mesh-controller/cmd/mesh-controller/references.go

package main

import (
	"context"
	"encoding/json"

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

// What a build is recorded as, and what it is announced and handed on as.
//
// **Recorded by what it is; routed where it is used** (novox/hq 04-ISSUES/102). The builder
// announces each artifact by the reference it pushed — `<registry>:<port>/<module>/<artifact>@sha256:…`
// — and the manifest with those references in it. The mesh records the digest and the path
// (catalogue.Recorded) and composes the store's address back in wherever a machine or a builder
// needs a reference it can fetch: a declaration, a replay to the catalogue, the bases a build is
// given. Nothing recorded carries a port, so moving the store is a settings change and not a
// rebuild of everything the mesh has ever built.

// recordedManifest is a build's manifest with the store's address taken off every reference the
// build itself made. Other references — an image a module runs from a public registry — are what
// they were, which is why this rewrites only what `made` names rather than everything that looks
// like an address.
func recordedManifest(raw json.RawMessage, made []inventory.Artifact) json.RawMessage {
	announced := map[string]bool{}
	for _, a := range made {
		announced[a.Reference] = true
	}
	return withReferences(raw, func(ref string) (string, bool) {
		if !announced[ref] {
			return ref, false
		}
		return catalogue.Recorded(ref), true
	})
}

// routedManifest is a recorded manifest with the store's address, as this network reaches it now,
// composed into every reference the build made — recorded either way, before or after references
// were kept without their address.
func routedManifest(raw json.RawMessage, made []inventory.Artifact, address string) json.RawMessage {
	recorded := map[string]bool{}
	for _, a := range made {
		recorded[catalogue.Recorded(a.Reference)] = true
	}
	return withReferences(raw, func(ref string) (string, bool) {
		if !recorded[catalogue.Recorded(ref)] {
			return ref, false
		}
		return catalogue.Rerouted(ref, address), true
	})
}

// withReferences applies `rewrite` to each resource's `image` and `source`, and hands the manifest
// back untouched — byte for byte — when nothing changed or it could not be read: what a manifest
// is, is the parser's to say, and it says so with a better sentence than anything here would.
func withReferences(raw json.RawMessage, rewrite func(string) (string, bool)) json.RawMessage {
	if len(raw) == 0 {
		return raw
	}
	var manifest map[string]any
	if err := json.Unmarshal(raw, &manifest); err != nil {
		return raw
	}
	resources, _ := manifest["resources"].([]any)
	changed := false
	for _, r := range resources {
		resource, ok := r.(map[string]any)
		if !ok {
			continue
		}
		for _, key := range []string{"image", "source"} {
			if written, ok := resource[key].(string); ok {
				if rewritten, did := rewrite(written); did && rewritten != written {
					resource[key] = rewritten
					changed = true
				}
			}
		}
	}
	if !changed {
		return raw
	}
	out, err := json.Marshal(manifest)
	if err != nil {
		return raw
	}
	return out
}

// routedArtifacts is a build's artifacts as something can fetch them now.
func routedArtifacts(made []inventory.Artifact, address string) []inventory.Artifact {
	if address == "" {
		return made
	}
	out := make([]inventory.Artifact, 0, len(made))
	for _, a := range made {
		out = append(out, inventory.Artifact{Name: a.Name, Kind: a.Kind,
			Reference: catalogue.Rerouted(a.Reference, address)})
	}
	return out
}

// whereTheStoreIs is the artifact store's address as something on `forNode` reaches it, or "" —
// read for a caller that has the inventory open and nothing else in hand. With no node named, the
// store's own node: loopback when nothing is on the network yet.
func whereTheStoreIs(ctx context.Context, inv *inventory.Inventory, forNode string) (string, error) {
	shelf, err := inv.Catalogue(ctx)
	if err != nil {
		return "", err
	}
	if forNode == "" {
		if holder, _, found, err := artifactStoreHolder(ctx, inv); err != nil {
			return "", err
		} else if found {
			forNode = holder
		}
	}
	return artifactStoreAddress(ctx, inv, shelf, forNode)
}

// whereABuilderReachesTheStore is the store's address for the machine that builds: the network's
// when there is one, else loopback on the store's own node — when that node also holds a module
// requiring the store, which is what a builder is (genesis: one node holds both).
func whereABuilderReachesTheStore(ctx context.Context, inv *inventory.Inventory) (string, error) {
	shelf, err := inv.Catalogue(ctx)
	if err != nil {
		return "", err
	}
	holder, _, found, err := artifactStoreHolder(ctx, inv)
	if err != nil || !found {
		return "", err
	}
	assigned, err := inv.Assigned(ctx, holder)
	if err != nil {
		return "", err
	}
	besideIt := false
	for _, a := range assigned {
		for _, r := range shelf[a].Requires {
			if r == catalogue.ArtifactStoreProvision {
				besideIt = true
			}
		}
	}
	if !besideIt {
		holder = ""
	}
	return artifactStoreAddress(ctx, inv, shelf, holder)
}