diff --git a/src/helpers.js b/src/helpers.js
index 965f812..4f57ef4 100644
--- a/src/helpers.js
+++ b/src/helpers.js
@@ -1,483 +1,15 @@
-import {
-  mapValues,
-  clone as _clone,
-  isArray,
-  orderBy,
-  minBy,
-  maxBy,
-  sumBy,
-  meanBy,
-} from 'lodash-es';
-import FastBitSet from 'fastbitset';
-import booleanParser from 'boolean-parser';
-
-export const clone = function(val) {
-  try {
-    return structuredClone(val);
-  } catch (e) {
-    try {
-      return JSON.parse(JSON.stringify(val));
-    } catch (e) {
-      return val;
-    }
-  }
-};
-
-export const humanize = function(str) {
-  return str
-    .replace(/^[\s_]+|[\s_]+$/g, '')
-    .replace(/[_\s]+/g, ' ')
-    .replace(/^[a-z]/, function(m) {
-      return m.toUpperCase();
-    });
-};
-
-export const combination_indexes = function(facets, filters) {
-  const indexes = {};
-
-  filters.forEach(filter => {
-    if (Array.isArray(filter[0])) {
-      let facet_union = new FastBitSet();
-      const filter_keys = new Set();
-
-      filter.forEach(disjunctive_filter => {
-        const [filter_key, filter_val] = disjunctive_filter;
-        filter_keys.add(filter_key);
-        const bits =
-          facets.bits_data[filter_key]?.[filter_val] || new FastBitSet();
-        facet_union = facet_union.new_union(bits);
-      });
-
-      filter_keys.forEach(filter_key => {
-        indexes[filter_key] = facet_union;
-      });
-    }
-  });
-
-  return indexes;
-};
-
-export const filters_matrix = function(facets, query_filters) {
-  // We use cloneDeepWith with a custom cloning function
-  // const temp_facet = _.cloneDeepWith(facets, customClone);
-  const temp_facet = _clone(facets);
-
-  // Initialize bits_data_temp if it does not exist
-  if (!temp_facet.bits_data_temp) {
-    temp_facet.bits_data_temp = {};
-  }
-
-  if (!temp_facet.is_temp_copied) {
-    for (const key in temp_facet.bits_data) {
-      temp_facet.bits_data_temp[key] = {};
-      for (const key2 in temp_facet.bits_data[key]) {
-        temp_facet.bits_data_temp[key][key2] = temp_facet.bits_data[key][key2];
-      }
-    }
-  }
-
-  let union = null;
-
-  // Ensure that query_filters is an array
-  if (Array.isArray(query_filters)) {
-    // Processing conjunctive filters
-    query_filters.forEach(conjunction => {
-      let conjunctive_index = null;
-
-      conjunction.forEach(filter => {
-        const [filter_key, filter_val] = filter;
-
-        if (!temp_facet.bits_data_temp[filter_key]) {
-          throw new Error('Panic. The key does not exist in facets lists.');
-        }
-
-        const facetData = temp_facet.bits_data_temp[filter_key][filter_val];
-
-        if (facetData) {
-          if (conjunctive_index) {
-            conjunctive_index = conjunctive_index.new_intersection(facetData);
-          } else {
-            conjunctive_index = facetData;
-          }
-        } else {
-          conjunctive_index = new FastBitSet();
-        }
-      });
-
-      if (conjunctive_index) {
-        if (union) {
-          union = union.new_union(conjunctive_index);
-        } else {
-          union = conjunctive_index;
-        }
-      }
-    });
-  }
-
-  if (union !== null) {
-    for (const key in temp_facet.bits_data_temp) {
-      for (const key2 in temp_facet.bits_data_temp[key]) {
-        temp_facet.bits_data_temp[key][key2] =
-          temp_facet.bits_data_temp[key][key2].new_intersection(union);
-      }
-    }
-  }
-
-  return temp_facet;
-};
-
-export const matrix = function(facets, filters = []) {
-  const temp_facet = _clone(facets);
-
-  // Kopiujemy bits_data do bits_data_temp
-  temp_facet.bits_data_temp = {};
-  for (const key in temp_facet.bits_data) {
-    temp_facet.bits_data_temp[key] = {};
-    for (const key2 in temp_facet.bits_data[key]) {
-      temp_facet.bits_data_temp[key][key2] = temp_facet.bits_data[key][key2];
-    }
-  }
-
-  temp_facet.is_temp_copied = true;
-
-  let conjunctive_index;
