// Package frombus fills mesh-sdk's composition input from what is on the bus, so a node agent, the composition check
// and the grants part compose with one composer over the same inputs (novox/hq ADR 0547 §2, ADR 0549 §3; issue 1126).
//
// **One composer, three callers.** compose.Compositions is the composer; Input is how each caller fills its
// compose.Input from the bus: the node agent for its own node (ADR 0547 §2), the assigner's composition check for every
// node (ADR 0539 §6's check, ADR 0547 §4), and the grants part (ADR 0547 §5). Each reads the bus with its own credential
// through a Reader, so this package holds no bus client, no store and no timer: what it is given is all it reads.
//
// **What it reads, and from whom.**
//   - which modules run on each node, with their pins, holdings, host ports, bindings and settings placement: the
//     indexer's state `placement`, one key per node (ADR 0549 §2);
//   - what a person decided of each node (its endpoint, site, hub, address on the private network, public domain and
//     accounts): the same placement key, Placement.Decided;
//   - what each node observes of itself (its tunnel key, capabilities, keys, certificate, links and networks): the
//     node's own have key, `<node>.node` (HaveNode.Record); the tunnel found at a node's adoption and the names of the hub's peers are decided,
//     in its placement, and whether the hub took the tunnel over and who enrolled under a peer's key are read from both;
//   - every module's manifest: the indexer's `modules.<module>` and its manifests by digest; for each module placed on
//     the composing node, its built manifest instead: the builder's done key at the trunk's FP2, or at the fingerprint
//     the node's want names where it runs another build (Scope.KeptAt), resolved by the controller's own take-in rule
//     (takein.Manifest), a moved module's templates archive read in the artifact store (issue 1126);
//   - each module's config values on a node: mesh-config's resolved state, the composing node's slice alone unless the
//     caller composes every node (ADR 0547 §2, the prepare step's L4); of another node, only the keys its modules'
//     served values fill (catalogue.ServedSettings), which every consumer is told (issue 1126).
//
// **Own secrets and pair credentials** come from the vault sealed to the composing node's key (OwnSecrets, Credentials),
// for that node alone: as a consumer and as a provider, exactly the keys compose.CredentialsNeeded names. **Not yet
// read** (each a later subtask of issue 1126): licences (none is placed today) and core boxes. Without one
// the composition stands in for it, and Compose refuses a composition that stands in for anything (compose.ErrStoodIn):
// a node never applies a stand-in. No node is joining before ADR 0547's third milestone (ADR 0550 §6), so Joining is
// always empty.
package frombus

import (
	"context"
	"encoding/json"
	"fmt"
	"net/netip"
	"slices"
	"sort"
	"strings"

	"git.novox.be/novox/mesh-sdk/go/catalogue"
	"git.novox.be/novox/mesh-sdk/go/compose"
	"git.novox.be/novox/mesh-sdk/go/declaration"
	"git.novox.be/novox/mesh-sdk/go/delivery"
	"git.novox.be/novox/mesh-sdk/go/overlay"
	"git.novox.be/novox/mesh-sdk/go/takein"
)

