package main

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"flag"
	"fmt"
	"os"
	"sort"
	"strings"

	"github.com/novox/mesh-controller/internal/broker"
	"github.com/novox/mesh-controller/internal/catalogue"
	"github.com/novox/mesh-controller/internal/inventory"
	"github.com/novox/mesh-controller/internal/licences"
	"github.com/novox/mesh-controller/internal/overlay"
)

// working out what one machine should be.
//
// Split out of main.go, which had reached 2,769 lines because appending was always the
// cheapest next step. That is how novox/hq ADR 0001 records `hal/sdk` reaching 34,636:
// nothing in it was wrong, and no one edit was the one that should have been a new file.

// notResolvable marks the one failure in planFor that is a statement about the node: its assigned
// modules do not compose. Every other failure means the mesh could not be *asked* — the store was
// unreachable, a key could not be read — and says nothing about the node at all.
//
// The distinction exists because three callers gather something across every machine and must carry
// on when one machine's set is broken. Each of them read a plain error as "their set does not
// resolve", and so read a store that was briefly unreachable as a machine that runs nothing. On the
// roster of routed names that is not a degraded answer but a false one: it states, to every machine
// at once, that another machine's names do not exist. A control node spent hours replacing every
// container it ran, on a six-minute cycle, because each pass restarted the store this is read from,
// the read failed, one name left the roster, and the roster is part of every container's identity
// (novox/hq 04-ISSUES/152, and 04-ISSUES/151 for why a changed roster is a changed container).
//
// So: skip a node that cannot resolve, and never a node that could not be read.
type notResolvable struct{ err error }

func (n notResolvable) Error() string { return n.err.Error() }
func (n notResolvable) Unwrap() error { return n.err }

// unresolvable reports whether err is a node's own set failing to compose, rather than the mesh
// being unable to answer.
func unresolvable(err error) bool {
	var n notResolvable
	return errors.As(err, &n)
}

// planFor works out everything a node should run, from what was assigned to it.
//
// A failure to compose the node's own modules is wrapped as notResolvable; every other failure is
// returned as it is. Callers gathering across the mesh must tell them apart — see notResolvable.
func planFor(ctx context.Context, open *stores, nodeName string) (catalogue.Resolution, catalogue.SettingsBy, error) {
	inv := open.inventory
	shelf, err := inv.Catalogue(ctx)
	if err != nil {
		return catalogue.Resolution{}, nil, err
	}
	assigned, err := inv.Assigned(ctx, nodeName)
	if err != nil {
		return catalogue.Resolution{}, nil, err
	}
	capabilities, err := inv.ProfileOf(ctx, nodeName)
	if err != nil {
		return catalogue.Resolution{}, nil, err
	}

	places, err := inv.Overlays(ctx)
	if err != nil {
		return catalogue.Resolution{}, nil, err
	}
	var site string
	for _, p := range places {
		if p.Name == nodeName {
			site = p.Site
		}
	}

	world, err := theRestOfTheMesh(ctx, inv, shelf, nodeName)
	if err != nil {
		return catalogue.Resolution{}, nil, err
	}
	world.Pinned, err = inv.PinsFor(ctx, nodeName)
	if err != nil {
		return catalogue.Resolution{}, nil, err
	}

	onNetwork, err := whereEveryoneIs(ctx, inv, shelf)
	if err != nil {
		return catalogue.Resolution{}, nil, err
	}

	// What this mesh can answer with a record rather than a machine, and which record each of
	// this node's modules was put on. Read across a context boundary by name, which is what
	// crossing one is allowed to carry (novox/hq ADR 0008).
	world.Licences, world.Using, err = licencesFor(ctx, open, nodeName)
	if err != nil {
		return catalogue.Resolution{}, nil, err
	}

	// The domain this node composes its routed names under (novox/hq ADR 0066). A route
	// contribution carries only a label; the resolver joins <label>.<public-domain> for this node,
	// so the fact travels on the node it belongs to rather than being looked up where the name is
	// composed.
	publicDomain, err := inv.PublicDomainOf(ctx, nodeName)
	if err != nil {
		return catalogue.Resolution{}, nil, err
	}

	// The operator account this node logs a person in as, and where its home is (novox/hq to-be
	// 29) — carried so a home-scoped file's owner and path resolve for this machine.
	who, err := inv.NodeByName(ctx, nodeName)
	if err != nil {
		return catalogue.Resolution{}, nil, err
	}

	resolved, err := catalogue.Resolve(shelf, assigned,
		catalogue.Node{Name: nodeName, Site: site, Capabilities: capabilities,
			At: onNetwork[nodeName], PublicDomain: publicDomain,
			Account: who.Account, AccountHome: who.AccountHome}, world)
	if err != nil {
		// The node's own set does not compose. Marked, because this is the only failure here that
		// a mesh-wide gatherer may pass over — see notResolvable.
		return catalogue.Resolution{}, nil, notResolvable{err}
	}

	// The credential for each thing this node takes from elsewhere. Made once and kept, so the
	// password a provider is told to create is the one its consumer was given — and sealed to
	// this node before it was ever written down, so nothing between here and there can read it.
	for i, n := range resolved.Needs {
		if n.ByRecord {
			// Answered by something the mesh holds, so there is no pair-wise secret between two
			// machines. Its key was supplied by a person and sealed to this node then; the mesh
			// discarded the plaintext and cannot make another.
			sealed, err := keyFor(ctx, open, n.From, nodeName, n.For)
			if err != nil {
				return catalogue.Resolution{}, nil, err
			}
			resolved.Needs[i].Sealed = sealed
			// If this holder is the licence's manager, hand it the manager node's PUBLIC sealing key
			// in its bound facts (novox/hq ADR 0050). It is safe to disclose — a public key — and it
			// is what the manager module needs to re-seal a rotated refresh token to this same node,
			// having been given no private key of its own. A consumer holder gets none.
			pub, err := managerPublicKeyFor(ctx, open, inv, n.From, nodeName, n.For)
			if err != nil {
				return catalogue.Resolution{}, nil, err
			}
			if pub != "" {
				serves := map[string]any{}
				for k, v := range resolved.Needs[i].Serves {
					serves[k] = v
				}
				serves["manager_public_key"] = pub
				resolved.Needs[i].Serves = serves
				// The manager holder: its empty pre-adoption refresh token is a waiting state, not a
				// missing consumer key, so the declaration tolerates it rather than refusing.
				resolved.Needs[i].Manager = true
			}
			continue
		}
		var secret inventory.Secret
		var err error
		if n.SharedOwn != "" {
			// The provider's one credential, sealed to this consumer too (novox/hq ADR 0158).
			secret, err = inv.SharedSecretFor(ctx, n.Name, nodeName, n.For, n.From, providerModuleOf(resolved, open, ctx, n), n.Local, n.SharedOwn)
		} else {
			secret, err = inv.SecretFor(ctx, n.Name, nodeName, n.For, n.From, n.Local)
		}
		if err != nil {
			// Said rather than skipped. A machine that resolves cleanly and receives no
			// credential is one that will fail to authenticate at some later, less obvious
			// moment.
			return catalogue.Resolution{}, nil, fmt.Errorf(
				"%s on %s needs %s from %s and no credential could be made for it: %w",
				n.For, nodeName, n.Name, n.From, err)
		}
		resolved.Needs[i].Sealed = secret.ForConsumer
	}

