Dynamic Interface Proxy Generation Using reflect.MakeFunc for Test Mocks

package main
 
import (
	"fmt"
	"reflect"
)
 
type Calculator func(int, int) int
 
func CreateLoggingProxy(fn Calculator) Calculator {
	fnVal := reflect.ValueOf(fn)
	fnType := fnVal.Type()
 
	proxy := reflect.MakeFunc(fnType, func(args []reflect.Value) []reflect.Value {
		a := args[0].Int()
		b := args[1].Int()
		fmt.Printf("[LOG] Intercepted call with args: %d, %d\n", a, b)
		out := fnVal.Call(args)
		fmt.Printf("[LOG] Return value: %d\n", out[0].Int())
		return out
	})
 
	return proxy.Interface().(Calculator)
}
 
func main() {
	add := func(a, b int) int { return a + b }
	proxyAdd := CreateLoggingProxy(add)
	res := proxyAdd(5, 7)
	fmt.Println("Result:", res)
}