onefunction

Onefunction is a software design concept that centers around a single, well-defined function as the primary unit of work for a module, service, or API. It does not refer to a specific language or library, but rather to a pattern in which complexity is managed through composition rather than internal branching within a single file.

Onefunction builds on principles from functional programming and clean architecture. The idea is that the central function acts as an orchestrator: it receives inputs, delegates tasks to smaller pure functions, handles results, and manages side effects in a controlled manner, often via dependency injection or effect handlers. The central function is typically parameterized by a configuration object and returns a new function that can be invoked with data, enabling easy testing and reuse.

In a typical implementation, the onefunction will expose a minimal public interface: a single entry point that accepts a structured input and returns a predictable output, while internal work is delegated to composable, testable helpers. The approach emphasizes a small, stable surface area and predictable behavior.

Applications include command handling, request processing pipelines, and data transformation tasks where a single point of orchestration reduces boilerplate and clarifies flow. Benefits include improved testability, easier reasoning, and better isolation of side effects; criticisms include potential over-concentration of logic into a long function and the temptation to hide complexity behind abstractions.

Related concepts include functional programming, currying, higher-order functions, single-responsibility principle, and API design.