import {
  NavigationTransition,
  NavigationTransitionNavigationType,
  NavigationTransitionWait,
  NavigationIntercept,
} from "./navigation-transition";
import { Navigation } from "./navigation";
import { NavigationHistoryEntry } from "./navigation-entry";
import { InvalidStateError } from "./navigation-errors";

export interface NavigationTransitionPlannerOptions {
  transition: NavigationTransition;
  currentPlan?: NavigationTransitionPlan;
  finishedTransitions?: Set<NavigationTransition>;
  constructNavigation(): Navigation;
}

export const NavigationTransitionPlanNavigationSymbol = Symbol.for(
  "@virtualstate/navigation/transition/plan/Navigation"
);
export const NavigationTransitionPlanWhile = Symbol.for(
  "@virtualstate/navigation/transition/plan/while"
);
export const NavigationTransitionPlanWait = Symbol.for(
  "@virtualstate/navigation/transition/plan/wait"
);

export interface NavigationTransitionPlan<S = unknown> {
  [NavigationTransitionPlanNavigationSymbol]: Navigation;
  [NavigationTransitionPlanWhile](promise: Promise<unknown>): void;
  [NavigationTransitionPlanWait](): Promise<NavigationHistoryEntry<S>>;
  transitions: NavigationTransition[];
  known: Set<NavigationHistoryEntry<S>>;
  knownTransitions: Set<NavigationTransition>;
  resolve(): Promise<void>;
}

export function plan(options: NavigationTransitionPlannerOptions) {
  const { transition, currentPlan, constructNavigation, finishedTransitions } =
    options;
  const nextPlan: NavigationTransitionPlan = {
    [NavigationTransitionPlanNavigationSymbol]:
      currentPlan?.[NavigationTransitionPlanNavigationSymbol] ??
      constructNavigation(),
    transitions: [],
    ...currentPlan,
    knownTransitions: new Set(currentPlan?.knownTransitions ?? []),
    [NavigationTransitionPlanWhile]: transition[NavigationIntercept],
    [NavigationTransitionPlanWait]: transition[NavigationTransitionWait],
  };
  if (nextPlan.knownTransitions.has(transition)) {
    throw new InvalidStateError(
      "Transition already found in plan, this may lead to unexpected behaviour, please raise an issue at "
    );
  }
  nextPlan.knownTransitions.add(transition);
  if (transition[NavigationTransitionNavigationType] === "traverse") {
    nextPlan.transitions.push(transition);
  } else {
    // Reset on non traversal
    nextPlan.transitions = [].concat([transition]);
  }
  nextPlan.transitions = nextPlan.transitions
    // Remove finished transitions
    .filter((transition) => finishedTransitions?.has(transition));
  return nextPlan;
}