mnemo_cards/mnemo_cards_backend/lib/discounts/discounts_manager.dart

import 'dart:developer';

import 'package:injectable/injectable.dart';
import 'package:isar/isar.dart';
import 'package:mnemo_cards_backend/discounts/discount_campaign_ext.dart';
import 'package:mnemo_cards_common_backend/mnemo_cards_common_backend.dart';
import 'package:mnemo_cards_common/mnemo_cards_common.dart';

import '../main.dart';

@lazySingleton
class DiscountsManager {
  Future<void> applyDiscount({
    required Iterable<DiscountModel> discounts,
    required UserModel user,
  }) async {
    await isar.writeTxn(() async {
      await user.userData.load();
      final userData = user.userData.value!;
      userData.activeDiscounts.addAll(discounts);
      await user.userData.save();
    });
  }

  Future<void> changeCampaignStatus(DiscountCampaignModel campaign) async {
    final now = DateTime.now();
    var target = campaign.status;
    if (campaign.status == DiscountCampaignModelStatus.created &&
        now.isBetween(campaign.start, campaign.finish)) {
      target = DiscountCampaignModelStatus.active;
    } else if (campaign.status == DiscountCampaignModelStatus.active) {
      if (now.isBefore(campaign.start)) {
        target = DiscountCampaignModelStatus.created;
      } else if (now.isAfter(campaign.finish)) {
        target = DiscountCampaignModelStatus.expired;
      }
    }
    if (target != campaign.status) {
      await isar.writeTxn(() => isar.discountCampaignModels.put(
            campaign.copyWith(status: target),
          ));
    }
  }

  Future<DiscountError?> applyCampaign(DiscountCampaignModel campaign) async {
    final now = DateTime.now();
    if (!now.isBetween(campaign.start, campaign.finish)) {
      if (now.isBefore(campaign.start)) {
        return DiscountError(DiscountErrorType.notStarted);
      }
      return DiscountError(DiscountErrorType.expired);
    }
    // final usersData = await isar.txn(
    //   () => isar.userDataModels
    //       .filter()
    //       .optional(
    //         campaign.tags.isNotEmpty,
    //         (q) => q.anyOf(
    //           campaign.tags,
    //           (q, tag) => q.tagsElementContains(tag),
    //         ),
    //       )
    //       .findAll(),
    // );
    return null;
  }

  Future<void> removeDiscount({
    required DiscountCampaignModel campaign,
    required UserModel user,
  }) async {
    await isar.writeTxn(() async {
      await user.userData.load();
      final userData = user.userData.value!;
      userData.activeDiscounts.removeAll(campaign.discounts);
      await isar.userDataModels.put(userData);
    });
  }

  Future<double> getProductDiscount(
    MnemoCardsProductModel model,
    UserDataModel userData,
  ) async {
    double maxDiscount = 0;
    for (final discount in userData.activeDiscounts) {
      if (discount.discountPercent > maxDiscount &&
          discount.products.any((p) => p.equalsProduct(model))) {
        maxDiscount = discount.discountPercent;
      }
    }

    final activeCampaigns =
        await discountCampaignsForUser(userData, product: model);
    for (final campaign in activeCampaigns) {
      for (final discount in campaign.discounts) {
        if (discount.discountPercent > maxDiscount &&
            discount.products.any((p) => p.equalsProduct(model))) {
          maxDiscount = discount.discountPercent;
        }
      }
    }
    return maxDiscount;
  }

  Future<List<DiscountCampaignModel>> discountCampaignsForUser(
    UserDataModel userModel, {
    MnemoCardsProductModel? product,
  }) async {
    final activeCampaigns =
        await isar.txn(() async => isar.discountCampaignModels
            .filter()
            .statusEqualTo(DiscountCampaignModelStatus.active)
            .optional(userModel.tags.isEmpty, (q) => q.tagsIsEmpty())
            .optional(
              product != null,
              (q) => q.discounts(
                (d) => d.productsElement(
                  (p) => p.typeEqualTo(product!.type).productIdEqualTo(
                        product.id,
                      ),
                ),
              ),
            )
            .findAll());
    if (userModel.tags.isEmpty) {
      return activeCampaigns;
    } else {
      // todo check tags in query
      final userTags = userModel.tags.toSet();
      return activeCampaigns
          .where((campaign) => campaign.tags.hasIntersection(userTags))
          .toList();
    }
  }

  Future<List<DiscountCampaignDto>> discountCampaigns() async {
    final models = await isar
        .txn(() async => isar.discountCampaignModels.where().findAll());
    final dtos = await Future.wait(models.map((m) async => await m.toDto()));
    return dtos;
  }

  Future<String?> deleteDiscountCampaign(String stringId) async {
    try {
      final id = int.parse(stringId);
      isar.writeTxn(() async {
        final model = await isar.discountCampaignModels.get(id);
        if (model == null) {
          return 'Campaign $id not found';
        }
        if (model.status != DiscountCampaignModelStatus.disabled) {
          return 'Disable campaign before deleting';
        }
        isar.discountCampaignModels.delete(id);
      });
      return null;
    } catch (e, s) {
      log('Error when deleting discount campaign', error: e, stackTrace: s);
      return 'Error $e';
    }
  }

  Future<bool> addDiscount(DiscountCampaignDto dto) async {
    try {
      final model = DiscountCampaignModel(
        id: dto.id,
        start: dto.start,
        finish: dto.finish,
        status: dto.status.toModel(),
        name: dto.name,
        tags: dto.tags,
      );
      final discounts = dto.discounts.map((d) => d.toModel()).toList();
      await isar.writeTxn(() async {
        await isar.discountModels.putAll(discounts);
        await isar.discountCampaignModels.put(model);
        await model.discounts.reset();
        model.discounts.addAll(discounts);
        await model.discounts.save();
      });

      return true;
    } catch (e, s) {
      print('error when adding campaign');
      log('error when adding campaign', error: e, stackTrace: s);
      return false;
    }
  }

  const DiscountsManager();
}

class DiscountError {
  final String? message;
  final DiscountErrorType type;

  DiscountError(this.type, {this.message});
}

enum DiscountErrorType {
  notAvailable,
  notStarted,
  expired,
}