package ai

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

// 使用阿里云DashScope的OpenAI兼容模式（官方推荐）
const AliyunBaseURL = "https://dashscope.aliyuncs.com/compatible-mode/v1"

type AliyunClient struct {
	apiKey string
	model  string
}

func NewAliyunClient(cfg *Config) *AliyunClient {
	model := cfg.Model
	if model == "" {
		model = "qwen-turbo"
	}
	return &AliyunClient{
		apiKey: cfg.APIKey,
		model:  model,
	}
}

// OpenAI兼容格式的请求
type aliyunRequest struct {
	Model    string    `json:"model"`
	Messages []Message `json:"messages"`
	Stream   bool      `json:"stream,omitempty"`
}

// OpenAI兼容格式的响应
type aliyunResponse struct {
	ID      string `json:"id"`
	Object  string `json:"object"`
	Created int64  `json:"created"`
	Model   string `json:"model"`
	Choices []struct {
		Index   int `json:"index"`
		Message struct {
			Role    string `json:"role"`
			Content string `json:"content"`
		} `json:"message"`
		Delta struct {
			Content string `json:"content"`
		} `json:"delta"`
		FinishReason string `json:"finish_reason"`
	} `json:"choices"`
	Usage struct {
		PromptTokens     int `json:"prompt_tokens"`
		CompletionTokens int `json:"completion_tokens"`
		TotalTokens      int `json:"total_tokens"`
	} `json:"usage"`
	Error *struct {
		Message string `json:"message"`
		Type    string `json:"type"`
		Code    string `json:"code"`
	} `json:"error"`
}

func (c *AliyunClient) Chat(ctx context.Context, messages []Message) (string, error) {
	if c.apiKey == "" {
		return "", fmt.Errorf("阿里云通义千问 API Key 未配置，请在 config.yaml 中设置 ai.aliyun.api_key")
	}

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

	body, _ := json.Marshal(reqBody)
	req, err := http.NewRequestWithContext(ctx, "POST", AliyunBaseURL+"/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 aliyunResponse
	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
		return "", fmt.Errorf("解析AI响应失败: %v", err)
	}

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

	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 *AliyunClient) ChatStream(ctx context.Context, messages []Message, writer io.Writer) error {
	if c.apiKey == "" {
		return fmt.Errorf("阿里云通义千问 API Key 未配置")
	}

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

	body, _ := json.Marshal(reqBody)
	req, err := http.NewRequestWithContext(ctx, "POST", AliyunBaseURL+"/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 aliyunResponse
			if err := json.Unmarshal([]byte(data), &streamResp); err != nil {
				continue
			}

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

	return nil
}