e-book

purchase-contract-service.ts

public loadPurchaseContract(contractAddress: string): 
                            Observable<PurchaseContractModel> {
    
    const contract: Contract = 
      new ethers.Contract(contractAddress, this.abi, this.provider.getSigner());

    const crObservable: Observable<number | null> = 
      from(contract.commissionRate()).pipe(
      map((commission: ethers.utils.BigNumber) => commission.toNumber()),
      // only account with deployer or seller can retrieve this value,
      // otherwise the contract will throw error.
      catchError((err: Error) => of(null))
    );

    return zip(
      from(contract.key()),
      from(contract.seller()),
      from(contract.buyer()),
      from(contract.owner()),
      from(contract.price()),
      from(contract.balanceOf()),
      from(contract.description()),
      from(contract.ipfsImageHash()),
      from(contract.state()),
      from(crObservable),
    )
     .pipe(
        map(([key, sellerAddress, buyerAddress, ownerAddress, weiPrice,
          weiBalance, description, ipfsHash, state, commission]) => {

          const product: PurchaseContractModel = {
            productKey: utils.parseBytes32String(key as ethers.utils.Arrayish),
            contractAddress,
            sellerAddress: sellerAddress as string,
            buyerAddress: (buyerAddress === ethers.constants.AddressZero) ? 
                                null : buyerAddress as string,
            ownerAddress: ownerAddress as string,
            price: utils.formatEther(weiPrice as ethers.utils.BigNumberish),
            balance: utils.formatEther(weiBalance as ethers.utils.BigNumberish),
            description: description as string,
            ipfsHash: ipfsHash as string,
            state: state as ContractState,
            commission: commission ? commission as number : null
          };

          return product;
        }),
      );
  }