Exclude Message() method from sarah.Input interface about go-sarah HOT 1 CLOSED

This change may be ideal when we purely design an interface that represents user input. As a matter of fact, all inputs do not necessarily represent text messages; some represent images while some represent video clips. However, go-sarah has a handy feature to supply a regular expression to be run against user inputs.

If the design is to focus on rigorousness, there could be an idea to define an additional interface that represents a text format message, sarah.TextInput. The above method may check if the given sarah.Input implements sarah.TextInput and then run the current logic.
The question is if such rigorousness is preferred. Such changes unintentionally lead to more complexity and cumbersomeness since all sarah.Command implementation will have to check if the given input implements sarah.TextInput to do some common tasks. A command implementation can be somewhat like below:

type command struct {
}

func (*command) Execute(ctx context.Context, input sarah.Input) (*sarah.CommandResponse, error) {
	textInput, ok := input.(sarah.TextInput)
	if !ok {
		return nil, nil
	}

	message := textInput.Message()

	// TODO Do something with message

	return nil, nil
}

func (*command) Match(sarah.Input) bool {
	textInput, ok := input.(sarah.TextInput)
	if !ok {
		return false
	}

	return strings.HasPrefix(textInput.Message(), ".dummyPrefix")
}

func (*command) Identifier() string {
	panic("example")
}

func (*command) Instruction(input *sarah.HelpInput) string {
	panic(`input ".dummyPrefix xxx" to do some good`)
}

This is too complex comparing to current implementation where Input.Message() is always available with sarah.Input. Let the current interface stay. The current interface definition actually guides to return an empty message when the input does not represent a text message.

from go-sarah.