import { type NavigationContainerRefWithCurrent } from '@react-navigation/native';
import { reportScreenChangeOnNative } from '../nativeCommunication';
import {
  ScreenChangePayload,
  ScreenHierarchyElement,
} from '../ScreenChangePayload';
import {
  compareHierarchies,
  getScreenHierarchyFromRootState,
} from './screenHierarchyUtils';

/**
 * Tracks navigation changes by subscribing to React Navigation events.
 */
export default class ReactNavigationTracker {
  private previousScreenHierarchy: ScreenHierarchyElement[];
  private stopTrackingFunction?: () => void;

  constructor(
    private readonly navigationContainerRef: NavigationContainerRefWithCurrent<any>
  ) {
    this.previousScreenHierarchy = [];
  }

  startTracking() {
    this.stopTrackingFunction = this.navigationContainerRef.addListener(
      'state',
      () => {
        this.handleNavigationStateChange();
      }
    );
    // Handle the initial state
    this.handleNavigationStateChange();
  }

  stopTracking() {
    this.stopTrackingFunction?.();
    this.stopTrackingFunction = undefined;
  }

  private handleNavigationStateChange() {
    const currentScreenHierarchy = getScreenHierarchyFromRootState(
      this.navigationContainerRef
    );

    const changes = compareHierarchies(
      currentScreenHierarchy,
      this.previousScreenHierarchy
    );

    this.reportDisappearingScreens(
      this.previousScreenHierarchy,
      changes.commonPrefixLength
    );
    this.reportAppearingScreens(
      currentScreenHierarchy,
      changes.commonPrefixLength
    );

    this.previousScreenHierarchy = currentScreenHierarchy;
  }

  private reportDisappearingScreens(
    previousScreenHierarchy: ScreenHierarchyElement[],
    commonPrefixLength: number
  ) {
    for (
      let i = previousScreenHierarchy.length - 1;
      i >= commonPrefixLength;
      i--
    ) {
      const screenHierarchyUpToDisappearingScreen =
        previousScreenHierarchy.slice(0, i + 1);
      const screenDisappearPayload = new ScreenChangePayload(
        screenHierarchyUpToDisappearingScreen,
        'disappear',
        'auto'
      );
      reportScreenChangeOnNative(screenDisappearPayload);
    }
  }

  private reportAppearingScreens(
    currentScreenHierarchy: ScreenHierarchyElement[],
    commonPrefixLength: number
  ) {
    for (let i = commonPrefixLength; i < currentScreenHierarchy.length; i++) {
      const screenHierarchyUpToAppearingScreen = currentScreenHierarchy.slice(
        0,
        i + 1
      );
      const screenAppearPayload = new ScreenChangePayload(
        screenHierarchyUpToAppearingScreen,
        'appear',
        'auto'
      );
      reportScreenChangeOnNative(screenAppearPayload);
    }
  }
}