	// Settings for everything that resolved, including modules nobody assigned directly: a
	// requirement pulled in by something else is still configurable, and finding out that it is
	// not only when you try would be an arbitrary line nobody could predict.
	//
	// A setting that reaches nothing, or cannot compose with the definition it was stored for,
	// no longer refuses the machine here: it is judged where it is stored, and a definition that
	// moved under it costs that module its place in the declaration, said by name (novox/hq ADR
	// 0163, rule 6 — see Compose).
	settings := catalogue.SettingsBy{}
	for _, m := range resolved.Modules {
		layers, err := inv.SettingsFor(ctx, nodeName, m.Module)
		if err != nil {
			return catalogue.Resolution{}, nil, err
		}
		if len(layers) == 0 {
			continue
		}
		settings[m.Module] = layers
	}
	return resolved, settings, nil
}

// theRestOfTheMesh is what every other node holds and offers.
//
// Two things at once because they come from the same place — resolving the other nodes — and
// because both are facts about what is actually running rather than records that could disagree
// with it. A claim is held by whatever a node runs; a provision is offered by whatever a node
// runs; neither is a table somebody keeps up to date.
//
// **Two passes over the others.** What a node offers the mesh needs that node resolved, and
// resolving it may need what the mesh offers. So the first pass takes brokered requirements on
// trust and answers only *what does each node offer*; the second answers everything with that in
// hand. Nothing is ever declared from the first.
func theRestOfTheMesh(ctx context.Context, inv *inventory.Inventory,
	shelf map[string]catalogue.Manifest, exclude string) (catalogue.World, error) {

	// Every node, not only the placed ones. A machine that was never put on the private network
	// still runs modules, still holds claims, and still offers whatever it offers.
	// **Who holds each seat on record, before anything is resolved** (novox/hq ADR 0131). Both
	// passes below need it: without it, the assignment standing beside a seat's holder — the next
	// holder, waiting for the handover — is refused as a second holder, and its node's whole set
	// with it.
	holdings, err := inv.Holdings(ctx)
	if err != nil {
		return catalogue.World{}, err
	}

	nodes, err := inv.Nodes(ctx)
	if err != nil {
		return catalogue.World{}, err
	}
	places, err := inv.Overlays(ctx)
	if err != nil {
		return catalogue.World{}, err
	}
	siteOf := map[string]string{}
	for _, p := range places {
		siteOf[p.Name] = p.Site
	}
	// Which machines are actually on the private network, and what they are called there. Not
	// "has an address" — that was true of every placed machine and told you nothing about whether
	// anything could reach it. It is what resolved the module.
	onNetwork, err := whereEveryoneIs(ctx, inv, shelf)
	if err != nil {
		return catalogue.World{}, err
	}

	type candidate struct {
		node     catalogue.Node
		assigned []string
	}
	var others []candidate
	for _, n := range nodes {
		if n.Name == exclude {
			continue
		}
		theirs, err := inv.Assigned(ctx, n.Name)
		if err != nil || len(theirs) == 0 {
			continue
		}
		caps, _ := inv.ProfileOf(ctx, n.Name)
		others = append(others, candidate{
			catalogue.Node{Name: n.Name, Site: siteOf[n.Name], Capabilities: caps,
				At: onNetwork[n.Name]}, theirs})
	}

	offered := map[string][]catalogue.Provider{}
	var firstHeld []catalogue.Held
	for _, o := range others {
		got, err := catalogue.Resolve(shelf, o.assigned, o.node, catalogue.World{Unchecked: true, Holdings: holdings})
		if err != nil {
			// Said, not skipped: a machine dropped here offers nothing and holds nothing as far
			// as every other machine's plan can tell (novox/hq issue 188).
			fmt.Fprintf(os.Stderr, "%s is left out of the rest of the mesh: it does not resolve: %v\n", o.node.Name, err)
			continue
		}
		firstHeld = append(firstHeld, got.Claims...)
		for _, m := range got.Modules {
			for _, name := range m.OffersAt(catalogue.ScopeMesh) {
				// What that module says a consumer needs to know, with that node's settings on
				// it: a port somebody moved on the provider is a port its consumers must be told
				// about, and the two coming from different places is how they come to disagree.
				serves, err := servedOnNode(ctx, inv, o.node.Name, m, name)
				if err != nil {
					return catalogue.World{}, err
				}
				offered[name] = append(offered[name], catalogue.Provider{
					Node: o.node.Name, At: o.node.At, Serves: serves, Module: m.Module})
			}
		}
	}
	for k := range offered {
		sort.Slice(offered[k], func(i, j int) bool {
			return offered[k][i].Node < offered[k][j].Node
		})
	}

	// **The second pass is given the first pass's holdings.** A seat's holder answers a requirement
	// with several providers (novox/hq ADR 0110), so a node consuming one resolves only once the
	// holder is known. Without them its set is refused here, and a refused node's own claims drop
	// out of what the mesh holds — so a second holder of one of its seats would pass unrefused.
	world := catalogue.World{Offered: offered, Held: firstHeld, Holdings: holdings}
	var held []catalogue.Held
	for _, o := range others {
		// Each machine is resolved with its own pins, as its plan is: a machine that needs one to
		// settle two providers would otherwise be refused here and vanish from the mesh — every
		// seat it holds unheld, every build that needs one refused (2026-10-01, the control node;
		// novox/hq issue 188).
		theirs := world
		if pins, err := inv.PinsFor(ctx, o.node.Name); err == nil {
			theirs.Pinned = pins
		}
		got, err := catalogue.Resolve(shelf, o.assigned, o.node, theirs)
		if err != nil {
			// Said only for the whole-mesh view. With one machine excluded, the others are
			// resolved without its offers, and one that consumes them cannot resolve here by
			// design — that is not the machine being dropped, it is the view being partial.
			if exclude == "" {
				fmt.Fprintf(os.Stderr, "%s is left out of the rest of the mesh: it does not resolve: %v\n", o.node.Name, err)
			}
			continue
		}
		held = append(held, got.Claims...)
	}
	world.Held = held
	return world, nil
}

