Create decode_tx_input.rs (#1054)

* Create decode_tx_input.rs

* simplify calldata parsing

* chore: fmt

Co-authored-by: Georgios Konstantopoulos <me@gakonst.com>

examples/decode_tx_input.rs

@@ -0,0 +1,25 @@
+use ethers::{abi::AbiDecode, prelude::*};
+use eyre::Result;
+
+// Abigen creates a SwapExactTokensForTokensCall struct that can be used to decode
+// the call data for the swapExactTokensForTokens function in the IUniswapV2Router02 contract
+abigen!(
+    IUniswapV2Router02,
+    r#"[
+        swapExactTokensForTokens(uint256 amountIn, uint256 amountOutMin, address[] calldata path, address to, uint256 deadline)
+    ]"#,
+);
+fn main() -> Result<()> {
+    println!("Decoding https://etherscan.io/tx/0xd1b449d8b1552156957309bffb988924569de34fbf21b51e7af31070cc80fe9a");
+    let tx_input = "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";
+    let calldata: Bytes = tx_input.parse().unwrap();
+    let decoded = SwapExactTokensForTokensCall::decode(&calldata)?;
+
+    let from = decoded.path.into_iter().next().unwrap();
+    println!(
+        "Swapped {} of token {} for {} of token {}",
+        decoded.amount_in, from, decoded.amount_out_min, decoded.to
+    );
+
+    Ok(())
+}