helper.fc

;; my_addr(MYADDR) get_jwa_method_id(103289) args(2) master_code ret(1) master_data
;;   RUNVM +1 +4 +32
;; address exitcode c4' c5'

slice vm::invoke_get_addr(cell master_code, cell master_data) asm
  "MYADDR          // mc md my_addr"
  "103829 PUSHINT  // mc md my_addr get_jwa_method_id"
  "2 PUSHINT       // mc md my_addr get_jwa_method_id args"
  "2 3 BLKSWAP     // my_addr get_jwa_method_id args mc md"
  "1 PUSHINT       // my_addr get_jwa_method_id args mc md ret"
  "SWAP            // my_addr get_jwa_method_id args mc ret md"
  "37 RUNVM        // address exit_code c4' c5'"
  "3 BLKDROP       // address";

slice calc_my_jetton_wallet(slice master_address, cell master_code, cell master_data) inline {
    cell master_si = begin_cell().store_uint(6, 5).store_ref(master_code).store_ref(master_data);
    (int wc, int master_hash) = master_address.parse_std_addr();
    throw_if(100, (master_si.cell_hash() != master_hash) | wc);
    
    return vm::invoke_get_addr(master_code, master_data);
}

main.tact

import "./helper.fc";

@name(calc_my_jetton_wallet)
native calcMyJettonWallet(master_address: Address, master_code: Cell, master_data: Cell): Address;


message(0x0f8a7ea5) JettonTransfer {
    query_id: Int as uint64;
    amount: Int as coins;
    destination: Address;
    response_destination: Address;
    custom_payload: Cell?;
    forward_ton_amount: Int as coins;
    forward_payload: Slice as remaining;
}


@interface("ton.experimental.pcrafter.jettonseller")
contract JettonSeller {
    const forward_ton_amount: Int = ton("0.000001");
    
    jetton_master: Address;
    jetton_wallet: Address;  // what we are selling
    nanoton_per_jetton: Int as coins;
    
    init(jetton_master: Address, master_code: Cell, master_data: Cell, nanoton_per_jetton: Int) {
        self.jetton_wallet = calcMyJettonWallet(jetton_master, master_code, master_data);
        self.nanoton_per_jetton = nanoton_per_jetton;
    }

    fun transferJettonTo(jetton_wallet: Address, destination: Address, amount: Int, query_id: Int, message: String) {
        if (amount > 0) {
            send(SendParameters{
                to: jetton_wallet,
                value: ton("0.1"),
                mode: 0,
                body: JettonTransfer{query_id: query_id, amount: amount, destination: destination, response_destination: destination, custom_payload: null, forward_ton_amount: self.forward_ton_amount, forward_payload: message.asComment()}.toCell()
            });
        }
    }

    receive() {
        let nanoton = context().value - ton("0.1");
        transferJettonTo(self.jetton_wallet, sender(), nanoton / self.nanoton_per_jetton, 0, "swap completed");
    }
    
    get fun getJetton(): Address {
        return self.jetton_master;
    }
    
    get fun getJettonPrice(): Int {
        return self.nanoton_per_jetton;
    }
}