Initial AI media hub implementation

backend/services/gemini.go

@@ -0,0 +1,175 @@
+package services
+
+import (
+	"bytes"
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"io"
+	"mime"
+	"net/http"
+	"strings"
+	"time"
+)
+
+type GeminiService struct {
+	APIKey string
+	Client *http.Client
+}
+
+type AIRecommendation struct {
+	Title        string `json:"title"`
+	Link         string `json:"link"`
+	ThumbnailURL string `json:"thumbnailUrl"`
+	Source       string `json:"source"`
+	Reason       string `json:"reason"`
+	Recommended  bool   `json:"recommended"`
+}
+
+func NewGeminiService(apiKey string) *GeminiService {
+	return &GeminiService{
+		APIKey: apiKey,
+		Client: &http.Client{Timeout: 40 * time.Second},
+	}
+}
+
+func (g *GeminiService) Recommend(query string, candidates []SearchResult) ([]AIRecommendation, error) {
+	if g.APIKey == "" {
+		return nil, fmt.Errorf("gemini api key is not configured")
+	}
+	if len(candidates) == 0 {
+		return []AIRecommendation{}, nil
+	}
+
+	type geminiPart map[string]any
+	parts := []geminiPart{
+		{
+			"text": `Analyze the provided images for the user's search intent. Return JSON only in this shape:
+{"recommendations":[{"index":0,"reason":"short reason","recommended":true}]}
+Mark only the best matches as recommended=true. Keep reasons concise. User query: ` + query,
+		},
+	}
+
+	maxImages := min(len(candidates), 8)
+	for idx := 0; idx < maxImages; idx++ {
+		img, mimeType, err := fetchImageAsInlineData(g.Client, candidates[idx].ThumbnailURL)
+		if err != nil {
+			continue
+		}
+		parts = append(parts,
+			geminiPart{"text": fmt.Sprintf("Candidate %d: title=%s source=%s link=%s", idx, candidates[idx].Title, candidates[idx].Source, candidates[idx].Link)},
+			geminiPart{"inlineData": map[string]string{"mimeType": mimeType, "data": img}},
+		)
+	}
+
+	body := map[string]any{
+		"contents": []map[string]any{
+			{"parts": parts},
+		},
+		"generationConfig": map[string]any{
+			"responseMimeType": "application/json",
+		},
+	}
+
+	rawBody, _ := json.Marshal(body)
+	endpoint := "https://generativelanguage.googleapis.com/v1beta/models/gemini-2.5-flash:generateContent?key=" + g.APIKey
+	resp, err := g.Client.Post(endpoint, "application/json", bytes.NewReader(rawBody))
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode >= 300 {
+		data, _ := io.ReadAll(io.LimitReader(resp.Body, 2048))
+		return nil, fmt.Errorf("gemini returned status %d: %s", resp.StatusCode, string(data))
+	}
+
+	var payload struct {
+		Candidates []struct {
+			Content struct {
+				Parts []struct {
+					Text string `json:"text"`
+				} `json:"parts"`
+			} `json:"content"`
+		} `json:"candidates"`
+	}
+	if err := json.NewDecoder(resp.Body).Decode(&payload); err != nil {
+		return nil, err
+	}
+	if len(payload.Candidates) == 0 || len(payload.Candidates[0].Content.Parts) == 0 {
+		return nil, fmt.Errorf("gemini returned no candidates")
+	}
+
+	var parsed struct {
+		Recommendations []struct {
+			Index       int    `json:"index"`
+			Reason      string `json:"reason"`
+			Recommended bool   `json:"recommended"`
+		} `json:"recommendations"`
+	}
+	if err := json.Unmarshal([]byte(payload.Candidates[0].Content.Parts[0].Text), &parsed); err != nil {
+		return nil, err
+	}
+
+	recommendations := make([]AIRecommendation, 0, len(parsed.Recommendations))
+	for _, rec := range parsed.Recommendations {
+		if rec.Index < 0 || rec.Index >= len(candidates) || !rec.Recommended {
+			continue
+		}
+		src := candidates[rec.Index]
+		recommendations = append(recommendations, AIRecommendation{
+			Title:        src.Title,
+			Link:         src.Link,
+			ThumbnailURL: src.ThumbnailURL,
+			Source:       src.Source,
+			Reason:       rec.Reason,
+			Recommended:  true,
+		})
+	}
+
+	if len(recommendations) == 0 {
+		for _, candidate := range candidates[:min(4, len(candidates))] {
+			recommendations = append(recommendations, AIRecommendation{
+				Title:        candidate.Title,
+				Link:         candidate.Link,
+				ThumbnailURL: candidate.ThumbnailURL,
+				Source:       candidate.Source,
+				Reason:       "Fallback result because Gemini returned no recommended items.",
+				Recommended:  true,
+			})
+		}
+	}
+
+	return recommendations, nil
+}
+
+func fetchImageAsInlineData(client *http.Client, imageURL string) (string, string, error) {
+	resp, err := client.Get(imageURL)
+	if err != nil {
+		return "", "", err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode >= 300 {
+		return "", "", fmt.Errorf("thumbnail fetch failed with %d", resp.StatusCode)
+	}
+
+	contentType := resp.Header.Get("Content-Type")
+	mimeType, _, _ := mime.ParseMediaType(contentType)
+	if mimeType == "" || !strings.HasPrefix(mimeType, "image/") {
+		mimeType = "image/jpeg"
+	}
+
+	data, err := io.ReadAll(io.LimitReader(resp.Body, 2*1024*1024))
+	if err != nil {
+		return "", "", err
+	}
+	return base64.StdEncoding.EncodeToString(data), mimeType, nil
+}
+
+func min(a, b int) int {
+	if a < b {
+		return a
+	}
+	return b
+}