// declarationFor is everything a node would be sent.
//
// One place, because there were three and one of them was written before credentials existed and
// silently produced a declaration missing them — a difference between what `plan` showed and what
// `plan --json` handed to anything reading it.
func declarationFor(ctx context.Context, open *stores, node string,
	plan catalogue.Resolution, settings catalogue.SettingsBy) (sendable, error) {
	gens, err := generators(ctx, open)
	if err != nil {
		return sendable{}, err
	}
	// **Allocating, because `plan` is the send without the sending.** It is one machine, named by
	// a person, who is asking what a push would do — so the port it shows and the secret it seals
	// have to be the ones a push would use, and both are kept once chosen. Showing numbers that a
	// later push would replace would make the command answer a question nobody asked.
	//
	// The line is not "a question may not write". It is who is asking and how often: this is a
	// person, about one machine, on purpose. What may not write is the comparison the mesh runs
	// over every machine to answer whether each is up to date — see Choosing.
	return declarationWith(ctx, open, node, plan, settings, gens, Allocating)
}

// declarationWith is the same, for a caller that has already worked out the generators once and
// is about to use them for every node.
// Choosing says whether this composition may allocate what has not been allocated yet.
//
// **The comparison the mesh runs over every machine must not change what it is comparing.**
// Composing a declaration assigns each module a machine port and seals its secrets, and `status`
// composes one for every node to answer *is this machine running what I would send it* — so that
// question allocated, minted, wrote, and contended with the very machine it was asking about. A
// status polled every two seconds while a node applies is then two writers on the same rows,
// which is how it came to hang rather than answer.
//
// `plan` sits on the other side of this and allocates, because it is a person asking what a push
// would do to one named machine. The distinction is not question versus command; it is a person
// asking once about one machine versus the mesh asking continuously about all of them.
//
// So the mesh chooses a port when it commits to sending one, and every other caller reads what
// was chosen. A module with nothing assigned yet has never been sent, which is exactly what a
// machine "waiting" means — the read needs no number to be right about that.
type Choosing bool

const (
	// Allocating is the send path: what is not assigned yet is assigned now and kept.
	Allocating Choosing = true
	// Reading is every question: what is assigned is used, and nothing is created.
	Reading Choosing = false
)

func declarationWith(ctx context.Context, open *stores, node string,
	plan catalogue.Resolution, settings catalogue.SettingsBy,
	gens map[string]catalogue.Generator, choosing Choosing) (sendable, error) {
	with, record, err := renderingFor(ctx, open, node, plan, settings, gens, choosing)
	if err != nil {
		return sendable{}, err
	}
	composed, err := plan.Compose(with)
	if err != nil {
		return sendable{}, err
	}
	// And what was taken on it, said in every declaration it is sent from this one place.
	adoption, err := adoptionOf(ctx, open.inventory, record, plan, composed)
	if err != nil {
		return sendable{}, err
	}
	return sendable{Resources: composed.Resources, Adoption: adoption,
		Received: composed.Received, Mesh: with.Mesh,
		LeftOut: sortedKeysOf(composed.LeftOut), leftOutWhy: composed.LeftOut}, nil
}

// sortedKeysOf is a map's keys, sorted — so what a declaration says it left out does not move
// for a reordering nobody made.
func sortedKeysOf(m map[string]string) []string {
	if len(m) == 0 {
		return nil
	}
	out := make([]string, 0, len(m))
	for k := range m {
		out = append(out, k)
	}
	sort.Strings(out)
	return out
}

// reportLeftOut says which of a machine's modules its declaration leaves out and why (novox/hq ADR
// 0163, rule 6), one line each: the machine is told everything else, and is told it was left out.
func reportLeftOut(node string, declared sendable) {
	for _, m := range declared.LeftOut {
		fmt.Printf("%s: %s left out — a setting stored for it cannot compose with its definition; "+
			"what the machine holds for it is kept and its containers are untouched. %s\n",
			node, m, declared.leftOutWhy[m])
	}
}

// renderingFor is everything a node's declaration is composed with, and the node's record.
func renderingFor(ctx context.Context, open *stores, node string,
	plan catalogue.Resolution, settings catalogue.SettingsBy,
	gens map[string]catalogue.Generator, choosing Choosing) (catalogue.Rendering, inventory.Node, error) {
	inv := open.inventory
	grants, err := grantsFor(ctx, open, node)
	if err != nil {
		return catalogue.Rendering{}, inventory.Node{}, err
	}
	// Where this machine puts what each module needs reachable (novox/hq ADR 0038).
	//
	// **Assigned here rather than written by a module**, because a module is written once and
	// assigned anywhere: any number it picks is a guess about a machine it has never seen. Made
	// before the declaration is composed, because the container's mapping, the rule set and what a
	// consumer is told are all derived from it.
	// What this machine was already given, for a composition that may not allocate.
	already := map[string]map[int]int{}
	if choosing == Reading {
		held, err := inv.PortsFor(ctx, node)
		if err != nil {
			return catalogue.Rendering{}, inventory.Node{}, err
		}
		for _, a := range held {
			if already[a.Module] == nil {
				already[a.Module] = map[int]int{}
			}
			already[a.Module][a.Wanted] = a.Machine
		}
	}

	// The machine ports this node was given for its modules (novox/hq ADR 0100): the foundation's
	// ports, as genesis chose them. A given port wins over anything assigned and over a manifest's
	// own long-form mapping.
	given := map[string]map[int]int{}
	for _, m := range plan.Modules {
		g, err := catalogue.GivenPorts(m, settings[m.Module])
		if err != nil {
			// A given port its definition no longer publishes: the module is left out of the
			// declaration, by name, when it is composed (novox/hq ADR 0163, rule 6) — never the
			// machine refused here for it.
			continue
		}
		if g != nil {
			given[m.Module] = g
		}
	}
	// And one holder per machine port across the node's modules: settings written before this was
	// refused where they are set are refused here rather than composed into two containers on
	// one port.
	holders := map[int]string{}
	for _, m := range plan.Modules {
		for _, at := range given[m.Module] {
			if other, twice := holders[at]; twice && other != m.Module {
				return catalogue.Rendering{}, inventory.Node{}, fmt.Errorf("%w: %s and %s are "+
					"both given machine port %d on %s", inventory.ErrPortTaken, other, m.Module,
					at, node)
			}
			holders[at] = m.Module
		}
	}

