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import { useCallback, useEffect, useState } from 'react';
import styled from 'styled-components';
import { NonEmptyArray } from '../../shared/utils';
import { IconButton } from '../lib/components';
import { colors } from '../lib/foundations';
import { useStyledRef } from '../lib/utility-hooks';
const PAGE_GAP = 16;
const StyledPageSliderContainer = styled.div({
display: 'flex',
flexDirection: 'column',
});
const StyledPageSlider = styled.div({
whiteSpace: 'nowrap',
overflow: 'scroll hidden',
scrollSnapType: 'x mandatory',
scrollBehavior: 'smooth',
'&&::-webkit-scrollbar': {
display: 'none',
},
});
const StyledPage = styled.div({
display: 'inline-block',
width: '100%',
whiteSpace: 'normal',
verticalAlign: 'top',
scrollSnapAlign: 'start',
'&&:not(:last-child)': {
marginRight: `${PAGE_GAP}px`,
},
});
interface PageSliderProps {
content: NonEmptyArray<React.ReactNode>;
}
export default function PageSlider(props: PageSliderProps) {
// A state is needed to trigger a rerender. This is needed to update the "disabled" and "$current"
// props of the arrows and page indicators.
const [, setPageNumberState] = useState(0);
const pageContainerRef = useStyledRef<HTMLDivElement>();
// Calculate the page number based on the scroll position.
const getPageNumber = useCallback(() => {
if (pageContainerRef.current) {
const scrollLeft = pageContainerRef.current.scrollLeft;
const pageWidth = pageContainerRef.current.offsetWidth + PAGE_GAP;
// Clamp it between 0 and props.content.length-1 to make sure it will correspond to a page.
return Math.max(0, Math.min(Math.round(scrollLeft / pageWidth), props.content.length - 1));
} else {
return 0;
}
}, [pageContainerRef, props.content.length]);
// These values are only intended to be used for display purposes. Using them when calculating
// next or prev page would increase the risk of race conditions.
const pageNumber = getPageNumber();
const hasNext = pageNumber < props.content.length - 1;
const hasPrev = pageNumber > 0;
// Scroll to a specific page.
const goToPage = useCallback(
(page: number) => {
if (pageContainerRef.current) {
const width = pageContainerRef.current.offsetWidth;
pageContainerRef.current.scrollTo({ left: width * page });
}
},
[pageContainerRef],
);
const next = useCallback(() => goToPage(getPageNumber() + 1), [goToPage, getPageNumber]);
const prev = useCallback(() => goToPage(getPageNumber() - 1), [goToPage, getPageNumber]);
// Callback that navigates when left and right arrows are pressed.
const handleKeyDown = useCallback(
(event: KeyboardEvent) => {
if (event.key === 'ArrowLeft') {
prev();
} else if (event.key === 'ArrowRight') {
next();
}
},
[next, prev],
);
// Trigger a rerender when the page number has changed. This needs to be done to update the
// states of the arrows and page indicators.
const handleScroll = useCallback(() => setPageNumberState(getPageNumber()), [getPageNumber]);
useEffect(() => {
document.addEventListener('keydown', handleKeyDown);
return () => document.removeEventListener('keydown', handleKeyDown);
}, [handleKeyDown]);
return (
<StyledPageSliderContainer>
<StyledPageSlider ref={pageContainerRef} onScroll={handleScroll}>
{props.content.map((page, i) => (
<StyledPage key={`page-${i}`}>{page}</StyledPage>
))}
</StyledPageSlider>
<Controls
goToPage={goToPage}
hasNext={hasNext}
hasPrev={hasPrev}
next={next}
prev={prev}
pageNumber={pageNumber}
numberOfPages={props.content.length}
/>
</StyledPageSliderContainer>
);
}
const StyledControlsContainer = styled.div({
display: 'flex',
marginTop: '12px',
alignItems: 'center',
});
const StyledControlElement = styled.div({
flex: '1 0 60px',
display: 'flex',
});
const StyledArrows = styled(StyledControlElement)({
display: 'flex',
justifyContent: 'right',
gap: '12px',
});
const StyledPageIndicators = styled(StyledControlElement)({
display: 'flex',
flexGrow: 2,
justifyContent: 'center',
});
const StyledTransparentButton = styled.button({
border: 'none',
background: colors.transparent,
padding: '4px',
margin: 0,
});
const StyledPageIndicator = styled.div<{ $current: boolean }>((props) => ({
width: '8px',
height: '8px',
borderRadius: '50%',
backgroundColor: props.$current ? colors.whiteAlpha80 : colors.whiteAlpha40,
[`${StyledTransparentButton}:hover &&`]: {
backgroundColor: colors.whiteAlpha80,
},
}));
interface ControlsProps {
pageNumber: number;
numberOfPages: number;
hasNext: boolean;
hasPrev: boolean;
next: () => void;
prev: () => void;
goToPage: (page: number) => void;
}
function Controls(props: ControlsProps) {
return (
<StyledControlsContainer>
<StyledControlElement>{/* spacer to make page indicators centered */}</StyledControlElement>
<StyledPageIndicators>
{[...Array(props.numberOfPages)].map((_, i) => (
<PageIndicator
key={i}
current={i === props.pageNumber}
pageNumber={i}
goToPage={props.goToPage}
/>
))}
</StyledPageIndicators>
<StyledArrows>
<IconButton disabled={!props.hasPrev} onClick={props.prev}>
<IconButton.Icon icon="chevron-left" />
</IconButton>
<IconButton disabled={!props.hasNext} onClick={props.next}>
<IconButton.Icon icon="chevron-right" />
</IconButton>
</StyledArrows>
</StyledControlsContainer>
);
}
interface PageIndicatorProps {
pageNumber: number;
goToPage: (page: number) => void;
current: boolean;
}
function PageIndicator(props: PageIndicatorProps) {
const { goToPage } = props;
const onClick = useCallback(() => {
goToPage(props.pageNumber);
}, [goToPage, props.pageNumber]);
return (
<StyledTransparentButton onClick={onClick}>
<StyledPageIndicator $current={props.current} />
</StyledTransparentButton>
);
}
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