// Reader is the bus as a caller reads it with its own credential. Each method reads one part's state; an error is a
// read that failed, never an absent key (an absent key is an empty answer).
type Reader interface {
	// Placements is every node's placement, by node (delivery.PlacementBucket).
	Placements(ctx context.Context) (map[string]delivery.Placement, error)
	// Records is every node's record, by node: HaveNode.Record of each node's own have key, `<node>.node` of
	// delivery.HaveBucket (ADR 0555 §3).
	Records(ctx context.Context) (map[string]delivery.NodeRecord, error)
	// Modules is every module the indexer holds, by module (delivery.ModulesBucket).
	Modules(ctx context.Context) (map[string]delivery.Module, error)
	// Manifest is the raw manifest of a digest (delivery.ManifestsBucket).
	Manifest(ctx context.Context, digest string) ([]byte, error)
	// Values is one module's config values on one node as mesh-config resolved them (mesh-config's state `resolved`,
	// keys `<node>.<module>.<key>`), decoded; nil when it has none.
	Values(ctx context.Context, node, module string) (map[string]any, error)
	// OwnSecrets is the own secrets of the composing node's modules, each sealed to that node's key, as the vault answers
	// the node's engine (the vault's verb `own`, ADR 0550 §5); asked only for the node composing itself.
	OwnSecrets(ctx context.Context, node string) ([]compose.OwnSecretRow, error)
	// Credentials is, for the composing node, each pair credential it reads as a consumer, held and sealed to its key,
	// and each it grants as a provider, with the copy sealed to it (the vault's `own` with the keys, ADR 0550 §5). A key
	// the vault holds no value for is left out; the composition then stands in for it, and Compose refuses it.
	Credentials(ctx context.Context, node string, asConsumer, asProvider []compose.CredentialKey) ([]compose.Credential, []compose.Issued, error)
	// Build is a module's build at a fingerprint, the builder's key (delivery.BuilderBuildsBucket, BuilderBuildKey); nil
	// when the builder holds none. The composing node composes each of its modules from its build (issue 1126).
	Build(ctx context.Context, module, fp string) (*delivery.BuilderBuild, error)
	// Archive is the archive at url, a kept reference routed to the artifact store as the composing node reaches it
	// (catalogue.Routed), checked against digest: a moved module's templates archive, read back for its texts as the
	// controller's take-in reads it (takein.Built).
	Archive(ctx context.Context, url, digest string) ([]byte, error)
	// Served is, of one module's config values on another node than the composing one (mesh-config's state `resolved`,
	// keys `<node>.<module>.<key>`), the keys named, decoded: the keys its served values and zone name fill
	// (catalogue.ServedSettings), which every consumer is told and so every node may read (issue 1126). Nil when none
	// is set.
	Served(ctx context.Context, node, module string, keys []string) (map[string]any, error)
}

// Mesh is what is true of the whole mesh and is no part's state on the bus yet: the private network's range and the
// internal names' suffix as genesis was told them, and the mesh's authority certificate (public). Empty fields take
// compose's defaults.
type Mesh struct {
	OverlayCIDR    string
	InternalSuffix string
	Authority      string
	// Predefined is the list of predefined keys mesh-config published, which a manifest's values falling back to a
	// predefined key are judged against; nil reads each manifest as the indexer does (catalogue.ParseManifestForInputs).
	Predefined catalogue.PredefinedList
}

// Scope says who composes. Node is the node composing; only its config values are read unless Every is set, as the
// composition check sets it to compose every node (of another node's modules, only the values their served values fill
// are read, Reader.Served). KeptAt is, by module, the fingerprint the composing node's want names where it differs from
// the indexer's trunk: that node composes the module from its build at that fingerprint, as it runs it.
//
// **Composed from its build** (issue 1126): each module placed on the composing node, and each in KeptAt, composes from
// its built manifest (takein.Manifest over the builder's done key at the trunk's FP2 or the kept fingerprint), as the
// controller composes from the manifest its take-in resolved: so a moved module is handed to the provisioner, a resource
// naming an artifact names what was built, and a templated file has its text. A placed module the builder holds no done
// build of at the trunk's FP2 composes from the indexer's manifest, as before. Every leaves the catalogue as the indexer
// read it: the check of every node judges placement, and reads no archive.
//
// Placements, when set, stands in for the indexer's placement of the nodes it names: a node's candidate placement
// (delivery.PlacementCandidate), so a node composes in shadow with a catalogue pull request's placement and compares
// the result with what it runs (issue 1126); a nil value removes the node's placement. The rest is read as always.
//
// InOwn is the modules the composing node runs inside its own composition (InOwn of what it runs), composed there again
// (compose.Node.InOwn) rather than cut out as modules no build is given for (issue 1126).
//
// Running is what the composing node runs; of it, its own composition (`<node>.node`) is given to the composition
// (compose.Node.RunsOwn), so a module folded there that names a build of the old form is left to the node, carried
// as it runs (issue 1126). Nil composes every folded module from its manifest.
type Scope struct {
	Node       string
	Every      bool
	KeptAt     map[string]string
	Placements map[string]*delivery.Placement
	InOwn      []string
	Running    []delivery.Composed
	// SameValue, in an answer, says whether two sealed values open to the same value (the node opens them with its own
	// key), so a differing resource shows a value sealed again as such (delivery.CompareComposedWith). Nil shows them
	// as differing.
	SameValue func(a, b string) (same, known bool)
}