	ports := map[string]map[int]int{}
	for _, m := range plan.Modules {
		for _, l := range m.Listens {
			if at, isGiven := given[m.Module][l.Port]; isGiven {
				if ports[m.Module] == nil {
					ports[m.Module] = map[int]int{}
				}
				ports[m.Module][l.Port] = at
				continue
			}
			// **Only a port the module actually publishes is the mesh's to move.** A container's
			// mapping is the thing that translates; without one the software binds what it binds,
			// and an assignment would not move the service — it would open the wrong number in the
			// rule set and leave the real one shut. Recorded either way, because this map means
			// *where this module's port is on this machine* and every reader of it needs that
			// answer whether or not the mesh was the one who chose it.
			where, mayAssign := m.MachineSide(l.Port)
			switch {
			case mayAssign && choosing == Allocating:
				at, err := inv.PortFor(ctx, node, m.Module, l.Port, l.Fixed)
				if err != nil {
					return catalogue.Rendering{}, inventory.Node{}, fmt.Errorf(
						"%s needs %d reachable on %s and it could not be assigned: %w",
						m.Module, l.Port, node, err)
				}
				where = at.Machine
			case mayAssign:
				// Whatever was chosen last time, and nothing if there was no last time.
				if at, known := already[m.Module][l.Port]; known {
					where = at
				}
			}
			if ports[m.Module] == nil {
				ports[m.Module] = map[int]int{}
			}
			ports[m.Module][l.Port] = where
		}
	}

	// And each module's own secrets — a superuser password, an administrator, an account. Made
	// per node, so a module running on three machines has three.
	needed := map[string]map[string]string{}
	for _, m := range plan.Modules {
		for name := range m.OwnSecrets {
			// Minted on the send path and only read on every other. Making one is an insert, and
			// a question that writes is a question that can block against the machine it is about.
			var sealed string
			var err error
			if choosing == Allocating {
				// **The broker credential is never invented here** (novox/hq issue 203). Every other
				// own secret is the mesh's to make — a password nobody else knows — but this one
				// is an account on the bus, minted by `module issue` and sealed by it; a push that
				// made a random one would deliver a file the process cannot read and report the
				// machine applied. Refused by name, with the verb.
				if name == "broker" {
					user := broker.Principal{Kind: broker.KindModule, Node: node, Module: m.Module}.Username()
					if _, minted, err := inv.BusUserHash(ctx, user); err != nil {
						return catalogue.Rendering{}, inventory.Node{}, err
					} else if !minted {
						return catalogue.Rendering{}, inventory.Node{}, fmt.Errorf(
							"%s on %s has no bus credential: nothing was issued for %s, and a push "+
								"would seal a placeholder its process cannot read (novox/hq issue 203). "+
								"`module issue %s --node %s`, then push again",
							m.Module, node, user, m.Module, node)
					}
				}
				sealed, err = inv.SecretForModule(ctx, node, m.Module, name)
			} else {
				var held bool
				sealed, held, err = inv.ModuleSecretIfIssued(ctx, node, m.Module, name)
				if err == nil && !held {
					// Never issued, so this machine cannot be running it. Left out rather than
					// invented: an empty string here would compose a declaration that differs
					// from what would be sent, and the comparison this feeds would then be
					// answering about a declaration nothing will ever push.
					continue
				}
			}
			if err != nil {
				return catalogue.Rendering{}, inventory.Node{}, err
			}
			if needed[m.Module] == nil {
				needed[m.Module] = map[string]string{}
			}
			needed[m.Module][name] = sealed
		}
	}
	// And a certificate for this machine's name inside the mesh, when anything on it asks. Issued
	// rather than stored: the node's key does not change, so signing again produces an equally
	// valid certificate and there is nothing to keep in step.
	var certificate, authority string
	for _, m := range plan.Modules {
		if m.Certificate == nil {
			continue
		}
		issued, meshCA, err := certificateFor(ctx, open, node)
		if err != nil {
			return catalogue.Rendering{}, inventory.Node{}, err
		}
		certificate, authority = issued, meshCA
		break
	}

	// And who else is on the private network, which is what a rule saying "from the mesh"
	// resolves to. Every node's address, including this one's: a machine reaching itself by its
	// own overlay address rather than by loopback is ordinary, and leaving it out would filter
	// the node's own traffic to itself with no rule naming why.
	// One reading of the catalogue for the three questions below that resolve the whole mesh.
	shelf, err := inv.Catalogue(ctx)
	if err != nil {
		return catalogue.Rendering{}, inventory.Node{}, err
	}
	private, err := onThePrivateNetwork(ctx, inv, shelf)
	if err != nil {
		return catalogue.Rendering{}, inventory.Node{}, err
	}
	// The private network's range, offered to a module as ${machine:mesh-range} — a module that must
	// name the whole mesh (an intrusion filter that must never ban a tunnel peer) names it here
	// rather than hardcoding a value it cannot know.
	meshRange, err := overlayRange(ctx, inv)
	if err != nil {
		return catalogue.Rendering{}, inventory.Node{}, err
	}

	// The artifact store as this node reaches it now — the address every image and archive the
	// mesh built is fetched through, composed here and recorded nowhere — with what the mesh has
	// built, so a reference recorded with an address before that is re-routed too.
	artifactStore, err := artifactStoreAddress(ctx, inv, shelf, node)
	if err != nil {
		return catalogue.Rendering{}, inventory.Node{}, err
	}
	held, err := inv.Held(ctx)
	if err != nil {
		return catalogue.Rendering{}, inventory.Node{}, err
	}
	built := make(map[string]bool, len(held))
	for repository := range held {
		built[repository] = true
	}

	// And every machine's name, so a container can reach one. The same set that writes the
	// machine's own hosts file — one reading, so a container and its machine cannot disagree
	// about where another machine is.
	names, err := namesInTheMesh(ctx, inv, shelf)
	if err != nil {
		return catalogue.Rendering{}, inventory.Node{}, err
	}

	// Each machine's operator account, so an ssh Host block can name the login for every node
	// (novox/hq to-be 29). Keyed by the bare node name, which entriesFrom falls back to.
	allNodes, err := inv.Nodes(ctx)
	if err != nil {
		return catalogue.Rendering{}, inventory.Node{}, err
	}
	accounts := map[string]string{}
	for _, n := range allNodes {
		if n.Account != "" {
			accounts[n.Name] = n.Account
		}
	}

