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import React, {useCallback, useEffect, useMemo, useRef, useState} from 'react'
import {LayoutChangeEvent, ScrollView, StyleSheet, View} from 'react-native'
import {usePalette} from '#/lib/hooks/usePalette'
import {useWebMediaQueries} from '#/lib/hooks/useWebMediaQueries'
import {isNative} from '#/platform/detection'
import {PressableWithHover} from '../util/PressableWithHover'
import {Text} from '../util/text/Text'
import {DraggableScrollView} from './DraggableScrollView'
export interface TabBarProps {
testID?: string
selectedPage: number
items: string[]
indicatorColor?: string
onSelect?: (index: number) => void
onPressSelected?: (index: number) => void
}
// How much of the previous/next item we're showing
// to give the user a hint there's more to scroll.
const OFFSCREEN_ITEM_WIDTH = 20
export function TabBar({
testID,
selectedPage,
items,
indicatorColor,
onSelect,
onPressSelected,
}: TabBarProps) {
const pal = usePalette('default')
const scrollElRef = useRef<ScrollView>(null)
const itemRefs = useRef<Array<Element>>([])
const [itemXs, setItemXs] = useState<number[]>([])
const indicatorStyle = useMemo(
() => ({borderBottomColor: indicatorColor || pal.colors.link}),
[indicatorColor, pal],
)
const {isDesktop, isTablet} = useWebMediaQueries()
const styles = isDesktop || isTablet ? desktopStyles : mobileStyles
useEffect(() => {
if (isNative) {
// On native, the primary interaction is swiping.
// We adjust the scroll little by little on every tab change.
// Scroll into view but keep the end of the previous item visible.
let x = itemXs[selectedPage] || 0
x = Math.max(0, x - OFFSCREEN_ITEM_WIDTH)
scrollElRef.current?.scrollTo({x})
} else {
// On the web, the primary interaction is tapping.
// Scrolling under tap feels disorienting so only adjust the scroll offset
// when tapping on an item out of view--and we adjust by almost an entire page.
const parent = scrollElRef?.current?.getScrollableNode?.()
if (!parent) {
return
}
const parentRect = parent.getBoundingClientRect()
if (!parentRect) {
return
}
const {
left: parentLeft,
right: parentRight,
width: parentWidth,
} = parentRect
const child = itemRefs.current[selectedPage]
if (!child) {
return
}
const childRect = child.getBoundingClientRect?.()
if (!childRect) {
return
}
const {left: childLeft, right: childRight, width: childWidth} = childRect
let dx = 0
if (childRight >= parentRight) {
dx += childRight - parentRight
dx += parentWidth - childWidth - OFFSCREEN_ITEM_WIDTH
} else if (childLeft <= parentLeft) {
dx -= parentLeft - childLeft
dx -= parentWidth - childWidth - OFFSCREEN_ITEM_WIDTH
}
let x = parent.scrollLeft + dx
x = Math.max(0, x)
x = Math.min(x, parent.scrollWidth - parentWidth)
if (dx !== 0) {
parent.scroll({
left: x,
behavior: 'smooth',
})
}
}
}, [scrollElRef, itemXs, selectedPage, styles])
const onPressItem = useCallback(
(index: number) => {
onSelect?.(index)
if (index === selectedPage) {
onPressSelected?.(index)
}
},
[onSelect, selectedPage, onPressSelected],
)
// calculates the x position of each item on mount and on layout change
const onItemLayout = React.useCallback(
(e: LayoutChangeEvent, index: number) => {
const x = e.nativeEvent.layout.x
setItemXs(prev => {
const Xs = [...prev]
Xs[index] = x
return Xs
})
},
[],
)
return (
<View testID={testID} style={[pal.view, styles.outer]}>
<DraggableScrollView
testID={`${testID}-selector`}
horizontal={true}
showsHorizontalScrollIndicator={false}
ref={scrollElRef}
contentContainerStyle={styles.contentContainer}>
{items.map((item, i) => {
const selected = i === selectedPage
return (
<PressableWithHover
testID={`${testID}-selector-${i}`}
key={`${item}-${i}`}
ref={node => (itemRefs.current[i] = node as any)}
onLayout={e => onItemLayout(e, i)}
style={styles.item}
hoverStyle={pal.viewLight}
onPress={() => onPressItem(i)}>
<View style={[styles.itemInner, selected && indicatorStyle]}>
<Text
type={isDesktop || isTablet ? 'xl-bold' : 'lg-bold'}
testID={testID ? `${testID}-${item}` : undefined}
style={[
selected ? pal.text : pal.textLight,
{lineHeight: 20},
]}>
{item}
</Text>
</View>
</PressableWithHover>
)
})}
</DraggableScrollView>
<View style={[pal.border, styles.outerBottomBorder]} />
</View>
)
}
const desktopStyles = StyleSheet.create({
outer: {
flexDirection: 'row',
width: 598,
},
contentContainer: {
paddingHorizontal: 0,
backgroundColor: 'transparent',
},
item: {
paddingTop: 14,
paddingHorizontal: 14,
justifyContent: 'center',
},
itemInner: {
paddingBottom: 12,
borderBottomWidth: 3,
borderBottomColor: 'transparent',
},
outerBottomBorder: {
position: 'absolute',
left: 0,
right: 0,
top: '100%',
borderBottomWidth: StyleSheet.hairlineWidth,
},
})
const mobileStyles = StyleSheet.create({
outer: {
flexDirection: 'row',
},
contentContainer: {
backgroundColor: 'transparent',
paddingHorizontal: 6,
},
item: {
paddingTop: 10,
paddingHorizontal: 10,
justifyContent: 'center',
},
itemInner: {
paddingBottom: 10,
borderBottomWidth: 3,
borderBottomColor: 'transparent',
},
outerBottomBorder: {
position: 'absolute',
left: 0,
right: 0,
top: '100%',
borderBottomWidth: StyleSheet.hairlineWidth,
},
})
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