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import React from 'react';
import { withStyles } from '@material-ui/core/styles';
import {
getContrastRatio,
darken,
} from '@material-ui/core/styles/colorManipulator';
import * as allColors from '@material-ui/core/colors';
import { common } from '@material-ui/core/colors';
// JS's modulo returns negative numbers sometimes.
// This ensures the result is positive.
const mod = (n, m) => ((n % m) + m) % m;
// Minimum contrast between the background and the text color
const contrastThreshold = 2.5;
// Filter out the "common" color
const labelColors = Object.entries(allColors)
.filter(([key, value]) => value !== common)
.map(([key, value]) => value);
// Generate a hash (number) from a string
const hash = string =>
string.split('').reduce((a, b) => ((a << 5) - a + b.charCodeAt(0)) | 0, 0);
// Get the background color from the label
const getColor = label =>
labelColors[mod(hash(label), labelColors.length)][500];
// Guess the text color based on the background color
const getTextColor = background =>
getContrastRatio(background, common.white) >= contrastThreshold
? common.white // White on dark backgrounds
: common.black; // And black on light ones
const _genStyle = background => ({
backgroundColor: background,
color: getTextColor(background),
borderBottomColor: darken(background, 0.2),
});
// Generate a style object (text, background and border colors) from the label
const genStyle = label => _genStyle(getColor(label));
const styles = theme => ({
label: {
...theme.typography.body2,
padding: '0 6px',
fontSize: '0.9em',
margin: '0 1px',
borderRadius: '3px',
display: 'inline-block',
borderBottom: 'solid 1.5px',
verticalAlign: 'bottom',
},
});
const Label = ({ label, classes }) => (
<span className={classes.label} style={genStyle(label)}>
{label}
</span>
);
export default withStyles(styles)(Label);
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