	// **The roster is the machines and nothing else** (novox/hq ADR 0191). Each node has one internal
	// domain, `<node>.internal`, and every route on it is a name under that domain (ADR 0151), which
	// the resolver answers with one wildcard per machine — so no route needs a line of its own. A
	// node's public domains are the operator's and public DNS answers them; the mesh gives no private
	// answer for any of them. The roster once carried every routed name, public ones included, and a
	// resolver that also serves a LAN handed a phone a tunnel address for the mail server.
	// `.Names` and `.Machines` stay two fields so a module's template keeps rendering (issue 111).
	machines := make(map[string]string, len(names))
	for name, at := range names {
		machines[name] = at
	}

	// **The bus is never public** (novox/hq ADR 0169). It was a foundation port — widened from the
	// broker's own `from: mesh` to from-anywhere on the broker's host, so a machine could enrol
	// before it had an address on the private network. A machine joins through the tunnel now, and
	// every link to the bus crosses it, so its reach is what the `nats` module declares: the mesh.
	// Nothing the mesh itself needs is opened beyond what a module declares.
	var foundation []int

	// And, for a module that keeps them, every operator-sealed secret in the mesh — the vault's
	// copy, outside the store (novox/hq ADR 0085, amended). Read only; nothing here mints. The
	// export changes whenever any secret in the mesh is made or rotated, so the vault's declaration
	// changes with it and the vault node is sent again: that is what keeps its copy current, and
	// the cost is one two-table read per composition of the vault's node, in every mode.
	var kept *catalogue.KeptExport
	for _, m := range plan.Modules {
		if m.Keeps == "" {
			continue
		}
		if kept, err = inv.OperatorExport(ctx); err != nil {
			return catalogue.Rendering{}, inventory.Node{}, err
		}
		break
	}

	// Whether this node is adopted (novox/hq ADR 0100): then the found firewall stays in force, and
	// the declaration carries openings and the mesh's guard in place of a filter.
	record, err := inv.NodeByName(ctx, node)
	if err != nil {
		return catalogue.Rendering{}, inventory.Node{}, err
	}
	// And, on an adopted node, which modules were taken there: the guard is derived from those
	// only (novox/hq ADR 0103).
	var taken map[string]bool
	if record.Adopted {
		list, err := inv.Taken(ctx, node)
		if err != nil {
			return catalogue.Rendering{}, inventory.Node{}, err
		}
		taken = map[string]bool{}
		for _, m := range list {
			taken[m] = true
		}
	}
	// Where this node put the foundation's servers, for the control plane's own connections
	// (novox/hq 04-ISSUES/102): read from the node's settings for whatever claims each seat,
	// exactly as a consumer's binding is, never from what genesis wrote into a secret.
	seats, err := seatsOn(ctx, inv, shelf, node, plan.Modules, record.Adopted, taken)
	if err != nil {
		return catalogue.Rendering{}, inventory.Node{}, err
	}
	// The bus's user list, for the machine that runs the bus. Composed per push rather than kept,
	// because it is a function of the mesh's records and a kept copy could disagree with them.
	busUsers, err := composeBusUsers(ctx, inv, plan.Modules)
	if err != nil {
		return catalogue.Rendering{}, inventory.Node{}, err
	}
	memberships, err := inv.BusMemberships(ctx)
	if err != nil {
		return catalogue.Rendering{}, inventory.Node{}, err
	}
	// Which of this machine's links face outside, which is what the derived filter is written
	// around (novox/hq ADR 0140). Reported by the machine, never set.
	outwardLinks, err := inv.OutwardLinksOf(ctx, node)
	if err != nil {
		return catalogue.Rendering{}, inventory.Node{}, err
	}
	return catalogue.Rendering{
		BusMembership: memberships[node],
		Settings:      settings, Generators: gens, Grants: grants, Needed: needed, Ports: ports,
		Certificate: certificate, Authority: authority, Mesh: private, Names: names,
		Machines: machines,
		Suffix:   overlay.Suffix(), MeshRange: meshRange, TunnelInterface: overlay.Interface, Accounts: accounts, Foundation: foundation,
		Kept: kept, Adopted: record.Adopted, OutwardLinks: outwardLinks,
		Given: given, Taken: taken, Seats: seats, ArtifactStore: artifactStore, Built: built,
		BusUsers: busUsers,
	}, record, nil
}

// certificateFor is what the mesh certifies about one machine's internal name.
//
// It reaches across two contexts and reads neither one's store from the other: `inventory` knows
// the machine and whether it is on the private network, `identity` holds the authority and the
// key that machine reported. The process holding both grants asks each for its part
// (novox/hq ADR 0008).
func certificateFor(ctx context.Context, open *stores, node string) (string, string, error) {
	inv := open.inventory
	ident, err := open.Identity(ctx)
	if err != nil {
		return "", "", err
	}

	record, err := inv.NodeByName(ctx, node)
	if err != nil {
		return "", "", err
	}
	serving, err := ident.ServingKeyOf(ctx, record.ID)
	if err != nil {
		return "", "", err
	}
	if serving == "" {
		// The machine joined before it had one, or never reported it. Said plainly, because the
		// remedy is on the machine and no amount of pushing from here will produce one.
		return "", "", fmt.Errorf(
			"%s wants a certificate and has never told the mesh what key it serves with; it "+
				"joins again to report one", node)
	}

	// The name it is certified for. Only a machine on the private network has one — a certificate
	// for a name nothing resolves is a certificate nothing can check.
	//
	// With the catalogue, not without it. Being on the private network is a conclusion about what
	// a node resolves to, so a nil shelf resolves nothing and every machine looks like it is on no
	// network — which refused every certificate the mesh was asked for, and said the machine was
	// not on a network it plainly was.
	shelf, err := inv.Catalogue(ctx)
	if err != nil {
		return "", "", err
	}
	where, err := whereEveryoneIs(ctx, inv, shelf)
	if err != nil {
		return "", "", err
	}
	name := where[node]
	if name == "" {
		return "", "", fmt.Errorf(
			"%s wants a certificate and is not on the private network, so it has no name inside "+
				"the mesh to be certified for", node)
	}

	issued, err := ident.Certify(ctx, node, name, serving)
	if err != nil {
		return "", "", err
	}
	authority, err := ident.EstablishAuthority(ctx)
	if err != nil {
		return "", "", err
	}
	return issued, authority.Certificate, nil
}