// InOwn is, of the modules p places on its node, those whose resources the node's own composition it runs
// (`<node>.node` in running) carries, by the module their ids name (declaration.ModuleGuess), sorted: the modules the
// controller's composed writer folded there because no fingerprint of the new form names them (mesh-wireguard, a module
// run at a build of the old form; issue 1126). A node composing itself passes it as Scope.InOwn, so its own
// composition keeps them as it runs them until a want names a build of the new form for one.
func InOwn(running []delivery.Composed, p delivery.Placement) []string {
	placed := map[string]bool{}
	for _, m := range p.Modules {
		placed[m.Module] = true
	}
	in := map[string]bool{}
	for _, c := range running {
		if c.Module != "" {
			continue
		}
		for _, raw := range c.Resources {
			var head struct {
				ID     string `json:"id"`
				Module string `json:"module"`
			}
			if json.Unmarshal(raw, &head) != nil || head.Module != "" {
				continue
			}
			if m, ok := declaration.ModuleGuess(head.ID); ok && placed[m] {
				in[m] = true
			}
		}
	}
	return sortedKeys(in)
}

// Input is the composition input for s, read through r.
func Input(ctx context.Context, r Reader, mesh Mesh, s Scope) (compose.Input, error) {
	return input(ctx, r, mesh, s, nil)
}

// input is Input; with refuse set, a module placed on the composing node whose build cannot be read or taken in is
// handed to refuse and composed as a stub (compose.Stub, kept for that node alone) rather than ending the read, so a
// node's answer names every module it cannot compose (issue 1126).
func input(ctx context.Context, r Reader, mesh Mesh, s Scope, refuse func(module string, err error)) (compose.Input, error) {
	placements, err := r.Placements(ctx)
	if err != nil {
		return compose.Input{}, fmt.Errorf("frombus: placement: %w", err)
	}
	if len(s.Placements) > 0 {
		given := make(map[string]delivery.Placement, len(placements)+len(s.Placements))
		for node, p := range placements {
			given[node] = p
		}
		for node, p := range s.Placements {
			if p == nil {
				delete(given, node)
				continue
			}
			if p.Node != node {
				return compose.Input{}, fmt.Errorf("frombus: the placement given for %s names the node %q", node, p.Node)
			}
			given[node] = *p
		}
		placements = given
	}
	records, err := r.Records(ctx)
	if err != nil {
		return compose.Input{}, fmt.Errorf("frombus: node records: %w", err)
	}
	modules, err := r.Modules(ctx)
	if err != nil {
		return compose.Input{}, fmt.Errorf("frombus: the indexer's modules: %w", err)
	}
	if _, ok := placements[s.Node]; !ok && !s.Every {
		return compose.Input{}, fmt.Errorf("frombus: %s has no placement in the catalogue", s.Node)
	}

	in := compose.Input{OverlayCIDR: mesh.OverlayCIDR, InternalSuffix: mesh.InternalSuffix, Authority: mesh.Authority,
		Catalogue: map[string]catalogue.Manifest{}}
	if in.Authority == "" {
		// The mesh's own certificate, public, as the composing node holds it; for the check of every node, as the first
		// node holding one does.
		if rec, ok := records[s.Node]; ok && rec.Authority != "" {
			in.Authority = rec.Authority
		} else {
			for _, node := range sortedKeys(records) {
				if a := records[node].Authority; a != "" {
					in.Authority = a
					break
				}
			}
		}
	}
	parse := func(raw []byte) (catalogue.Manifest, error) {
		if mesh.Predefined != nil {
			return catalogue.ParseManifestWith(raw, mesh.Predefined)
		}
		return catalogue.ParseManifestForInputs(raw)
	}
	read := func(module, digest string) (catalogue.Manifest, error) {
		raw, err := r.Manifest(ctx, digest)
		if err != nil {
			return catalogue.Manifest{}, fmt.Errorf("frombus: the manifest of %s (digest %s): %w", module, digest, err)
		}
		return parse(raw)
	}
	for _, name := range sortedKeys(modules) {
		m := modules[name]
		if m.Manifest == "" {
			continue // a registered module the indexer has not read: nothing to compose it from
		}
		man, err := read(name, m.Manifest)
		if err != nil {
			return compose.Input{}, err
		}
		in.Catalogue[name] = man
	}

