@react-navigation/stack/src/views/Stack/CardStack.tsx

import {
  Background,
  getDefaultHeaderHeight,
  SafeAreaProviderCompat,
} from '@react-navigation/elements';
import type {
  ParamListBase,
  Route,
  StackNavigationState,
} from '@react-navigation/native';
import Color from 'color';
import * as React from 'react';
import {
  Animated,
  LayoutChangeEvent,
  Platform,
  StyleSheet,
} from 'react-native';
import type { EdgeInsets } from 'react-native-safe-area-context';

import {
  forModalPresentationIOS,
  forNoAnimation as forNoAnimationCard,
} from '../../TransitionConfigs/CardStyleInterpolators';
import {
  DefaultTransition,
  ModalFadeTransition,
  ModalTransition,
} from '../../TransitionConfigs/TransitionPresets';
import type {
  Layout,
  Scene,
  StackDescriptor,
  StackDescriptorMap,
  StackHeaderMode,
  StackNavigationOptions,
} from '../../types';
import findLastIndex from '../../utils/findLastIndex';
import getDistanceForDirection from '../../utils/getDistanceForDirection';
import type { Props as HeaderContainerProps } from '../Header/HeaderContainer';
import { MaybeScreen, MaybeScreenContainer } from '../Screens';
import { getIsModalPresentation } from './Card';
import CardContainer from './CardContainer';

type GestureValues = {
  [key: string]: Animated.Value;
};

type Props = {
  insets: EdgeInsets;
  state: StackNavigationState<ParamListBase>;
  descriptors: StackDescriptorMap;
  routes: Route<string>[];
  openingRouteKeys: string[];
  closingRouteKeys: string[];
  onOpenRoute: (props: { route: Route<string> }) => void;
  onCloseRoute: (props: { route: Route<string> }) => void;
  getPreviousRoute: (props: {
    route: Route<string>;
  }) => Route<string> | undefined;
  renderHeader: (props: HeaderContainerProps) => React.ReactNode;
  renderScene: (props: { route: Route<string> }) => React.ReactNode;
  isParentHeaderShown: boolean;
  isParentModal: boolean;
  onTransitionStart: (
    props: { route: Route<string> },
    closing: boolean
  ) => void;
  onTransitionEnd: (props: { route: Route<string> }, closing: boolean) => void;
  onGestureStart: (props: { route: Route<string> }) => void;
  onGestureEnd: (props: { route: Route<string> }) => void;
  onGestureCancel: (props: { route: Route<string> }) => void;
  detachInactiveScreens?: boolean;
};

type State = {
  routes: Route<string>[];
  descriptors: StackDescriptorMap;
  scenes: Scene[];
  gestures: GestureValues;
  layout: Layout;
  headerHeights: Record<string, number>;
};

const EPSILON = 1e-5;

const STATE_INACTIVE = 0;
const STATE_TRANSITIONING_OR_BELOW_TOP = 1;
const STATE_ON_TOP = 2;

const FALLBACK_DESCRIPTOR = Object.freeze({ options: {} });

const getInterpolationIndex = (scenes: Scene[], index: number) => {
  const { cardStyleInterpolator } = scenes[index].descriptor.options;

  // Start from current card and count backwards the number of cards with same interpolation
  let interpolationIndex = 0;

  for (let i = index - 1; i >= 0; i--) {
    const cardStyleInterpolatorCurrent =
      scenes[i]?.descriptor.options.cardStyleInterpolator;

    if (cardStyleInterpolatorCurrent !== cardStyleInterpolator) {
      break;
    }

    interpolationIndex++;
  }

  return interpolationIndex;
};

const getIsModal = (
  scene: Scene,
  interpolationIndex: number,
  isParentModal: boolean
) => {
  if (isParentModal) {
    return true;
  }

  const { cardStyleInterpolator } = scene.descriptor.options;
  const isModalPresentation = getIsModalPresentation(cardStyleInterpolator);
  const isModal = isModalPresentation && interpolationIndex !== 0;

  return isModal;
};

const getHeaderHeights = (
  scenes: Scene[],
  insets: EdgeInsets,
  isParentHeaderShown: boolean,
  isParentModal: boolean,
  layout: Layout,
  previous: Record<string, number>
) => {
  return scenes.reduce<Record<string, number>>((acc, curr, index) => {
    const {
      headerStatusBarHeight = isParentHeaderShown ? 0 : insets.top,
      headerStyle,
    } = curr.descriptor.options;

