class AppError(Exception):
    code = "internal_error"
    message = "An unexpected error occurred."

    def __init__(self, message: str | None = None) -> None:
        super().__init__(message or self.message)
        self.detail = message or self.message


class NotFoundError(AppError):
    code = "not_found"
    message = "Resource not found."


class ConflictError(AppError):
    code = "conflict"
    message = "Resource conflict."


class ValidationError(AppError):
    code = "validation_error"
    message = "Validation failed."


class UnauthorizedError(AppError):
    code = "unauthorized"
    message = "Authentication is required."


class AuthenticationFailedError(UnauthorizedError):
    code = "authentication_failed"
    message = "Invalid username or password."


class AuthSessionExpiredError(UnauthorizedError):
    code = "auth_session_expired"
    message = "Authentication session is no longer valid."


class DirectoryNotFoundError(NotFoundError):
    code = "directory_not_found"
    message = "Directory does not exist."


class DirectoryConflictError(ConflictError):
    code = "directory_conflict"
    message = "Directory already exists."


class FileNotFoundError(NotFoundError):
    code = "file_not_found"
    message = "File does not exist."


class FileConflictError(ConflictError):
    code = "file_conflict"
    message = "File already exists."


class UploadNotFoundError(NotFoundError):
    code = "upload_not_found"
    message = "Upload session does not exist."


class UploadConflictError(ConflictError):
    code = "upload_conflict"
    message = "Upload state conflict."


class RangeNotSatisfiableError(AppError):
    code = "range_not_satisfiable"
    message = "Requested byte range is not satisfiable."


class PreviewNotSupportedError(AppError):
    code = "preview_not_supported"
    message = "Preview is not supported for this file type."