import { Injectable, NotFoundException } from '@nestjs/common';

import { add, type Decimal, decimalFromString, divide, formatDecimal, subtract } from '#src/common/decimal';
import { StructuredLogger } from '#src/common/logging/structured-logger.service';
import { TbankAccessService } from '#src/integrations/tbank/tbank-access.service';

import { moscowDate } from '../investment-calendar';
import { MarketIndexHistoryService } from '../market-index/market-index.service';
import { isCompleteValuation } from '../portfolio/domain/complete-valuation';
import { hasPerformanceCoverage, PerformanceUnavailableReason } from './domain/performance-availability';
import { candidateTransfers, type PerformanceFlow, readPerformanceOperations, sumFlows } from './domain/performance-flows';
import { shadowIndex } from './domain/shadow-index';
import { xirr } from './domain/xirr';
import { PerformanceRepository } from './infrastructure/performance.repository';
import {
  PerformanceDto, PerformanceExcludedAccountDto, PerformanceIndexDto, PerformanceResourceDto,
  PerformanceReturnDto, PerformanceSeriesPointDto,
} from './presentation/performance.dto';

const DAY_MS = 86_400_000;
const DAYS_IN_YEAR = 365;
const RATE_SCALE = 6;
const MONEY_SCALE = 2;
const RUB = 'RUB';
const ZERO = 0;
const ONE = 1;
const ZERO_DECIMAL = decimalFromString('0');
const LAST_FLOW = -1;
const ONE_DECIMAL = decimalFromString('1');

type Account = NonNullable<Awaited<ReturnType<PerformanceRepository['read']>>>['accounts'][number];
type Included = { account: Account; flows: PerformanceFlow[]; to: string; value: Decimal };
type IncludedResult = { included: Included | null; reason: null | PerformanceUnavailableReason };

function money(value: Decimal) {
  return { currency: RUB, value: formatDecimal(divide(value, ONE_DECIMAL, MONEY_SCALE)) };
}

function unavailable(accountId: string, name: string, reason: PerformanceUnavailableReason): PerformanceExcludedAccountDto {
  return { accountId, name, reason };
}

function duration(from: string, to: string) {
  return (Date.parse(`${to}T00:00:00Z`) - Date.parse(`${from}T00:00:00Z`)) / DAY_MS;
}

// Float rate → exact decimal string, rounded by the shared money helper.
function roundRate(value: number): string {
  return formatDecimal(divide(decimalFromString(value.toFixed(RATE_SCALE + ONE)), ONE_DECIMAL, RATE_SCALE));
}

function rate(flows: PerformanceFlow[], endValue: Decimal, to: string, days: number): PerformanceReturnDto {
  const basis = days >= DAYS_IN_YEAR ? 'annual' : 'period';
  const result = xirr([
    ...flows.map((flow) => ({ date: flow.date, amount: { value: -flow.amount.value, scale: flow.amount.scale } })),
    { date: to, amount: endValue },
  ]);
  if (result.value === null) {
    return { value: null, basis, unavailableReason: result.reason === 'AMBIGUOUS_RETURN'
      ? PerformanceUnavailableReason.AmbiguousReturn
      : PerformanceUnavailableReason.NoSolution };
  }
  const raw = Number(result.value);
  const value = basis === 'annual' ? raw : Math.pow(ONE + raw, days / DAYS_IN_YEAR) - ONE;
  return { value: roundRate(value), basis, unavailableReason: null };
}

@Injectable()
export class PerformanceService {
  constructor(
    private readonly access: TbankAccessService,
    private readonly repository: PerformanceRepository,
    private readonly indexes: MarketIndexHistoryService,
    private readonly logger: StructuredLogger,
  ) {}

