import 'dotenv/config.js';
import { WebSocketProvider, formatUnits } from 'ethers';
import { sortBy } from 'lodash';
import { Observable, throwError } from 'rxjs';
import { catchError, map, scan, retry } from 'rxjs/operators';

import { GasPrices } from '../types/gasPrices';

const rpcUrl = process.env.RPC_URL || "wss://ropsten.infura.io/ws/v3/YOUR_INFURA_PROJECT_ID";

const provider = new WebSocketProvider(rpcUrl);

const blockGasPricesObservable = new Observable<GasPrices>((observer) => {
  provider.on('block', async (blockNumber) => {
    try {
      const block = await provider.getBlock(blockNumber, true);

      if (!block) throw new Error(`Error fetching block! ${blockNumber}`);

      const gasPrices = sortBy(block.prefetchedTransactions, ['gasPrice']).map(x => x.gasPrice);
      const fast = Number(formatUnits(gasPrices[Math.floor(gasPrices.length * 0.9)], "gwei"));
      const average = Number(formatUnits(gasPrices[Math.floor(gasPrices.length / 2)], "gwei"));
      const slow = Number(formatUnits(gasPrices[Math.floor(gasPrices.length * 0.05)], "gwei"));

      // Log averages every 10 blocks
      if (blockNumber % 10 == 0) console.log(`Found new block data for ${blockNumber}!
      Gas price spreads: ⚡ ${fast.toFixed(2)} ⦚⦚ 🚶 ${average.toFixed(2)} ⦚⦚ 🐢 ${slow.toFixed(2)} Gwei`)

      observer.next({ fast, average, slow } as GasPrices);
    } catch (error) {
      observer.error(`Error fetching block! ${error}`);
    }
  });
});

const averageGasPricesObservable = blockGasPricesObservable.pipe(
  scan((acc, curr) => [...acc.slice(-19), curr], [] as GasPrices[]),
  map((blocks) => {
    const { fast, average, slow } = blocks
      .reduce((sum, block) =>
        ({ // Find sums
          fast: sum.fast + block.fast,
          average: sum.average + block.average,
          slow: sum.slow + block.slow
        }), { fast: 0, average: 0, slow: 0 } as GasPrices);
    return { // Then average them
      fast: Math.round(fast / blocks.length),
      average: Math.round(average / blocks.length),
      slow: Math.round(slow / blocks.length),
    } as GasPrices;
  }),
  catchError(err => throwError(() => new Error(err))),
  retry(2)
);

export { averageGasPricesObservable };