Add API validation and consistent JSON error responses

main.py

@@ -3,7 +3,7 @@
 import sys
 import signal
 from datetime import datetime, timezone
-from flask import Flask, request, render_template, abort
+from flask import Flask, request, render_template, abort, jsonify
 from markupsafe import Markup
 import mistune
 import uuid
@@ -88,6 +88,31 @@ def get_chat_history(user_id):
     return db.list_by_user(user_id, 10)
 
 
+def api_error(message, status_code=400):
+    """return a consistent API error payload"""
+    logging.error(message)
+    return jsonify({"error": {"message": message}}), status_code
+
+
+def parse_api_question():
+    """validate and normalize question from API JSON payload"""
+    body = request.get_json(silent=True)
+    log.debug(body)
+    if not isinstance(body, dict):
+        return None, api_error(
+            "invalid request body: expected JSON object", 400)
+
+    question = body.get("question")
+    if not isinstance(question, str):
+        return None, api_error("missing field: question", 400)
+
+    question = question.strip()
+    if question == "":
+        return None, api_error("field 'question' cannot be empty", 400)
+
+    return question, None
+
+
 @app.route("/")
 def index():
     """home page"""
@@ -189,7 +214,6 @@ def ask_internal(conversation, question):
 
     # fetch latest conversation
     conversation = db.get(conversation_id, user_id)
-    sources = []
 
     return answer, conversation, sources
 
@@ -213,14 +237,10 @@ def get_conversation(id):
 def ask_api_new():
     """returns an answer to a question in a new conversation"""
 
-    # get request json from body
-    body = request.get_json()
-    log.debug(body)
-    if "question" not in body:
-        m = "missing field: question"
-        logging.error(m)
-        abort(400, m)
-    question = body["question"]
+    question, error = parse_api_question()
+    if error is not None:
+        return error
+    user_id = get_current_user_id()
 
     conversation = {
         "conversationId": str(uuid.uuid4()),
@@ -241,21 +261,14 @@ def ask_api_new():
 def ask_api(id):
     """returns an answer to a question in a conversation"""
 
-    # get request json from body
-    body = request.get_json()
-    log.debug(body)
-    if "question" not in body:
-        m = "missing field: question"
-        logging.error(m)
-        abort(400, m)
-    question = body["question"]
+    question, error = parse_api_question()
+    if error is not None:
+        return error
 
     user_id = get_current_user_id()
 
     if id == "":
-        m = "conversation id is required"
-        logging.error(m)
-        abort(400, m)
+        return api_error("conversation id is required", 400)
     else:
         conversation = db.get(id, user_id)
         logging.info("fetched conversation")