// SPDX-License-Identifier: MIT
pragma solidity >0.5.0 <0.8.0;
pragma experimental ABIEncoderV2;

/* Library Imports */
import { Lib_EIP155Tx } from "../../libraries/codec/Lib_EIP155Tx.sol";
import { Lib_ExecutionManagerWrapper } from "../../libraries/wrappers/Lib_ExecutionManagerWrapper.sol";
import { iOVM_ECDSAContractAccount } from "../../iOVM/predeploys/iOVM_ECDSAContractAccount.sol";

/**
 * @title OVM_SequencerEntrypoint
 * @dev The Sequencer Entrypoint is a predeploy which, despite its name, can in fact be called by
 * any account. It accepts a more efficient compressed calldata format, which it decompresses and
 * encodes to the standard EIP155 transaction format.
 * Compiler used: optimistic-solc
 * Runtime target: OVM
 */
contract OVM_SequencerEntrypoint {

    /*************
     * Libraries *
     *************/

    using Lib_EIP155Tx for Lib_EIP155Tx.EIP155Tx;


    /*********************
     * Fallback Function *
     *********************/

    /**
     * Expects an RLP-encoded EIP155 transaction as input. See the EIP for a more detailed
     * description of this transaction format:
     * https://github.com/ethereum/EIPs/blob/master/EIPS/eip-155.md
     */
    fallback()
        external
    {
        // We use this twice, so it's more gas efficient to store a copy of it (barely).
        bytes memory encodedTx = msg.data;

        // Decode the tx with the correct chain ID.
        Lib_EIP155Tx.EIP155Tx memory transaction = Lib_EIP155Tx.decode(
            encodedTx,
            Lib_ExecutionManagerWrapper.ovmCHAINID()
        );

        // Value is computed on the fly. Keep it in the stack to save some gas.
        address target = transaction.sender();

        bool isEmptyContract;
        assembly {
            isEmptyContract := iszero(extcodesize(target))
        }

        // If the account is empty, deploy the default EOA to that address.
        if (isEmptyContract) {
            Lib_ExecutionManagerWrapper.ovmCREATEEOA(
                transaction.hash(),
                transaction.recoveryParam,
                transaction.r,
                transaction.s
            );
        }

        // Forward the transaction over to the EOA.
        (bool success, bytes memory returndata) = target.call(
            abi.encodeWithSelector(iOVM_ECDSAContractAccount.execute.selector, transaction)
        );

        if (success) {
            assembly {
                return(add(returndata, 0x20), mload(returndata))
            }
        } else {
            assembly {
                revert(add(returndata, 0x20), mload(returndata))
            }
        }
    }
}
