How can i fetch price of USDT in EGLD using exchange in rust??

[itsabinashb]

I am trying to fetch price of USDT in EGLD. I am using this: https://github.com/multiversx/mx-exchange-sc/blob/main/dex/pair/src/lib.rs#L604 endpoint to fetch the price. But not sure that it is right process to do it. One community member suggested me to do this.

My code is:

#![no_std]

multiversx_sc::imports!();

pub mod callee_proxy {
    multiversx_sc::imports!();
    #[multiversx_sc::proxy]
    pub trait CalleeContract {
        #[view(getAmountOut)]
        fn get_amount_out_view(&self, token_in: TokenIdentifier, amount_in: BigUint) -> BigUint;
    }
}

#[multiversx_sc::contract]
pub trait MinterContract {
    #[init]
    fn init(&self, address: ManagedAddress, price: BigUint, token_id: TokenIdentifier, usdt_token_id: TokenIdentifier)  {
         self.set_address().set(&address);
         self.set_esdt_price().set(&price);
         self.set_token_id().set(&token_id);
         self.set_usdt_token_id().set(&usdt_token_id);
    }

    #[payable("*")]
    #[endpoint]
    fn buy_token(&self, amount: BigUint) {
        require!(amount >= 1000, "Withdrawal of token amount of less than 1000 is not allowed");
        require!(amount <= 10000, "Withdrawal of token amount of more than 10000 is not allowed");
        let _price : BigUint = amount.clone() * self.set_esdt_price().get();
       let _output_amount_as_egld: BigUint = self.contract_proxy(self.set_address().get()).get_amount_out_view(self.set_token_id().get(), _price).execute_on_dest_context();

       require!(self.call_value().egld_value().clone_value() >= _output_amount_as_egld, "Not enough ELGD paid!");
       self.send().direct_esdt(&self.blockchain().get_caller(), &self.set_token_id().get(), 0, &amount);
      
        
    }

    #[endpoint]
    fn get_usdt_to_egld(&self, amount: BigUint) -> BigUint{
        let output_amount: BigUint = self.contract_proxy(self.set_address().get()).get_amount_out_view(self.set_usdt_token_id().get(), amount).execute_on_dest_context() ;
        output_amount
    }

    #[proxy]
    fn contract_proxy(&self, sc_address: ManagedAddress) -> callee_proxy::Proxy<Self::Api>;

    #[storage_mapper("Key_tokenId")]
    fn set_token_id(&self) -> SingleValueMapper<TokenIdentifier>;

    #[storage_mapper("Key_tokenId")]
    fn set_usdt_token_id(&self) -> SingleValueMapper<TokenIdentifier>;


    #[storage_mapper("key_address")]
    fn set_address(&self) -> SingleValueMapper<ManagedAddress>;

    #[storage_mapper("key_price")]
    fn set_esdt_price(&self) -> SingleValueMapper<BigUint>;

    
    
}

As you can see i created proxy like this, and declared that target endpoint. I am using this address: erd1qqqqqqqqqqqqqpgqeel2kumf0r8ffyhth7pqdujjat9nx0862jpsg2pqaq as exchange address from here: https://explorer.multiversx.com/accounts/erd1qqqqqqqqqqqqqpgqeel2kumf0r8ffyhth7pqdujjat9nx0862jpsg2pqaq/tokens. But when i called the get_usdt_to_egld() like this: mxpy --verbose contract call erd1qqqqqqqqqqqqqpgq027dusnhgjug07pwzhdaqv0sxt7j0hsn2nfsww256n --chain D --pem="../walletKey.pem" --gas-limit=2000000 --function="get_usdt_to_egld" --arguments 1000 --proxy="https://devnet-gateway.multiversx.com" --recall-nonce --send my transaction get failed, see the transaction here: https://devnet-explorer.multiversx.com/transactions/bae86eec15ce3a3a6aac39447bd3d7a6f4197b98b448b5188ea0bc8756b4369a#decimal.

And when i queried like this: mxpy contract query erd1qqqqqqqqqqqqqpgq027dusnhgjug07pwzhdaqv0sxt7j0hsn2nfsww256n --proxy="https://devnet-gateway.multiversx.com" --function="get_usdt_to_egld" --arguments 10000 i got this error:

RuntimeError: Query failed: invalid contract code (not found)

What i want to do? => I want to implement the logic:

1. I minted my token and funded the contract with that token. Price of my token is 0.005 USDT
2. I want user will enter the amount of token they want to buy in buy_token().
3. Now in buy_token() the amount(given by user) will be multiplied by 500 as USDT has 6 decimal. So we will get the price of total amount of token in USDT.
4. Then I wanna use the exchange to get the price of those tokens ( which are now in USDT form )
   in EGLD.
5. After getting the EGLD value i will put a require statement where the condition will be egld_value() should be equal to the EGLD value we got.
6. Then we will transfer the amount of token to user wallet.
   This is what i want to implement. Help me to implement it.