add comments to ethprovider

lib/connextclient/ethprovider.ts

@@ -4,6 +4,7 @@ import { from, Observable } from 'rxjs';
 import { mergeMap } from 'rxjs/operators';
 // This file will be a separate module with the above dependencies.
 
+// gets the Ethereum provider object to read data from the chain
 const getProvider = (host: string, port: number, name: string, chainId: number): ethers.providers.JsonRpcProvider => {
   return new ethers.providers.JsonRpcProvider(
     { url: `http://${host}:${port}/ethprovider/${chainId}` },
@@ -14,19 +15,26 @@ const getProvider = (host: string, port: number, name: string, chainId: number):
   );
 };
 
+// gets the signer object necessary for write access (think unlock wallet)
 const getSigner = (provider: ethers.providers.JsonRpcProvider, seed: string): ethers.Wallet => {
   return ethers.Wallet.fromMnemonic(seed).connect(provider);
 };
 
+// We curry getContract so that we can provide its arguments one at a time.
+// This allows us to provide some of the necessary arguments (that we already have) before we export the function.
+// Read more: https://ramdajs.com/docs/#curry
 const getContract = curry(
   (signer: ethers.Wallet, contractAddress: string): ethers.Contract => {
+    // we use the minimum viable contract ABI for ERC20 tokens
+    // for full contract ABI we should compile it from the solidity source
     const erc20abi = ['function balanceOf(address) view returns (uint)', 'function transfer(address to, uint amount)'];
     return new ethers.Contract(contractAddress, erc20abi, signer);
   },
 );
 
-// we curry the functions below so that arguments
-// can be provided 1 by 1 if necessary
+// Sends on-chain ERC20 transfer
+// We also curry this function, just like the previous one.
+// All the functions that we export out of the package will be curried
 const onChainSendERC20 = curry(
   (
     signer: ethers.Wallet,
@@ -45,6 +53,7 @@ const onChainSendERC20 = curry(
   },
 );
 
+// Sends on-chain ETH transfer
 const onChainSendETH = curry(
   (signer: ethers.Wallet, destinationAddress: string, units: string): Observable<ethers.ContractTransaction> => {
     return from(signer.provider.getGasPrice()).pipe(
@@ -61,19 +70,26 @@ const onChainSendETH = curry(
   },
 );
 
+// returns ETH on-chain balance for the address in wei
 const getEthBalanceByAddress = curry((provider: ethers.providers.JsonRpcProvider, address: string) =>
   from(provider.getBalance(address)),
 );
 
+// returns ERC20 on-chain balance for the contract address in the smallest unit
 const getERC20Balance = curry(
   (address: string, contract: ethers.Contract): Observable<ethers.BigNumber> => {
     return from(contract.balanceOf(address)) as Observable<ethers.BigNumber>;
   },
 );
 
+// This is the main function that has to be called before this package exposes more functions.
+// Think of it as a constructor where we create the interal state of the module before
+// we export more functionality to the consumer.
 const getEthprovider = (host: string, port: number, name: string, chainId: number, seed: string) => {
+  // create the internal state
   const provider = getProvider(host, port, name, chainId);
   const signer = getSigner(provider, seed);
+  // because the functions below are curried we can only provide some of the arguments
   const getERC20BalanceWithSigner = getERC20Balance(signer.address);
   const getContractWithSigner = getContract(signer);
   const onChainSendERC20WithSigner = onChainSendERC20(signer);
@@ -87,10 +103,9 @@ const getEthprovider = (host: string, port: number, name: string, chainId: numbe
       return onChainSendERC20WithSigner(contract, destinationAddress, units);
     }
   };
+  // expose functionality to the consumer
   return {
     getEthBalance: () => from(signer.getBalance()),
-    // before exposing the functions we provide signer and provider
-    // when required
     getEthBalanceByAddress: getEthBalanceByAddressWithProvider,
     getContract: getContractWithSigner,
     getERC20Balance: getERC20BalanceWithSigner,