/**
 * Uniswap v3 pool stats — TVL / 24h volume / 24h fees / APR.
 *
 * Источник: GeckoTerminal API (бесплатный, БЕЗ ключа — та же on-chain data network что у Uniswap).
 * Раньше использовался The Graph gateway, но он требует платный THEGRAPH_API_KEY (hosted service
 * закрыт) → без ключа возвращал null. GeckoTerminal не требует авторизации.
 *
 * fees24h выводится из volume24h × feeTier (не полагаемся на отдельное поле GT).
 * APR = fees24h / TVL × 365 × 100.
 *
 * Fallback (если GeckoTerminal недоступен): on-chain TVL = balanceOf(token0/token1) × USD-цена из
 * price-oracle (CoinGecko). Объём/комиссии/APR в фолбэке остаются null (on-chain недоступны дёшево).
 *
 * Только чтение, НИКОГДА не влияет на суммы транзакций. KeyDB-кэш 5 мин. Всё graceful → null-поля.
 */

import { ethers } from 'ethers';
import { getRedis } from '../config/redis';
import { logger } from './logger';
import { ETH_RPCS, UNIV3_POOL_ABI, ERC20_META_ABI } from './defi-contracts';
import { pickProxiedEvmProvider } from './outbound-proxy';
import { getPricesBySymbols } from '../services/price-oracle.service';

const GECKOTERMINAL_POOL_URL = (addr: string) =>
  `https://api.geckoterminal.com/api/v2/networks/eth/pools/${addr}`;
const CACHE_TTL_SEC = 300;
const HTTP_TIMEOUT_MS = 8000;

export interface PoolStats {
  poolAddress: string;
  totalValueLockedUSD: number | null;
  volumeUSD24h: number | null;
  feesUSD24h: number | null;
  aprPercent: number | null;
}

/**
 * Статистика пула (с кэшем). null-поля если источники недоступны.
 * @param feeTier uint24 fee пула (напр. 3000 = 0.3%) — нужен для расчёта fees/APR. Если не задан,
 *   fees/APR останутся null.
 */
export async function getPoolStats(poolAddress: string, feeTier?: number): Promise<PoolStats> {
  const id = poolAddress.toLowerCase();
  const cacheKey = `univ3:poolstats:${id}`;

  try {
    const cached = await getRedis().get(cacheKey);
    if (cached) return JSON.parse(cached) as PoolStats;
  } catch { /* ignore cache errors */ }

  const empty: PoolStats = {
    poolAddress: id,
    totalValueLockedUSD: null,
    volumeUSD24h: null,
    feesUSD24h: null,
    aprPercent: null,
  };

  let stats = empty;

  // ── Primary: GeckoTerminal ──
  const gt = await fetchGeckoTerminal(id, feeTier);
  if (gt) {
    stats = gt;
  } else {
    // ── Fallback: on-chain TVL (balances × prices) ──
    const onchainTvl = await fetchOnChainTvl(id).catch(() => null);
    if (onchainTvl !== null) {
      stats = { ...empty, totalValueLockedUSD: onchainTvl };
    }
  }

  try {
    await getRedis().set(cacheKey, JSON.stringify(stats), 'EX', CACHE_TTL_SEC);
  } catch { /* ignore */ }

  return stats;
}

async function fetchGeckoTerminal(id: string, feeTier?: number): Promise<PoolStats | null> {
  const controller = new AbortController();
  const t = setTimeout(() => controller.abort(), HTTP_TIMEOUT_MS);
  try {
    const res = await fetch(GECKOTERMINAL_POOL_URL(id), {
      headers: { Accept: 'application/json' },
      signal: controller.signal,
    });
    if (!res.ok) {
      logger.warn(`GeckoTerminal HTTP ${res.status} for pool ${id}`);
      return null;
    }
    const j: any = await res.json();
    const attr = j?.data?.attributes;
    if (!attr) return null;

    const tvl = num(attr.reserve_in_usd);
    const vol24h = num(attr.volume_usd?.h24);
    // fees = volume × feeRate. feeTier uint24: 3000 = 0.3% = 3000/1e6.
    const fees24h = vol24h !== null && feeTier ? vol24h * (feeTier / 1_000_000) : null;
    const apr = fees24h !== null && tvl && tvl > 0 ? (fees24h / tvl) * 365 * 100 : null;

    return {
      poolAddress: id,
      totalValueLockedUSD: tvl,
      volumeUSD24h: vol24h,
      feesUSD24h: fees24h,
      aprPercent: apr,
    };
  } catch (err: any) {
    logger.warn(`GeckoTerminal fetch failed for ${id}: ${err?.message}`);
    return null;
  } finally {
    clearTimeout(t);
  }
}

/** Best-effort on-chain TVL: balanceOf(token0)+balanceOf(token1) × USD-цена по символу. */
async function fetchOnChainTvl(poolAddr: string): Promise<number | null> {
  const provider = await pickProxiedEvmProvider(ETH_RPCS, 1);
  const pool = new ethers.Contract(poolAddr, UNIV3_POOL_ABI, provider);
  const [token0, token1] = await Promise.all([
    pool.token0() as Promise<string>,
    pool.token1() as Promise<string>,
  ]);
  const t0 = new ethers.Contract(token0, ERC20_META_ABI, provider);
  const t1 = new ethers.Contract(token1, ERC20_META_ABI, provider);
  const [dec0, dec1, sym0, sym1, bal0, bal1] = await Promise.all([
    t0.decimals() as Promise<number>,
    t1.decimals() as Promise<number>,
    t0.symbol().catch(() => '') as Promise<string>,
    t1.symbol().catch(() => '') as Promise<string>,
    t0.balanceOf(poolAddr) as Promise<ethers.BigNumber>,
    t1.balanceOf(poolAddr) as Promise<ethers.BigNumber>,
  ]);

  const prices = await getPricesBySymbols([
    { chain: 'ETH', symbol: normSym(sym0) },
    { chain: 'ETH', symbol: normSym(sym1) },
  ]);
  const p0 = prices.get(`ETH:${normSym(sym0)}`);
  const p1 = prices.get(`ETH:${normSym(sym1)}`);
  if (p0 == null && p1 == null) return null;

  const human = (bal: ethers.BigNumber, dec: number) => Number(ethers.utils.formatUnits(bal, dec));
  let tvl = 0;
  if (p0 != null) tvl += human(bal0, Number(dec0)) * p0;
  if (p1 != null) tvl += human(bal1, Number(dec1)) * p1;
  return Number.isFinite(tvl) && tvl > 0 ? tvl : null;
}

/** WETH→ETH для резолва цены через token-registry (WETH часто не зарегистрирован отдельно). */
function normSym(sym: string): string {
  const s = (sym || '').toUpperCase();
  return s === 'WETH' ? 'ETH' : s;
}

function num(v: unknown): number | null {
  const n = Number(v);
  return Number.isFinite(n) ? n : null;
}