Validating the query parameter and parsing it using regular expression - regex

Question

I am new to regex, can you please tell me how to take a query parameter with all the below combinations.
(ParamName=Operator:ParamValue) is my set of query parameter value. This will be separated with ;(AND) or ,(OR) and i want to group them within braces. Like in below example
Ex: http://,host:port>/get?search=(date=gt:2020-02-06T00:00:00.000Z;(name=eq:Test,department=co:Prod))
Here the date should be greater than 2020-02-06 and name = Test or department contains Prod.
How to parse these query parameters. Please suggest.
Thanks, Vijay

Answer 1

So, I wrote a solution in JavaScript, but it should be adaptable in other languages as well, with a bit of research.
It's quite a bit of code, but what you're looking to achieve is not super easy!
So here's the code bellow, it's thoroughly commented, but please, if you there is something you don't understand, ask away, and I'll be happy to answer you :)
//
// The 2 first regexes are a parameter, which looks like date=gt:2020-02-06T00:00:00.000Z for example.
// The difference between those 2 is that the 1st one has **named capture group**
// For example '(?<operator>...)' is a capture group named 'operator'.
// This will come in handy in the code, to keep things clean
//
const RX_NAMED_PARAMETER = /(?:(?<param>\w+)=(?<operator>\w+):(?<value>[\w-:.]+))/
const parameter = "((\\w+)=(\\w+):([\\w-:.]+)|(true|false))"
//
// The 3rd parameter is an operation between 2 parameters
//
const RX_OPERATION = new RegExp(`\\((?<param1>${parameter})(?:(?<and_or>[,;])(?<param2>${parameter}))?\\)`, '');
// '---------.---------' '-------.------' '----------.---------'
// 1st parameter AND or OR 2nd parameter
my_data = {
date: new Date(2000, 01, 01),
name: 'Joey',
department: 'Production'
}
/**
* This function compates the 2 elements, and returns the bigger one.
* The elements might be dates, numbers, or anything that can be compared.
* The elements **need** to be of the same type
*/
function isGreaterThan(elem1, elem2) {
if (elem1 instanceof Date) {
const date = new Date(elem2).getTime();
if (isNaN(date))
throw new Error(`${elem2} - Not a valid date`);
return elem1.getTime() > date;
}
if (typeof elem1 === 'number') {
const num = Number(elem2);
if (isNaN(num))
throw new Error(`${elem2} - Not a number`);
return elem1 > num;
}
return elem1 > elem2;
}
/**
* Makes an operation as you defined them in your
* post, you might want to change that to suit your needs
*/
function operate(param, operator, value) {
if (!(param in my_data))
throw new Error(`${param} - Invalid parameter!`);
switch (operator) {
case 'eq':
return my_data[param] == value;
case 'co':
return my_data[param].includes(value);
case 'lt':
return isGreaterThan(my_data[param], value);
case 'gt':
return !isGreaterThan(my_data[param], value);
default:
throw new Error(`${operator} - Unsupported operation`);
}
}
/**
* This parses the URL, and returns a boolean
*/
function parseUri(uri) {
let finalResult;
// As long as there are operations (of the form <param1><; or ,><param2>) on the URL
while (RX_OPERATION.test(uri)) {
// We replace the 1st operation by the result of this operation ("true" or "false")
uri = uri.replace(RX_OPERATION, rawOperation => {
// As long as there are parameters in the operations (e.g. "name=eq:Bob")
while (RX_NAMED_PARAMETER.test(rawOperation)) {
// We replace the 1st parameter by its value ("true" or "false")
rawOperation = rawOperation.replace(RX_NAMED_PARAMETER, rawParameter => {
const res = RX_NAMED_PARAMETER.exec(rawParameter);
return '' + operate(
res.groups.param,
res.groups.operator,
res.groups.value,
);
// The "res.groups.xxx" syntax is allowed by the
// usage of capture groups. See the top of the file.
});
}
// At this point, the rawOperation should look like
// (true,false) or (false;false) for example
const res = RX_OPERATION.exec(rawOperation);
let operation;
if (res.groups.param2 === undefined)
operation = res.groups.param1; // In case this is an isolated operation
else
operation = res.groups.param1 + ({',': ' || ', ';': ' && '}[res.groups.and_or]) + res.groups.param2;
finalResult = eval(operation);
return '' + finalResult;
});
}
return finalResult;
}
let res;
res = parseUri("http://,host:port>/get?search=(date=gt:2020-02-06T00:00:00.000Z;(name=eq:Test,department=co:Prod))");
console.log(res);
res = parseUri("http://,host:port>/get?search=(date=lt:2020-02-06T00:00:00.000Z)");
console.log(res);