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instrumental/app/javascript/mastodon/components/animated_number.tsx

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import React, { useCallback, useState } from 'react';
import { TransitionMotion, spring } from 'react-motion';
import { reduceMotion } from '../initial_state';
import ShortNumber from './short_number';
const obfuscatedCount = (count: number) => {
if (count < 0) {
return 0;
} else if (count <= 1) {
return count;
} else {
return '1+';
}
};
interface Props {
value: number;
obfuscate?: boolean;
}
export const AnimatedNumber: React.FC<Props> = ({ value, obfuscate }) => {
const [previousValue, setPreviousValue] = useState(value);
const [direction, setDirection] = useState<1 | -1>(1);
if (previousValue !== value) {
setPreviousValue(value);
setDirection(value > previousValue ? 1 : -1);
}
const willEnter = useCallback(() => ({ y: -1 * direction }), [direction]);
const willLeave = useCallback(
() => ({ y: spring(1 * direction, { damping: 35, stiffness: 400 }) }),
[direction]
);
if (reduceMotion) {
return obfuscate ? (
<>{obfuscatedCount(value)}</>
) : (
<ShortNumber value={value} />
);
}
const styles = [
{
key: `${value}`,
data: value,
style: { y: spring(0, { damping: 35, stiffness: 400 }) },
},
];
return (
<TransitionMotion
styles={styles}
willEnter={willEnter}
willLeave={willLeave}
>
{(items) => (
<span className='animated-number'>
{items.map(({ key, data, style }) => (
<span
key={key}
style={{
position: direction * style.y > 0 ? 'absolute' : 'static',
transform: `translateY(${style.y * 100}%)`,
}}
>
{obfuscate ? (
obfuscatedCount(data as number)
) : (
<ShortNumber value={data as number} />
)}
</span>
))}
</span>
)}
</TransitionMotion>
);
};