    const style = StyleSheet.flatten(headerStyle || {});

    const height =
      'height' in style && typeof style.height === 'number'
        ? style.height
        : previous[curr.route.key];

    const interpolationIndex = getInterpolationIndex(scenes, index);
    const isModal = getIsModal(curr, interpolationIndex, isParentModal);

    acc[curr.route.key] =
      typeof height === 'number'
        ? height
        : getDefaultHeaderHeight(layout, isModal, headerStatusBarHeight);

    return acc;
  }, {});
};

const getDistanceFromOptions = (
  layout: Layout,
  descriptor?: StackDescriptor
) => {
  const {
    presentation,
    gestureDirection = presentation === 'modal'
      ? ModalTransition.gestureDirection
      : DefaultTransition.gestureDirection,
  } = (descriptor?.options || {}) as StackNavigationOptions;

  return getDistanceForDirection(layout, gestureDirection);
};

const getProgressFromGesture = (
  gesture: Animated.Value,
  layout: Layout,
  descriptor?: StackDescriptor
) => {
  const distance = getDistanceFromOptions(
    {
      // Make sure that we have a non-zero distance, otherwise there will be incorrect progress
      // This causes blank screen on web if it was previously inside container with display: none
      width: Math.max(1, layout.width),
      height: Math.max(1, layout.height),
    },
    descriptor
  );

  if (distance > 0) {
    return gesture.interpolate({
      inputRange: [0, distance],
      outputRange: [1, 0],
    });
  }

  return gesture.interpolate({
    inputRange: [distance, 0],
    outputRange: [0, 1],
  });
};

export default class CardStack extends React.Component<Props, State> {
  static getDerivedStateFromProps(
    props: Props,
    state: State
  ): Partial<State> | null {
    if (
      props.routes === state.routes &&
      props.descriptors === state.descriptors
    ) {
      return null;
    }

    const gestures = props.routes.reduce<GestureValues>((acc, curr) => {
      const descriptor = props.descriptors[curr.key];
      const { animationEnabled } = descriptor?.options || {};

      acc[curr.key] =
        state.gestures[curr.key] ||
        new Animated.Value(
          props.openingRouteKeys.includes(curr.key) &&
          animationEnabled !== false
            ? getDistanceFromOptions(state.layout, descriptor)
            : 0
        );

      return acc;
    }, {});

    const scenes = props.routes.map((route, index, self) => {
      const previousRoute = self[index - 1];
      const nextRoute = self[index + 1];

      const oldScene = state.scenes[index];

      const currentGesture = gestures[route.key];
      const previousGesture = previousRoute
        ? gestures[previousRoute.key]
        : undefined;
      const nextGesture = nextRoute ? gestures[nextRoute.key] : undefined;

      const descriptor =
        props.descriptors[route.key] ||
        state.descriptors[route.key] ||
        (oldScene ? oldScene.descriptor : FALLBACK_DESCRIPTOR);

      const nextDescriptor =
        props.descriptors[nextRoute?.key] || state.descriptors[nextRoute?.key];

      const previousDescriptor =
        props.descriptors[previousRoute?.key] ||
        state.descriptors[previousRoute?.key];

      // When a screen is not the last, it should use next screen's transition config
      // Many transitions also animate the previous screen, so using 2 different transitions doesn't look right
      // For example combining a slide and a modal transition would look wrong otherwise
      // With this approach, combining different transition styles in the same navigator mostly looks right
      // This will still be broken when 2 transitions have different idle state (e.g. modal presentation),
      // but majority of the transitions look alright
      const optionsForTransitionConfig =
        index !== self.length - 1 &&
        nextDescriptor &&
        nextDescriptor.options.presentation !== 'transparentModal'
          ? nextDescriptor.options
          : descriptor.options;

      let defaultTransitionPreset =
        optionsForTransitionConfig.presentation === 'modal'
          ? ModalTransition
          : optionsForTransitionConfig.presentation === 'transparentModal'
          ? ModalFadeTransition
          : DefaultTransition;

