enhance rag retrieval + summary

backend/src/main/java/com/aiteacher/book/BookEmbeddingService.java

@@ -92,7 +92,7 @@ public class BookEmbeddingService {
             ChapterEntity chapter = new ChapterEntity(chapterId, bookId, 1, bookTitle, 1);
             chapterRepository.save(chapter);
 
-            // Step 1: Parse with Marker — JSON (structured) + Markdown (per-page) in parallel
+            // Step 1: Parse with Marker — split into 100-page chunks, then merge results
             ParsedBook parsed = markerPageParser.parse(pdfPath);
 
             List<PageResult> pageResults = parsed.pages();
@@ -125,25 +125,32 @@ public class BookEmbeddingService {
             log.info("Saved {} HTML pages to S3 for book {}", parsed.htmlByPage().size(), bookId);
 
             // Step 5: Vision analysis (description + visible text) → embed figure chunks
-            for (FigureEntity figure : figures) {
-                byte[] imageBytes = figureStorageService.getBytes(figure.getImagePath());
-                VisionDescriptionService.ImageAnalysis analysis =
-                        visionDescriptionService.analyze(imageBytes, figure.getCaption());
+            Map<String, SectionEntity> sectionById = new HashMap<>();
+            for (SectionEntity s : sections) sectionById.put(s.getId(), s);
 
+            for (FigureEntity figure : figures) {
+                // Prefer caption extracted from the linked section's full text
                 if (figure.getCaption() == null || figure.getCaption().isBlank()) {
-                    figure.setCaption(analysis.description());
-                    figureRepository.save(figure);
+                    String sectionCaption = extractCaptionFromSection(sectionById.get(figure.getSectionId()));
+                    if (sectionCaption != null) {
+                        figure.setCaption(sectionCaption);
+                        figureRepository.save(figure);
+                    } else {
+                        byte[] imageBytes = figureStorageService.getBytes(figure.getImagePath());
+                        VisionDescriptionService.ImageAnalysis analysis =
+                                visionDescriptionService.analyze(imageBytes, figure.getCaption());
+                        figure.setCaption(analysis.description());
+                        figureRepository.save(figure);
+                    }
                 }
 
-                // Embedding content: description + caption + visible image text
-                String embeddingContent = analysis.description()
-                        + (figure.getCaption() != null ? "\n" + figure.getCaption() : "")
-                        + (analysis.imageText().isEmpty() ? "" : "\n" + analysis.imageText());
+                // Embedding content: description
+                String embeddingContent = (figure.getCaption() != null ? "\n" + figure.getCaption() : "");
 
                 String embeddingId = UUID.randomUUID().toString();
                 if (!skipEmbedding) {
                     Document figureDoc = new Document(embeddingId, embeddingContent,
-                            buildFigureMetadata(figure, bookTitle, embeddingId, analysis.imageText()));
+                            buildFigureMetadata(figure, bookTitle, embeddingId, ""));
                     vectorStore.add(List.of(figureDoc));
                     figure.setCaptionEmbeddingId(UUID.fromString(embeddingId));
                 }
@@ -163,7 +170,7 @@ public class BookEmbeddingService {
             }
 
             book.setStatus(BookStatus.READY);
-            book.setPageCount(sections.size());
+            book.setPageCount(parsed.htmlByPage().size());
             book.setProcessedAt(Instant.now());
             bookRepository.save(book);
 
@@ -210,7 +217,7 @@ public class BookEmbeddingService {
             if (page.orderedText().isBlank()) continue;
 
             String sectionId = bookId + "-p" + page.pageNumber();
-            String title = page.headingTitle() != null ? page.headingTitle() : "Page " + page.pageNumber();
+            String title = truncate(page.headingTitle() != null ? page.headingTitle() : "Page " + page.pageNumber(), 500);
 
             SectionEntity section = new SectionEntity(
                     sectionId, chapterId, bookId,
@@ -271,6 +278,17 @@ public class BookEmbeddingService {
         return html;
     }
 
+    private String extractCaptionFromSection(SectionEntity section) {
+        if (section == null) return null;
+        for (String line : section.getFullText().split("\n")) {
+            String trimmed = line.strip();
+            if (trimmed.startsWith("Fig.") || trimmed.startsWith("Figure") || trimmed.startsWith("Algorithm")) {
+                return trimmed;
+            }
+        }
+        return null;
+    }
+
     private String truncate(String msg, int max) {
         if (msg == null) return null;
         return msg.length() <= max ? msg : msg.substring(0, max);