feat: add in ability to supply custom command matching interface

[kmcgovern-apixio]

currently when using command groups or spaces in commands, commands can leak between groups. This can cause undesired and confusing results.

example:

I have 2 commands. one in a group and one not in a group

package main

import (
	"context"
	"fmt"
	"os"

	"github.com/slack-io/slacker"
)

func hello() *slacker.CommandDefinition{

	return &slacker.CommandDefinition{
		Description: "Echo a message",
		Command:     "hello <message>",
		Examples:    []string{"hello hello"},
		Middlewares: []slacker.CommandMiddlewareHandler{},
		Handler: func(ctx *slacker.CommandContext) {
			message := fmt.Sprintf("Why hello there: %v", ctx.Request().Properties().StringParam("message", "nothing"))
			ctx.Response().Reply(message)
		},
	}
}

func echo() *slacker.CommandDefinition{
	return &slacker.CommandDefinition{
		Description: "Echo a message",
		Command:     "echo <message>",
		Examples:    []string{"hello hello"},
		Middlewares: []slacker.CommandMiddlewareHandler{},
		Handler: func(ctx *slacker.CommandContext) {
			message := fmt.Sprintf("reply: %v", ctx.Request().Properties().StringParam("message", "nothing"))
			ctx.Response().Reply(message)
		},
	}
}

func main() {
	botToken := os.Getenv("SLACK_BOT_TOKEN")
	appToken := os.Getenv("SLACK_APP_TOKEN")
	server := slacker.NewClient(botToken, appToken)

	personGroup := server.AddCommandGroup("person")
	personGroup.AddCommand(hello())
	server.AddCommand(echo())
	server.Listen(context.Background())
}

here is an example conversation. Using @ mentions for ease of testing, but same behavior is seen with registered / commands

kmcgovern

@demobot person hello

demobot

Why hello there: nothing

kmcgovern

@demobot person echo oh no!

demobot

reply: oh no!

kmcgovern

@demobot hello this does nothing

@demobot echo this is also ok

demobot

reply: this is also ok

my expectation would be that /person echo does nothing instead of the current behavior of calling the echo command as it is only registered as a top-level command.

From my investigation into this, it looks like intended behavior from the commander package. The tokenize and match functions are pretty straight forward and I can see why someone might want the current functionality. For my use-case i do not want the current behavior and require no cross-leakage of commands/words. Since Command is defined as an interface in slacker, I thought it would be good allow providing a custom implementation rather than potentially breaking some functionality of the commander package.

[raed-shomali]

Thank you for your awesome work. Could you do me a favor and create an example for your new changes under the examples folder?

[kmcgovern-apixio]

@raed-shomali thanks for the quick response! i added an example that's based off of what was done already in slacker.

[raed-shomali]

Great work!

Make sure to update your commit message to start with "docs:"

[raed-shomali]

LGTM

[kmcgovern-apixio]

@raed-shomali this should be good now! LMK if you need anything else from me on this :)