      const {
        animationEnabled = Platform.OS !== 'web' &&
          Platform.OS !== 'windows' &&
          Platform.OS !== 'macos',
        gestureEnabled = Platform.OS === 'ios' && animationEnabled,
        gestureDirection = defaultTransitionPreset.gestureDirection,
        transitionSpec = defaultTransitionPreset.transitionSpec,
        cardStyleInterpolator = animationEnabled === false
          ? forNoAnimationCard
          : defaultTransitionPreset.cardStyleInterpolator,
        headerStyleInterpolator = defaultTransitionPreset.headerStyleInterpolator,
        cardOverlayEnabled = (Platform.OS !== 'ios' &&
          optionsForTransitionConfig.presentation !== 'transparentModal') ||
          getIsModalPresentation(cardStyleInterpolator),
      } = optionsForTransitionConfig;

      const headerMode: StackHeaderMode =
        descriptor.options.headerMode ??
        (!(
          optionsForTransitionConfig.presentation === 'modal' ||
          optionsForTransitionConfig.presentation === 'transparentModal' ||
          nextDescriptor?.options.presentation === 'modal' ||
          nextDescriptor?.options.presentation === 'transparentModal' ||
          getIsModalPresentation(cardStyleInterpolator)
        ) &&
        Platform.OS === 'ios' &&
        descriptor.options.header === undefined
          ? 'float'
          : 'screen');

      const scene = {
        route,
        descriptor: {
          ...descriptor,
          options: {
            ...descriptor.options,
            animationEnabled,
            cardOverlayEnabled,
            cardStyleInterpolator,
            gestureDirection,
            gestureEnabled,
            headerStyleInterpolator,
            transitionSpec,
            headerMode,
          },
        },
        progress: {
          current: getProgressFromGesture(
            currentGesture,
            state.layout,
            descriptor
          ),
          next:
            nextGesture &&
            nextDescriptor?.options.presentation !== 'transparentModal'
              ? getProgressFromGesture(
                  nextGesture,
                  state.layout,
                  nextDescriptor
                )
              : undefined,
          previous: previousGesture
            ? getProgressFromGesture(
                previousGesture,
                state.layout,
                previousDescriptor
              )
            : undefined,
        },
        __memo: [
          state.layout,
          descriptor,
          nextDescriptor,
          previousDescriptor,
          currentGesture,
          nextGesture,
          previousGesture,
        ],
      };

      if (
        oldScene &&
        scene.__memo.every((it, i) => {
          // @ts-expect-error: we haven't added __memo to the annotation to prevent usage elsewhere
          return oldScene.__memo[i] === it;
        })
      ) {
        return oldScene;
      }

      return scene;
    });

    return {
      routes: props.routes,
      scenes,
      gestures,
      descriptors: props.descriptors,
      headerHeights: getHeaderHeights(
        scenes,
        props.insets,
        props.isParentHeaderShown,
        props.isParentModal,
        state.layout,
        state.headerHeights
      ),
    };
  }

  constructor(props: Props) {
    super(props);

    this.state = {
      routes: [],
      scenes: [],
      gestures: {},
      layout: SafeAreaProviderCompat.initialMetrics.frame,
      descriptors: this.props.descriptors,
      // Used when card's header is null and mode is float to make transition
      // between screens with headers and those without headers smooth.
      // This is not a great heuristic here. We don't know synchronously
      // on mount what the header height is so we have just used the most
      // common cases here.
      headerHeights: {},
    };
  }

  private handleLayout = (e: LayoutChangeEvent) => {
    const { height, width } = e.nativeEvent.layout;

    const layout = { width, height };

    this.setState((state, props) => {
      if (height === state.layout.height && width === state.layout.width) {
        return null;
      }

      return {
        layout,
        headerHeights: getHeaderHeights(
          state.scenes,
          props.insets,
          props.isParentHeaderShown,
          props.isParentModal,
          layout,
          state.headerHeights
        ),
      };
    });
  };

  private handleHeaderLayout = ({
    route,
    height,
  }: {
    route: Route<string>;
    height: number;
  }) => {
    this.setState(({ headerHeights }) => {
      const previousHeight = headerHeights[route.key];

      if (previousHeight === height) {
        return null;
      }

      return {
        headerHeights: {
          ...headerHeights,
          [route.key]: height,
        },
      };
    });
  };

