Init

app/exceptions.py

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+"""
+    This file defines and handles all the errors
+    The ExceptionHandlerRoute class is used by all the routes
+"""
+
+from enum            import Enum
+from typing          import Any, Coroutine, Type
+from fastapi         import Request, Response
+from fastapi.routing import APIRoute
+from pydantic        import BaseModel, ConfigDict
+from collections.abc import Callable
+from sqlalchemy.exc  import NoResultFound, SQLAlchemyError
+
+
+class ProblemType(str, Enum):
+    ITEM_NOT_FOUND        = 'ITEM_NOT_FOUND'
+    INTERNAL_SERVER_ERROR = 'INTERNAL_SERVER_ERROR'
+    INVALID_CREDENTIALS   = 'INVALID_CREDENTIALS'
+    UNIQUE_CONSTRAINT     = 'UNIQUE_CONSTRAINT'
+    INVALID_REQUEST       = 'INVALID_REQUEST'
+    BLANK                 = 'BLANK'
+
+class ProblemDetail(BaseModel):
+    """ RFC 7807 Problem Details for HTTP APIs """
+    type   : ProblemType = ProblemType.BLANK
+    status : int | None  = None
+    title  : str | None  = None
+    detail : str | None  = None
+
+model_config = ConfigDict(from_attributes=True)
+
+class ItemNotFoundException(Exception):
+    def __init__(self, model: Type, key : Any = ""):
+        self.model = model.__name__
+        self.key   = str(key)
+
+
+class ExceptionHandlerRoute(APIRoute):
+    def get_route_handler(self) -> Callable:
+        original_route_handler = super().get_route_handler()
+
+        async def custom_route_handler(request: Request) -> Response:
+            try:
+                return await original_route_handler(request)
+            except SQLAlchemyError as exc:
+
+                problem = ProblemDetail(status = 422)
+
+                if type(exc) == NoResultFound:
+                    problem.type   = ProblemType.ITEM_NOT_FOUND
+                    problem.title  = f'{exc.model} Not Found'
+                    problem.detail = { 'key' : exc.key}
+                    problem.status = 404
+
+                elif type(exc.orig) == UniqueViolation:
+                    problem.detail = str(exc.orig).split('\n')[1].split(':  ')[1]
+                    problem.type   = ProblemType.UNIQUE_VALIDATION
+                    problem.title  = 'Unique violation'
+
+                elif type(exc.orig) == ForeignKeyViolation:
+                    problem.type   = ProblemType.FOREIGN_KEY_VIOLATION
+                    problem.title  = 'Foreign Key Violation'
+                    problem.detail = str(exc.orig).split('\n')[1].split(':  ')[1]
+
+                return JSONResponse(
+                    status_code = problem.status,
+                    content     = problem.model_dump(exclude_none = True),
+                    headers     = {'Content-Type': 'application/problem+json'} 
+                )
+                raise HTTPException(status_code = 422, detail = detail)
+
+            except Exception as exc:
+                problem        = ProblemDetail(status = 500)
+                problem.title  = 'Internal Server Error please report the bug'
+                problem.type   = ProblemType.INTERNAL_SERVER_ERROR
+                problem.detail = str(exc)
+
+                if type(exc) == ItemNotFoundException:
+                    problem.type   = ProblemType.ITEM_NOT_FOUND
+                    problem.title  = f'{exc.model} Not Found'
+                    problem.detail = { 'key' : exc.key}
+                    problem.status = 404
+
+                if type(exc) == RequestValidationError:
+                    problem.type   = ProblemType.INVALID_REQUEST
+                    problem.title  = "Input validation error" 
+                    problem.detail = exc.errors()
+                    problem.status = 422
+
+                if type(exc) == HTTPException:
+                    print(exc.status_code)
+                    problem.title  = "Credientials error" 
+                    problem.detail = exc.detail
+                    problem.status = exc.status_code
+
+
+                if problem.status == 401:
+                    problem.type = ProblemType.INVALID_CREDENTIALS
+
+                return JSONResponse(
+                    status_code = problem.status,
+                    content     = problem.model_dump(exclude_none = True),
+                    headers     = {'Content-Type': 'application/problem+json'} 
+                )
+
+        return custom_route_handler
+
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