	// The module the mesh provides itself (the private network) has no repository the indexer reads: its manifest comes
	// with mesh-sdk and always wins, as the controller's providedModules and the grants part have it.
	provided, err := json.Marshal(overlay.Manifest())
	if err != nil {
		return compose.Input{}, err
	}
	var private catalogue.Manifest
	if err := json.Unmarshal(provided, &private); err != nil {
		return compose.Input{}, fmt.Errorf("frombus: the private network's manifest mesh-sdk provides: %w", err)
	}
	in.Catalogue[overlay.Name] = private

	var missing []string
	for _, node := range nodesOf(placements, records) {
		rec, hasRecord := records[node]
		p := placements[node]
		if !hasRecord {
			if len(p.Modules) > 0 {
				missing = append(missing, node)
			}
			continue
		}
		n := nodeOf(rec, p)
		withValues := s.Every || node == s.Node
		for _, m := range p.Modules {
			var values map[string]any
			if withValues {
				if values, err = r.Values(ctx, node, m.Module); err != nil {
					return compose.Input{}, fmt.Errorf("frombus: %s's config values on %s: %w", m.Module, node, err)
				}
			} else if keys := catalogue.ServedSettings(in.Catalogue[m.Module]); len(keys) > 0 {
				// What a provider elsewhere serves from its settings is told to every consumer: the composing node reads
				// those keys of it, and no other (issue 1126: mailu's smtp domain, a consumer's on shanks).
				if values, err = r.Served(ctx, node, m.Module, keys); err != nil {
					return compose.Input{}, fmt.Errorf("frombus: what %s serves on %s (%s): %w", m.Module, node,
						strings.Join(keys, ", "), err)
				}
			}
			if layers := m.Layers(node, values); layers != nil {
				if n.Settings == nil {
					n.Settings = map[string][]catalogue.Layer{}
				}
				n.Settings[m.Module] = layers
			}
		}
		if node == s.Node {
			for _, module := range s.InOwn {
				if n.InOwn == nil {
					n.InOwn = map[string]bool{}
				}
				n.InOwn[module] = true
			}
			for i := range s.Running {
				if s.Running[i].Module == "" {
					own := s.Running[i]
					n.RunsOwn = &own
					// Its bus membership as it runs it: the controller composes it from its store, which the node does
					// not read; until the grants part hands memberships sealed to the node, the node's own composition
					// carries the one it runs (issue 1126, seed #531 on novox: "bus-membership in what runs, not
					// composed", which applied would have taken the node's bus credential away).
					if sealed := membershipOf(own); sealed != "" {
						if in.BusMemberships == nil {
							in.BusMemberships = map[string]string{}
						}
						in.BusMemberships[s.Node] = sealed
					}
				}
			}
		}
		in.Nodes = append(in.Nodes, n)
		in.Holdings = append(in.Holdings, p.Held()...)
		// A tunnel found at adoption is the node's private network's when the node's tunnel key is the tunnel's (the
		// controller's inv.Tunnels); the hub's found tunnel is the mesh's adopted one whether or not the hub took it over
		// (inv.AdoptedTunnel), and its peers are carried once it did (inv.CarriedPeers).
		if t := p.Decided.Tunnel; t != nil {
			if rec.TunnelKey == t.PublicKey {
				if in.Tunnels == nil {
					in.Tunnels = map[string]compose.FoundTunnel{}
				}
				in.Tunnels[node] = compose.FoundTunnel{Tunnel: tunnelOf(*t), NodeAdopted: p.Decided.Adopted}
			}
			if p.Decided.Hub {
				in.Adopted = &compose.AdoptedTunnel{Tunnel: tunnelOf(*t), Hub: node, Adopted: rec.TunnelKey == t.PublicKey}
			}
		}
	}
	if in.Adopted != nil && in.Adopted.Adopted {
		in.CarriedPeers = carriedPeers(in.Adopted.Tunnel, placements[in.Adopted.Hub].Decided.PeerNames, records)
	}
	if len(missing) > 0 {
		return compose.Input{}, fmt.Errorf("frombus: modules are placed on %s, whose agent has written no record yet",
			strings.Join(missing, ", "))
	}
	if !s.Every {
		if _, ok := records[s.Node]; !ok {
			return compose.Input{}, fmt.Errorf("frombus: %s has written no record of itself yet", s.Node)
		}
		if err := fromBuilds(ctx, r, &in, s, placements[s.Node], modules, read, parse, refuse); err != nil {
			return compose.Input{}, err
		}
		// Its own modules' secrets, sealed to its own key by the vault: a composition carries them sealed (ADR 0550 §5).
		// Asked only when a module placed on it declares one: a node none of whose modules has a secret composes
		// whether or not the vault answers.
		if declaresOwnSecrets(in, s.Node) {
			if in.OwnSecrets, err = r.OwnSecrets(ctx, s.Node); err != nil {
				return compose.Input{}, fmt.Errorf("frombus: the own secrets of %s's modules: %w", s.Node, err)
			}
		}
		// The core's credentials travel as the vault's box sealed to the machine (ADR 0349 §16): the same values, which
		// the composition reads for a core module as its kept boxes.
		for _, o := range in.OwnSecrets {
			if json.Valid([]byte(o.Sealed)) {
				in.KeptCoreBoxes = append(in.KeptCoreBoxes, compose.CoreBox{Node: o.Node, Module: o.Module, Name: o.Name,
					SealedTo: o.SealedTo, Box: json.RawMessage(o.Sealed)})
			}
		}
	}
	return in, nil
}

