action(Action callback) {
final actionKey = callbacks.length.toString();
callbacks[actionKey] = callback;
return Uri(queryParameters: {
sessionParam: sessionKey,
continuationParam: continuationKey,
actionKey: '',