// SPDX-License-Identifier: LGPL-3.0-only
pragma solidity 0.8.17;

/// @title SecuredTokenTransfer - Secure token transfer
abstract contract SecuredTokenTransfer {
    /// @dev Transfers a token and returns if it was a success
    /// @param token Token that should be transferred
    /// @param receiver Receiver to whom the token should be transferred
    /// @param amount The amount of tokens that should be transferred
    function transferToken(
        address token,
        address receiver,
        uint256 amount
    ) internal returns (bool transferred) {
        require(token != address(0), "token can not be zero address");
        require(token.code.length > 0, "token contract doesn't exist");
        // 0xa9059cbb - keccack("transfer(address,uint256)")
        bytes memory data = abi.encodeWithSelector(
            0xa9059cbb,
            receiver,
            amount
        );
        // solhint-disable-next-line no-inline-assembly
        assembly {
            // We write the return value to scratch space.
            // See https://docs.soliditylang.org/en/v0.8.17/internals/layout_in_memory.html#layout-in-memory
            let success := call(
                sub(gas(), 10000),
                token,
                0,
                add(data, 0x20),
                mload(data),
                0,
                0x20
            )
            switch returndatasize()
            case 0 {
                transferred := success
            }
            case 0x20 {
                transferred := iszero(or(iszero(success), iszero(mload(0))))
            }
            default {
                transferred := 0
            }
        }
    }
}