Simplify call_contract() in Rust canister (#48)

* Simplify

* Adjust readme

* Refactor for cleaner 'call_contract()' input args

* Support overloaded functions

* Simplify

README.md

@@ -63,6 +63,7 @@ Here is one way to acquire tokens and NFTs on the [Sepolia](https://www.alchemy.
 
 **Ethereum Integration:**
 - [Rust](https://www.rust-lang.org/): a secure, high-performance canister programming language
+- [ethers-core](https://github.com/gakonst/ethers-rs): a popular Rust library for working with Ethereum data structures
 - [MetaMask](https://metamask.io/): a wallet and browser extension for interacting with Ethereum dapps
 
 ## 📚 Documentation

canisters/ic_eth/src/eth_rpc.rs

@@ -1,4 +1,4 @@
-use ethers_core::abi::{Function, Token};
+use ethers_core::abi::{Contract, FunctionExt, Token};
 use ic_cdk::api::management_canister::http_request::{
  http_request, CanisterHttpRequestArgument, HttpHeader, HttpMethod, HttpResponse, TransformArgs,
  TransformContext,
@@ -47,11 +47,10 @@ macro_rules! include_abi {
  }};
 }
 
-thread_local! {
- static NEXT_ID: RefCell<u64> = RefCell::default();
-}
-
 fn next_id() -> u64 {
+ thread_local! {
+ static NEXT_ID: RefCell<u64> = RefCell::default();
+ }
  NEXT_ID.with(|next_id| {
  let mut next_id = next_id.borrow_mut();
  let id = *next_id;
@@ -73,9 +72,25 @@ fn get_rpc_endpoint(network: &str) -> &'static str {
 pub async fn call_contract(
  network: &str,
  contract_address: String,
- f: &Function,
+ abi: &Contract,
+ function_name: &str,
  args: &[Token],
 ) -> Vec<Token> {
+ let f = match abi.functions_by_name(function_name).map(|v| &v[..]) {
+ Ok([f]) => f,
+ Ok(fs) => panic!(
+ "Found {} function overloads. Please pass one of the following: {}",
+ fs.len(),
+ fs.iter()
+ .map(|f| format!("{:?}", f.abi_signature()))
+ .collect::<Vec<_>>()
+ .join(", ")
+ ),
+ Err(_) => abi
+ .functions()
+ .find(|f| function_name == f.abi_signature())
+ .expect("Function not found"),
+ };
  let data = f
  .encode_input(args)
  .expect("Error while encoding input args");
@@ -140,6 +155,6 @@ pub fn transform(args: TransformArgs) -> HttpResponse {
  body: args.response.body,
  // Strip headers as they contain the Date which is not necessarily the same
  // and will prevent consensus on the result.
- headers: Vec::<HttpHeader>::new(),
+ headers: Vec::new(),
  }
 }

canisters/ic_eth/src/lib.rs

@@ -11,9 +11,6 @@ use util::to_hex;
 mod eth_rpc;
 mod util;
 
-/// Required for HTTPS outcalls.
-pub use eth_rpc::transform;
-
 // Load relevant ABIs (Ethereum equivalent of Candid interfaces)
 thread_local! {
  static ERC_721: Rc<Contract> = Rc::new(include_abi!("../abi/erc721.json"));
@@ -37,20 +34,21 @@ pub fn verify_ecdsa(eth_address: String, message: String, signature: String) ->
 #[ic_cdk_macros::update]
 #[candid_method]
 pub async fn erc721_owner_of(network: String, contract_address: String, token_id: u64) -> String {
- // TODO: whitelist / access control
+ // TODO: access control
  // TODO: cycles estimation for HTTP outcalls
 
- let abi = ERC_721.with(Rc::clone);
+ let abi = &ERC_721.with(Rc::clone);
  let result = call_contract(
  &network,
  contract_address,
- abi.function("ownerOf").unwrap(),
+ abi,
+ "ownerOf",
  &[Token::Uint(token_id.into())],
  )
  .await;
  match result.get(0) {
  Some(Token::Address(a)) => to_hex(a.as_bytes()),
- _ => panic!("Unexpected JSON output"),
+ _ => panic!("Unexpected result"),
  }
 }
 
@@ -68,11 +66,12 @@ pub async fn erc1155_balance_of(
  let owner_address =
  ethers_core::types::Address::from_str(&owner_address).expect("Invalid owner address");
 
- let abi = ERC_1155.with(Rc::clone);
+ let abi = &ERC_1155.with(Rc::clone);
  let result = call_contract(
  &network,
  contract_address,
- abi.function("balanceOf").unwrap(),
+ abi,
+ "balanceOf",
  &[
  Token::Address(owner_address.into()),
  Token::Uint(token_id.into()),
@@ -81,6 +80,6 @@ pub async fn erc1155_balance_of(
  .await;
  match result.get(0) {
  Some(Token::Uint(n)) => n.as_u64(),
- _ => panic!("Unexpected JSON output"),
+ _ => panic!("Unexpected result"),
  }
 }