更新

backend/link_cards.py

@@ -0,0 +1,186 @@
+"""链接卡片落地页：带 SEO meta 与自动跳转。"""
+from __future__ import annotations
+
+import html
+import json
+import os
+import re
+import secrets
+from io import BytesIO
+from typing import Optional, TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from fastapi import Request
+
+_SLUG_RE = re.compile(r"^[a-zA-Z0-9_-]{6,64}$")
+
+FAVICON_SIZE = 32
+COVER_SIZE = 256
+FAVICON_MIME = "image/png"
+
+
+def generate_slug() -> str:
+    return secrets.token_urlsafe(9).replace("-", "_").replace(".", "_")[:12]
+
+
+def is_valid_slug(slug: str) -> bool:
+    return bool(_SLUG_RE.match(slug or ""))
+
+
+def public_base_url(request: Optional["Request"] = None) -> str:
+    env = os.getenv("KEFU_PUBLIC_BASE_URL", "").strip().rstrip("/")
+    if env:
+        return env
+    if request is not None:
+        return str(request.base_url).rstrip("/")
+    return ""
+
+
+def absolute_media_url(path: str, request: Optional["Request"] = None) -> str:
+    path = (path or "").strip()
+    if not path:
+        return ""
+    if path.startswith("http://") or path.startswith("https://"):
+        return path
+    base = public_base_url(request)
+    if not base:
+        return path
+    if not path.startswith("/"):
+        path = f"/{path}"
+    return f"{base}{path}"
+
+
+def favicon_mime(image_path: str) -> str:
+    ext = (image_path or "").rsplit(".", 1)[-1].lower()
+    return {
+        "svg": "image/svg+xml",
+        "png": "image/png",
+        "gif": "image/gif",
+        "webp": "image/webp",
+        "jpg": "image/jpeg",
+        "jpeg": "image/jpeg",
+        "ico": "image/x-icon",
+    }.get(ext, FAVICON_MIME)
+
+
+def favicon_path_for_cover(cover_path: str) -> str:
+    """由封面路径推导同名 favicon 文件路径。"""
+    path = (cover_path or "").strip()
+    if not path:
+        return ""
+    if path.endswith(".favicon.png"):
+        return path
+    if path.endswith(".png"):
+        return f"{path[:-4]}.favicon.png"
+    base, _ = os.path.splitext(path)
+    return f"{base}.favicon.png"
+
+
+def media_path_to_disk(upload_dir: str, media_path: str) -> str:
+    prefix = "/api/media/link-cards/"
+    path = (media_path or "").strip()
+    if not path.startswith(prefix):
+        return ""
+    rel = path[len(prefix) :].replace("/", os.sep)
+    return os.path.join(upload_dir, rel)
+
+
+def process_card_upload(raw: bytes) -> tuple[bytes, bytes]:
+    """将任意位图转为封面 PNG (256x256) 与 favicon PNG (32x32)。"""
+    if not raw:
+        raise ValueError("图片为空")
+    try:
+        from PIL import Image
+    except ImportError as exc:
+        raise RuntimeError("服务器未安装 Pillow，无法转换 favicon") from exc
+
+    try:
+        with Image.open(BytesIO(raw)) as img:
+            if getattr(img, "is_animated", False):
+                img.seek(0)
+            if img.mode not in ("RGB", "RGBA"):
+                img = img.convert("RGBA")
+            else:
+                img = img.copy()
+
+            width, height = img.size
+            if width < 1 or height < 1:
+                raise ValueError("图片尺寸无效")
+
+            side = min(width, height)
+            left = (width - side) // 2
+            top = (height - side) // 2
+            square = img.crop((left, top, left + side, top + side))
+
+            resample = Image.Resampling.LANCZOS
+            cover = square.resize((COVER_SIZE, COVER_SIZE), resample)
+            favicon = square.resize((FAVICON_SIZE, FAVICON_SIZE), resample)
+
+            cover_buf = BytesIO()
+            cover.save(cover_buf, format="PNG", optimize=True)
+            favicon_buf = BytesIO()
+            favicon.save(favicon_buf, format="PNG", optimize=True)
+            return cover_buf.getvalue(), favicon_buf.getvalue()
+    except ValueError:
+        raise
+    except Exception as exc:
+        raise ValueError("无法识别图片格式，请上传 JPG、PNG、GIF 或 WebP") from exc
+
+
+def normalize_target_url(url: str) -> str:
+    url = (url or "").strip()
+    if not url:
+        return ""
+    if not url.startswith("http://") and not url.startswith("https://"):
+        url = f"https://{url}"
+    return url
+
+
+def build_keywords(title: str, content: str) -> str:
+    parts = [p.strip() for p in (title, content) if p and p.strip()]
+    return ", ".join(dict.fromkeys(parts))
+
+
+def render_link_card_page(
+    *,
+    title: str,
+    content: str,
+    keywords: str,
+    cover_url: str,
+    favicon_url: str,
+    target_url: str,
+) -> str:
+    safe_title = html.escape(title or "跳转中")
+    safe_desc = html.escape(content or title or "")
+    safe_keywords = html.escape(keywords or build_keywords(title, content))
+    safe_cover = html.escape(cover_url or "")
+    safe_favicon = html.escape(favicon_url or cover_url or "")
+    redirect_url = normalize_target_url(target_url)
+    safe_target = html.escape(redirect_url)
+    js_target = json.dumps(redirect_url, ensure_ascii=False)
+
+    favicon_tag = ""
+    og_image_tag = ""
+    if safe_favicon:
+        favicon_tag = f'  <link rel="icon" type="{FAVICON_MIME}" href="{safe_favicon}" />\n'
+    if safe_cover:
+        og_image_tag = f'  <meta property="og:image" content="{safe_cover}" />\n'
+
+    return f"""<!DOCTYPE html>
+<html lang="zh-CN">
+<head>
+  <meta charset="utf-8" />
+  <meta name="viewport" content="width=device-width, initial-scale=1" />
+  <title>{safe_title}</title>
+  <meta name="description" content="{safe_desc}" />
+  <meta name="keywords" content="{safe_keywords}" />
+  <meta property="og:title" content="{safe_title}" />
+  <meta property="og:description" content="{safe_desc}" />
+{og_image_tag}{favicon_tag}  <meta http-equiv="refresh" content="0;url={safe_target}" />
+  <script>location.replace({js_target});</script>
+</head>
+<body>
+  <p>正在跳转到目标页面…</p>
+  <p><a href="{safe_target}">若未自动跳转，请点击这里</a></p>
+</body>
+</html>"""