permit2.rs

//! `Permit2` bytecode and immutable encoding.
//!
//! Uniswap's `Permit2` provides gas-efficient token approval management
//! via signature-based permits (EIP-2612 style) for any ERC-20 token.
//!
//! ## Immutables (in bytecode, not storage)
//!
//! | Variable                    | Type    | Offset |
//! |-----------------------------|---------|--------|
//! | `_CACHED_CHAIN_ID`          | uint256 | \[6945\] |
//! | `_CACHED_DOMAIN_SEPARATOR`  | bytes32 | \[6983\] |
//!
//! Both come from the EIP-712 base contract (`src/EIP712.sol`).  The
//! constructor normally caches `block.chainid` and the resulting domain
//! separator so that `DOMAIN_SEPARATOR()` can skip recomputation when the
//! chain ID hasn't changed.  For a genesis deploy we patch the correct
//! values directly into the bytecode.
//!
//! ## Storage layout
//!
//! Permit2 has no storage that needs initialization at genesis.  All state
//! (allowances, nonces, …) starts at zero.

use crate::{
    config::Permit2Config,
    contracts::{
        immutables::{patch_bytes, patch_u256, ImmutableRef},
        GenesisContract,
    },
};
use alloy_primitives::{hex, keccak256, Bytes, B256, U256};
use std::collections::BTreeMap;

/// `Permit2` runtime bytecode compiled from Uniswap/permit2 (commit cc56ad0)
/// with solc 0.8.17 (via-ir, optimizer `1_000_000` runs, `bytecode_hash="none"`).
///
/// Compiled with placeholder immutables (all zeros).  Actual values are patched
/// at genesis time via [`build`].
///
/// Regenerate with:
/// ```sh
/// cd contracts/lib/permit2 && forge inspect Permit2 deployedBytecode
/// ```
const PERMIT2_BYTECODE: &[u8] = &hex!("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// ── Immutable reference offsets (from compiled artifact `immutableReferences`) ──

/// `_CACHED_CHAIN_ID` (uint256) — from `EIP712.sol`.
const CACHED_CHAIN_ID_REFS: &[ImmutableRef] = &[ImmutableRef {
    start: 6945,
    length: 32,
}];

/// `_CACHED_DOMAIN_SEPARATOR` (bytes32) — from `EIP712.sol`.
const CACHED_DOMAIN_SEPARATOR_REFS: &[ImmutableRef] = &[ImmutableRef {
    start: 6983,
    length: 32,
}];

/// EIP-712 type hash: `keccak256("EIP712Domain(string name,uint256 chainId,address verifyingContract)")`
const EIP712_TYPE_HASH: B256 = B256::new(hex!(
    "8cad95687ba82c2ce50e74f7b754645e5117c3a5bec8151c0726d5857980a866"
));

/// `keccak256("Permit2")`
const HASHED_NAME: B256 = B256::new(hex!(
    "9ac997416e8ff9d2ff6bebeb7149f65cdae5e32e2b90440b566bb3044041d36a"
));

/// Build a genesis alloc entry for `Permit2`.
pub(crate) fn build(config: &Permit2Config, chain_id: u64) -> GenesisContract {
    let mut bytecode = PERMIT2_BYTECODE.to_vec();

    // Patch _CACHED_CHAIN_ID
    let chain_id_u256 = U256::from(chain_id);
    patch_u256(&mut bytecode, CACHED_CHAIN_ID_REFS, chain_id_u256);

    // Compute and patch _CACHED_DOMAIN_SEPARATOR:
    //   keccak256(abi.encode(_TYPE_HASH, _HASHED_NAME, chainId, contractAddress))
    let mut buf = [0u8; 128];
    buf[0..32].copy_from_slice(EIP712_TYPE_HASH.as_slice());
    buf[32..64].copy_from_slice(HASHED_NAME.as_slice());
    buf[64..96].copy_from_slice(&B256::from(chain_id_u256).0);
    buf[96..128].copy_from_slice(config.address.into_word().as_slice());
    let domain_separator = keccak256(buf);
    patch_bytes(
        &mut bytecode,
        CACHED_DOMAIN_SEPARATOR_REFS,
        &domain_separator.0,
    );