  private getFocusedRoute = () => {
    const { state } = this.props;

    return state.routes[state.index];
  };

  private getPreviousScene = ({ route }: { route: Route<string> }) => {
    const { getPreviousRoute } = this.props;
    const { scenes } = this.state;

    const previousRoute = getPreviousRoute({ route });

    if (previousRoute) {
      const previousScene = scenes.find(
        (scene) => scene.descriptor.route.key === previousRoute.key
      );

      return previousScene;
    }

    return undefined;
  };

  render() {
    const {
      insets,
      state,
      routes,
      closingRouteKeys,
      onOpenRoute,
      onCloseRoute,
      renderHeader,
      renderScene,
      isParentHeaderShown,
      isParentModal,
      onTransitionStart,
      onTransitionEnd,
      onGestureStart,
      onGestureEnd,
      onGestureCancel,
      detachInactiveScreens = Platform.OS === 'web' ||
        Platform.OS === 'android' ||
        Platform.OS === 'ios',
    } = this.props;

    const { scenes, layout, gestures, headerHeights } = this.state;

    const focusedRoute = state.routes[state.index];
    const focusedHeaderHeight = headerHeights[focusedRoute.key];

    const isFloatHeaderAbsolute = this.state.scenes.slice(-2).some((scene) => {
      const options = scene.descriptor.options ?? {};
      const { headerMode, headerTransparent, headerShown = true } = options;

      if (
        headerTransparent ||
        headerShown === false ||
        headerMode === 'screen'
      ) {
        return true;
      }

      return false;
    });

    let activeScreensLimit = 1;

    for (let i = scenes.length - 1; i >= 0; i--) {
      const { options } = scenes[i].descriptor;
      const {
        // By default, we don't want to detach the previous screen of the active one for modals
        detachPreviousScreen = options.presentation === 'transparentModal'
          ? false
          : getIsModalPresentation(options.cardStyleInterpolator)
          ? i !==
            findLastIndex(scenes, (scene) => {
              const { cardStyleInterpolator } = scene.descriptor.options;

              return (
                cardStyleInterpolator === forModalPresentationIOS ||
                cardStyleInterpolator?.name === 'forModalPresentationIOS'
              );
            })
          : true,
      } = options;

      if (detachPreviousScreen === false) {
        activeScreensLimit++;
      } else {
        // Check at least last 2 screens before stopping
        // This will make sure that screen isn't detached when another screen is animating on top of the transparent one
        // For example, (Opaque -> Transparent -> Opaque)
        if (i <= scenes.length - 2) {
          break;
        }
      }
    }

    const floatingHeader = (
      <React.Fragment key="header">
        {renderHeader({
          mode: 'float',
          layout,
          scenes,
          getPreviousScene: this.getPreviousScene,
          getFocusedRoute: this.getFocusedRoute,
          onContentHeightChange: this.handleHeaderLayout,
          style: [
            styles.floating,
            isFloatHeaderAbsolute && [
              // Without this, the header buttons won't be touchable on Android when headerTransparent: true
              { height: focusedHeaderHeight },
              styles.absolute,
            ],
          ],
        })}
      </React.Fragment>
    );

    return (
      <Background>
        {isFloatHeaderAbsolute ? null : floatingHeader}
        <MaybeScreenContainer
          enabled={detachInactiveScreens}
          style={styles.container}
          onLayout={this.handleLayout}
        >
          {routes.map((route, index, self) => {
            const focused = focusedRoute.key === route.key;
            const gesture = gestures[route.key];
            const scene = scenes[index];

            // For the screens that shouldn't be active, the value is 0
            // For those that should be active, but are not the top screen, the value is 1
            // For those on top of the stack and with interaction enabled, the value is 2
            // For the old implementation, it stays the same it was
            let isScreenActive: Animated.AnimatedInterpolation | 2 | 1 | 0 = 1;

