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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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