import { Injectable, ServiceUnavailableException } from '@nestjs/common';
import { RequestContextService } from '../common/logging/request-context.service';
import {
  add,
  decimal,
  formatDecimal,
  isZero,
  multiply,
  subtract,
} from './decimal';
import { totalsByCurrency } from './portfolio-totals';
import { MoneyDto, PortfolioDto, PortfolioPositionDto } from './portfolio.dto';
import { TbankAccessService } from './tbank-access.service';
import { InstrumentMetadataService } from './instrument-metadata.service';
import { TbankClient, TbankMoney } from './tbank.client';

const freshForMs = 30_000;
const fallbackForMs = 300_000;
const types: Record<string, string> = {
  share: 'STOCK',
  bond: 'BOND',
  etf: 'FUND',
  currency: 'CURRENCY',
  futures: 'FUTURE',
  option: 'OPTION',
  sp: 'STRUCTURED_NOTE',
  dfa: 'DIGITAL_FINANCIAL_ASSET',
};

type CachedSnapshot = { snapshot: PortfolioDto; storedAt: number };

@Injectable()
export class PortfolioService {
  private readonly snapshots = new Map<string, CachedSnapshot>();

  constructor(
    private readonly access: TbankAccessService,
    private readonly tbank: TbankClient,
    private readonly requestContext: RequestContextService,
    private readonly metadata: InstrumentMetadataService,
  ) {}

  async get(userId: string, accountId: string): Promise<PortfolioDto> {
    this.requestContext.set({ userId, brokerageAccountId: accountId });
    const key = `${userId}:${accountId}`;
    const cached = this.snapshots.get(key);
    if (cached && Date.now() - cached.storedAt <= freshForMs)
      return cached.snapshot;
    try {
      const snapshot = await this.access.withAccount(
        userId,
        accountId,
        async ({ token }) => {
          const [portfolio, positions] = await Promise.all([
            this.tbank.getPortfolio(token, accountId),
            this.tbank.getPositions(token, accountId),
          ]);
          return this.normalize(
            token,
            portfolio.positions ?? [],
            positions.money ?? [],
          );
        },
      );
      this.snapshots.set(key, { snapshot, storedAt: Date.now() });
      return snapshot;
    } catch (error) {
      if (
        error instanceof ServiceUnavailableException &&
        cached &&
        Date.now() - cached.storedAt <= fallbackForMs
      ) {
        return { ...cached.snapshot, isStale: true };
      }
      throw error;
    }
  }

  invalidate(userId: string): void {
    for (const key of this.snapshots.keys())
      if (key.startsWith(`${userId}:`)) this.snapshots.delete(key);
  }

  private async normalize(
    token: string,
    upstream: {
      figi?: string;
      instrumentUid?: string;
      instrumentType?: string;
      quantity?: { units?: string | number; nano?: string | number };
      currentPrice?: TbankMoney;
      averagePositionPrice?: TbankMoney;
    }[],
    money: TbankMoney[],
  ): Promise<PortfolioDto> {
    const positions = await Promise.all(
      upstream.map((position) => this.position(token, position)),
    );
    const cash = new Map<string, ReturnType<typeof decimal>>();
    for (const value of money) {
      const currency = value.currency?.trim().toUpperCase();
      const amount = decimal(value);
      if (!currency || isZero(amount)) continue;
      cash.set(currency, add(cash.get(currency) ?? decimal({}), amount));
    }
    const cashBalances = [...cash].map(([currency, value]) => ({
      currency,
      value: formatDecimal(value),
    }));
    return {
      lastSuccessfulAt: new Date().toISOString().replace(/\.\d{3}Z$/, 'Z'),
      isStale: false,
      totalsByCurrency: totalsByCurrency(upstream, money),
      positions: positions.filter(
        (position): position is PortfolioPositionDto => position !== null,
      ),
      cashBalances,
    };
  }

  private async position(
    token: string,
    position: Parameters<PortfolioService['normalize']>[1][number],
  ): Promise<PortfolioPositionDto | null> {
    const quantity = decimal(position.quantity ?? {});
    if (isZero(quantity)) return null;
    const figi = position.figi?.trim() || null;
    const instrumentUid = position.instrumentUid?.trim() || null;
    const currentPrice = this.money(position.currentPrice);
    const averagePurchasePrice = this.money(position.averagePositionPrice);
    const currentValue = currentPrice && this.value(quantity, currentPrice);
    const absoluteReturn =
      currentPrice &&
      averagePurchasePrice &&
      currentPrice.currency === averagePurchasePrice.currency
        ? {
            currency: currentPrice.currency,
            value: formatDecimal(
              multiply(
                subtract(
                  decimal(position.currentPrice!),
                  decimal(position.averagePositionPrice!),
                ),
                quantity,
              ),
            ),
          }
        : null;
    const metadata = await this.metadata.resolve(token, instrumentUid, figi);
    return {
      figi,
      displayName:
        metadata?.name?.trim() ||
        metadata?.ticker?.trim() ||
        figi ||
        'Unknown instrument',
      type: types[position.instrumentType?.toLowerCase() ?? ''] ?? 'OTHER',
      quantity: formatDecimal(quantity),
      currentValue,
      averagePurchasePrice,
      absoluteReturn,
      isin: metadata?.isin?.trim() || null,
      ticker: metadata?.ticker?.trim() || null,
      logoName: metadata?.brand?.logoName?.trim() || null,
    };
  }

  private value(
    quantity: ReturnType<typeof decimal>,
    price: MoneyDto,
  ): MoneyDto {
    return {
      currency: price.currency,
      value: formatDecimal(multiply(quantity, decimalFromString(price.value))),
    };
  }

  private money(value: TbankMoney | undefined): MoneyDto | null {
    const currency = value?.currency?.trim().toUpperCase();
    return currency && value
      ? { currency, value: formatDecimal(decimal(value)) }
      : null;
  }
}

function decimalFromString(value: string) {
  const negative = value.startsWith('-');
  const [whole, fraction = ''] = (negative ? value.slice(1) : value).split('.');
  return {
    value: (negative ? -1n : 1n) * BigInt(`${whole}${fraction}`),
    scale: fraction.length,
  };
}