PuduLangMediator.Compose

type: module path: "@root/src/PuduLangMediator/Compose.pudu" fidelity: Active grammar: "[[grammar/pudu]]" depth_score: 0.8 depth_status: DEEP tags: [module, backbone] aliases: [PuduLangMediator.Compose]

Purpose

One kind's pipeline from its route and the open components, composed once at build time, plus the finishers that compose each kind and answer its envelopes.

Interface

Signatures

export fn requestHandler[Q, R, E](info: &Message.Info, route: &Request.Route[Q, R, E], assembly: &Catalog.Assembly) -> Request.Handler[Q, R, E]

export fn publication[N, E](info: &Message.Info, route: &Notification.Route[N, E], assembly: &Catalog.Assembly) -> Notification.Handler[N, E]

export fn streamHandler[Q, T, E](info: &Message.Info, route: &Stream.Route[Q, T, E], assembly: &Catalog.Assembly) -> Stream.Handler[Q, T, E]

export fn requestFinish[Q, R, E](subject: Request.Kind[Q, R, E]) -> fn(Erasure.Packed, Catalog.Assembly) -> Catalog.Compiled

export fn notificationFinish[N, E](subject: Notification.Kind[N, E]) -> fn(Erasure.Packed, Catalog.Assembly) -> Catalog.Compiled

export fn streamFinish[Q, T, E](subject: Stream.Kind[Q, T, E]) -> fn(Erasure.Packed, Catalog.Assembly) -> Catalog.Compiled

Linkage

• Requires: [[src/PuduLangMediator]], [[src/PuduLangMediator/Catalog]], [[src/PuduLangMediator/Context]], [[src/PuduLangMediator/Domain/Order]], [[src/PuduLangMediator/Message]], [[src/PuduLangMediator/Notification]], [[src/PuduLangMediator/Open]], [[src/PuduLangMediator/Publishing]], [[src/PuduLangMediator/Request]], [[src/PuduLangMediator/Stream]], [[src/PuduLangMediator/Utils/Erasure]].
• Consumed by: [[src/PuduLangMediator/Mediator]], [[src/PuduLangMediator/Registration]].

Algorithm

1. A request handler is wrapped, outermost first, in: exception actions and exception handlers (actions outside for ForUnhandled, inside for ForAll), the pre-processors, the post-processors, and the behaviors in registration order.
2. Pre-processors run in registration order before the rest; post-processors run in registration order after a value; exception handlers are tried in order and the first value wins; actions all observe a failure that keeps propagating.
3. A publication collects the kind's own and the open notification handlers in registration order and hands them to the strategy as executors.
4. A stream handler is wrapped in its stream behaviors, open and its own, in registration order.

Negative Logic (Prohibited Paths)

• A layer with no components is left out entirely, so an unused feature costs nothing per message.
• Composition happens once per kind at build time; a message pays only for the closures it passes through.

Edge Cases

• A route without a handler composes to Unhandled; a build refuses such a request or stream kind first.

Depth

DEPTH 0.8 (DEEP). Tested by the suite mirroring this module under test/.

Grill Log

• Q: Why exception layers outermost and processors before behaviors? A: Exception handling must see failures from every inner layer, processors bracket the handler for every behavior to observe, and behaviors keep the order they were registered in; this is the documented order of [[decisions/ADR-0003-pipeline-order]]. _Rejected:_ processors as ordinary behaviors in registration order (their place would depend on where they were registered).
• Q: Why compose at build time? A: Every message of a kind runs the same layers; composing once leaves a lookup and a call on the hot path. _Rejected:_ composing per message.

Referenced by

[[CHANGELOG]] · [[architecture/_MOC]] · [[decisions/ADR-0003-pipeline-order]] · [[domain/Pipeline]] · [[src/PuduLangMediator]] · [[src/PuduLangMediator/Catalog]] · [[src/PuduLangMediator/Context]] · [[src/PuduLangMediator/Domain/Order]] · [[src/PuduLangMediator/Mediator]] · [[src/PuduLangMediator/Message]] · [[src/PuduLangMediator/Notification]] · [[src/PuduLangMediator/Open]] · [[src/PuduLangMediator/Publishing]] · [[src/PuduLangMediator/Registration]] · [[src/PuduLangMediator/Request]] · [[src/PuduLangMediator/Stream]] · [[src/PuduLangMediator/Utils/Erasure]] · [[src/PuduLangMediator/_MOC]] · [[subsystems/Requests]]