/* ldgallery - A static generator which turns a collection of tagged
--             pictures into a searchable web gallery.
--
-- Copyright (C) 2019-2022  Guillaume FOUET
--
-- This program is free software: you can redistribute it and/or modify
-- it under the terms of the GNU Affero General Public License as
-- published by the Free Software Foundation, either version 3 of the
-- License, or (at your option) any later version.
--
-- This program is distributed in the hope that it will be useful,
-- but WITHOUT ANY WARRANTY; without even the implied warranty of
-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-- GNU Affero General Public License for more details.
--
-- You should have received a copy of the GNU Affero General Public License
-- along with this program.  If not, see <https://www.gnu.org/licenses/>.
*/

import { Item } from '@/@types/gallery';
import { Operation } from '@/@types/operation';
import { TagSearch, TagSearchByOperation } from '@/@types/tag';

function _extractTagsByOperation(searchTags: TagSearch[]): TagSearchByOperation {
  const byOperation: TagSearchByOperation = {};
  Object.values(Operation).forEach(
    operation => (byOperation[operation] = searchTags.filter(tag => tag.operation === operation)),
  );
  return byOperation;
}

function _extractIntersection(byOperation: TagSearchByOperation): Set<Item> {
  const intersection = new Set<Item>();
  if (byOperation[Operation.INTERSECTION].length > 0) {
    byOperation[Operation.INTERSECTION]
      .map(tag => tag.items)
      .reduce((a, b) => a.filter(c => b.includes(c)))
      .flatMap(items => items)
      .forEach(item => intersection.add(item));
  }
  return intersection;
}

function _extractSubstraction(byOperation: TagSearchByOperation): Set<Item> {
  const substraction = new Set<Item>();
  if (byOperation[Operation.SUBSTRACTION].length > 0) {
    byOperation[Operation.SUBSTRACTION].flatMap(tag => tag.items).forEach(item => substraction.add(item));
  }
  return substraction;
}

function _aggregateAll(
  byOperation: TagSearchByOperation,
  intersection: Set<Item>,
  substraction: Set<Item>,
): Item[] {
  byOperation[Operation.ADDITION].flatMap(tag => tag.items).forEach(item => intersection.add(item));
  substraction.forEach(item => intersection.delete(item));
  return [...intersection];
}

// ---

export const useIndexSearch = () => {
  // Results of the search (by tags)
  function indexSearch(searchTags: TagSearch[]): Item[] {
    const byOperation = _extractTagsByOperation(searchTags);
    const intersection = _extractIntersection(byOperation);
    const substraction = _extractSubstraction(byOperation);
    return _aggregateAll(byOperation, intersection, substraction);
  }

  return indexSearch;
};