backend/src/modules/investments/brokerage-accounts/brokerage-accounts.service.ts

import { Injectable } from '@nestjs/common';
import { createHash } from 'node:crypto';

import {
  add,
  decimalFromString,
  divide,
  formatDecimal,
  isZero,
  multiply,
} from '#src/common/decimal';

import { investmentResourceMeta } from '../investment-resource.mapper';
import { PortfolioPositionDto, PortfolioService } from '../portfolio/portfolio.api';
import { hourlyAttempt, TbankSyncRepository } from '../tbank-sync/tbank-sync.api';
import {
  BrokerageAccountDto,
  BrokerageAccountsResourceDto,
  UnrealizedReturnDto,
} from './brokerage-account.dto';

const PERCENT_DECIMAL_PLACES = 2;
const ZERO_QUANTITY = 0n;

function unrealizedReturn(positions: PortfolioPositionDto[]): UnrealizedReturnDto {
  const absoluteReturn = positions.reduce(
    (sum, position) => position.absoluteReturn
      ? add(sum, decimalFromString(position.absoluteReturn.value))
      : sum,
    decimalFromString('0'),
  );
  const costBasis = positions
    .filter((position) => position.absoluteReturn && position.averagePurchasePrice)
    .reduce(
      (sum, position) =>
        // eslint-disable-next-line @typescript-eslint/no-non-null-assertion -- Guarded by the filter above.
        add(sum, multiply(decimalFromString(position.averagePurchasePrice!.value), decimalFromString(position.quantity))),
      decimalFromString('0'),
    );
  const partial = positions.some(
    (position) => !position.absoluteReturn && (position.averagePurchasePrice || position.currentValue),
  );
  // A short position has negative cost basis, so a percent would flip sign or net out.
  const withShorts = positions.some(
    (position) =>
      (position.absoluteReturn ?? position.averagePurchasePrice ?? position.currentValue) &&
      decimalFromString(position.quantity).value < ZERO_QUANTITY,
  );
  return {
    absolute: formatDecimal(absoluteReturn),
    costBasis: formatDecimal(costBasis),
    percent: isZero(costBasis) || withShorts
      ? null
      : formatDecimal(divide(
          multiply(absoluteReturn, decimalFromString('100')),
          costBasis,
          PERCENT_DECIMAL_PLACES,
        )),
    partial,
  };
}

@Injectable()
export class BrokerageAccountsService {
  constructor(
    private readonly portfolio: PortfolioService,
    private readonly sync: TbankSyncRepository,
  ) {}

  async list(userId: string): Promise<BrokerageAccountsResourceDto> {
    const saved = await this.portfolio.saved(userId, 'all');
    const data: BrokerageAccountDto[] | null =
      saved.membership.completeness === 'incomplete'
        ? null
        : saved.accounts.map((account) => ({
            id: account.id,
            name: account.name,
            type: account.type as BrokerageAccountDto['type'],
            openedOn: account.openedOn,
            portfolioSummary: account.snapshot
              ? {
                  totals: account.snapshot.totals,
                  cash: account.snapshot.cash,
                  structure: account.snapshot.structure,
                  unrealizedReturn: unrealizedReturn(account.snapshot.positions),
                  stockPositionCount: account.snapshot.positions.filter(
                    (position) => position.type === 'STOCK',
                  ).length,
                  bondPositionCount: account.snapshot.positions.filter(
                    (position) => position.type === 'BOND',
                  ).length,
                  fundPositionCount: account.snapshot.positions.filter(
                    (position) => position.type === 'FUND',
                  ).length,
                  // The snapshot mapper already drops zero-quantity positions.
                  totalPositionCount: account.snapshot.positions.length,
                }
              : null,
          }));
    // The read-only result of the last hourly walk; never starts one.
    const hourly = await this.sync.hourly(userId);
    return {
      data,
      meta: investmentResourceMeta({
        resourceKey: 'accounts',
        dataRevision: createHash('sha256')
          .update(
            JSON.stringify([
              saved.membership.dataRevision,
              saved.accounts.map((account) => [
                account.id,
                account.meta.dataRevision,
              ]),
            ]),
          )
          .digest('base64url'),
        availability:
          data === null
            ? 'missing'
            : 'complete',
        fetchedAt: saved.membership.lastSuccessfulAt
          ? new Date(saved.membership.lastSuccessfulAt)
          : null,
        freshForMs: 3_600_000,
        work: null,
        lastAttempt: hourlyAttempt(hourly, ['membership', 'portfolio']),
        dependencies: saved.accounts.map((account) => account.meta),
      }),
      sync: hourly
        ? {
            state: hourly.state,
            startedAt: hourly.startedAt.toISOString(),
            finishedAt: hourly.finishedAt?.toISOString() ?? null,
            problems: hourly.sections.map((section) => ({
              ...section,
              accountId: section.accountId ?? null,
            })),
          }
        : null,
    };
  }
}