// grantsFor is every credential this node must create, because something elsewhere uses it.
//
// The mirror of what a consumer is given, and the half that makes the credential real: a password
// nothing was told to create is a password that authenticates nowhere. Sealed to this node, so
// the mesh hands over something it cannot itself use.
func grantsFor(ctx context.Context, open *stores, node string) ([]catalogue.Grant, error) {
	inv := open.inventory
	issued, err := inv.SecretsFrom(ctx, node)
	if err != nil {
		return nil, err
	}

	// Where each consumer is, so a provider that must reach back to one does not have to know how
	// the mesh names machines.
	shelf, err := inv.Catalogue(ctx)
	if err != nil {
		return nil, err
	}
	onNetwork, err := whereEveryoneIs(ctx, inv, shelf)
	if err != nil {
		return nil, err
	}

	// What each consumer actually asked for, taken from that machine's own resolution rather than
	// from a record beside it. A provider told to create a password and not what to create it for
	// can do nothing with it, and the name a consumer wants is the consumer's to say.
	out := make([]catalogue.Grant, 0, len(issued))
	for _, s := range issued {
		plan, settings, err := planFor(ctx, open, s.Consumer)
		switch {
		case unresolvable(err):
			// Their set does not resolve. Skipped rather than fatal: this node is not the place
			// to report another machine's problem, and a grant for something that is not going to
			// run would have the provider create a user nothing uses.
			continue
		case err != nil:
			// The mesh could not be asked what they wanted, which is not the same as their wanting
			// nothing — and withholding a grant on that reading takes a consumer's access away
			// (novox/hq 04-ISSUES/152).
			return nil, fmt.Errorf("what %s asked of %s cannot be read: %w", s.Consumer, s.Name, err)
		}
		values, asks, err := plan.ContributionsFrom(s.Name, s.ConsumerModule, settings)
		if err != nil {
			return nil, err
		}
		// A port in there is the consumer's software port until this. The consumer is on another
		// machine, so the assignment that moved it is that machine's — fetched here rather than
		// looked for in this one's, which is the whole reason the co-located fix could not reach
		// this case (novox/hq 04-ISSUES/038, the cross-node half).
		published, err := portsOn(ctx, inv, s.Consumer, s.ConsumerModule)
		if err != nil {
			return nil, err
		}
		values = catalogue.AtPublishedPort(values, s.ConsumerModule, published)
		from := s.ConsumerModule
		if !asks {
			// That module no longer wants this. Left empty, which is what the declaration reads
			// as "nobody asks for it any more" — and is how a login is withdrawn rather than kept
			// working for ever after its consumer went away.
			from = ""
		}
		// The consumer's identity slug, from its own manifest, carried on the grant so the provider
		// derives the same login the consumer does (novox/hq ADR 0049). Refused here if it still would
		// not fit the tightest backend — the mesh chose the name, so the mesh refuses it, with the
		// remedy a short slug rather than a login a provider silently shortened.
		slug := ""
		for _, mm := range plan.Modules {
			if mm.Module == s.ConsumerModule {
				slug = mm.Slug
				break
			}
		}
		if from != "" {
			if err := catalogue.CheckIdentity(s.Consumer, catalogue.IdentitySource(slug, s.ConsumerModule)); err != nil {
				return nil, err
			}
		}
		out = append(out, catalogue.Grant{
			Provision: s.Name, Consumer: s.Consumer, At: onNetwork[s.Consumer],
			From: from, Values: values, Slug: slug, Sealed: s.ForProvider, Local: s.Local})
	}
	return out, nil
}

// listensLines is what a person is told about what this module would open, and why — the same
// `why` every listens entry already carries for the firewall it also feeds (novox/hq ADR 0007), so
// deciding whether to assign a module can see what it would open before it opens it, not only
// after. A module with nothing to listen on prints nothing extra, same as today.
func listensLines(m catalogue.Manifest) []string {
	var out []string
	for _, l := range m.Listens {
		if l.Why == "" {
			out = append(out, fmt.Sprintf("    listens %d/%s from %s", l.Port, l.At(), l.From))
			continue
		}
		out = append(out, fmt.Sprintf("    listens %d/%s from %s — %s", l.Port, l.At(), l.From, l.Why))
	}
	return out
}

func planCommand(ctx context.Context, args []string) error {
	set := flag.NewFlagSet("plan", flag.ContinueOnError)
	// Because "one resource" does not tell you whether the settings landed. Being able to read
	// the file before it is sent is the difference between believing a merge worked and knowing.
	show := set.Bool("files", false, "print the files this node would be given")
	// The declaration exactly as the node would receive it. For handing to something else --
	// checking it against the host's own parser, most usefully, which is the only way to know
	// that what the control plane emits is what the host accepts.
	asJSON := set.Bool("json", false, "print the declaration this node would be sent")
	positionals, err := parseAround(set, args)
	if err != nil {
		return err
	}
	if len(positionals) != 1 {
		return errors.New("plan <node> [--files] [--json]")
	}
	args = positionals
	open, err := openStores(ctx)
	if err != nil {
		return err
	}
	defer open.Close()

	plan, settings, err := planFor(ctx, open, args[0])
	if err != nil {
		return err
	}
	if len(plan.Modules) == 0 {
		fmt.Printf("%s is assigned nothing\n", args[0])
		return nil
	}
	if *asJSON {
		declared, err := declarationFor(ctx, open, args[0], plan, settings)
		if err != nil {
			return err
		}
		// The bytes a push would send, indented: one marshaller, so `plan --json` cannot show an
		// envelope other than the one sent.
		body, err := declared.Body()
		if err != nil {
			return err
		}
		var indented bytes.Buffer
		if err := json.Indent(&indented, body, "", "  "); err != nil {
			return err
		}
		fmt.Println(indented.String())
		return nil
	}