-  const disjunctive_indexes = combination_indexes(facets, filters);
-
-  // Processing conjunctive filters
-  filters.forEach(filter => {
-    if (!Array.isArray(filter[0])) {
-      const [filter_key, filter_val] = filter;
-      const facetData = temp_facet.bits_data_temp[filter_key]?.[filter_val];
-
-      if (conjunctive_index && facetData) {
-        conjunctive_index = facetData.new_intersection(conjunctive_index);
-      } else if (conjunctive_index && !facetData) {
-        conjunctive_index = new FastBitSet([]);
-      } else {
-        conjunctive_index = facetData;
-      }
-    }
-  });
-
-  // Intersect all facets with conjunctive indexes
-  if (conjunctive_index) {
-    for (const key in temp_facet.bits_data_temp) {
-      for (const key2 in temp_facet.bits_data_temp[key]) {
-        temp_facet.bits_data_temp[key][key2] = temp_facet.bits_data_temp[key][key2].new_intersection(conjunctive_index);
-      }
-    }
-  }
-
-  // Processing negative filters
-  filters.forEach(filter => {
-    if (filter.length === 3 && filter[1] === '-') {
-      const [filter_key, , filter_val] = filter;
-      const negative_bits = temp_facet.bits_data_temp[filter_key][filter_val].clone();
-
-      for (const key in temp_facet.bits_data_temp) {
-        for (const key2 in temp_facet.bits_data_temp[key]) {
-          temp_facet.bits_data_temp[key][key2] = temp_facet.bits_data_temp[key][key2].new_difference(negative_bits);
-        }
-      }
-    }
-  });
-
-  // Intersect all facets with disjunctive indexes
-  for (const key in temp_facet.bits_data_temp) {
-    for (const key2 in temp_facet.bits_data_temp[key]) {
-      for (const disjunctive_key in disjunctive_indexes) {
-        if (disjunctive_key !== key) {
-          temp_facet.bits_data_temp[key][key2] = temp_facet.bits_data_temp[key][key2].new_intersection(disjunctive_indexes[disjunctive_key]);
-        }
-      }
-    }
-  }
-
-  return temp_facet;
-};
-
-export const index = function(items = [], fields = []) {
-  const facets = {
-    data: Object.create(null),
-    bits_data: Object.create(null),
-    bits_data_temp: Object.create(null),
-  };
-
-  let nextId = 1;
-
-  // Initialize facets.data for each field
-  fields.forEach(field => {
-    facets.data[field] = Object.create(null);
-  });
-
-  // Assign _id to items without this identifier
-  items.forEach(item => {
-    if (!item._id) {
-      item._id = nextId++;
-    }
-  });
-
-  // Build facets.data
-  items.forEach(item => {
-    fields.forEach(field => {
-      const fieldValue = item[field];
-
-      if (Array.isArray(fieldValue)) {
-        fieldValue.forEach(value => {
-          if (!facets.data[field][value]) {
-            facets.data[field][value] = [];
-          }
-          facets.data[field][value].push(item._id);
-        });
-      } else if (typeof fieldValue !== 'undefined') {
-        const value = fieldValue;
-        if (!facets.data[field][value]) {
-          facets.data[field][value] = [];
-        }
-        facets.data[field][value].push(item._id);
-      }
-    });
-  });
-
-  // Building facets.bits_data and facets.bits_data_temp
-  Object.keys(facets.data).forEach(field => {
-    facets.bits_data[field] = Object.create(null);
-    facets.bits_data_temp[field] = Object.create(null);
-
-    const values = facets.data[field];
-    Object.keys(values).forEach(filter => {
-      const indexes = values[filter];
-      const sorted_indexes = indexes.sort((a, b) => a - b);
-      facets.bits_data[field][filter] = new FastBitSet(sorted_indexes);
-      // Updating facets.data with sorted indexes
-      facets.data[field][filter] = sorted_indexes;
-    });
-  });
-
-  return facets;
-};
-
-/**
- * calculates ids for filters
- */
-export const filters_ids = function(facets_data) {
-  return Object.values(facets_data).reduce((output, values) => {
-    Object.values(values).forEach(facet_indexes => {
-      output = output.new_union(facet_indexes);
