Add chat completions (#90)

chat.go

@@ -0,0 +1,68 @@
+package gogpt
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"net/http"
+)
+
+var (
+	ErrChatCompletionInvalidModel = errors.New("currently, only gpt-3.5-turbo and gpt-3.5-turbo-0301 are supported")
+)
+
+type ChatCompletionMessage struct {
+	Role    string `json:"role"`
+	Content string `json:"content"`
+}
+
+// ChatCompletionRequest represents a request structure for chat completion API.
+type ChatCompletionRequest struct {
+	Model    string                  `json:"model"`
+	Messages []ChatCompletionMessage `json:"messages"`
+}
+
+type ChatCompletionChoice struct {
+	Index        int                   `json:"index"`
+	Message      ChatCompletionMessage `json:"message"`
+	FinishReason string                `json:"finish_reason"`
+}
+
+// ChatCompletionResponse represents a response structure for chat completion API.
+type ChatCompletionResponse struct {
+	ID      string                 `json:"id"`
+	Object  string                 `json:"object"`
+	Created int64                  `json:"created"`
+	Model   string                 `json:"model"`
+	Choices []ChatCompletionChoice `json:"choices"`
+	Usage   Usage                  `json:"usage"`
+}
+
+// CreateChatCompletion — API call to Creates a completion for the chat message.
+func (c *Client) CreateChatCompletion(
+	ctx context.Context,
+	request ChatCompletionRequest,
+) (response ChatCompletionResponse, err error) {
+	model := request.Model
+	if model != GPT3Dot5Turbo0301 && model != GPT3Dot5Turbo {
+		err = ErrChatCompletionInvalidModel
+		return
+	}
+
+	var reqBytes []byte
+	reqBytes, err = json.Marshal(request)
+	if err != nil {
+		return
+	}
+
+	urlSuffix := "/chat/completions"
+	req, err := http.NewRequest("POST", c.fullURL(urlSuffix), bytes.NewBuffer(reqBytes))
+	if err != nil {
+		return
+	}
+
+	req = req.WithContext(ctx)
+	err = c.sendRequest(req, &response)
+	return
+}