[ENHANCEMENT] Add Request ID Middleware and Structured Error Handling

api/main.py

@@ -1,12 +1,18 @@
 from contextlib import asynccontextmanager
 import os
+import uuid
+
+from fastapi import FastAPI, Request
+from fastapi.middleware.cors import CORSMiddleware
+from fastapi.responses import JSONResponse
+from fastapi.exceptions import RequestValidationError
+from starlette.middleware.base import BaseHTTPMiddleware
+from starlette.exceptions import HTTPException as StarletteHTTPException
 
-from fastapi import FastAPI
 from api.routes import templates, forms
 from api.db.init_db import init_db
 from api.errors.handlers import register_exception_handlers
-from fastapi.middleware.cors import CORSMiddleware
-from api.routes import forms, templates
+
 
 @asynccontextmanager
 async def lifespan(app: FastAPI):
@@ -20,6 +26,71 @@ async def lifespan(app: FastAPI):
 
 register_exception_handlers(app)
 
+class RequestIDMiddleware(BaseHTTPMiddleware):
+    async def dispatch(self, request: Request, call_next):
+        request_id = str(uuid.uuid4())
+        request.state.request_id = request_id
+        response = await call_next(request)
+        response.headers["X-Request-ID"] = request_id
+        return response
+
+app.add_middleware(RequestIDMiddleware)
+
+@app.exception_handler(StarletteHTTPException)
+async def http_exception_handler(request: Request, exc: StarletteHTTPException):
+    return JSONResponse(
+        status_code=exc.status_code,
+        content={
+            "error": {
+                "type": "HTTPException",
+                "message": exc.detail,
+                "details": {}
+            }
+        },
+    )
+
+
+@app.exception_handler(RequestValidationError)
+async def validation_exception_handler(request: Request, exc: RequestValidationError):
+    formatted_errors = []
+
+    for err in exc.errors():
+        loc = err.get("loc", [])
+        field = loc[-1] if loc else "unknown"
+        issue = err.get("msg", "Invalid value")
+        expected = err.get("type", "")
+
+        formatted_errors.append({
+            "field": field,
+            "issue": issue,
+            "expected": expected
+        })
+
+    return JSONResponse(
+        status_code=422,
+        content={
+            "error": {
+                "type": "ValidationError",
+                "message": "Invalid request data",
+                "details": formatted_errors,
+            }
+        },
+    )
+
+
+@app.exception_handler(Exception)
+async def general_exception_handler(request: Request, exc: Exception):
+    return JSONResponse(
+        status_code=500,
+        content={
+            "error": {
+                "type": "InternalServerError",
+                "message": str(exc),
+                "details": {}
+            }
+        },
+    )
+
 default_origins = "http://127.0.0.1:5173"
 allowed_origins = [
     origin.strip()
@@ -36,4 +107,4 @@ async def lifespan(app: FastAPI):
 )
 
 app.include_router(templates.router)
-app.include_router(forms.router)
+app.include_router(forms.router)

api/schemas/forms.py

@@ -1,9 +1,15 @@
-from pydantic import BaseModel
+from pydantic import BaseModel, field_validator
 
 class FormFill(BaseModel):
     template_id: int
     input_text: str
 
+    @field_validator("input_text")
+    def validate_input_text(cls, value):
+        if not value or not value.strip():
+            raise ValueError("Input text cannot be empty")
+        return value
+
 
 class FormFillResponse(BaseModel):
     id: int