-    });
-    return output;
-  }, new FastBitSet([]));
-};
-
-/**
- * Calculates identifiers for facets
- * If there are no filters, returns null to save resources during OR calculations
- * null means that the facets did not match any of the searched items
- */
-export const facets_ids = function(facets_data, filters) {
-  if (!facets_data || typeof facets_data !== 'object') {
-    throw new Error('Invalid facets_data provided.');
-  }
-
-  if (!filters || typeof filters !== 'object') {
-    return null;
-  }
-
-  const allFilters = Object.entries(filters).flatMap(
-    ([field, filterArray]) => 
-      Array.isArray(filterArray) 
-        ? filterArray.map(filter => ({ field, filter })) 
-        : []
-  );
-
-  if (allFilters.length === 0) {
-    return null;
-  }
-
-  const output = allFilters.reduce((acc, { field, filter }) => {
-    const bitset = facets_data[field]?.[filter] || new FastBitSet([]);
-    return acc.new_union(bitset);
-  }, new FastBitSet([]));
-
-  return output;
-};
-
-export const getBuckets = function(data, input, aggregations) {
-  let position = 1;
-
-  return mapValues(data['bits_data_temp'], (v, k) => {
-    let order;
-    let sort;
-    let size;
-    let title;
-    let show_facet_stats;
-    let chosen_filters_on_top;
-    let hide_zero_doc_count;
-
-    if (aggregations[k]) {
-      order = aggregations[k].order;
-      sort = aggregations[k].sort;
-      size = aggregations[k].size;
-      title = aggregations[k].title;
-      show_facet_stats = aggregations[k].show_facet_stats || false;
-      chosen_filters_on_top = aggregations[k].chosen_filters_on_top !== false;
-      hide_zero_doc_count = aggregations[k].hide_zero_doc_count || false;
-    }
-
-    let buckets = Object.entries(v)
-      .map((v2) => {
-        let filters = [];
-
-        if (input && input.filters && input.filters[k]) {
-          filters = input.filters[k];
-        }
-
-        const doc_count = v2[1].array().length;
-        const isSelected = filters.some((f) => String(f) === String(v2[0]));
-
-        //hide zero_doc_count facet only if it is not selected
-        if (hide_zero_doc_count && doc_count === 0 && !isSelected) {
-          return;
-        }
-
-        return {
-          key: v2[0],
-          doc_count: doc_count,
-          selected: isSelected,
-        };
-      })
-      .filter(Boolean);
-
-    let iteratees;
-    let sort_order;
-
-    if (isArray(sort)) {
-      iteratees = sort || ['key'];
-      sort_order = order || ['asc'];
-    } else {
-      if (sort === 'term' || sort === 'key') {
-        iteratees = ['key'];
-        sort_order = [order || 'asc'];
-      } else {
-        iteratees = ['doc_count', 'key'];
-        sort_order = [order || 'desc', 'asc'];
-      }
-
-      if (chosen_filters_on_top) {
-        iteratees.unshift('selected');
-        sort_order.unshift('desc');
-      }
-    }
-
-    buckets = orderBy(buckets, iteratees, sort_order);
-
-    buckets = buckets.slice(0, size || 10);
-
-    // Calculate the facet_stats
-    let facet_stats;
-    let calculated_facet_stats;
-
-    if (show_facet_stats) {
-      facet_stats = [];
-      Object.entries(v).forEach((v2) => {
-        if (isNaN(v2[0])) {
-          throw new Error('You cant use chars to calculate the facet_stats.');
-        }
-
-        // Doc_count
-        if (v2[1].array().length > 0) {
-          v2[1].forEach((/*doc_count*/) => {
-            facet_stats.push(parseInt(v2[0]));
-          });
-        }
-      });
-
-      calculated_facet_stats = {
-        min: minBy(facet_stats),
-        max: maxBy(facet_stats),
-        avg: meanBy(facet_stats),
-        sum: sumBy(facet_stats),
-      };
-    }
-
-    return {
-      name: k,
-      title: title || humanize(k),
-      position: position++,
-      buckets: buckets,
-      ...(show_facet_stats && { facet_stats: calculated_facet_stats }),
-    };
-  });
-};
-