// Compose is the node's compositions over the bus (ADR 0547 §2): Input for s, then compose.CompositionsApplied at the
// fingerprints fps gives each module: composed in the Reading mode as the controller composes them, and refused when it
// stands in for anything the input does not carry (compose.ErrStoodIn), since the node applies what it composed.
func Compose(ctx context.Context, r Reader, mesh Mesh, s Scope, fps map[string]string) (map[string]delivery.Composed, []string, error) {
	in, err := Input(ctx, r, mesh, s)
	if err != nil {
		return nil, nil, err
	}
	// The pair credentials its composition reads, asked of the vault sealed to it (ADR 0550 §5).
	asConsumer, asProvider, err := compose.CredentialsNeeded(in, s.Node)
	if err != nil {
		return nil, nil, err
	}
	if len(asConsumer)+len(asProvider) > 0 {
		if in.Credentials, in.Issued, err = r.Credentials(ctx, s.Node, asConsumer, asProvider); err != nil {
			return nil, nil, fmt.Errorf("frombus: the credentials of %s: %w", s.Node, err)
		}
	}
	return compose.CompositionsApplied(in, s.Node, fps)
}

// fromBuilds puts in the built manifest of each module placed on the composing node, at the trunk's FP2, and of each
// module it keeps at another build (Scope.KeptAt, into its node's Kept), read from the builder's done key and resolved
// by the one take-in rule (takein.Manifest), a templates archive read in the artifact store as the node reaches it
// (issue 1126).
func fromBuilds(ctx context.Context, r Reader, in *compose.Input, s Scope, p delivery.Placement, modules map[string]delivery.Module,
	read func(module, digest string) (catalogue.Manifest, error), parse func([]byte) (catalogue.Manifest, error),
	refuse func(module string, err error)) error {
	// stub keeps a refused module in the composition as a stub for this node alone (compose.Stub): what it provides
	// and requires still shapes the rest.
	stub := func(module string, err error) {
		refuse(module, err)
		for i := range in.Nodes {
			if in.Nodes[i].Name != s.Node {
				continue
			}
			man, ok := in.Nodes[i].Kept[module]
			if !ok {
				man, ok = in.Catalogue[module]
			}
			if !ok {
				return
			}
			if in.Nodes[i].Kept == nil {
				in.Nodes[i].Kept = map[string]catalogue.Manifest{}
			}
			in.Nodes[i].Kept[module] = compose.Stub(man)
		}
	}
	address, addressErr := "", error(nil)
	addressed := false
	archive := func(ctx context.Context, reference, digest string) ([]byte, error) {
		if !addressed {
			address, addressErr = compose.ArtifactStoreAddress(*in, s.Node)
			addressed = true
		}
		switch {
		case addressErr != nil:
			return nil, addressErr
		case address == "":
			return nil, fmt.Errorf("%s reaches no artifact store (%s)", s.Node, storeSought(*in))
		}
		return r.Archive(ctx, catalogue.Routed(reference, address), digest)
	}
