import type {
  NavigationContainerRefWithCurrent,
  NavigationState,
  PartialState,
} from '@react-navigation/native';
import { ScreenHierarchyElement } from '../ScreenChangePayload';

/**
 * Compares screen hierarchies and returns information about what changed.
 */
export function compareHierarchies(
  currentScreenHierarchy: ScreenHierarchyElement[],
  previousScreenHierarchy: ScreenHierarchyElement[]
) {
  const commonPrefixLength = findCommonPrefixLength(
    currentScreenHierarchy,
    previousScreenHierarchy
  );

  return {
    commonPrefixLength,
    disappearingScreens: previousScreenHierarchy.slice(commonPrefixLength),
    appearingScreens: currentScreenHierarchy.slice(commonPrefixLength),
  };
}

/**
 * Extracts screen hierarchy from the navigation state.
 */
export function getScreenHierarchyFromRootState(
  navigationContainerRef: NavigationContainerRefWithCurrent<any>
): ScreenHierarchyElement[] {
  const rootState = navigationContainerRef.getRootState();
  const rootNavigator: ScreenHierarchyElement[] = rootState?.type
    ? [new ScreenHierarchyElement('RootNavigator', rootState.type)]
    : [];

  return getScreenHierarchyRecursively(rootState, rootNavigator);
}

function findCommonPrefixLength(
  current: ScreenHierarchyElement[],
  previous: ScreenHierarchyElement[]
): number {
  const maxPossiblePrefixLength = Math.min(current.length, previous.length);
  for (let i = 0; i < maxPossiblePrefixLength; i++) {
    const currentScreen = current[i];
    const previousScreen = previous[i];
    if (currentScreen?.screenName !== previousScreen?.screenName) {
      return i;
    }
  }
  return maxPossiblePrefixLength;
}

function getScreenHierarchyRecursively(
  state: NavigationState | PartialState<NavigationState>,
  screenHierarchy: ScreenHierarchyElement[] = []
): ScreenHierarchyElement[] {
  if (state?.index === undefined) {
    return screenHierarchy;
  }

  const route = state?.routes?.[state.index];
  if (!route) return screenHierarchy;

  let screenType = route?.state?.type ?? 'screen';

  const updatedHierarchy = [
    ...screenHierarchy,
    new ScreenHierarchyElement(route.name, screenType),
  ];

  if (route.state) {
    return getScreenHierarchyRecursively(route.state, updatedHierarchy);
  }

  return updatedHierarchy;
}