-export const mergeAggregations = function(aggregations, input) {
-  const result = {};
-
-  for (const key in aggregations) {
-    const val = { ...aggregations[key] };
-
-    val.field = val.field || key;
-    val.filters = (input.filters && input.filters[key]) || [];
-    val.not_filters =
-      (input.exclude_filters && input.exclude_filters[key]) ||
-      (input.not_filters && input.not_filters[key]) ||
-      [];
-
-    result[key] = val;
-  }
-
-  return result;
-};
-
-export const input_to_facet_filters = function(input, config) {
-  const filters = [];
-
-  // Processing positive filters
-  for (const key in input.filters) {
-    const values = input.filters[key];
-    if (values && values.length) {
-      if (config[key]?.conjunction !== false) {
-        values.forEach(value => {
-          filters.push([key, value]);
-        });
-      } else {
-        const temp = values.map(value => [key, value]);
-        filters.push(temp);
-      }
-    }
-  }
-
-// Processing negative filters
-  for (const key in input.not_filters) {
-    const values = input.not_filters[key];
-    if (values && values.length) {
-      values.forEach(value => {
-        filters.push([key, '-', value]);
-      });
-    }
-  }
-
-  return filters;
-};
-
-export const parse_boolean_query = function(query) {
-  const result = booleanParser.parseBooleanQuery(query);
-
-  return result.map((v1) => {
-    if (Array.isArray(v1)) {
-      return v1.map((v2) => {
-        if (Array.isArray(v2)) {
-          return v2.map((v3) => {
-            return v3;
-          });
-        } else {
-          return v2.split(':');
-        }
-      });
-    } else {
-      return v1.split(':');
-    }
-  });
-};
-
-export const getFacets = getBuckets;
+export { clone, humanize } from './utils/object.js';
+export {
+  combination_indexes,
+  filters_matrix,
+  matrix,
+  filters_ids,
+  facets_ids,
+} from './utils/facets.js';
+export { index } from './utils/indexBuilder.js';
+export { getBuckets, getBuckets as getFacets } from './utils/aggregation.js';
+export {
+  mergeAggregations,
+  input_to_facet_filters,
+  parse_boolean_query,
+} from './utils/config.js';
diff --git a/src/utils/aggregation.js b/src/utils/aggregation.js
new file mode 100644
index 0000000..48fa51f
--- /dev/null
+++ b/src/utils/aggregation.js
@@ -0,0 +1,114 @@
+import {
+  mapValues,
+  isArray,
+  orderBy,
+  minBy,
+  maxBy,
+  sumBy,
+  meanBy,
+} from 'lodash-es';
+import { humanize } from './object.js';
+
+export const getBuckets = function (data, input, aggregations) {
+  let position = 1;
+
+  return mapValues(data['bits_data_temp'], (v, k) => {
+    let order;
+    let sort;
+    let size;
+    let title;
+    let show_facet_stats;
+    let chosen_filters_on_top;
+    let hide_zero_doc_count;
+
+    if (aggregations[k]) {
+      order = aggregations[k].order;
+      sort = aggregations[k].sort;
+      size = aggregations[k].size;
+      title = aggregations[k].title;
+      show_facet_stats = aggregations[k].show_facet_stats || false;
+      chosen_filters_on_top = aggregations[k].chosen_filters_on_top !== false;
+      hide_zero_doc_count = aggregations[k].hide_zero_doc_count || false;
+    }
+
+    let buckets = Object.entries(v)
+      .map((v2) => {
+        let filters = [];
+
+        if (input && input.filters && input.filters[k]) {
+          filters = input.filters[k];
+        }
+
+        const doc_count = v2[1].array().length;
+        const isSelected = filters.some((f) => String(f) === String(v2[0]));
+
+        if (hide_zero_doc_count && doc_count === 0 && !isSelected) {
+          return;
+        }
+
+        return {
+          key: v2[0],
+          doc_count: doc_count,
+          selected: isSelected,
+        };
+      })
+      .filter(Boolean);
+
+    let iteratees;
+    let sort_order;
+
+    if (isArray(sort)) {
+      iteratees = sort || ['key'];
+      sort_order = order || ['asc'];
+    } else {
