ai-mailer/internal/ai/ai.go

package ai

import (
	"bytes"
	"encoding/json"
	"fmt"
	"net/http"
	"paraclub-ai-mailer/config"
	"paraclub-ai-mailer/internal/logger"

	"github.com/sirupsen/logrus"
)

type AI struct {
	config config.AIConfig
	client *http.Client
}

type OpenRouterRequest struct {
	Model       string    `json:"model"`
	Messages    []Message `json:"messages"`
	Temperature float32   `json:"temperature"`
	MaxTokens   int       `json:"max_tokens"`
}

type Message struct {
	Role    string `json:"role"`
	Content string `json:"content"`
}

type OpenRouterResponse struct {
	Choices []struct {
		Message struct {
			Content string `json:"content"`
		} `json:"message"`
	} `json:"choices"`
}

func New(cfg config.AIConfig) *AI {
	return &AI{
		config: cfg,
		client: &http.Client{},
	}
}

func (a *AI) detectLanguage(emailContent string) (string, error) {
	logger.WithField("emailContentLength", len(emailContent)).Debug("Starting language detection")

	systemMsg := "You are a language detection assistant. Analyze the provided text and respond ONLY with the language name (e.g., 'English', 'German', 'French', etc.). No other text or explanation."
	userMsg := fmt.Sprintf("Detect the language of this text:\n\n%s", emailContent)

	messages := []Message{
		{Role: "system", Content: systemMsg},
		{Role: "user", Content: userMsg},
	}

	response, err := a.makeAPIRequest(messages)
	if err != nil {
		return "", fmt.Errorf("language detection failed: %v", err)
	}

	// The response should be just the language code
	langCode := response
	logger.WithField("detectedLanguage", langCode).Debug("Language detection completed")
	return langCode, nil
}

func (a *AI) GenerateReply(emailContent string, contextContent map[string]string) (string, error) {
	logger.WithFields(logrus.Fields{
		"emailContentLength": len(emailContent),
		"contextUrls":        len(contextContent),
	}).Debug("Starting AI reply generation")

	// First, detect the language
	lang, err := a.detectLanguage(emailContent)
	if err != nil {
		return "", err
	}

	// Prepare context from all URLs
	var context string
	for url, content := range contextContent {
		context += fmt.Sprintf("\nContext from %s:\n%s\n", url, content)
		logger.WithFields(logrus.Fields{
			"url":           url,
			"contentLength": len(content),
		}).Debug("Added context from URL")
	}

	// Prepare the system message with language-specific instruction
	systemMsg := fmt.Sprintf(`You are a helpful assistant who responds to emails.
Your primary goal is to answer the user's query based on the provided email and context.

Instructions:
- Language: Your response must be entirely in %s, regardless of the language used in the email content or context.
- Format: Your reply must be raw HTML. Use appropriate HTML tags for structure and styling.
- Markdown: Do NOT wrap the HTML in markdown code blocks (e.g., %s).
- Extraneous Text: Do not include a subject line. Do not include explanations, commentary, or any extra text that is not part of the direct answer.
- Closing: Avoid generic closing statements like "If you have further questions...". Focus solely on answering the email.
`, lang, "```html ... ```")
	logger.WithFields(logrus.Fields{
		"systemprompt": systemMsg,
	}).Debug("Generating system prompt")
	userMsg := fmt.Sprintf("### Additional Context:\n%s\n\n### Email Body:\n%s", context, emailContent)

	messages := []Message{
		{Role: "system", Content: systemMsg},
		{Role: "user", Content: userMsg},
	}

	return a.makeAPIRequest(messages)
}

func (a *AI) makeAPIRequest(messages []Message) (string, error) {
	const maxRetries = 3
	var lastErr error

	for attempt := 0; attempt < maxRetries; attempt++ {
		logger.WithField("attempt", attempt+1).Debug("Making API request attempt")

		reqBody := OpenRouterRequest{
			Model:       a.config.Model,
			Messages:    messages,
			Temperature: a.config.Temperature,
			MaxTokens:   a.config.MaxTokens,
		}

		logger.WithFields(logrus.Fields{
			"model":       reqBody.Model,
			"temperature": reqBody.Temperature,
			"maxTokens":   reqBody.MaxTokens,
		}).Debug("Prepared API request")

		jsonData, err := json.Marshal(reqBody)
		if err != nil {
			logger.WithError(err).Error("Failed to marshal request body")
			return "", err
		}

		req, err := http.NewRequest("POST", "https://openrouter.ai/api/v1/chat/completions", bytes.NewBuffer(jsonData))
		if err != nil {
			logger.WithError(err).Error("Failed to create HTTP request")
			return "", err
		}

		req.Header.Set("Content-Type", "application/json")
		req.Header.Set("Authorization", fmt.Sprintf("Bearer %s", a.config.OpenRouterAPIKey))

		resp, err := a.client.Do(req)
		if err != nil {
			logger.WithFields(logrus.Fields{
				"error":   err,
				"attempt": attempt + 1,
			}).Debug("API request failed, will retry")
			lastErr = err
			continue
		}
		defer resp.Body.Close()

		if resp.StatusCode != http.StatusOK {
			logger.WithFields(logrus.Fields{
				"statusCode": resp.StatusCode,
				"attempt":    attempt + 1,
			}).Debug("API returned non-200 status code")
			lastErr = fmt.Errorf("OpenRouter API returned status code: %d", resp.StatusCode)
			continue
		}

		var result OpenRouterResponse
		if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
			logger.WithFields(logrus.Fields{
				"error":   err,
				"attempt": attempt + 1,
			}).Debug("Failed to decode API response")
			lastErr = err
			continue
		}

		if len(result.Choices) == 0 || result.Choices[0].Message.Content == "" {
			logger.WithField("attempt", attempt+1).Debug("Received empty response from API")
			lastErr = fmt.Errorf("empty response received")
			continue
		}

		responseLength := len(result.Choices[0].Message.Content)
		logger.WithFields(logrus.Fields{
			"attempt":        attempt + 1,
			"responseLength": responseLength,
		}).Debug("Successfully generated AI reply")
		return result.Choices[0].Message.Content, nil
	}

	logger.WithFields(logrus.Fields{
		"maxRetries": maxRetries,
		"lastError":  lastErr,
	}).Error("Failed to generate AI reply after all attempts")
	return "", fmt.Errorf("failed after %d attempts, last error: %v", maxRetries, lastErr)
}