go-svc-ai/internal/factory/factory.go

package factory

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

// 极简HTTP客户端实现
type SimpleHTTPClient struct {
	config *ModelConfig
	client *http.Client
}

// NewSimpleHTTPClient 创建客户端（每次请求创建新的）
func NewSimpleHTTPClient(config *ModelConfig) *SimpleHTTPClient {
	return &SimpleHTTPClient{
		config: config,
		client: &http.Client{
			Timeout: time.Duration(config.Timeout) * time.Second,
		},
	}
}

// Chat 一次性返回（阻塞式）
func (c *SimpleHTTPClient) Chat(ctx context.Context, messages []ChatMessage) (string, error) {
	// 构建请求
	reqBody := map[string]interface{}{
		"model":       c.config.Model,
		"messages":    messages,
		"max_tokens":  c.config.MaxTokens,
		"temperature": c.config.Temperature,
		"stream":      false,
	}

	// 根据不同提供商调整请求格式
	reqBody = c.adjustRequestForProvider(reqBody)

	// 发送请求
	resp, err := c.doRequest(ctx, reqBody)
	if err != nil {
		return "", err
	}
	defer resp.Body.Close()

	// 解析响应
	var result map[string]interface{}
	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
		return "", fmt.Errorf("解析响应失败: %v", err)
	}

	// 提取回复内容
	return c.extractContent(result), nil
}

// ChatStream 流式返回
func (c *SimpleHTTPClient) ChatStream(ctx context.Context, messages []ChatMessage) (<-chan string, error) {
	ch := make(chan string)

	go func() {
		defer close(ch)

		// 构建请求
		reqBody := map[string]interface{}{
			"model":       c.config.Model,
			"messages":    messages,
			"max_tokens":  c.config.MaxTokens,
			"temperature": c.config.Temperature,
			"stream":      true,
		}

		reqBody = c.adjustRequestForProvider(reqBody)

		// 发送请求
		resp, err := c.doRequest(ctx, reqBody)
		if err != nil {
			ch <- fmt.Sprintf("错误: %v", err)
			return
		}
		defer resp.Body.Close()

		// 流式读取
		reader := c.createStreamReader(resp.Body)
		for {
			select {
			case <-ctx.Done():
				return
			default:
				line, err := reader()
				if err != nil {
					if err != io.EOF {
						ch <- fmt.Sprintf("读取错误: %v", err)
					}
					return
				}
				if line != "" {
					ch <- line
				}
			}
		}
	}()

	return ch, nil
}

// doRequest 执行HTTP请求
func (c *SimpleHTTPClient) doRequest(ctx context.Context, body map[string]interface{}) (*http.Response, error) {
	// 序列化请求体
	jsonData, err := json.Marshal(body)
	if err != nil {
		return nil, fmt.Errorf("序列化请求失败: %v", err)
	}

	// 确定端点URL
	endpoint := c.getEndpointURL()

	// 创建请求
	req, err := http.NewRequestWithContext(ctx, "POST", endpoint, strings.NewReader(string(jsonData)))
	if err != nil {
		return nil, fmt.Errorf("创建请求失败: %v", err)
	}

	// 设置请求头
	c.setHeaders(req)

	// 发送请求
	resp, err := c.client.Do(req)
	if err != nil {
		return nil, fmt.Errorf("请求失败: %v", err)
	}

	// 检查状态码
	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		resp.Body.Close()
		return nil, fmt.Errorf("API错误: %s, 响应: %s", resp.Status, string(body))
	}

	return resp, nil
}

// getEndpointURL 获取API端点URL
func (c *SimpleHTTPClient) getEndpointURL() string {
	switch c.config.Provider {
	case "openai":
		return c.config.BaseURL + "/chat/completions"
	case "deepseek":
		return c.config.BaseURL + "/chat/completions"
	case "claude":
		return c.config.BaseURL + "/messages"
	default:
		return c.config.BaseURL + "/chat/completions"
	}
}

// setHeaders 设置请求头
func (c *SimpleHTTPClient) setHeaders(req *http.Request) {
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Authorization", "Bearer "+c.config.APIKey)

	// 提供商特定头
	switch c.config.Provider {
	case "claude":
		req.Header.Set("x-api-key", c.config.APIKey)
		req.Header.Set("anthropic-version", "2023-06-01")
	case "openai", "deepseek":
		// 标准头
	}
}