+      if (sort === 'term' || sort === 'key') {
+        iteratees = ['key'];
+        sort_order = [order || 'asc'];
+      } else {
+        iteratees = ['doc_count', 'key'];
+        sort_order = [order || 'desc', 'asc'];
+      }
+
+      if (chosen_filters_on_top) {
+        iteratees.unshift('selected');
+        sort_order.unshift('desc');
+      }
+    }
+
+    buckets = orderBy(buckets, iteratees, sort_order);
+
+    buckets = buckets.slice(0, size || 10);
+
+    let calculated_facet_stats;
+
+    if (show_facet_stats) {
+      const facet_stats = [];
+      Object.entries(v).forEach((v2) => {
+        if (isNaN(v2[0])) {
+          throw new Error('You cant use chars to calculate the facet_stats.');
+        }
+
+        if (v2[1].array().length > 0) {
+          v2[1].forEach(() => {
+            facet_stats.push(parseInt(v2[0]));
+          });
+        }
+      });
+
+      calculated_facet_stats = {
+        min: minBy(facet_stats),
+        max: maxBy(facet_stats),
+        avg: meanBy(facet_stats),
+        sum: sumBy(facet_stats),
+      };
+    }
+
+    return {
+      name: k,
+      title: title || humanize(k),
+      position: position++,
+      buckets: buckets,
+      ...(show_facet_stats && { facet_stats: calculated_facet_stats }),
+    };
+  });
+};
diff --git a/src/utils/config.js b/src/utils/config.js
new file mode 100644
index 0000000..c821d07
--- /dev/null
+++ b/src/utils/config.js
@@ -0,0 +1,69 @@
+import booleanParser from 'boolean-parser';
+
+export const mergeAggregations = function (aggregations, input) {
+  const result = {};
+
+  for (const key in aggregations) {
+    const val = { ...aggregations[key] };
+
+    val.field = val.field || key;
+    val.filters = (input.filters && input.filters[key]) || [];
+    val.not_filters =
+      (input.exclude_filters && input.exclude_filters[key]) ||
+      (input.not_filters && input.not_filters[key]) ||
+      [];
+
+    result[key] = val;
+  }
+
+  return result;
+};
+
+export const input_to_facet_filters = function (input, config) {
+  const filters = [];
+
+  for (const key in input.filters) {
+    const values = input.filters[key];
+    if (values && values.length) {
+      if (config[key]?.conjunction !== false) {
+        values.forEach((value) => {
+          filters.push([key, value]);
+        });
+      } else {
+        const temp = values.map((value) => [key, value]);
+        filters.push(temp);
+      }
+    }
+  }
+
+  for (const key in input.not_filters) {
+    const values = input.not_filters[key];
+    if (values && values.length) {
+      values.forEach((value) => {
+        filters.push([key, '-', value]);
+      });
+    }
+  }
+
+  return filters;
+};
+
+export const parse_boolean_query = function (query) {
+  const result = booleanParser.parseBooleanQuery(query);
+
+  return result.map((v1) => {
+    if (Array.isArray(v1)) {
+      return v1.map((v2) => {
+        if (Array.isArray(v2)) {
+          return v2.map((v3) => {
+            return v3;
+          });
+        } else {
+          return v2.split(':');
+        }
+      });
+    } else {
+      return v1.split(':');
+    }
+  });
+};
diff --git a/src/utils/facets.js b/src/utils/facets.js
new file mode 100644
index 0000000..b847323
--- /dev/null
+++ b/src/utils/facets.js
@@ -0,0 +1,41 @@
+import FastBitSet from 'fastbitset';
+import { combination_indexes, filters_matrix, matrix } from './facetsCore.js';
+
+export { combination_indexes, filters_matrix, matrix };
+
+export const filters_ids = function (facets_data) {
+  return Object.values(facets_data).reduce((output, values) => {
+    Object.values(values).forEach((facet_indexes) => {
+      output = output.new_union(facet_indexes);
+    });
+    return output;
+  }, new FastBitSet([]));
+};
+
+export const facets_ids = function (facets_data, filters) {
+  if (!facets_data || typeof facets_data !== 'object') {
+    throw new Error('Invalid facets_data provided.');
+  }
+
