Sample Eliza functionality using regex in Go

eliza.go

package main

import (
	"fmt"
	"math/rand"
	"regexp"
	"strings"
	"time"
)

type Response struct {
	pattern         *regexp.Regexp
	possibleAnswers []string
}

func substituteWords(answer string, reflectionMap map[string]string) string {
	allWords := strings.Split(answer, " ") // get slices of the words {"words", "in", "sentence"}
	for index, word := range allWords {
		if val, ok := reflectionMap[word]; ok {
			allWords[index] = val // substitite the value
		}
	}
	return strings.Join(allWords, " ") // join back into string "words in sentence"
}

func main() {
	rand.Seed(time.Now().UnixNano())

	re := regexp.MustCompile("I like (.*)") // capture anything the after the phrase 'I like '
	// other possible patterns
	// "I want (.*)", "I hate (.*)" etc.
	answers := []string{"Why do you like %s?", "How long have you liked %s?"} // these be saved in a file and read in when you launch the program.
	// ideally have a load of these, one for I Want, I like, I love etc. Can put them all in a file. Not coded into application.

	likeResponse := Response{re, answers} // Responses could be read from files.

	userInput := "I like you" // this would actually come from GET / POST request.

	// we want to swap certain words so Eliza is actually talking about "you" and not just mimicing what was said, "I",
	// a lot more useful swaps can be found here https://www.smallsurething.com/implementing-the-famous-eliza-chatbot-in-python/

	reflectionMap := map[string]string{
		"I":   "you",
		"was": "were",
		"am":  "are",
		"you": "me",
		// and plenty more
	}

	if likeResponse.pattern.MatchString(userInput) {
		match := re.FindStringSubmatch(userInput)             // the pattern matched, so let's look for all the text after I like. ie. everything in (.*) - (.*) means "anything", so this pattern will match any text the user entered.
		topic := match[1]                                     // 0 is the full string, 1 is first match.
		topic = substituteWords(topic, reflectionMap)         // instead of saying "Why do you like you" it maps to "Why do you like me" because of the reflection map.
		index := rand.Intn(len(likeResponse.possibleAnswers)) // index of random possible answer
		chosenResponse := likeResponse.possibleAnswers[index] // pick the answer
		finalResponse := fmt.Sprintf(chosenResponse, topic)   // sub the "topic" into the response - since the response has a %s for this purpose
		fmt.Println(finalResponse)                            // we actually want to display this in the html page or template or something.

		// The output will be "How long have you liked me?" or "Why do you like me?"
	} else {
		fmt.Println("I don't know what you said.") // there was no regex match so just say some default answer.
	}

}