| /** |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, |
| * software distributed under the License is distributed on an |
| * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| * KIND, either express or implied. See the License for the |
| * specific language governing permissions and limitations |
| * under the License. |
| */ |
| |
| // https://en.wikipedia.org/wiki/Linear_congruential_generator |
| function stringAsciiPRNG(value: string, m: number) { |
| // Xn+1 = (a * Xn + c) % m |
| // 0 < a < m |
| // 0 <= c < m |
| // 0 <= X0 < m |
| |
| const charCodes = [...value].map(letter => letter.charCodeAt(0)); |
| const len = charCodes.length; |
| |
| const a = (len % (m - 1)) + 1; |
| const c = charCodes.reduce((current, next) => current + next) % m; |
| |
| let random = charCodes[0] % m; |
| |
| [...new Array(len)].forEach(() => { |
| random = (a * random + c) % m; |
| }); |
| |
| return random; |
| } |
| |
| export function getRandomColor(sampleValue: string, colorList: string[]) { |
| // if no value is passed, always return transparent color for consistency |
| if (!sampleValue) return 'transparent'; |
| |
| // value based random color index, |
| // ensuring the same sampleValue always resolves to the same color |
| return colorList[stringAsciiPRNG(sampleValue, colorList.length)]; |
| } |