abi.rs

use anyhow::Result;
use eth_types::{Bytes, U256};

/// encodes an abi call (e.g. "f(uint) 1")
pub fn encode_funccall(spec: &str) -> Result<Bytes> {
    use ethers_core::abi::{Function, Param, ParamType, StateMutability, Token};

    // split parts into `func_name` ([`func_params`]) `args`

    let tokens: Vec<_> = spec.split(' ').collect();
    let func = tokens[0];
    let args = &tokens[1..];

    let func_name_params: Vec<_> = func.split([',', '(', ')']).collect();
    let func_name = func_name_params[0];
    let func_params = &func_name_params[1..func_name_params.len() - 1];

    // transform func_params and args into the appropiate types

    let map_type = |t| match t {
        "uint" => ParamType::Uint(256),
        "uint256" => ParamType::Uint(256),
        "bool" => ParamType::Bool,
        _ => panic!("unimplemented abi type {t:?}"),
    };

    let encode_type = |t, v: &str| match t {
        ParamType::Uint(256) => {
            if let Some(hex) = v.strip_prefix("0x") {
                U256::from_str_radix(hex, 16).map(Token::Uint)
            } else {
                U256::from_str_radix(v, 10).map(Token::Uint)
            }
        }
        ParamType::Bool => match v.to_lowercase().as_str() {
            "true" | "0x01" => Ok(Token::Bool(true)),
            "false" | "0x00" => Ok(Token::Bool(false)),
            _ => panic!("unexpected boolean '{v}'"),
        },
        _ => unimplemented!(),
    };

    let func_params: Vec<_> = func_params
        .iter()
        .enumerate()
        .map(|(n, t)| Param {
            name: format!("p{n}"),
            kind: map_type(t),
            internal_type: None,
        })
        .collect();

    let args: Vec<Token> = func_params
        .iter()
        .zip(args)
        .map(|(typ, val)| encode_type(typ.kind.clone(), val))
        .collect::<std::result::Result<_, _>>()?;

    // generate and return calldata

    #[allow(deprecated)]
    let func = Function {
        name: func_name.to_string(),
        inputs: func_params,
        outputs: vec![],
        state_mutability: StateMutability::Payable,
        constant: Some(false),
    };

    Ok(Bytes::from(func.encode_input(&args)?))
}

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    fn test_abi_encoding() -> Result<()> {
        // matches with https://raw.githubusercontent.com/ethereum-lists/4bytes/master/with_parameter_names/b3de648b
        assert_eq!(
            hex::encode(encode_funccall("f(uint) 4")?),
            "b3de648b0000000000000000000000000000000000000000000000000000000000000004"
        );
        assert_eq!(
            hex::encode(encode_funccall("f(uint) 0x04")?),
            "b3de648b0000000000000000000000000000000000000000000000000000000000000004"
        );
        Ok(())
    }
}