mesh-delivery/modules/mesh-grants/internal/buscompose/process_grants.go

package buscompose

import (
	"fmt"
	"strings"
)

// The bus account of one process of a module that declares bus (novox/hq ADR 0436 §1, §2, §3, §5).
//
// **Never the module's own account's grants, never the tool runner's.** A process's authority is read
// straight from its bus declaration — its emits, its queue's consumer, its state, whether it reads the
// records of its module's own asks, and the tools and seat verbs it calls — and nothing else: it holds no
// seat, serves no tool and hears no module stream; it answers a seat's verb only where its resource declares `serves` beside its bus (design 47 G A-109). Modelled on
// provisionerGrants, the other kind of process account the mesh mints (ADR 0349 clauses 6 and 11).

// answeredSubjects are the subscribes of the seat verbs an account answers, each seat:<seat>.<verb>: the call and tool subjects
// of each (design 47 G A-107, A-109, A-115).
func answeredSubjects(verbs []string) ([]string, error) {
	var sub []string
	for _, v := range verbs {
		seat, verb, ok := strings.Cut(strings.TrimPrefix(v, "seat:"), ".")
		if !strings.HasPrefix(v, "seat:") || !ok || seat == "" || verb == "" {
			return nil, fmt.Errorf("%q does not name a seat's verb: one serves seat:<seat>.<verb>", v)
		}
		sub = append(sub, "mesh.seat."+seat+".call."+verb+".*", "mesh.seat."+seat+".tool."+verb)
	}
	return sub, nil
}

// processGrants is one process's whole authority: to publish, and to subscribe.
func processGrants(p Principal) (pub, sub []string, err error) {
	// 1. Its own events, under its module's own namespace — the same subjects the module's own principal
	// would publish them on, had it declared them there instead (novox/hq ADR 0436 §1).
	own := "mesh.mod." + p.Module
	for _, e := range p.Emits {
		pub = append(pub, own+".event."+e)
	}

	// 2. The one durable consumer of each work-queue stream its bus names (novox/hq ADR 0436 §1, §2, §6):
	// asked about, pulled from and acknowledged, by the same name ConsumersOf composes the consumer under
	// (QueueConsumer) — and no other stream's.
	for _, q := range p.Queues {
		consumer := p.Node + "_" + p.Module + "_" + q.Process
		pub = append(pub,
			"$JS.API.CONSUMER.INFO."+q.Stream+"."+consumer,
			"$JS.API.CONSUMER.MSG.NEXT."+q.Stream+"."+consumer,
			"$JS.ACK."+q.Stream+"."+consumer+".>")
	}

	// 3. Its module's own state, by the local names its bus names alone — never the whole of what the
	// module keeps (novox/hq ADR 0436 §1), read and written as stateGrants gives any module's own bucket.
	kept := stateAccess{Module: p.Module, Node: p.Node, Keeps: p.State}
	pub = append(pub, stateGrants(kept)...)
	// And it hears each of them created, so one not on the bus at its start is bound when it appears (novox/hq issue
	// 1790; process.AwaitBucket).
	sub = append(sub, stateCreatedHeard(kept)...)

	// 4. The router's records of its module's own asks (novox/hq ADR 0436 §1, ADR 0259 §3): the same
	// direct-get subjects a module's own principal reads for the seats its Uses names that keep them —
	// read here from the one list, so the two cannot disagree.
	if p.Asks {
		pub = append(pub, SeatTrafficOf(p.Module, nil, p.Uses, nil).Records...)
	}

	// 5. The tools and seat verbs it calls (novox/hq ADR 0152, ADR 0436 §1): the same derivation a
	// module's own principal's invokes takes, so `callerNamed` (applied to every non-controller principal)
	// adds the caller-named `call` variants for it exactly as it would for a module.
	invoked, err := invokedSubjects(p.Invokes)
	if err != nil {
		return nil, nil, err
	}
	pub = append(pub, invoked...)

	// 5b. The seat verbs it answers (design 47 G A-107, A-109): its subscribe of each verb's call and tool subjects (and
	// the chunk subjects, chunks.go).
	answered, err := answeredSubjects(p.AnswersSeat)
	if err != nil {
		return nil, nil, err
	}
	sub = append(sub, answered...)

	// 6. The bus module's process (busstate.go, ADR 0595 §4, §5): every module's bus state it keeps, by name; its own
	// consumer of what its module consumes; its module's own stream's events; and its conditions through the seats its
	// module uses (the operator channel's accept.condition in its module's name).
	if p.KeepsBus {
		pub = append(pub, busStateKeeperGrants(p.KeepsBusState)...)
		// And its standing restore of the streams ADR 0436 §3 restricts, used on a `snapshot-restore` call alone (design 47 G §681, A-60).
		pub = append(pub, restoreGrants(p.KeepsRestricted)...)
		if c, ok := keeperConsumer(p); ok {
			pub = append(pub, keeperConsumerGrants(c)...)
		}
		pub = append(pub, ownStreamGrants(p.Module, p.Streams)...)
		pub = append(pub, p.SaysSeatEvents...)
		tp, ts := seatTrafficGrants(SeatTrafficOf(p.Module, nil, p.Uses, nil))
		pub, sub = append(pub, tp...), append(sub, ts...)
	}

	return pub, sub, nil
}