// Transaction makes payment of X units from A to B
func (t *SimpleChaincode) invoke(stub shim.ChaincodeStubInterface, args []string) pb.Response {
	var A, B string    // Entities
	var Aval, Bval int // Asset holdings
	var X int          // Transaction value
	var err error

	if len(args) != 3 {
		return shim.Error("Incorrect number of arguments. Expecting 3")
	}

	A = args[0]
	B = args[1]

	// Get the state from the ledger
	// TODO: will be nice to have a GetAllState call to ledger
	Avalbytes, err := stub.GetState(A)
	if err != nil {
		return shim.Error("Failed to get state")
	}
	if Avalbytes == nil {
		return shim.Error("Entity not found")
	}
	Aval, _ = strconv.Atoi(string(Avalbytes))

	Bvalbytes, err := stub.GetState(B)
	if err != nil {
		return shim.Error("Failed to get state")
	}
	if Bvalbytes == nil {
		return shim.Error("Entity not found")
	}
	Bval, _ = strconv.Atoi(string(Bvalbytes))

	// Perform the execution
	X, err = strconv.Atoi(args[2])
	if err != nil {
		return shim.Error("Invalid transaction amount, expecting a integer value")
	}
	Aval = Aval - X
	Bval = Bval + X
	fmt.Printf("Aval = %d, Bval = %d\n", Aval, Bval)

	// Write the state back to the ledger
	err = stub.PutState(A, []byte(strconv.Itoa(Aval)))
	if err != nil {
		return shim.Error(err.Error())
	}

	err = stub.PutState(B, []byte(strconv.Itoa(Bval)))
	if err != nil {
		return shim.Error(err.Error())
	}

        err = stub.SetEvent("EventInvoke", []byte("------event test------"))
        if err != nil {
                return shim.Error(err.Error())
        }

	return shim.Success(nil)
}