Initial commit: PastPaper Master full stack

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/app/services/text_extractor.py

@@ -0,0 +1,48 @@
+"""PDF 文本提取 — 复用 SOS 的 text_extractor 逻辑"""
+
+import base64
+import fitz  # PyMuPDF
+from dataclasses import dataclass
+
+
+@dataclass
+class ExtractedContent:
+    pages_text: list[str]           # 每页文本
+    page_images: dict[int, str]     # 页码 → base64 图片（图片密集型页面）
+    total_pages: int
+    has_images: bool
+
+
+def extract_pdf(file_bytes: bytes) -> ExtractedContent:
+    """从 PDF 提取文本和图片"""
+    doc = fitz.open(stream=file_bytes, filetype="pdf")
+    pages_text = []
+    page_images = {}
+
+    for i, page in enumerate(doc):
+        text = page.get_text("text")
+        pages_text.append(text)
+
+        # 如果某页文本很少但有图片，可能是扫描件 → 保存为图片用于 Vision OCR
+        if len(text.strip()) < 50:
+            pix = page.get_pixmap(dpi=200)
+            img_bytes = pix.tobytes("png")
+            page_images[i] = base64.b64encode(img_bytes).decode("utf-8")
+
+    doc.close()
+
+    return ExtractedContent(
+        pages_text=pages_text,
+        page_images=page_images,
+        total_pages=len(pages_text),
+        has_images=len(page_images) > 0,
+    )
+
+
+def get_full_text(extracted: ExtractedContent) -> str:
+    """合并所有页面文本"""
+    return "\n\n".join(
+        f"--- Page {i+1} ---\n{text}"
+        for i, text in enumerate(extracted.pages_text)
+        if text.strip()
+    )