+  if (!filters || typeof filters !== 'object') {
+    return null;
+  }
+
+  const allFilters = Object.entries(filters).flatMap(
+    ([field, filterArray]) =>
+      Array.isArray(filterArray)
+        ? filterArray.map((filter) => ({ field, filter }))
+        : []
+  );
+
+  if (allFilters.length === 0) {
+    return null;
+  }
+
+  const output = allFilters.reduce((acc, { field, filter }) => {
+    const bitset = facets_data[field]?.[filter] || new FastBitSet([]);
+    return acc.new_union(bitset);
+  }, new FastBitSet([]));
+
+  return output;
+};
diff --git a/src/utils/facetsCore.js b/src/utils/facetsCore.js
new file mode 100644
index 0000000..0b40e6b
--- /dev/null
+++ b/src/utils/facetsCore.js
@@ -0,0 +1,163 @@
+import { clone as _clone } from 'lodash-es';
+import FastBitSet from 'fastbitset';
+
+export const combination_indexes = function (facets, filters) {
+  const indexes = {};
+
+  filters.forEach((filter) => {
+    if (Array.isArray(filter[0])) {
+      let facet_union = new FastBitSet();
+      const filter_keys = new Set();
+
+      filter.forEach((disjunctive_filter) => {
+        const [filter_key, filter_val] = disjunctive_filter;
+        filter_keys.add(filter_key);
+        const bits =
+          facets.bits_data[filter_key]?.[filter_val] || new FastBitSet();
+        facet_union = facet_union.new_union(bits);
+      });
+
+      filter_keys.forEach((filter_key) => {
+        indexes[filter_key] = facet_union;
+      });
+    }
+  });
+
+  return indexes;
+};
+
+export const filters_matrix = function (facets, query_filters) {
+  const temp_facet = _clone(facets);
+
+  if (!temp_facet.bits_data_temp) {
+    temp_facet.bits_data_temp = {};
+  }
+
+  if (!temp_facet.is_temp_copied) {
+    for (const key in temp_facet.bits_data) {
+      temp_facet.bits_data_temp[key] = {};
+      for (const key2 in temp_facet.bits_data[key]) {
+        temp_facet.bits_data_temp[key][key2] = temp_facet.bits_data[key][key2];
+      }
+    }
+  }
+
+  let union = null;
+
+  if (Array.isArray(query_filters)) {
+    query_filters.forEach((conjunction) => {
+      let conjunctive_index = null;
+
+      conjunction.forEach((filter) => {
+        const [filter_key, filter_val] = filter;
+
+        if (!temp_facet.bits_data_temp[filter_key]) {
+          throw new Error('Panic. The key does not exist in facets lists.');
+        }
+
+        const facetData = temp_facet.bits_data_temp[filter_key][filter_val];
+
+        if (facetData) {
+          if (conjunctive_index) {
+            conjunctive_index = conjunctive_index.new_intersection(facetData);
+          } else {
+            conjunctive_index = facetData;
+          }
+        } else {
+          conjunctive_index = new FastBitSet();
+        }
+      });
+
+      if (conjunctive_index) {
+        if (union) {
+          union = union.new_union(conjunctive_index);
+        } else {
+          union = conjunctive_index;
+        }
+      }
+    });
+  }
+
+  if (union !== null) {
+    for (const key in temp_facet.bits_data_temp) {
+      for (const key2 in temp_facet.bits_data_temp[key]) {
+        temp_facet.bits_data_temp[key][key2] =
+          temp_facet.bits_data_temp[key][key2].new_intersection(union);
+      }
+    }
+  }
+
+  return temp_facet;
+};
+
+export const matrix = function (facets, filters = []) {
+  const temp_facet = _clone(facets);
+
+  temp_facet.bits_data_temp = {};
+  for (const key in temp_facet.bits_data) {
+    temp_facet.bits_data_temp[key] = {};
+    for (const key2 in temp_facet.bits_data[key]) {
+      temp_facet.bits_data_temp[key][key2] = temp_facet.bits_data[key][key2];
+    }
+  }
+
+  temp_facet.is_temp_copied = true;
+
+  let conjunctive_index;
+  const disjunctive_indexes = combination_indexes(facets, filters);
+
+  filters.forEach((filter) => {
+    if (!Array.isArray(filter[0])) {
+      const [filter_key, filter_val] = filter;
+      const facetData = temp_facet.bits_data_temp[filter_key]?.[filter_val];
