// SPDX-License-Identifier: LGPL-3.0-only
pragma solidity >=0.7.0 <0.9.0;

/// @title Multi Send - Allows to batch multiple transactions into one.
/// @author Nick Dodson - <nick.dodson@consensys.net>
/// @author Gonçalo Sá - <goncalo.sa@consensys.net>
/// @author Stefan George - <stefan@gnosis.io>
/// @author Richard Meissner - <richard@gnosis.io>
contract MultiSend {
  address private immutable multisendSingleton;

  constructor() {
    multisendSingleton = address(this);
  }

  /// @dev Sends multiple transactions and reverts all if one fails.
  /// @param transactions Encoded transactions. Each transaction is encoded as a packed bytes of
  ///                     operation as a uint8 with 0 for a call or 1 for a delegatecall (=> 1 byte),
  ///                     to as a address (=> 20 bytes),
  ///                     value as a uint256 (=> 32 bytes),
  ///                     data length as a uint256 (=> 32 bytes),
  ///                     data as bytes.
  ///                     see abi.encodePacked for more information on packed encoding
  /// @notice This method is payable as delegatecalls keep the msg.value from the previous call
  ///         If the calling method (e.g. execTransaction) received ETH this would revert otherwise
  function multiSend(bytes memory transactions) public payable {
    require(address(this) != multisendSingleton, "MultiSend should only be called via delegatecall");
    // solhint-disable-next-line no-inline-assembly
    assembly {
      let length := mload(transactions)
      let i := 0x20
      for {
        // Pre block is not used in "while mode"
      } lt(i, length) {
        // Post block is not used in "while mode"
      } {
        // First byte of the data is the operation.
        // We shift by 248 bits (256 - 8 [operation byte]) it right since mload will always load 32 bytes (a word).
        // This will also zero out unused data.
        let operation := shr(0xf8, mload(add(transactions, i)))
        // We offset the load address by 1 byte (operation byte)
        // We shift it right by 96 bits (256 - 160 [20 address bytes]) to right-align the data and zero out unused data.
        let to := shr(0x60, mload(add(transactions, add(i, 0x01))))
        // We offset the load address by 21 byte (operation byte + 20 address bytes)
        let value := mload(add(transactions, add(i, 0x15)))
        // We offset the load address by 53 byte (operation byte + 20 address bytes + 32 value bytes)
        let dataLength := mload(add(transactions, add(i, 0x35)))
        // We offset the load address by 85 byte (operation byte + 20 address bytes + 32 value bytes + 32 data length bytes)
        let data := add(transactions, add(i, 0x55))
        let success := 0
        switch operation
        case 0 {
          success := call(gas(), to, value, data, dataLength, 0, 0)
        }
        case 1 {
          success := delegatecall(gas(), to, data, dataLength, 0, 0)
        }
        if eq(success, 0) {
          revert(0, 0)
        }
        // Next entry starts at 85 byte + data length
        i := add(i, add(0x55, dataLength))
      }
    }
  }
}