Also allow conversion from POST upload

app.py

@@ -1,4 +1,4 @@
-import os
+from typing import Literal
 import httpx
 import nbformat
 from nbformat import NotebookNode, ValidationError
@@ -21,47 +21,63 @@ async def healthz(_):
     return JSONResponse({"success": True})
 
 
-async def convert(req: Request):
-    url = req.query_params.get("url")
-    if not url:
-        raise HTTPException(400, "Param url is missing")
-    print("\n===", url)
-    theme = req.query_params.get("theme")
-    r = await client.get(
-        url,
-        follow_redirects=True,
-        # httpx no follow redirect by default
-    )
-    if r.status_code != 200:
-        raise HTTPException(
-            400, f"Got an error {r.status_code} when fetching remote file"
-        )
-
+def convert(s: str, theme: Literal["light", "dark"], debug_info: str) -> str:
     # Capture potential validation error:
     try:
         notebook_node: NotebookNode = nbformat.reads(
-            r.text,
+            s,
             as_version=nbformat.current_nbformat,
         )
     except nbformat.reader.NotJSONError:
-        print(400, f"Notebook is not JSON ({url})")
-        raise HTTPException(400, f"Notebook is not JSON ({url})")
+        print(400, f"Notebook is not JSON. {debug_info}")
+        raise HTTPException(400, f"Notebook is not JSON. {debug_info}")
     except ValidationError as e:
         print(
             400,
-            f"Notebook is invalid according to nbformat: {e} ({url})",
+            f"Notebook is invalid according to nbformat: {e}. {debug_info}",
         )
         raise HTTPException(
             400,
-            f"Notebook is invalid according to nbformat: {e} ({url})",
+            f"Notebook is invalid according to nbformat: {e}. {debug_info}",
         )
 
     print(f"Input: nbformat v{notebook_node.nbformat}.{notebook_node.nbformat_minor}")
-    html_exporter.theme = "dark" if theme == "dark" else "light"
+    html_exporter.theme = theme
     body, _ = html_exporter.from_notebook_node(notebook_node)
     # TODO(customize or simplify template?)
     # TODO(also check source code for jupyter/nbviewer)
-    return HTMLResponse(body)
+    return body
+
+
+async def convert_from_url(req: Request):
+    url = req.query_params.get("url")
+    theme = "dark" if req.query_params.get("theme") == "dark" else "light"
+
+    if not url:
+        raise HTTPException(400, "Param url is missing")
+    print("\n===", url)
+    r = await client.get(
+        url,
+        follow_redirects=True,
+        # httpx no follow redirect by default
+    )
+    if r.status_code != 200:
+        raise HTTPException(
+            400, f"Got an error {r.status_code} when fetching remote file"
+        )
+
+    return HTMLResponse(content=convert(r.text, theme=theme, debug_info=f"url={url}"))
+
+
+async def convert_from_upload(req: Request):
+    theme = "dark" if req.query_params.get("theme") == "dark" else "light"
+
+    s = (await req.body()).decode("utf-8")
+    return HTMLResponse(
+        content=convert(
+            s, theme=theme, debug_info=f"upload_from={req.headers.get('user-agent')}"
+        )
+    )
 
 
 app = Starlette(
@@ -69,6 +85,7 @@ app = Starlette(
     routes=[
         Route("/", homepage),
         Route("/healthz", healthz),
-        Route("/convert", convert),
+        Route("/convert", convert_from_url),
+        Route("/upload", convert_from_upload, methods=["POST"]),
     ],
 )