package ai

import (
	"bufio"
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strings"
)

type OpenAIClient struct {
	apiKey  string
	baseURL string
	model   string
}

func NewOpenAIClient(cfg *Config) *OpenAIClient {
	baseURL := cfg.BaseURL
	if baseURL == "" {
		baseURL = "https://api.openai.com/v1"
	}
	model := cfg.Model
	if model == "" {
		model = "gpt-3.5-turbo"
	}
	return &OpenAIClient{
		apiKey:  cfg.APIKey,
		baseURL: baseURL,
		model:   model,
	}
}

type openAIRequest struct {
	Model    string    `json:"model"`
	Messages []Message `json:"messages"`
	Stream   bool      `json:"stream"`
}

type openAIResponse struct {
	Choices []struct {
		Message struct {
			Content string `json:"content"`
		} `json:"message"`
		Delta struct {
			Content string `json:"content"`
		} `json:"delta"`
	} `json:"choices"`
	Error *struct {
		Message string `json:"message"`
	} `json:"error"`
}

func (c *OpenAIClient) Chat(ctx context.Context, messages []Message) (string, error) {
	if c.apiKey == "" {
		return "", fmt.Errorf("OpenAI API Key 未配置，请在 config.yaml 中设置 ai.openai.api_key")
	}

	reqBody := openAIRequest{
		Model:    c.model,
		Messages: messages,
		Stream:   false,
	}

	body, _ := json.Marshal(reqBody)
	req, err := http.NewRequestWithContext(ctx, "POST", c.baseURL+"/chat/completions", bytes.NewReader(body))
	if err != nil {
		return "", err
	}

	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Authorization", "Bearer "+c.apiKey)

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return "", fmt.Errorf("调用AI服务失败: %v", err)
	}
	defer resp.Body.Close()

	var result openAIResponse
	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
		return "", fmt.Errorf("解析AI响应失败: %v", err)
	}

	if result.Error != nil {
		return "", fmt.Errorf("AI服务错误: %s", result.Error.Message)
	}

	if len(result.Choices) == 0 {
		return "", fmt.Errorf("AI未返回有效响应")
	}

	return result.Choices[0].Message.Content, nil
}

func (c *OpenAIClient) ChatStream(ctx context.Context, messages []Message, writer io.Writer) error {
	if c.apiKey == "" {
		return fmt.Errorf("OpenAI API Key 未配置")
	}

	reqBody := openAIRequest{
		Model:    c.model,
		Messages: messages,
		Stream:   true,
	}

	body, _ := json.Marshal(reqBody)
	req, err := http.NewRequestWithContext(ctx, "POST", c.baseURL+"/chat/completions", bytes.NewReader(body))
	if err != nil {
		return err
	}

	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Authorization", "Bearer "+c.apiKey)

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()

	// 解析 SSE 流
	reader := bufio.NewReader(resp.Body)
	for {
		line, err := reader.ReadString('\n')
		if err == io.EOF {
			break
		}
		if err != nil {
			return err
		}

		line = strings.TrimSpace(line)
		if strings.HasPrefix(line, "data:") {
			data := strings.TrimPrefix(line, "data:")
			data = strings.TrimSpace(data)
			if data == "[DONE]" {
				break
			}

			var streamResp openAIResponse
			if err := json.Unmarshal([]byte(data), &streamResp); err != nil {
				continue
			}

			if len(streamResp.Choices) > 0 {
				content := streamResp.Choices[0].Delta.Content
				writer.Write([]byte(content))
			}
		}
	}

	return nil
}