[ENHANCEMENT] Add centralized error response handling using global exception handlers

api/main.py

@@ -1,7 +1,56 @@
 from fastapi import FastAPI
+from api.routes import templates, forms
+from fastapi import Request
+from fastapi.responses import JSONResponse
+from fastapi.exceptions import RequestValidationError
+from starlette.exceptions import HTTPException as StarletteHTTPException
+
 from api.routes import templates, forms
 
 app = FastAPI()
 
+
+@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):
+    return JSONResponse(
+        status_code=422,
+        content={
+            "error": {
+                "type": "ValidationError",
+                "message": "Invalid request data",
+                "details": exc.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": {}
+            }
+        },
+    )
+
+
 app.include_router(templates.router)
 app.include_router(forms.router)

api/routes/forms.py

@@ -11,14 +11,15 @@
 
 @router.post("/fill", response_model=FormFillResponse)
 def fill_form(form: FormFill, db: Session = Depends(get_db)):
-    if not get_template(db, form.template_id):
-        raise AppError("Template not found", status_code=404)
-
     fetched_template = get_template(db, form.template_id)
-
+    if not fetched_template:
+        raise AppError("Template not found", status_code=404)
     controller = Controller()
-    path = controller.fill_form(user_input=form.input_text, fields=fetched_template.fields, pdf_form_path=fetched_template.pdf_path)
-
+    path = controller.fill_form(
+        user_input=form.input_text,
+        fields=fetched_template.fields,
+        pdf_form_path=fetched_template.pdf_path
+    )
     submission = FormSubmission(**form.model_dump(), output_pdf_path=path)
     return create_form(db, submission)
 

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