Sell using Defibox multi-hop on incoming transfer

defiboxsell.cpp

#include <eosio.token.hpp>

using namespace eosio;

static constexpr extended_symbol EOS{{"EOS", 4}, "eosio.token"_n };
static constexpr extended_symbol USDT{{"USDT", 4}, "tethertether"_n };

class [[eosio::contract]] defiboxsell : public contract {
public:
    using contract::contract;

    [[eosio::on_notify("eosio.token::transfer")]]
    void on_transfer( const name from, const name to, const asset quantity, const std::string memo )
    {
        require_auth( from );
        if ( to != get_self() ) return;

        // sell EOS=>PBTC on Defibox
        const int64_t amount = quantity.amount;
        transfer( get_self(), "swap.defi"_n, { amount, EOS }, "swap,0,177" );
    }

    [[eosio::on_notify("tethertether::transfer")]]
    void on_transfer( const name from, const name to, const asset quantity, const std::string memo )
    {
        require_auth( from );
        if ( to != get_self() ) return;

        // sell USDT=>EOS=>PBTC on Defibox using multi-hop
        const int64_t amount = quantity.amount;
        transfer( get_self(), "swap.defi"_n, { amount, USDT }, "swap,0,12-177" );
    }

private:
    void transfer( const name from, const name to, const extended_asset value, const std::string memo )
    {
        eosio::token::transfer_action transfer( value.contract, { from, "active"_n });
        transfer.send( from, to, value.quantity, memo );
    }
};