syntax="proto3";
package retail_shop;
service OrderService {
   rpc UpdateOrder(Item) returns (Order);
}
message Item {
   string itemNumber = 1;
   int32 quantity = 2;
}
message Order {
   string itemNumber = 1;
   int32 totalQuantity = 2;
   float subTotal = 3;

$ ballerina grpc --mode service --input proto/order.proto --output gen_code

import ballerina/grpc;
listener grpc:Listener ep = new (9090);
service OrderService on ep {
   resource function UpdateOrder(grpc:Caller caller, Item value) {
       // Implementation goes here.
       // You should return an Order
   }
}
public type Order record {|
   string itemNumber = "";
   int totalQuantity = 0;
   float subTotal = 0.0;
|};
public type Item record {|
   string itemNumber = "";
   int quantity = 0;
|};

$ ballerina grpc --mode client --input proto/order.proto --output gen_code

public remote function UpdateOrder(Item req, grpc:Headers? headers = ()) returns ([Order, grpc:Headers]|grpc:Error) {
       var payload = check self.grpcClient->blockingExecute("retail_shop.OrderService/UpdateOrder", req, headers);
       grpc:Headers resHeaders = new;
       anydata result = ();
       [result, resHeaders] = payload;
       return [<Order>result, resHeaders];
   }
};

syntax="proto3";
package retail_shop;
service CheckoutService {
   rpc Checkout(stream Order) returns (FinalBill) {}
}
message Order {
   string itemNumber = 1;
   int32 totalQuantity = 2;
   float subTotal = 3;
}
message FinalBill {
   float total = 1;
}

service CheckoutService on ep {
   resource function Checkout(grpc:Caller caller, stream<Order,error> clientStream) {
       float totalBill = 0;
       //Iterating through streamed messages here
       error? e = clientStream.forEach(function(Order order) {
           totalBill += order.subTotal;
       });
       //Once the client completes stream, a grpc:EOS error is returned to indicate it
       if (e is grpc:EOS) {
           FinalBill finalBill = {
               total:totalBill
           };
           //Sending the total bill to the client
           grpc:Error? result = caller->send(finalBill);
           if (result is grpc:Error) {
               log:printError("Error occurred when sending the Finalbill: " +
result.message() + " - " + <string>result.detail()["message"]);
           } else {
               log:printInfo ("Sending Final Bill Total: " +
finalBill.total.toString());
           }
           result = caller->complete();
           if (result is grpc:Error) {
               log:printError("Error occurred when closing the connection: " +
result.message() +" - " + <string>result.detail()["message"]);
           }
       }
       //If the client sends an error instead it can be handled here
       else if (e is grpc:Error) {
           log:printError("An unexpected error occured: " + e.message() + " - " +
                                                   <string>e.detail()["message"]);
       }
   }
}

$ ballerina grpc --mode client --input proto/checkout.proto --output gencode

syntax="proto3";
package retail_shop;
option go_package = "../stock;gen";
import "google/api/annotations.proto";
service StockService {
   rpc UpdateStock(UpdateStockRequest) returns (Stock) {
       option (google.api.http) = {
           // Route to this method from POST requests to /api/v1/stock
           put: "/api/v1/stock"
           body: "*"
       };
   }
}
message UpdateStockRequest {
   string itemNumber = 1;
   int32 quantity = 2;
}
message Stock {
   string itemNumber = 1;
   int32 quantity = 2;

protoc -I/usr/local/include -I. \
-I$GOROOT/src \
-I$GOROOT/src/github.com/grpc-ecosystem/grpc-gateway/third_party/googleapis \
--go_out=plugins=grpc:. \
stock.proto

protoc -I/usr/local/include -I. \
-I$GOROOT/src \
-I$GOROOT/src/github.com/grpc-ecosystem/grpc-gateway/third_party/googleapis \
--grpc-gateway_out=logtostderr=true:. \
stock.proto

protoc -I/usr/local/include -I. \
-I$GOROOT/src \
-I$GOROOT/src/github.com/grpc-ecosystem/grpc-gateway/third_party/googleapis \
-I$GOROOT/src \
--swagger_out=logtostderr=true:../stock/gen/. \
./stock.proto