Run Loop in firestore rules

Question

It is requirement to run loops in data validation. In my case I have document with schema:

interface SomeDoc {
    // ...other props
    "prop-with-map": { [key: string]: number };
}

still there is no way to validate SomeDoc["prop-with-map"]

I let user create this document, then they can't update so need to check schema in firestore-rules. Without loops or schema check support in rules I have to make background function.

OR

I know there can't be more then 5 fields in SomeDoc["prop-with-map"]. So I can check them one by one. Or create js function that generates code firestore-rule-function that checks in arr one by one.

Answer 1

SOLUTION

/**
 * @param {string} functionName   what function name you would like.
 * @param {string} validate       what is validator function name.
 * @param {number} iteration      max iteration before exiting loop.
 * @return {string}               function code used in firestore rules
 */
function generateFirestoreLoopForList(functionName, validate, iteration) {
  let func = `function ${functionName}(arr) {\n return arr.size() == 0 ? true : ${validate}(arr[0])`;
  for (let i = 1; i <= iteration; i++) {
    let addAtIndex = func.length - i + 1;
    func =
      func.substring(0, addAtIndex) +
      `&& (arr.size() == ${i} ? true : ${validate}(arr[${i}]))` +
      func.substring(addAtIndex);
  }
  func += "\n }";
  console.log(func);
  return func;
}

then your rules can go like

rules_version = '2';
service cloud.firestore {
    match /databases/{database}/documents {
        match /{document=**} {
            allow read, write: if false;
        }
        match /TEST/TEST {
            allow create: if checkOtherProps() && hasAllOdd(request.resource.data["prop-with-map"].values());
            function checkOtherProps() {
                return // validate props and return accordingly;
            }
            function isInt(x) {
                return x is int;
            }
            // outuput of generateFirestoreLoopForList("hasAllInts", "isInt", 5);
            function hasAllInts(arr) {
                return arr.size() == 0 ? true : isInt(arr[0])&& (arr.size() == 1 ? true : isInt(arr[1])&& (arr.size() == 2 ? true : isInt(arr[2])&& (arr.size() == 3 ? true : isInt(arr[3])&& (arr.size() == 4 ? true : isInt(arr[4])&& (arr.size() == 5 ? true : isInt(arr[5]))))));
            }
        }
    }
}