Add CountTokens function and test

This commit adds a CountTokens function that counts the number of tokens in a
given slice of messages. The function uses the go-gpt-3-encoder package to
encode the messages and count the tokens. A test for the CountTokens function
is also added to the aichat_test.go file.

aichat.go

@@ -11,6 +11,7 @@ import (
 	"strings"
 
 	"github.com/pborman/getopt/v2"
+	tokenizer "github.com/samber/go-gpt-3-encoder"
 	gogpt "github.com/sashabaranov/go-gpt3"
 )
 
@@ -179,6 +180,13 @@ func main() {
 		if verbose {
 			log.Printf("messages: %+v", messages)
 		}
+		cnt, err := CountTokens(mapSlice(messages, func(m gogpt.ChatCompletionMessage) string { return m.Content }))
+		if err != nil {
+			log.Fatal(err)
+		}
+		if cnt > 4096 {
+			log.Fatalf("total tokens %d exceeds 4096", cnt)
+		}
 		request := gogpt.ChatCompletionRequest{
 			Model:       gogpt.GPT3Dot5Turbo,
 			Messages:    messages,
@@ -196,3 +204,30 @@ func main() {
 	}
 
 }
+
+// mapSlice maps a slice of type T to a slice of type M using the function f.
+func mapSlice[T any, M any](a []T, f func(T) M) []M {
+	r := make([]M, len(a))
+	for i, v := range a {
+		r[i] = f(v)
+	}
+	return r
+}
+
+// CountTokens returns the number of tokens in the messages.
+func CountTokens(messages []string) (int, error) {
+	count := 0
+	encoder, err := tokenizer.NewEncoder()
+	if err != nil {
+		return 0, err
+	}
+	for _, message := range messages {
+		// Encode string with GPT tokenizer
+		encoded, err := encoder.Encode(message)
+		if err != nil {
+			return 0, err
+		}
+		count += len(encoded)
+	}
+	return count, nil
+}

aichat_test.go

@@ -0,0 +1,19 @@
+package main
+
+import (
+	"testing"
+)
+
+func TestCountTokens(t *testing.T) {
+	messages := []string{
+		"Hello, world!",
+		"How are you?",
+	}
+	count, err := CountTokens(messages)
+	if err != nil {
+		t.Errorf("CountTokens() returned an error: %v", err)
+	}
+	if count != 8 {
+		t.Errorf("CountTokens() returned %d, expected 8", count)
+	}
+}

go.mod

@@ -4,6 +4,13 @@ go 1.20
 
 require (
 	github.com/pborman/getopt/v2 v2.1.0
+	github.com/samber/go-gpt-3-encoder v0.3.1
 	github.com/sashabaranov/go-gpt3 v1.4.0
 	gopkg.in/yaml.v3 v3.0.1
 )
+
+require (
+	github.com/dlclark/regexp2 v1.8.1 // indirect
+	github.com/samber/lo v1.37.0 // indirect
+	golang.org/x/exp v0.0.0-20230310171629-522b1b587ee0 // indirect
+)

go.sum

@@ -1,7 +1,18 @@
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/dlclark/regexp2 v1.8.1 h1:6Lcdwya6GjPUNsBct8Lg/yRPwMhABj269AAzdGSiR+0=
+github.com/dlclark/regexp2 v1.8.1/go.mod h1:DHkYz0B9wPfa6wondMfaivmHpzrQ3v9q8cnmRbL6yW8=
 github.com/pborman/getopt/v2 v2.1.0 h1:eNfR+r+dWLdWmV8g5OlpyrTYHkhVNxHBdN2cCrJmOEA=
 github.com/pborman/getopt/v2 v2.1.0/go.mod h1:4NtW75ny4eBw9fO1bhtNdYTlZKYX5/tBLtsOpwKIKd0=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/samber/go-gpt-3-encoder v0.3.1 h1:YWb9GsGYUgSX/wPtsEHjyNGRQXsQ9vDCg9SU2x9uMeU=
+github.com/samber/go-gpt-3-encoder v0.3.1/go.mod h1:27nvdvk9ZtALyNtgs9JsPCMYja0Eleow/XzgjqwRtLU=
+github.com/samber/lo v1.37.0 h1:XjVcB8g6tgUp8rsPsJ2CvhClfImrpL04YpQHXeHPhRw=
+github.com/samber/lo v1.37.0/go.mod h1:9vaz2O4o8oOnK23pd2TrXufcbdbJIa3b6cstBWKpopA=
 github.com/sashabaranov/go-gpt3 v1.4.0 h1:UqHYdXgJNtNvTtbzDnnQgkQ9TgTnHtCXx966uFTYXvU=
 github.com/sashabaranov/go-gpt3 v1.4.0/go.mod h1:BIZdbwdzxZbCrcKGMGH6u2eyGe1xFuX9Anmh3tCP8lQ=
+github.com/stretchr/testify v1.8.1 h1:w7B6lhMri9wdJUVmEZPGGhZzrYTPvgJArz7wNPgYKsk=
+golang.org/x/exp v0.0.0-20230310171629-522b1b587ee0 h1:LGJsf5LRplCck6jUCH3dBL2dmycNruWNF5xugkSlfXw=
+golang.org/x/exp v0.0.0-20230310171629-522b1b587ee0/go.mod h1:CxIveKay+FTh1D0yPZemJVgC/95VzuuOLq5Qi4xnoYc=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=