// adjustRequestForProvider 调整请求格式
func (c *SimpleHTTPClient) adjustRequestForProvider(reqBody map[string]interface{}) map[string]interface{} {
	switch c.config.Provider {
	case "claude":
		// Claude使用不同的格式
		return map[string]interface{}{
			"model":      c.config.Model,
			"messages":   reqBody["messages"],
			"max_tokens": c.config.MaxTokens,
		}
	default:
		return reqBody
	}
}

// extractContent 从响应中提取内容
func (c *SimpleHTTPClient) extractContent(resp map[string]interface{}) string {
	switch c.config.Provider {
	case "openai", "deepseek":
		if choices, ok := resp["choices"].([]interface{}); ok && len(choices) > 0 {
			if choice, ok := choices[0].(map[string]interface{}); ok {
				if message, ok := choice["message"].(map[string]interface{}); ok {
					if content, ok := message["content"].(string); ok {
						return content
					}
				}
			}
		}
	case "claude":
		if content, ok := resp["content"].([]interface{}); ok && len(content) > 0 {
			if first, ok := content[0].(map[string]interface{}); ok {
				if text, ok := first["text"].(string); ok {
					return text
				}
			}
		}
	}
	return ""
}

// createStreamReader 创建流式读取器
func (c *SimpleHTTPClient) createStreamReader(body io.Reader) func() (string, error) {
	buf := make([]byte, 4096)
	var leftover []byte

	return func() (string, error) {
		// 读取数据
		n, err := body.Read(buf)
		if err != nil {
			return "", err
		}

		data := append(leftover, buf[:n]...)
		lines := strings.Split(string(data), "\n")

		// 处理完整的行
		var result strings.Builder
		for i, line := range lines {
			if i == len(lines)-1 {
				// 最后一行可能不完整，留到下次
				leftover = []byte(line)
				continue
			}

			line = strings.TrimSpace(line)
			if line == "" || !strings.HasPrefix(line, "data: ") {
				continue
			}

			// 去除"data: "前缀
			line = line[6:]
			if line == "[DONE]" {
				return "", io.EOF
			}

			// 解析JSON
			var chunk map[string]interface{}
			if err := json.Unmarshal([]byte(line), &chunk); err != nil {
				continue
			}

			// 提取内容
			content := c.extractStreamContent(chunk)
			if content != "" {
				result.WriteString(content)
			}
		}

		return result.String(), nil
	}
}

// extractStreamContent 提取流式响应内容
func (c *SimpleHTTPClient) extractStreamContent(chunk map[string]interface{}) string {
	switch c.config.Provider {
	case "openai", "deepseek":
		if choices, ok := chunk["choices"].([]interface{}); ok && len(choices) > 0 {
			if choice, ok := choices[0].(map[string]interface{}); ok {
				if delta, ok := choice["delta"].(map[string]interface{}); ok {
					if content, ok := delta["content"].(string); ok {
						return content
					}
				}
			}
		}
	case "claude":
		if content, ok := chunk["content"].([]interface{}); ok && len(content) > 0 {
			if first, ok := content[0].(map[string]interface{}); ok {
				if text, ok := first["text"].(string); ok {
					return text
				}
			}
		}
	}
	return ""
}

// ==================== 工厂函数 ====================

// CreateClient 工厂函数：根据配置创建客户端
func CreateClient(configKey string) (AIClient, error) {
	// 这里模拟从"数据库"读取配置
	// 实际项目中应该从数据库/配置中心读取
	config, err := GetConfigFromMockDB(configKey)
	if err != nil {
		return nil, err
	}

	return NewSimpleHTTPClient(config), nil
}

// GetConfigFromMockDB 模拟从数据库获取配置
func GetConfigFromMockDB(configKey string) (*ModelConfig, error) {
	// 这里调用模拟数据库
	// 实际应该调用数据库查询
	return &ModelConfig{
		Provider:    "openai",
		BaseURL:     "https://api.openai.com/v1",
		APIKey:      "fake-key-for-demo",
		Model:       "gpt-3.5-turbo",
		MaxTokens:   1000,
		Temperature: 0.7,
		Timeout:     30,
	}, nil
}