ui/lib/shared/addon/utils/evaluate.js

import { get } from '@ember/object'

function getVariables(showIf, operator) {
  if ( showIf.indexOf(operator) > -1 ) {
    const array = showIf.split(operator);

    if ( array.length === 2 ) {
      return {
        left:  array[0],
        right: array[1]
      };
    } else {
      return null;
    }
  }

  return null;
}

function getAnswer(variable, questions) {
  const found = questions.find((q) => q.variable === variable);

  if ( found ) {
    return found.answer;
  } else {
    return variable;
  }
}

function isEqual(showIf, allQuestions) {
  showIf = showIf.trim();
  const variables = getVariables(showIf, '=');

  if ( variables ) {
    const left = stringifyAnswer(getAnswer(variables.left, allQuestions));
    const right = stringifyAnswer(variables.right);

    return left === right;
  }

  return false;
}

function isNotEqual(showIf, allQuestions) {
  showIf = showIf.trim();
  const variables = getVariables(showIf, '!=');

  if ( variables ) {
    const left = stringifyAnswer(getAnswer(variables.left, allQuestions));
    const right = stringifyAnswer(variables.right);

    return left !== right;
  }

  return false;
}

function calExpression(showIf, allQuestions) {
  if ( showIf.indexOf('!=') > -1  ) {
    return isNotEqual(showIf, allQuestions);
  } else {
    return isEqual(showIf, allQuestions);
  }
}

export function evaluate(question, allQuestions) {
  if ( !question.showIf ) {
    return true;
  }

  const and = question.showIf.split('&&');
  const or = question.showIf.split('||');

  let result;

  if ( get(or, 'length') > 1 ) {
    result = or.some((showIf) => calExpression(showIf, allQuestions));
  } else {
    result = and.every((showIf) => calExpression(showIf, allQuestions));
  }

  return result;
}

export function stringifyAnswer(answer) {
  if ( answer === undefined || answer === null ) {
    return '';
  } else if ( typeof answer === 'string' ) {
    return answer;
  } else {
    return `${ answer  }`;
  }
}