superset-frontend/packages/superset-ui-core/src/math-expression/index.ts

/*
 * 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.
 */

import Mexp from 'math-expression-evaluator';

const mexp = new Mexp();

const REPLACE_OPERATORS: [RegExp, string][] = [
  [new RegExp(/==/g), 'Eq'],
  [new RegExp(/>=/g), 'Gte'],
  [new RegExp(/<=/g), 'Lte'],
  [new RegExp(/>/g), 'Gt'],
  [new RegExp(/</g), 'Lt'],
];

const TOKENS = [
  {
    type: 3,
    token: 'x',
    show: 'x',
    value: 'x',
  },
  {
    type: 2,
    token: '&',
    show: '&',
    value: (a: number, b: number): number => a & b,
  },
  {
    type: 2,
    token: '|',
    show: '|',
    value: (a: number, b: number): number => a | b,
  },
  {
    type: 2,
    token: 'and',
    show: 'and',
    value: (a: number, b: number): number => a && b,
  },
  {
    type: 2,
    token: 'xor',
    show: 'xor',
    value: (a: number, b: number): number => a ^ b,
  },
  {
    type: 2,
    token: 'or',
    show: 'or',
    value: (a: number, b: number): number => Number(a || b),
  },
  {
    type: 2,
    token: 'Eq',
    show: 'Eq',
    value: (a: number, b: number): number => Number(a === b),
  },
  {
    type: 2,
    token: 'Lt',
    show: 'Lt',
    value: (a: number, b: number): number => Number(a < b),
  },
  {
    type: 2,
    token: 'Lte',
    show: 'Lte',
    value: (a: number, b: number): number => Number(a <= b),
  },
  {
    type: 2,
    token: 'Gt',
    show: 'Gt',
    value: (a: number, b: number): number => Number(a > b),
  },
  {
    type: 2,
    token: 'Gte',
    show: 'Gte',
    value: (a: number, b: number): number => Number(a >= b),
  },
];

export function evalExpression(expression: string, value: number): number {
  let parsedExpression = expression;
  // replace `<` with `Lt` (and others) to avoid clashes with builtin function operators
  // that are not needed in Superset.
  REPLACE_OPERATORS.forEach(([key, value]) => {
    parsedExpression = parsedExpression.replace(key, value);
  });
  const subExpressions = String(parsedExpression).split('=');
  parsedExpression = subExpressions[1] ?? subExpressions[0];
  // we can ignore the type requirement on `TOKENS`, as value is always `number`
  // and doesn't need to consider `number | undefined`.
  // @ts-ignore
  return Number(mexp.eval(parsedExpression, TOKENS, { x: value }));
}

export function isValidExpression(expression: string): boolean {
  try {
    evalExpression(expression, 0);
  } catch (err) {
    return false;
  }
  return true;
}