mattermost-mobile-upstream/app/components/keyboard_aware_post_draft_container.tsx

// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
// See LICENSE.txt for license information.

import React, {useCallback, useEffect, useRef, type ReactNode} from 'react';
import {BackHandler, DeviceEventEmitter, Platform, type StyleProp, StyleSheet, type ViewStyle, View, type LayoutChangeEvent} from 'react-native';
import {KeyboardGestureArea} from 'react-native-keyboard-controller';
import Animated, {scrollTo, useAnimatedStyle} from 'react-native-reanimated';
import {scheduleOnUI} from 'react-native-worklets';

import CustomEmojiPicker from '@components/post_draft/custom_emoji_picker';
import {Events} from '@constants';
import {useKeyboardState} from '@context/keyboard_state';
import useDidMount from '@hooks/did_mount';
import {dismissKeyboard} from '@utils/keyboard';

type Props = {
    children: ReactNode;
    renderList: () => ReactNode;
    textInputNativeID: string;
    containerStyle?: StyleProp<ViewStyle>;
};

const styles = StyleSheet.create({
    gestureArea: {
        justifyContent: 'flex-end',
        flex: 1,
    },
    inputContainer: {
        position: 'absolute',
        bottom: 0,
        left: 0,
        right: 0,
    },
});

/**
 * Wrapper component that provides keyboard-aware behavior for post draft screens
 * Handles keyboard animations, scroll adjustments, and input container positioning
*/
export const KeyboardAwarePostDraftContainer = ({
    children,
    renderList,
    textInputNativeID,
    containerStyle,
}: Props) => {
    const {
        stateContext,
        showInputAccessoryView,
        closeInputAccessoryView,
        listRef,
    } = useKeyboardState();

    const inputContainerAnimatedStyle = useAnimatedStyle(
        () => {
            return {
                transform: [{translateY: -stateContext.postInputTranslateY.value}],
            };
        },
        [],
    );

    useDidMount(() => {
        return () => {
            dismissKeyboard();
        };
    });

    // Ref to track if a layout update is already scheduled
    const layoutUpdateScheduledRef = useRef(false);
    const pendingHeightRef = useRef<number | null>(null);

    // Helper to apply the batched height update
    const applyBatchedHeightUpdate = useCallback(() => {
        layoutUpdateScheduledRef.current = false;

        if (pendingHeightRef.current !== null) {
            const heightToSet = pendingHeightRef.current;
            pendingHeightRef.current = null;

            // Only update if the rounded height changed by more than 0.5px (a real change).
            // This prevents jitter in FlatList paddingTop and improves performance.
            const currentHeight = stateContext.postInputContainerHeight.value;
            const roundedCurrentHeight = Math.round(currentHeight);
            if (roundedCurrentHeight !== heightToSet) {
                stateContext.postInputContainerHeight.value = heightToSet;
            }
        }

        // eslint-disable-next-line react-hooks/exhaustive-deps
    }, []);

    const onLayout = useCallback((e: LayoutChangeEvent) => {
        const newHeight = e.nativeEvent.layout.height;
        const roundedHeight = Math.round(newHeight);

        // Store the latest height value
        pendingHeightRef.current = roundedHeight;

        // If an update is already scheduled, skip scheduling another one
        // This batches all layout updates during animations to a single update per frame
        if (layoutUpdateScheduledRef.current) {
            return;
        }

        // Schedule update for next frame to batch rapid layout changes during animations
        layoutUpdateScheduledRef.current = true;
        requestAnimationFrame(applyBatchedHeightUpdate);
    }, [applyBatchedHeightUpdate]);

    useEffect(() => {
        if (Platform.OS !== 'android') {
            return undefined;
        }

        const backHandler = BackHandler.addEventListener('hardwareBackPress', () => {
            if (showInputAccessoryView) {
                closeInputAccessoryView();
                return true;
            }

            return false;
        });

        return () => backHandler.remove();
    }, [closeInputAccessoryView, showInputAccessoryView]);

    useEffect(() => {
        const listener = DeviceEventEmitter.addListener(Events.CLOSE_INPUT_ACCESSORY_VIEW, () => {
            closeInputAccessoryView();
        });

        return () => listener.remove();
    }, [closeInputAccessoryView]);

    const scrollToEmojiPickerCompensation = useCallback((offset: number) => {
        scheduleOnUI(() => scrollTo(listRef, 0, offset, false));
    }, [listRef]);

    // After emoji picker renders, adjust heights and scroll to keep messages visible
    // On iOS, contentInset changes cause the list to shift, so we need to scroll to compensate
    // On Android, marginBottom is used instead and doesn't require scroll adjustment
    useEffect(() => {
        if (showInputAccessoryView) {

            // Wait one frame to ensure emoji picker has rendered
            requestAnimationFrame(() => {
                // Use targetHeight instead of inputAccessoryHeight because inputAccessoryHeight
                // is still animating (via withTiming) when this runs, so we'd capture a tiny intermediate value
                const emojiPickerHeight = stateContext.targetHeight.value;
                const currentScroll = stateContext.scrollPosition.value;

                // Only perform scroll adjustment on iOS
                // Android uses marginBottom which doesn't require scroll compensation
                if (Platform.OS === 'ios' && listRef.current) {
                    // For inverted list: when bottomInset increases, content shifts UP visually. Scroll UP to compensate.
                    scrollToEmojiPickerCompensation(currentScroll - emojiPickerHeight);
                }
            });
        }

        // Only depend on showInputAccessoryView - the effect should only run when emoji picker visibility changes
        // eslint-disable-next-line react-hooks/exhaustive-deps
    }, [showInputAccessoryView]);

    return (
        <KeyboardGestureArea
            textInputNativeID={textInputNativeID}
            style={styles.gestureArea}
            enableSwipeToDismiss={false} // this applies only to Android
        >
            <View style={styles.gestureArea}>
                <View style={containerStyle}>
                    {renderList()}
                </View>
                <Animated.View
                    style={[
                        inputContainerAnimatedStyle,
                        styles.inputContainer,
                    ]}
                >
                    <View onLayout={onLayout}>
                        {children}
                    </View>
                </Animated.View>
                {showInputAccessoryView && <CustomEmojiPicker/>}
            </View>
        </KeyboardGestureArea>
    );
};