import { addMonths, endOfMonth, startOfMonth } from 'date-fns';
import { GraphQLError } from 'graphql';
import { Repeater } from 'graphql-yoga';
import { validatePcn874 } from '@accounter/pcn874-generator';
import type { ResolversTypes } from '../../../__generated__/types.js';
import { dateToTimelessDateString } from '../../../shared/helpers/index.js';
import { TimelessDateString } from '../../../shared/types/index.js';
import { AdminContextProvider } from '../../admin-context/providers/admin-context.provider.js';
import { getPcn874String } from '../helpers/pcn.helper.js';
import { VatReportProvider } from '../providers/vat-report.provider.js';
import type { ReportsModule } from '../types.js';

export const pcn874Resolvers: ReportsModule.Resolvers = {
  Query: {
    pcnFile: async (_, { monthDate: rawMonthDate, financialEntityId }, { injector }) => {
      const { reportContent, monthDate, reportMonth, financialEntity } = await getPcn874String(
        injector,
        financialEntityId,
        rawMonthDate,
      );

      // if not exists, insert the report
      try {
        const existingContent = await injector
          .get(VatReportProvider)
          .getReportByBusinessIdAndMonthDateLoader.load([financialEntityId, monthDate]);
        if (!existingContent && reportContent.split('\n').length > 2) {
          if (validatePcn874(reportContent)) {
            throw new GraphQLError('Invalid PCN874 content');
          }
          // insert the report
          await injector.get(VatReportProvider).insertReport({
            businessId: financialEntityId,
            monthDate,
            content: reportContent,
          });
        }
      } catch (error) {
        console.error('Error inserting report:', error);
        // TODO: let user know about the error
      }

      const fileName = `pcn874_${financialEntity.vat_number}_${reportMonth}.txt`;

      return { reportContent, fileName };
    },
    pcnByDate: async (_, { businessId, fromMonthDate, toMonthDate }, { injector }, __) => {
      const { ownerId } = await injector.get(AdminContextProvider).getVerifiedAdminContext();
      const financialEntityId = businessId || ownerId;
      const months: TimelessDateString[] = [];
      let startTimestamp = startOfMonth(new Date(fromMonthDate)).getTime();
      const endTimestamp = endOfMonth(new Date(toMonthDate)).getTime();
      while (startTimestamp <= endTimestamp) {
        const currMonth = startOfMonth(new Date(startTimestamp));
        months.push(dateToTimelessDateString(currMonth));
        const nextMonth = addMonths(currMonth, 1);
        startTimestamp = nextMonth.getTime();
      }

      return new Repeater<ResolversTypes['Pcn874Records']>(async (push, stop) => {
        await Promise.all(
          months.map(async monthDate => {
            try {
              const [savedReport, { reportContent: generatedReport, financialEntity }] =
                await Promise.all([
                  injector
                    .get(VatReportProvider)
                    .getReportByBusinessIdAndMonthDateLoader.load([financialEntityId, monthDate]),
                  getPcn874String(injector, financialEntityId, monthDate),
                ]);

              if (savedReport) {
                push({
                  id: `${monthDate}-${financialEntityId}`,
                  date: monthDate,
                  business: financialEntity,
                  content: generatedReport,
                  diffContent: savedReport === generatedReport ? undefined : savedReport,
                });
              } else {
                if (generatedReport.split('\n').length > 2) {
                  if (!validatePcn874(generatedReport)) {
                    throw new GraphQLError('Invalid PCN874 content');
                  }
                  // insert the report
                  await injector.get(VatReportProvider).insertReport({
                    businessId: financialEntityId,
                    monthDate,
                    content: generatedReport,
                  });
                }
                push({
                  id: `${monthDate}-${financialEntityId}`,
                  date: monthDate,
                  business: financialEntity,
                  content: generatedReport,
                });
              }
            } catch (error) {
              const message = `Error fetching report for month ${monthDate}`;
              console.error(message, error);
              throw new Error(message, { cause: error });
            }
          }),
        );
        stop();
      }) as unknown as Promise<readonly ResolversTypes['Pcn874Records'][]>;
    },
  },
  Mutation: {
    updatePcn874: async (_, { monthDate, businessId, content }, context, __) => {
      try {
        const normalizedMonthDate = dateToTimelessDateString(startOfMonth(new Date(monthDate)));
        if (!validatePcn874(content)) {
          throw new GraphQLError('Invalid PCN874 content');
        }
        await context.injector.get(VatReportProvider).updateReport({
          businessId,
          monthDate: normalizedMonthDate,
          content,
        });
        return true;
      } catch (error) {
        const message = `Error updating report for month ${monthDate}`;
        console.error(message, error);
        throw new GraphQLError(message);
      }
    },
  },
};