    GenesisContract {
        address: config.address,
        code: Bytes::from(bytecode),
        storage: BTreeMap::new(),
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use alloy_primitives::{address, Address};
    use std::{path::PathBuf, process::Command};

    fn test_config() -> Permit2Config {
        Permit2Config {
            address: address!("000000000022D473030F116dDEE9F6B43aC78BA3"),
        }
    }

    #[test]
    fn no_storage_entries() {
        let contract = build(&test_config(), 1234);
        assert!(
            contract.storage.is_empty(),
            "Permit2 should have no storage at genesis"
        );
    }

    #[test]
    fn bytecode_is_patched_with_chain_id() {
        let contract = build(&test_config(), 42);
        let code = contract.code.to_vec();
        let word = &code[6945..6945 + 32];
        assert_eq!(word[31], 42);
        assert_eq!(word[0..31], [0u8; 31]);
    }

    #[test]
    fn bytecode_is_patched_with_domain_separator() {
        let config = test_config();
        let chain_id: u64 = 1234;
        let contract = build(&config, chain_id);
        let code = contract.code.to_vec();

        // Compute expected domain separator
        let mut buf = [0u8; 128];
        buf[0..32].copy_from_slice(EIP712_TYPE_HASH.as_slice());
        buf[32..64].copy_from_slice(HASHED_NAME.as_slice());
        buf[64..96].copy_from_slice(&B256::from(U256::from(chain_id)).0);
        buf[96..128].copy_from_slice(config.address.into_word().as_slice());
        let expected = keccak256(buf);

        let word = &code[6983..6983 + 32];
        assert_eq!(word, expected.as_slice());
    }

    #[test]
    fn domain_separator_changes_with_chain_id() {
        let config = test_config();
        let c1 = build(&config, 1);
        let c2 = build(&config, 2);

        let ds1 = &c1.code[6983..6983 + 32];
        let ds2 = &c2.code[6983..6983 + 32];
        assert_ne!(
            ds1, ds2,
            "different chain IDs should produce different domain separators"
        );
    }

    #[test]
    fn domain_separator_changes_with_address() {
        let c1 = build(
            &Permit2Config {
                address: Address::repeat_byte(0x01),
            },
            1234,
        );
        let c2 = build(
            &Permit2Config {
                address: Address::repeat_byte(0x02),
            },
            1234,
        );

        let ds1 = &c1.code[6983..6983 + 32];
        let ds2 = &c2.code[6983..6983 + 32];
        assert_ne!(
            ds1, ds2,
            "different addresses should produce different domain separators"
        );
    }

    #[test]
    fn eip712_constants_are_correct() {
        // Verify the hardcoded constants match the expected values
        assert_eq!(
            EIP712_TYPE_HASH,
            keccak256("EIP712Domain(string name,uint256 chainId,address verifyingContract)"),
        );
        assert_eq!(HASHED_NAME, keccak256("Permit2"));
    }

    #[test]
    #[ignore = "requires forge CLI"]
    fn permit2_bytecode_matches_solidity_source() {
        let contracts_root = PathBuf::from(env!("CARGO_MANIFEST_DIR"))
            .ancestors()
            .nth(2)
            .unwrap()
            .join("contracts")
            .join("lib")
            .join("permit2");

        let output = Command::new("forge")
            .args(["inspect", "Permit2", "deployedBytecode", "--root"])
            .arg(&contracts_root)
            .output()
            .expect("forge not found");

        assert!(
            output.status.success(),
            "forge inspect failed: {}",
            String::from_utf8_lossy(&output.stderr)
        );

        let forge_hex = String::from_utf8(output.stdout)
            .unwrap()
            .trim()
            .strip_prefix("0x")
            .unwrap()
            .to_lowercase();

        let hardcoded_hex = hex::encode(PERMIT2_BYTECODE);

        assert_eq!(
            forge_hex, hardcoded_hex,
            "Permit2 bytecode mismatch! Regenerate with: \
             cd contracts/lib/permit2 && forge inspect Permit2 deployedBytecode"
        );
    }
}