	built := func(module, fp string, b *delivery.BuilderBuild) (catalogue.Manifest, error) {
		if b.Manifest == "" {
			return catalogue.Manifest{}, fmt.Errorf("frombus: the build of %s at %s names no manifest", module, fp)
		}
		src, err := read(module, b.Manifest)
		if err != nil {
			return catalogue.Manifest{}, err
		}
		resolved, err := takein.Manifest(ctx, src, *b, archive)
		if err != nil {
			return catalogue.Manifest{}, fmt.Errorf("frombus: %s at %s: %w", module, fp, err)
		}
		// Read back as the mesh holds a built manifest (the controller keeps the resolved manifest's bytes and reads them
		// as any manifest): a template's text is then in the manifest's own words, its ${config:…} in the settings form.
		raw, err := json.Marshal(resolved)
		if err != nil {
			return catalogue.Manifest{}, err
		}
		if resolved, err = parse(raw); err != nil {
			return catalogue.Manifest{}, fmt.Errorf("frombus: the built manifest of %s at %s: %w", module, fp, err)
		}
		return resolved, nil
	}
	for _, pm := range p.Modules {
		m, ok := modules[pm.Module]
		if !ok || m.FP2 == "" || s.KeptAt[pm.Module] != "" || slices.Contains(s.InOwn, pm.Module) {
			// A module it runs inside its own composition is composed there as before: no build of the new form is what
			// it runs (Scope.InOwn).
			continue
		}
		if man, ok := in.Catalogue[pm.Module]; !ok || (man.Build == nil && !man.Templated()) {
			continue // nothing is built of it: its manifest is what it composes from
		}
		b, err := r.Build(ctx, pm.Module, m.FP2)
		if err != nil {
			err = fmt.Errorf("frombus: the build of %s at %s: %w", pm.Module, m.FP2, err)
			if refuse == nil {
				return err
			}
			stub(pm.Module, err)
			continue
		}
		if b == nil || b.State != delivery.BuildDone {
			continue // no done build at the trunk's: composed from the indexer's manifest, as before
		}
		resolved, err := built(pm.Module, m.FP2, b)
		if err != nil {
			if refuse == nil {
				return err
			}
			stub(pm.Module, err)
			continue
		}
		in.Catalogue[pm.Module] = resolved
	}
	for i := range in.Nodes {
		if in.Nodes[i].Name != s.Node {
			continue
		}
		for _, module := range sortedKeys(s.KeptAt) {
			fp := s.KeptAt[module]
			b, err := r.Build(ctx, module, fp)
			switch {
			case err != nil:
				err = fmt.Errorf("frombus: the build of %s at %s: %w", module, fp, err)
			case b == nil || b.State != delivery.BuildDone:
				err = fmt.Errorf("frombus: %s is wanted at %s, of which the builder holds no done build", module, fp)
			}
			var resolved catalogue.Manifest
			if err == nil {
				resolved, err = built(module, fp, b)
			}
			if err != nil {
				if refuse == nil {
					return err
				}
				stub(module, err)
				continue
			}
			if in.Nodes[i].Kept == nil {
				in.Nodes[i].Kept = map[string]catalogue.Manifest{}
			}
			in.Nodes[i].Kept[module] = resolved
		}
	}
	return nil
}