	// Which modules a push would leave out, and why — said before the plan, since the plan is of
	// what the machine would be told (novox/hq ADR 0163, rule 6). Judged, never composed: `plan`
	// without --json allocates nothing.
	if record, err := open.inventory.NodeByName(ctx, args[0]); err == nil {
		left := plan.LeftOut(settings, record.Adopted)
		reportLeftOut(args[0], sendable{LeftOut: sortedKeysOf(left), leftOutWhy: left})
	}
	// And a setting that reaches nothing — refused where it is stored, and said here for one
	// stored before its definition moved from under it.
	for _, m := range plan.Modules {
		for _, stray := range catalogue.UnusedSettings(m, settings[m.Module]) {
			fmt.Printf("%s: a setting reaches nothing — %s\n", args[0], stray)
		}
	}
	fmt.Printf("%s would run:\n", args[0])
	for _, m := range plan.Modules {
		fmt.Printf("  %-20s %s\n", m.Module, plan.Because[m.Module])
		for _, line := range listensLines(m) {
			fmt.Println(line)
		}
	}
	// What was assigned here and cannot run here. Said with the rest rather than as a refusal: it is
	// one module on the wrong machine, the others still run, and the remedy is to move this one.
	for _, u := range plan.Unhostable {
		for _, c := range u.Missing {
			fmt.Printf("  %-20s not applied — %s\n", u.Module, catalogue.WrongMachine(u.Module, c, args[0]))
		}
	}
	for _, c := range plan.Claims {
		fmt.Printf("  holds %s, one per %s\n", c.Claim, c.Scope)
	}
	// What this machine depends on that is not on it. Worth saying out loud: it is the only part
	// of a node's set that stops working when a *different* machine goes away, and nothing else
	// in this output would have told anybody that.
	for _, n := range plan.Needs {
		fmt.Printf("  needs %s from %s, for %s\n", n.Name, n.From, n.For)
	}
	declared, err := declarationFor(ctx, open, args[0], plan, settings)
	if err != nil {
		return err
	}
	resources := declared.Resources
	for module, layers := range settings {
		for _, layer := range layers {
			fmt.Printf("  %-20s settings from %s\n", module, layer.From)
		}
	}
	fmt.Printf("\n%d resource(s)\n", len(resources))

	if *show {
		for _, r := range resources {
			content, ok := r["content"].(string)
			if !ok {
				continue
			}
			fmt.Printf("\n--- %s ---\n%s", shownAs(r), content)
		}
	}
	return nil
}

// shownAs is the heading `plan --show` puts over a resource's content.
//
// **A file written into says so.** Its content is the mesh's part of a file that is otherwise the
// machine's — the keys of a JSON document (novox/hq ADR 0102), the region of a hosts file (issue
// 128). Shown under a bare path it reads as the whole file, and a person checking what a take
// replaces would see a hosts file of a dozen lines where the machine keeps thirty.
func shownAs(r map[string]any) string {
	heading := fmt.Sprintf("%v  %v", r["id"], r["path"])
	if into, ok := r["into"].(string); ok && into != "" {
		heading += fmt.Sprintf(" (written into, %s)", into)
	}
	return heading
}

// licencesFor is what this node can be answered with by record, and what it was put on.
//
// A mesh with no licences at all is the ordinary case and must not be an error: every existing
// mesh is one, and a control plane that refused to plan because nobody had bought an API key
// would be unusable for the thing it already does.
func licencesFor(ctx context.Context, open *stores, node string) (
	map[string][]catalogue.Record, map[string]map[string]catalogue.Record, error) {

	held, err := open.Licences(ctx)
	if err != nil {
		return nil, nil, err
	}

	all, err := held.All(ctx)
	if err != nil {
		return nil, nil, err
	}
	if len(all) == 0 {
		return nil, nil, nil
	}

	offered := map[string][]catalogue.Record{}
	byName := map[string]catalogue.Record{}
	for _, one := range all {
		record := catalogue.Record{Name: one.Name, Serves: one.Serves}
		offered[licences.Provision] = append(offered[licences.Provision], record)
		byName[one.Name] = record
	}

	using := map[string]map[string]catalogue.Record{}
	for _, one := range all {
		holders, err := held.HoldersOf(ctx, one.Name)
		if err != nil {
			return nil, nil, err
		}
		for _, h := range holders {
			if h.Node != node {
				continue
			}
			if using[h.Module] == nil {
				using[h.Module] = map[string]catalogue.Record{}
			}
			using[h.Module][licences.Provision] = byName[one.Name]
		}
	}
	return offered, using, nil
}

// keyFor is the licence key sealed to one machine, for one module.
//
// **Empty is not an error here.** The mesh discarded the plaintext when it was supplied, so a
// holder recorded afterwards genuinely has no key — and the declaration refuses that by name,
// where the module and the path are both in view, rather than here.
func keyFor(ctx context.Context, open *stores, licence, node, module string) (string, error) {
	held, err := open.Licences(ctx)
	if err != nil {
		return "", err
	}
	return held.KeyFor(ctx, licence, node, module)
}

// managerPublicKeyFor is the manager node's public sealing key, but only when (node, module) is the
// licence's manager holder — empty otherwise.
//
// It is delivered to the manager module in its bound facts so it can re-seal a rotated refresh token
// to this node (novox/hq ADR 0050). Public, so it travels in the clear like any other bound fact; and
// scoped to the manager holder alone, so a consumer never receives it and nothing invites a consumer
// to seal anything.
func managerPublicKeyFor(
	ctx context.Context, open *stores, inv *inventory.Inventory, licence, node, module string,
) (string, error) {
	held, err := open.Licences(ctx)
	if err != nil {
		return "", err
	}
	managerNode, managerModule, err := held.ManagerOf(ctx, licence)
	if err != nil {
		return "", err
	}
	if managerNode == "" || node != managerNode || module != managerModule {
		return "", nil
	}
	return inv.SealingKeyOf(ctx, node)
}

// servedOnNode is what a module on a node tells a consumer of one of its provisions, with THAT
// node's ports on it: the port the node was given (novox/hq ADR 0100) over the one the mesh
// assigned over the manifest's own, settled with the node's settings layers.
//
// **The one derivation** for every reader of a provider's address — a consumer's binding, the
// artifact store's trust and the references composed through it (04-ISSUES/102). Unreadable
// given ports are that node's refusal to report, not this reader's.
func servedOnNode(ctx context.Context, inv *inventory.Inventory, node string,
	m catalogue.Manifest, provision string) (map[string]any, error) {
	ports, layers, err := portsGivenOn(ctx, inv, node, m)
	if err != nil {
		return nil, err
	}
	serves := catalogue.ServedOn(m, provision, ports)
	if len(serves) > 0 {
		serves, err = catalogue.Settle(serves, layers)
		if err != nil {
			return nil, err
		}
	}
	return serves, nil
}

// portsGivenOn is where a node puts a module's ports — assigned, then given over them — and the
// node's settings layers for the module, read once for both.
func portsGivenOn(ctx context.Context, inv *inventory.Inventory, node string,
	m catalogue.Manifest) (map[int]int, []catalogue.Layer, error) {
	ports, err := portsOn(ctx, inv, node, m.Module)
	if err != nil {
		return nil, nil, err
	}
	layers, err := inv.SettingsFor(ctx, node, m.Module)
	if err != nil {
		return nil, nil, err
	}
	if given, err := catalogue.GivenPorts(m, layers); err == nil {
		for wanted, at := range given {
			ports[wanted] = at
		}
	}
	return ports, layers, nil
}

