package buildstep

// **The late publish** (novox/hq ADR 0617 §1, design 51 *The versions*, *Publishing*; CAT-BG2, CAT-BI1): a trunk build
// whose number the builder did not know yet publishes its digest unnumbered; the builder says version.numbered once it
// numbers that fingerprint, and the build module publishes the held digest again under that version. Nothing travels:
// the publish names the one part by its digest, which the holder holds, so it answers held and tags the version (the
// holder asks builder_versions first, ADR 0605 §4). The bytes never stayed on the node, so a holder that no longer holds
// the digest is said and the event offered again. Every instance may hear the same event; the publish is the same call
// under the same transfer name, so a second one is answered held. One place for every build module: mesh-build-go's
// bundles and archives on oci-artifact-registry, mesh-build-image's images on container-image-registry.

import (
	"context"
	"errors"
	"fmt"
	"io"
	"log"
	"slices"
	"time"

	reg "git.novox.be/novox/mesh-delivery/contracts/go/seats/containerimageregistry"
	builds "git.novox.be/novox/mesh-delivery/modules/mesh-delivery-builder/builds"
	"git.novox.be/novox/mesh-delivery/sdk/parts"
	stdio "git.novox.be/novox/mesh-sdk/go"
)

// NumberedPattern is the event type a build module consumes for the late publish, as its manifest's `consumes` names it.
const NumberedPattern = builds.BuilderModule + "." + builds.VersionNumberedEvent

// errNotHere is a held part's Open: its bytes did not stay on the node.
var errNotHere = errors.New("the built bytes did not stay on the node; the holder must hold the digest")

// LatePublish publishes a numbered build's held digest under its version on seat, from the builder's version.numbered
// body, when its kind is one of kinds. It answers false, nil for an event that is not the module's to publish: another
// kind, another seat (an event naming none is the artifact seat's, as the builder wrote it before images), or a version
// numbered with no digest.
func LatePublish(ctx context.Context, call SeatCall, body []byte, seat string, kinds ...string) (bool, error) {
	n, err := builds.DecodeVersionNumbered(body)
	if err != nil {
		return false, err
	}
	on := n.Seat
	if on == "" {
		on = ArtifactSeat
	}
	if n.Digest == "" || on != seat || !slices.Contains(kinds, n.Kind) {
		return false, nil
	}
	in := reg.PublishInput{Name: n.Name, Kind: n.Kind, Version: n.Version, Tag: n.Tag, Digest: n.Digest,
		Fingerprint: n.Fingerprint, Commit: n.Commit, Transfer: TransferName(n.Name, "v"+n.Version, n.Digest)}
	sent, err := OnSeat(ctx, seat, "late publish of "+n.Name+" "+n.Version+" at "+n.Digest, func() (parts.Sent, error) {
		return PublishParts(ctx, call, seat, in, []parts.Part{{Digest: n.Digest,
			Open: func() (io.ReadCloser, error) { return nil, errNotHere }}})
	}, nil)
	if err != nil {
		return false, fmt.Errorf("the late publish of %s@%s (%s): %w", n.Name, n.Version, n.Digest, err)
	}
	if len(sent.Parts) > 0 {
		return false, fmt.Errorf("the late publish of %s@%s sent parts it should not have", n.Name, n.Version)
	}
	return true, nil
}

// HearNumbered subscribes late to the builder's version.numbered, asking again until the runtime takes it, and says
// each publish and each failure; an error is the event's, which is offered again.
func HearNumbered(ctx context.Context, late func(ctx context.Context, body []byte) (bool, error)) {
	handle := func(e stdio.Envelope) error {
		did, err := late(ctx, e.Body)
		if err != nil {
			log.Printf("%v", err)
			return err
		}
		if did {
			log.Printf("published a numbered build's held digest under its version (%s)", e.Headers["x-event-id"])
		}
		return nil
	}
	for wait := 2 * time.Second; ; wait = min(wait*2, time.Minute) {
		err := stdio.Subscribe(NumberedPattern, handle)
		if err == nil {
			log.Printf("listening for the builder's %s", NumberedPattern)
			return
		}
		log.Printf("not hearing the builder's %s yet (%v); asking again in %s", NumberedPattern, err, wait)
		select {
		case <-ctx.Done():
			return
		case <-time.After(wait):
		}
	}
}