// declaresOwnSecrets says a module assigned to node declares an own secret, in the manifest the node composes it from.
func declaresOwnSecrets(in compose.Input, node string) bool {
	for _, n := range in.Nodes {
		if n.Name != node {
			continue
		}
		for _, module := range n.Assigned {
			m, ok := n.Kept[module]
			if !ok {
				m = in.Catalogue[module]
			}
			if len(m.OwnSecrets) > 0 {
				return true
			}
		}
	}
	return false
}

// nodeOf is the composition's node from its record (what the machine observes) and its placement (what a person
// decided of it, and where its modules run).
func nodeOf(rec delivery.NodeRecord, p delivery.Placement) compose.Node {
	n := compose.Node{
		Name:         rec.Node,
		Place:        compose.Place{Key: rec.TunnelKey},
		SealingKey:   rec.SealingKey,
		OutwardLinks: rec.OutwardLinks, Networks: rec.Networks, NetworksSaid: rec.NetworksSaid,
		ServingKey: rec.ServingKey, Certificate: rec.Certificate, Contract: rec.Contract, Stated: rec.Contract > 0,
	}
	placeNode(&n, p)
	if len(rec.Capabilities) > 0 {
		n.Capabilities = make(map[string]bool, len(rec.Capabilities))
		for _, c := range rec.Capabilities {
			n.Capabilities[c] = true
		}
	}
	return n
}

// placeNode sets what a person decided of n and where its modules run, from its placement; what the machine observes
// (its keys, links, networks, certificate) and its settings layers are left as they are.
func placeNode(n *compose.Node, p delivery.Placement) {
	d := p.Decided
	n.Place = compose.Place{Key: n.Place.Key, Endpoint: d.Endpoint, Site: d.Site, Hub: d.Hub, Address: d.Address}
	n.Assigned, n.PublicDomain = p.Assigned(), d.PublicDomain
	n.Account, n.AccountHome, n.AgentAccount, n.AgentAccountHome = d.Account, d.AccountHome, d.AgentAccount, d.AgentHome
	n.Adopted, n.Taken = d.Adopted, d.Taken
	n.Pins, n.Bound, n.Ports = p.ChosenPins(), p.Bound(), p.HostPorts()
}

// Placed is in with the placements given standing in for those of the nodes they name (issue 1126): each such node's
// decided parts, modules, pins, bindings, host ports, settings placement and holdings are the given placement's, its
// config values those in already carries for it (the layer of the node's own name), and what the machine observes is
// kept. A nil placement leaves the node in the mesh with nothing placed on it. A node in does not hold is refused: it has
// no record to compose it from. The found tunnel and the hub's peers are read from in as they are, not from the given
// placement. It is how a check composes a change's own placement over an input already filled (composer.Case's
// Placements).
func Placed(in compose.Input, placements map[string]*delivery.Placement) (compose.Input, error) {
	if len(placements) == 0 {
		return in, nil
	}
	out := in
	out.Nodes = append([]compose.Node(nil), in.Nodes...)
	index := map[string]int{}
	for i, n := range out.Nodes {
		index[n.Name] = i
	}
	for _, node := range sortedKeys(placements) {
		p := placements[node]
		i, ok := index[node]
		if !ok {
			return compose.Input{}, fmt.Errorf("frombus: a placement is given for %s, which the input holds no node for", node)
		}
		if p == nil {
			p = &delivery.Placement{Node: node}
		}
		if p.Node != node {
			return compose.Input{}, fmt.Errorf("frombus: the placement given for %s names the node %q", node, p.Node)
		}
		n := out.Nodes[i]
		placeNode(&n, *p)
		settings := map[string][]catalogue.Layer{}
		for _, m := range p.Modules {
			var values map[string]any
			for _, l := range n.Settings[m.Module] {
				if l.From == node {
					values = l.Values
				}
			}
			if layers := m.Layers(node, values); layers != nil {
				settings[m.Module] = layers
			}
		}
		n.Settings = nil
		if len(settings) > 0 {
			n.Settings = settings
		}
		out.Nodes[i] = n
	}
	out.Holdings = nil
	for _, h := range in.Holdings {
		if _, given := placements[h.Node]; !given {
			out.Holdings = append(out.Holdings, h)
		}
	}
	for _, node := range sortedKeys(placements) {
		if p := placements[node]; p != nil {
			out.Holdings = append(out.Holdings, p.Held()...)
		}
	}
	return out, nil
}

