add: openai api client

bot/.env.sample

@@ -12,3 +12,5 @@ LIFF_URL=
 GOOGLE_CLIENT_ID=
 GOOGLE_CLIENT_SECRET=
 GOOGLE_REDIRECT=
+
+OPENAI_API_KEY=

bot/openai/gpt4v.go

@@ -0,0 +1,36 @@
+package openai
+
+import (
+	"context"
+	"errors"
+	"net/http"
+	"net/url"
+	"os"
+)
+
+var (
+	ErrNoApiKey = errors.New("apiKey is required")
+)
+
+type Gpt4Vision struct {
+	httpClient *http.Client
+	endpoint   *url.URL
+	apiKey     string
+	ctx        context.Context
+}
+
+func NewGpt4Vision(ctx context.Context) (*Gpt4Vision, error) {
+	c := &Gpt4Vision{
+		httpClient: http.DefaultClient,
+		apiKey:     os.Getenv("OPENAI_API_KEY"),
+		ctx:        ctx,
+	}
+
+	u, err := url.ParseRequestURI("https://api.openai.com/v1/chat/completions")
+	if err != nil {
+		return nil, err
+	}
+	c.endpoint = u
+
+	return c, nil
+}