query.js

'use strict';

const { resolve } = require('./utils');

const isOperator = (str) => str.startsWith('$');

function equals (a, b) {
  if (typeof a === 'string' && b instanceof RegExp) {
    return b.test(a);
  } else if (Array.isArray(a) && Array.isArray(b)) {
    if (a.length !== b.length) {
      return false;
    }
    for (let i = 0; i < a.length; i++) {
      if (!equals(a[i], b[i])) {
        return false;
      }
    }
    return true;
  }

  return a === b;
}

function query (value, filter = {}) {
  if (typeof filter === 'function') {
    return Boolean(filter(value));
  }

  let result = 1;

  for (const key in filter) {
    if (Object.hasOwn(filter, key)) {
      if (isOperator(key)) {
        if (key === '$eq') {
          result &= value === filter[key];
        } else if (key === '$ne') {
          result &= value !== filter[key];
        } else if (key === '$like') {
          result &= equals(value, filter[key]);
        } else if (key === '$regexp' || key === '$regex') {
          if (filter[key] instanceof RegExp) {
            result &= filter[key].test(value);
          } else {
            result &= false;
          }
        } else if (key === '$gt') {
          result &= value > filter[key];
        } else if (key === '$gte') {
          result &= value >= filter[key];
        } else if (key === '$lt') {
          result &= value < filter[key];
        } else if (key === '$lte') {
          result &= value <= filter[key];
        } else if (key === '$in') {
          result &= filter[key].includes(value);
        } else if (key === '$nin') {
          result &= ! filter[key].includes(value);
        } else if (key === '$and') {
          for (const and of filter[key]) {
            result &= query(value, and);
            if (result === 0) {
              break;
            }
          }
        } else if (key === '$or') {
          let intermediate = 0;
          for (const or of filter[key]) {
            intermediate |= query(value, or);
            if (intermediate) {
              break;
            }
          }
          result &= intermediate;
        } else if (key === '$nor') {
          let intermediate = 0;
          for (const nor of filter[key]) {
            intermediate |= query(value, nor);
          }
          result &= ! intermediate;
        } else if (key === '$not') {
          result &= !query(value, filter[key]);
        } else if (key === '$type') {
          result &= typeof value === filter[key];
        } else if (key === '$exists') {
          result &= typeof value !== 'undefined';
        } else if (key === '$size') {
          if (Array.isArray(value) && value.length === filter[key]) {
            result &= true;
          } else if (typeof value === 'object' &&
                   Object.keys(value).length === filter[key]) {
            result &= true;
          } else {
            result &= false;
          }
        } else if (key === '$mod') {
          const divisor = filter[key][0] || filter[key];
          const remainder = filter[key][1] || 0;
          result &= value % divisor === remainder;
        } else if (key === '$where') {
          if (typeof filter[key] === 'function') {
            result &= Boolean(filter[key](value));
          } else {
            result &= false;
          }
        } else if (key === '$elemMatch') {
          if (Array.isArray(value)) {
            let found = false;
            for (const item of value) {
              if (query(item, filter[key])) {
                found = true;
                break;
              }
            }
            result &= found;
          } else {
            result &= false;
          }
        } else if (key === '$all') {
          if (Array.isArray(value)) {
            for (const item of value) {
              result &= query(item, filter[key]);
              if (result === 0) {
                return false;
              }
            }
          } else {
            result &= false;
          }
        }
      } else if (Array.isArray(filter[key])) {
        result &= equals(resolve(value, key), filter[key]);
      } else if (typeof filter[key] === 'object') {
        result &= query(resolve(value, key), filter[key]);
      } else {
        result &= equals(resolve(value, key), filter[key]);
      }

      if (result === 0) {
        return false;
      }
    }
  }

  return Boolean(result);
}

module.exports = query;