func tunnelOf(t delivery.RecordTunnel) compose.Tunnel {
	out := compose.Tunnel{Interface: t.Interface, Unit: t.Unit, Config: t.Config, Port: t.Port, MTU: t.MTU,
		Address: t.Address, Range: t.Range, PublicKey: t.PublicKey}
	for _, p := range t.Peers {
		out.Peers = append(out.Peers, compose.TunnelPeer{PublicKey: p.PublicKey, Address: p.Address})
	}
	return out
}

// carriedPeers is every peer of the hub's adopted tunnel, by address, each with the node that enrolled under its key
// where one has (a node whose tunnel key is the peer's) and the name a person gave it (inv.CarriedPeers).
func carriedPeers(t compose.Tunnel, names map[string]string, records map[string]delivery.NodeRecord) []compose.CarriedPeer {
	byKey := map[string]string{}
	for node, rec := range records {
		if rec.TunnelKey != "" {
			byKey[rec.TunnelKey] = node
		}
	}
	var out []compose.CarriedPeer
	for _, p := range t.Peers {
		address, _, _ := strings.Cut(p.Address, "/")
		out = append(out, compose.CarriedPeer{PublicKey: p.PublicKey, Address: address, EnrolledAs: byKey[p.PublicKey], Named: names[p.PublicKey]})
	}
	sort.SliceStable(out, func(i, j int) bool {
		a, errA := netip.ParseAddr(out[i].Address)
		b, errB := netip.ParseAddr(out[j].Address)
		if errA != nil || errB != nil {
			return out[i].Address < out[j].Address
		}
		return a.Less(b)
	})
	return out
}

// nodesOf is every node named by a placement or a record, by name: the order the controller reads them in.
func nodesOf(placements map[string]delivery.Placement, records map[string]delivery.NodeRecord) []string {
	seen := map[string]bool{}
	for n := range placements {
		seen[n] = true
	}
	for n := range records {
		seen[n] = true
	}
	return sortedKeys(seen)
}

func sortedKeys[V any](m map[string]V) []string {
	out := make([]string, 0, len(m))
	for k := range m {
		out = append(out, k)
	}
	sort.Strings(out)
	return out
}

// storeSought says, for a node that reaches no artifact store, what the composition holds of one: the nodes it holds and
// where each module serving the artifact store is placed, so the refusal names why (issue 1126).
func storeSought(in compose.Input) string {
	var nodes, where []string
	for _, n := range in.Nodes {
		nodes = append(nodes, n.Name)
		for _, a := range n.Assigned {
			if m, ok := in.Catalogue[a]; ok {
				if _, serves := m.Serves[catalogue.ArtifactStoreProvision]; serves {
					where = append(where, a+" on "+n.Name)
				}
			}
		}
	}
	sort.Strings(nodes)
	sort.Strings(where)
	said := "the composition holds " + strings.Join(nodes, ", ")
	if len(where) == 0 {
		return said + "; no module placed there serves " + catalogue.ArtifactStoreProvision
	}
	return said + "; " + catalogue.ArtifactStoreProvision + " is served by " + strings.Join(where, ", ") +
		", none of it on the private network with a port"
}

// membershipOf is the sealed value of the bus membership resource (catalogue.BusMembershipID) of a node's own
// composition, or "".
func membershipOf(own delivery.Composed) string {
	for _, raw := range own.Resources {
		var r struct {
			ID     string `json:"id"`
			Sealed string `json:"sealed"`
		}
		if json.Unmarshal(raw, &r) == nil && r.ID == catalogue.BusMembershipID() {
			return r.Sealed
		}
	}
	return ""
}