flea-market-contract-service.ts

import { FleaMarketContractToken } from './tokens/flea-market-contract-token';
import { Observable, from, of } from 'rxjs';
import { map, tap, switchMap } from 'rxjs/operators';
import { utils } from 'ethers';

@Injectable({ providedIn: P2pBazaarAnchorModule })
export class FleaMarketContractService {
  constructor( private contractToken: FleaMarketContractToken ) {  
  }
  public createPurchaseContract(product: any): Observable<string> {

    const bytes32Key = utils.formatBytes32String(product.productKey);
    const wei = utils.parseEther(product.etherValue);

    // based on https://docs.ethers.io/ethers.js/html/cookbook-contracts.html
    // Call the contract method, getting back the transaction tx
    const token = this.contractToken.createPurchaseContract(bytes32Key, product.title, product.ipfsHash, {
      value: wei
    });
    return from(token)
    .pipe( 
        switchMap((tx: any) => {

            // Wait for transaction to be mined 
            // Returned a Promise which would resolve to the TransactionReceipt once it is mined.
            return  from(tx.wait()).pipe(
             
              // The receipt will have an "events" Array, which will have
              // the emitted event from the Contract. The "logNewPurchaseContract(address contractAddress)
              // call is the last event.
              map(txReceipt => txReceipt.events.pop()),
              // The 'contractAddress' is the first (and in this case only) parameter
              // in the "logNewPurchaseContract(address contractAddress)" event
              map(txEvent => txEvent.args['contractAddress'])
        }))
    }
}