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"`
	MaxTokens        int                     `json:"max_tokens,omitempty"`
	Temperature      float32                 `json:"temperature,omitempty"`
	TopP             float32                 `json:"top_p,omitempty"`
	N                int                     `json:"n,omitempty"`
	Stream           bool                    `json:"stream,omitempty"`
	Stop             []string                `json:"stop,omitempty"`
	PresencePenalty  float32                 `json:"presence_penalty,omitempty"`
	FrequencyPenalty float32                 `json:"frequency_penalty,omitempty"`
	LogitBias        map[string]int          `json:"logit_bias,omitempty"`
	User             string                  `json:"user,omitempty"`
}

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 Create 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.NewRequestWithContext(ctx, http.MethodPost, c.fullURL(urlSuffix), bytes.NewBuffer(reqBytes))
	if err != nil {
		return
	}

	err = c.sendRequest(req, &response)
	return
}