add: next img picker impl

main.py

@@ -1,4 +1,5 @@
 from fastapi import FastAPI
+import sqlite3
 
 # use database residing here
 DB_LOCATION = (
@@ -8,7 +9,7 @@ DB_LOCATION = (
 app = FastAPI()
 con = sqlite3.connect(DB_LOCATION)
 con.row_factory = sqlite3.Row
-cur = con.cursor()
+cur = con.cursor()  # NB! single is enough for now, we might require multiple later
 
 
 @app.get("/new_session")
@@ -32,7 +33,10 @@ async def next_picture(cookie: int):
     )
     sessionid = cur.fetchone()
     if sessionid is None:
-        return
+        return {
+            "picture_id": -2,
+            "picture_uri": "/path/to/new/session/placeholder",  # FIXME[2]
+        }  # Q: do we return something specific, or just use convention here?
 
     # take not rated picture from the database
     # do not insert anything in the database yet
@@ -55,7 +59,14 @@ async def next_picture(cookie: int):
         {"sessionid": sessionid["sessionid"]},
     )
     r = cur.fetchone()
-    return {"picture_id": r["imgid"]}
+    if r is not None:
+        return {"picture_id": r["imgid"], "picture_uri": r["resizedpath"]}
+    else:
+        # All available pics have been voted for by this sessionid
+        return {
+            "picture_id": -1,
+            "picture_uri": "/path/to/you/are/done/placeholder",  # FIXME[1]
+        }  # Q: do we return something specific, or just use a convention here?
 
 
 @app.get("/rate_picture/{session_id}/{picture_id}/{mark}")