            if (index < self.length - activeScreensLimit - 1) {
              // screen should be inactive because it is too deep in the stack
              isScreenActive = STATE_INACTIVE;
            } else {
              const sceneForActivity = scenes[self.length - 1];
              const outputValue =
                index === self.length - 1
                  ? STATE_ON_TOP // the screen is on top after the transition
                  : index >= self.length - activeScreensLimit
                  ? STATE_TRANSITIONING_OR_BELOW_TOP // the screen should stay active after the transition, it is not on top but is in activeLimit
                  : STATE_INACTIVE; // the screen should be active only during the transition, it is at the edge of activeLimit
              isScreenActive = sceneForActivity
                ? sceneForActivity.progress.current.interpolate({
                    inputRange: [0, 1 - EPSILON, 1],
                    outputRange: [1, 1, outputValue],
                    extrapolate: 'clamp',
                  })
                : STATE_TRANSITIONING_OR_BELOW_TOP;
            }

            const {
              headerShown = true,
              headerTransparent,
              headerStyle,
              headerTintColor,
              freezeOnBlur,
            } = scene.descriptor.options;

            const safeAreaInsetTop = insets.top;
            const safeAreaInsetRight = insets.right;
            const safeAreaInsetBottom = insets.bottom;
            const safeAreaInsetLeft = insets.left;

            const headerHeight =
              headerShown !== false ? headerHeights[route.key] : 0;

            let headerDarkContent: boolean | undefined;

            if (headerShown) {
              if (typeof headerTintColor === 'string') {
                headerDarkContent = Color(headerTintColor).isDark();
              } else {
                const flattenedHeaderStyle = StyleSheet.flatten(headerStyle);

                if (
                  flattenedHeaderStyle &&
                  'backgroundColor' in flattenedHeaderStyle &&
                  typeof flattenedHeaderStyle.backgroundColor === 'string'
                ) {
                  headerDarkContent = !Color(
                    flattenedHeaderStyle.backgroundColor
                  ).isDark();
                }
              }
            }

            // Start from current card and count backwards the number of cards with same interpolation
            const interpolationIndex = getInterpolationIndex(scenes, index);
            const isModal = getIsModal(
              scene,
              interpolationIndex,
              isParentModal
            );

            const isNextScreenTransparent =
              scenes[index + 1]?.descriptor.options.presentation ===
              'transparentModal';

            const detachCurrentScreen =
              scenes[index + 1]?.descriptor.options.detachPreviousScreen !==
              false;

            return (
              <MaybeScreen
                key={route.key}
                style={StyleSheet.absoluteFill}
                enabled={detachInactiveScreens}
                active={isScreenActive}
                freezeOnBlur={freezeOnBlur}
                pointerEvents="box-none"
              >
                <CardContainer
                  index={index}
                  interpolationIndex={interpolationIndex}
                  modal={isModal}
                  active={index === self.length - 1}
                  focused={focused}
                  closing={closingRouteKeys.includes(route.key)}
                  layout={layout}
                  gesture={gesture}
                  scene={scene}
                  safeAreaInsetTop={safeAreaInsetTop}
                  safeAreaInsetRight={safeAreaInsetRight}
                  safeAreaInsetBottom={safeAreaInsetBottom}
                  safeAreaInsetLeft={safeAreaInsetLeft}
                  onGestureStart={onGestureStart}
                  onGestureCancel={onGestureCancel}
                  onGestureEnd={onGestureEnd}
                  headerHeight={headerHeight}
                  isParentHeaderShown={isParentHeaderShown}
                  onHeaderHeightChange={this.handleHeaderLayout}
                  getPreviousScene={this.getPreviousScene}
                  getFocusedRoute={this.getFocusedRoute}
                  headerDarkContent={headerDarkContent}
                  hasAbsoluteFloatHeader={
                    isFloatHeaderAbsolute && !headerTransparent
                  }
                  renderHeader={renderHeader}
                  renderScene={renderScene}
                  onOpenRoute={onOpenRoute}
                  onCloseRoute={onCloseRoute}
                  onTransitionStart={onTransitionStart}
                  onTransitionEnd={onTransitionEnd}
                  isNextScreenTransparent={isNextScreenTransparent}
                  detachCurrentScreen={detachCurrentScreen}
                />
              </MaybeScreen>
            );
          })}
        </MaybeScreenContainer>
        {isFloatHeaderAbsolute ? floatingHeader : null}
      </Background>
    );
  }
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
  },
  absolute: {
    position: 'absolute',
    top: 0,
    left: 0,
    right: 0,
  },
  floating: {
    zIndex: 1,
  },
});