package openai

import (
	"bufio"
	"encoding/json"
	"io"
	"net/http"
	"strings"
	"time"

	"github.com/go-errors/errors"
	"github.com/go-resty/resty/v2"
)

type Client struct {
	rest *resty.Client
}

func NewClient(apiKey string) *Client {
	cli := resty.New().
		SetTransport(&http.Transport{
			Proxy:                 http.ProxyFromEnvironment,
			ResponseHeaderTimeout: 10 * time.Second,
		}).
		SetBaseURL("https://api.openai.com").
		SetHeader("Authorization", "Bearer "+apiKey).
		SetTimeout(5 * time.Minute) // hard cap

	return &Client{rest: cli}
}

func (c *Client) ChatCompletion(request ChatRequest) (*ChatResponse, error) {
	// Note: this function might not work due to the header timeout set on the http client.
	// We should probably not use this anyway.

	resp, err := c.rest.R().
		SetBody(request).
		SetHeader("Content-Type", "application/json").
		SetResult(&ChatResponse{}).
		Post(ChatAPIPath)

	if err != nil {
		return nil, errors.Wrap(err, 0)
	}

	if resp.StatusCode() != 200 {
		return nil, errors.Errorf("unexpected status code: %d", resp.StatusCode())
	}

	return resp.Result().(*ChatResponse), nil
}

func (c *Client) ChatCompletionStream(request ChatRequest) (*ChatResponseStream, error) {
	request.Stream = true
	resp, err := c.rest.R().
		SetBody(request).
		SetHeader("Content-Type", "application/json").
		SetDoNotParseResponse(true).
		Post(ChatAPIPath)

	if err != nil {
		return nil, errors.Wrap(err, 0)
	}
	rbody := resp.RawBody()
	if rbody == nil {
		return nil, errors.New("no response body")
	}

	if resp.StatusCode() != 200 {
		defer rbody.Close()
		var respBodyStr string
		if respBody, err := io.ReadAll(rbody); err == nil {
			respBodyStr = string(respBody)
		} else {
			respBodyStr = "failed to read: " + err.Error()
		}
		return nil, errors.Errorf("status code: %d, body: %q", resp.StatusCode(), respBodyStr)
	}

	ret := &ChatResponseStream{
		Stream: make(chan string, 1024),
		Done:   make(chan struct{}),
	}
	go func() {
		defer func() {
			rbody.Close()
			close(ret.Stream)
			close(ret.Done)
		}()

		var contentBegan bool
		sc := bufio.NewScanner(rbody)
		for sc.Scan() {
			line := sc.Bytes()
			if string(line[:6]) != "data: " {
				continue
			}
			data := line[6:]
			if string(data[:6]) == "[DONE]" {
				return
			}

			var chunk ChatResponseStreamChunk
			if err := json.Unmarshal(data, &chunk); err != nil {
				ret.Err = errors.WrapPrefix(err, "failed to decode chunk:", 0)
				return
			}
			if ret.ID == "" {
				ret.ID = chunk.ID
				ret.Object = chunk.Object
				ret.Created = chunk.Created
				ret.Model = chunk.Model
			}

			var delta string
			if len(chunk.Choices) > 0 {
				delta = chunk.Choices[0].Delta.Content
			}
			if !contentBegan {
				if strings.TrimSpace(delta) == "" {
					continue
				}
				contentBegan = true
			}
			ret.Stream <- delta
		}
		if sc.Err() != nil {
			ret.Err = errors.WrapPrefix(sc.Err(), "read response:", 0)
		}
	}()

	return ret, nil
}