1. Engines as adapters, the API as its own folder

Context

Operaton, CIB seven and Camunda 7 speak the same REST API today. Nothing guarantees that this stays so: the forks release on their own schedules and have started to rename things (operatonFormRef, camundaFormRef). pulse-cli drives its commands from a catalog generated from one OpenAPI spec, and its workflow commands call that catalog directly. A difference in one engine would have had to be handled with checks of the engine name across the code base.

Decision

Three questions, three folders.

• src/engine-port: what pulse-cli needs from an engine. EnginePort (call, find, list, text, preview, route) and EngineAdapter (name, catalog, port). Types only.
• src/engines/<name>/adapter.ts: who speaks to the engine. One adapter per engine.
• src/api/<api>: which language. camunda7-rest builds the catalog and the port for every engine that speaks the Camunda 7 REST API.

Today every adapter passes through. cibseven is createCamunda7RestClient('cibseven', …). A divergence is either a catalog of its own for that engine, generated with an extra spec patch, or a wrapper around the port in its adapter.

The engine is chosen before anything is registered. flavor (profile, PULSE_CLI_FLAVOR, --flavor, default camunda7; called platform before the move to Pulse) selects the adapter in run.ts; commands, help and describe then come from its catalog.

The rules are checked. dependency-cruiser fails the build when workflow imports an adapter or an API, when anything but an adapter imports an API, when adapters or APIs import each other, or when engine-port imports more than types.

The overview is in Architecture, the engine list in Engines.

Consequences

• A difference of one engine changes its catalog or its adapter. The other engines do not move.
• The workflow commands are written once, against the port.
• One generated catalog is committed and every adapter reads it while no engine diverges.
• Existing profiles keep working: without flavor pulse-cli behaves as before. Versions without the key reject a config file that contains it.
• src/catalog, src/operation and src/http still hold the Camunda 7 REST code. They move into src/api/camunda7-rest step by step, not in one move.
• No rule forbids if (name === 'cibseven') outside src/engines/<name>. Review does.

Rejected alternatives

• One adapter for all three engines. Simple today, but the first divergence brings checks of the engine name back into shared code.
• Three copied implementations. Each engine would get the full client. Every fix would have to be made three times while the engines are still the same.
• Detecting the engine from GET /version. It costs a request before every command and fails without a reachable engine, yet help and describe must work offline. It may come later as a hint in ping.
• Domain ports such as ProcessInstances or Tasks up front. They only pay off with a second API and would be guesses until then.