// seatsOn is where a node put the holder of each mesh-scoped seat, by seat and by the port the
// holder's software uses — what ${seat:…} answers with (novox/hq 04-ISSUES/102).
//
// Read for every module in the catalogue that claims a seat, in this node's set or not: the store
// and the broker are given their ports at genesis, as settings on a module that may be registered
// and not yet assigned (04-ISSUES/085), and the control plane must follow that setting from the
// first declaration it composes for itself. A holder in this node's set wins over one that is not.
func seatsOn(ctx context.Context, inv *inventory.Inventory, shelf map[string]catalogue.Manifest,
	node string, inSet []catalogue.Manifest, adopted bool, taken map[string]bool) (map[string]map[int]int, error) {
	assigned := map[string]bool{}
	for _, m := range inSet {
		assigned[m.Module] = true
	}
	names := make([]string, 0, len(shelf))
	for name := range shelf {
		names = append(names, name)
	}
	sort.Strings(names)
	seats := map[string]map[int]int{}
	for _, name := range names {
		m := shelf[name]
		var claims []string
		for _, c := range m.Claims {
			if c.At() == catalogue.ScopeMesh {
				claims = append(claims, c.Name)
			}
		}
		if len(claims) == 0 {
			continue
		}
		// **Only a port the node was given or the mesh assigned — never the manifest's own
		// number.** The sealed value the answer sits beside carries the port genesis wrote, which
		// on a given-port node is the predecessor's; a manifest's long-form mapping is the
		// catalogue's default, and answering with it would override the right number with one
		// the mesh never checked (the contract in seat_into.go). And on an adopted node a holder
		// assigned but not yet taken is the found container, on the ports it was found with, not
		// the declaration's — so its mesh-assigned ports do not count there either; a given port
		// does, because a given port is the found one by construction (ADR 0100).
		ports, _, err := portsGivenOn(ctx, inv, node, m)
		if err != nil {
			return nil, err
		}
		if adopted && !taken[name] {
			layers, err := inv.SettingsFor(ctx, node, m.Module)
			if err != nil {
				return nil, err
			}
			ports = map[int]int{}
			if given, err := catalogue.GivenPorts(m, layers); err == nil {
				ports = given
			}
		}
		if len(ports) == 0 {
			continue
		}
		for _, seat := range claims {
			if seats[seat] == nil {
				seats[seat] = map[int]int{}
			}
			for wanted, at := range ports {
				if _, said := seats[seat][wanted]; said && !assigned[name] {
					continue
				}
				seats[seat][wanted] = at
			}
		}
	}
	return seats, nil
}

// portsOn is one module's assignments on one machine, by the port the software uses.
func portsOn(
	ctx context.Context, inv *inventory.Inventory, node, module string,
) (map[int]int, error) {
	all, err := inv.PortsFor(ctx, node)
	if err != nil {
		return nil, err
	}
	out := map[int]int{}
	for _, a := range all {
		if a.Module == module {
			out[a.Wanted] = a.Machine
		}
	}
	return out, nil
}

// composeBusUsers is the bus's user list, for a push to the machine that runs the bus.
//
// Empty for every other machine, and for every machine while the mesh is on the bus it runs on
// today — where accounts are a management call and there is no file to write.
//
// **Composed on each push, never kept.** The list is a function of the mesh's records (who exists,
// what runs where, what each declares), and a stored copy would be a second account of who may reach
// the bus, able to disagree with the records while both looked internally consistent (ADR 0043).
//
// A user the mesh has never minted a password for is **left out and said**, not written as a user
// without one — the composer refuses that, because a user with no password is a user anybody is. That
// is an ordinary situation with an obvious remedy (`module issue`, or enrolling), so the push carries
// the rest rather than failing: a bus that is missing one module's user is a mesh where that module
// cannot connect, and a bus with no file at all is a mesh where nothing can.
func composeBusUsers(ctx context.Context, inv *inventory.Inventory,
	onThisNode []catalogue.Manifest) (string, error) {

	// **Not gated on which bus the controller is on, and that was a bug.** It read "compose this only
	// once the mesh is on the new bus" — which cannot work, because the server needs its user list
	// *before* anything moves onto it. Step 2 of the change is exactly that: the server stands in the
	// mesh carrying nothing, on its own ports, while every node is still on the old bus (novox/hq
	// ADR 0116). Under the old gating that step could not happen: the module would come up, find no
	// accounts file, and its entrypoint would wait for one the controller had decided not to write.
	//
	// So the question is only whether this machine runs the module that asked for the file. A mesh
	// that never moves has written a user list nothing reads, which costs a few hundred bytes on one
	// node; the reverse cost a step that cannot be taken.
	//
	// Asked of what this push resolves to rather than of the seat's holder mesh-wide: the file is a
	// resource of that module, so the question is whether it is here.
	holdsTheBus := false
	for _, m := range onThisNode {
		if m.BusUsers != "" && m.ClaimsSeat("mesh-broker") {
			holdsTheBus = true
		}
	}
	if !holdsTheBus {
		return "", nil
	}

	records, err := inv.BusRecords(ctx)
	if err != nil {
		return "", err
	}
	users, err := broker.Users(records)
	if err != nil {
		return "", err
	}
	kept, err := inv.BusUsers(ctx)
	if err != nil {
		return "", err
	}
	hashes := make(map[string]string, len(kept))
	for name, u := range kept {
		hashes[name] = u.PasswordHash
	}
	filled, missing := broker.WithPasswords(users, hashes)
	if len(missing) > 0 {
		fmt.Printf("the bus's user list leaves out %d user(s) the mesh has minted no credential "+
			"for: %s. Each is a user that cannot connect until one is issued\n",
			len(missing), strings.Join(missing, ", "))
	}
	if len(filled) == 0 {
		return "", fmt.Errorf(
			"this machine runs the bus and not one user has a credential, so the composed list " +
				"would refuse every connection in the mesh")
	}
	return broker.ComposeAccounts(filled)
}

// providerModuleOf is which module answers a need on the providing node: the one in this node's
// own set when the provider is here, else the one the catalogue says offers it.
func providerModuleOf(resolved catalogue.Resolution, open *stores, ctx context.Context, n catalogue.Needed) string {
	for _, m := range resolved.Modules {
		if _, shared := m.SharedCredentialOf(n.Name); shared {
			return m.Module
		}
	}
	shelf, err := open.inventory.Catalogue(ctx)
	if err != nil {
		return ""
	}
	for name, m := range shelf {
		if _, shared := m.SharedCredentialOf(n.Name); shared {
			return name
		}
	}
	return ""
}