  async read(userId: string, accountId: string): Promise<PerformanceResourceDto> {
    const started = Date.now();
    const connection = await this.access.local(userId, accountId);
    const saved = await this.repository.read(userId, connection.revision, accountId);
    if (accountId !== 'all' && saved?.membershipAt && !saved.accounts.length) throw new NotFoundException();
    const accounts = saved?.membershipAt ? saved.accounts : [];
    const excluded: PerformanceExcludedAccountDto[] = [];
    let included = accounts.flatMap((account) => {
      const result = this.includeAccount(account);
      if (result.reason) {
        excluded.push(unavailable(account.accountId, account.name, result.reason));
        return [];
      }
      return result.included ? [result.included] : [];
    });
    if (accountId === 'all' && included.length > ZERO) {
      const allOps = included.flatMap((item) => item.account.operations
        .filter((op) => item.account.portfolio && op.occurredAt <= item.account.portfolio.fetchedAt)
        .map((op) => ({ ...op, accountId: item.account.accountId })));
      const candidates = candidateTransfers(readPerformanceOperations(allOps));
      const affected = new Set(candidates.flatMap((candidate) => candidate.accountIds));
      if (affected.size) {
        included = included.filter((item) => {
          if (!affected.has(item.account.accountId)) return true;
          excluded.push(unavailable(item.account.accountId, item.account.name, PerformanceUnavailableReason.UnconfirmedTransfer));
          return false;
        });
      }
    }
    if (!included.length) return { data: null, meta: { dependencies: [], unavailable: excluded } };
    const dates = new Set(included.map((item) => item.to));
    if (dates.size > ONE) {
      return {
        data: null,
        meta: { dependencies: [], unavailable: [
          ...excluded,
          ...included.map((item) => unavailable(item.account.accountId, item.account.name,
            PerformanceUnavailableReason.AccountValuationDatesDiffer)),
        ] },
      };
    }
    const [to] = dates;
    const flows = included.flatMap((item) => item.flows).sort((a, b) => a.at.valueOf() - b.at.valueOf());
    // The period starts when money was first put in (owner decision), not at account opening.
    // eslint-disable-next-line security/detect-object-injection -- Fixed first element of a locally sorted array.
    const from = flows[ZERO]?.date ?? to;
    const days = duration(from, to);
    const invested = sumFlows(flows);
    const current = included.reduce((total, item) => add(total, item.value), ZERO_DECIMAL);
    const profit = subtract(current, invested);
    const ownReturn = rate(flows, current, to, days);
    const [benchmark, reference] = await Promise.all([
      this.indexResult('MCFTRR', flows, from, to, days),
      this.indexResult('IMOEX', flows, from, to, days),
    ]);
    const outperformance = ownReturn.value !== null && benchmark.index.return.value !== null && benchmark.index.value
      ? {
          percentagePoints: formatDecimal(subtract(decimalFromString(ownReturn.value),
            decimalFromString(benchmark.index.return.value))),
          money: money(subtract(current, decimalFromString(benchmark.index.value.value))),
        }
      : null;
    const referenceByDay = new Map(reference.points.map((point) => [point.date, point.value]));
    const series: PerformanceSeriesPointDto[] = benchmark.points.map((point) => ({
      date: point.date,
      netInvested: point.netInvested,
      benchmarkValue: point.value,
      referenceValue: referenceByDay.get(point.date) ?? null,
    }));
    const data: PerformanceDto = {
      accountId, period: { from, to, days }, netInvested: money(invested), currentValue: money(current),
      profit: money(profit), return: ownReturn, benchmark: benchmark.index, reference: reference.index,
      outperformance, series, completeness: excluded.length ? 'incomplete' : 'complete',
      excludedAccounts: excluded, calculatedAt: new Date().toISOString(),
    };
    this.logger.event('debug', 'performance.calculated', {
      count: included.length, durationMs: Date.now() - started,
    });
    return { data, meta: { dependencies: [], unavailable: [] } };
  }

  private includeAccount(account: Account): IncludedResult {
    const fail = (reason: PerformanceUnavailableReason): IncludedResult => ({ included: null, reason });
    if (account.historyBoundary !== 'known' || !account.historyFrom) {
      return fail(PerformanceUnavailableReason.HistoryStartUnknown);
    }
    const portfolio = account.portfolio;
    if (!portfolio) return fail(PerformanceUnavailableReason.PortfolioValuationIncomplete);
    const snapshot = portfolio.payload as { positions: { currentValue: unknown }[];
      totals: { value: string }; };
    if (!isCompleteValuation(snapshot)) return fail(PerformanceUnavailableReason.PortfolioValuationIncomplete);
    if (!hasPerformanceCoverage(account.accountId, account.historyFrom, portfolio.fetchedAt, account.coverage)) {
      return fail(PerformanceUnavailableReason.OperationsHistoryIncomplete);
    }
    const operations = account.operations.filter((op) => op.occurredAt <= portfolio.fetchedAt)
      .map((op) => ({ ...op, accountId: account.accountId }));
    const parsed = readPerformanceOperations(operations);
    if (parsed.missingAmountAccounts.size) return fail(PerformanceUnavailableReason.OperationsHistoryIncomplete);
    if (parsed.unvaluedAccounts.size) return fail(PerformanceUnavailableReason.UnvaluedSecuritiesTransfer);
    return {
      included: { account, flows: parsed.flows, value: decimalFromString(snapshot.totals.value),
        to: moscowDate(portfolio.fetchedAt) },
      reason: null,
    };
  }

  private async indexResult(code: 'IMOEX' | 'MCFTRR', flows: PerformanceFlow[], from: string, to: string, days: number) {
    const closes = await this.indexes.read(code, from, to, flows.at(LAST_FLOW)?.date ?? from);
    const shadow = closes && shadowIndex(flows, closes, from, to);
    const unavailableReason = shadow ? null : PerformanceUnavailableReason.IndexHistoryUnavailable;
    const result = shadow && rate(flows, decimalFromString(shadow.value), to, days);
    const index: PerformanceIndexDto = {
      code, value: shadow ? money(decimalFromString(shadow.value)) : null,
      return: result || { basis: days >= DAYS_IN_YEAR ? 'annual' : 'period', value: null, unavailableReason },
      asOf: shadow?.asOf ?? null, unavailableReason,
    };
    return { index, points: shadow?.points ?? [] };
  }
}