+
+      if (conjunctive_index && facetData) {
+        conjunctive_index = facetData.new_intersection(conjunctive_index);
+      } else if (conjunctive_index && !facetData) {
+        conjunctive_index = new FastBitSet([]);
+      } else {
+        conjunctive_index = facetData;
+      }
+    }
+  });
+
+  if (conjunctive_index) {
+    for (const key in temp_facet.bits_data_temp) {
+      for (const key2 in temp_facet.bits_data_temp[key]) {
+        temp_facet.bits_data_temp[key][key2] =
+          temp_facet.bits_data_temp[key][key2].new_intersection(
+            conjunctive_index
+          );
+      }
+    }
+  }
+
+  filters.forEach((filter) => {
+    if (filter.length === 3 && filter[1] === '-') {
+      const [filter_key, , filter_val] = filter;
+      const negative_bits = temp_facet.bits_data_temp[filter_key][filter_val].clone();
+
+      for (const key in temp_facet.bits_data_temp) {
+        for (const key2 in temp_facet.bits_data_temp[key]) {
+          temp_facet.bits_data_temp[key][key2] =
+            temp_facet.bits_data_temp[key][key2].new_difference(negative_bits);
+        }
+      }
+    }
+  });
+
+  for (const key in temp_facet.bits_data_temp) {
+    for (const key2 in temp_facet.bits_data_temp[key]) {
+      for (const disjunctive_key in disjunctive_indexes) {
+        if (disjunctive_key !== key) {
+          temp_facet.bits_data_temp[key][key2] =
+            temp_facet.bits_data_temp[key][key2].new_intersection(
+              disjunctive_indexes[disjunctive_key]
+            );
+        }
+      }
+    }
+  }
+
+  return temp_facet;
+};
diff --git a/src/utils/indexBuilder.js b/src/utils/indexBuilder.js
new file mode 100644
index 0000000..2a3edc6
--- /dev/null
+++ b/src/utils/indexBuilder.js
@@ -0,0 +1,57 @@
+import FastBitSet from 'fastbitset';
+
+export const index = function (items = [], fields = []) {
+  const facets = {
+    data: Object.create(null),
+    bits_data: Object.create(null),
+    bits_data_temp: Object.create(null),
+  };
+
+  let nextId = 1;
+
+  fields.forEach((field) => {
+    facets.data[field] = Object.create(null);
+  });
+
+  items.forEach((item) => {
+    if (!item._id) {
+      item._id = nextId++;
+    }
+  });
+
+  items.forEach((item) => {
+    fields.forEach((field) => {
+      const fieldValue = item[field];
+
+      if (Array.isArray(fieldValue)) {
+        fieldValue.forEach((value) => {
+          if (!facets.data[field][value]) {
+            facets.data[field][value] = [];
+          }
+          facets.data[field][value].push(item._id);
+        });
+      } else if (typeof fieldValue !== 'undefined') {
+        const value = fieldValue;
+        if (!facets.data[field][value]) {
+          facets.data[field][value] = [];
+        }
+        facets.data[field][value].push(item._id);
+      }
+    });
+  });
+
+  Object.keys(facets.data).forEach((field) => {
+    facets.bits_data[field] = Object.create(null);
+    facets.bits_data_temp[field] = Object.create(null);
+
+    const values = facets.data[field];
+    Object.keys(values).forEach((filter) => {
+      const indexes = values[filter];
+      const sorted_indexes = indexes.sort((a, b) => a - b);
+      facets.bits_data[field][filter] = new FastBitSet(sorted_indexes);
+      facets.data[field][filter] = sorted_indexes;
+    });
+  });
+
+  return facets;
+};
diff --git a/src/utils/object.js b/src/utils/object.js
new file mode 100644
index 0000000..506e261
--- /dev/null
+++ b/src/utils/object.js
@@ -0,0 +1,20 @@
+export const clone = function (val) {
+  try {
+    return structuredClone(val);
+  } catch (e) {
+    try {
+      return JSON.parse(JSON.stringify(val));
+    } catch (e2) {
+      return val;
+    }
+  }
+};
+
+export const humanize = function (str) {
+  return str
+    .replace(/^[\s_]+|[\s_]+$/g, '')
+    .replace(/[_\s]+/g, ' ')
+    .replace(/^[a-z]/, function (m) {
+      return m.toUpperCase();
+    });
+};