mesh-delivery/modules/mesh-delivery-builder/internal/versions/floor.go

package versions

import (
	"context"
	"fmt"
	"slices"
	"sort"
	"strings"
	"sync"
	"time"
)

// FloorSources are the three sources of a name's floor (design 51 *The floor*): each a tool call that answers the
// versions it knows of a name, or an error when it does not answer.
type FloorSources struct {
	// Seat is `seat:<registry>.versions` of the registry seat the name is published to.
	Seat func(ctx context.Context, seat, name string) ([]string, error)
	// Tags is the forge bridge's bridge_tags: the git tags of the repository the name is built from, under prefix.
	Tags func(ctx context.Context, repository, prefix string) ([]string, error)
	// Requirements is the indexer's indexer_requirements: the highest pseudo-versions consumers require.
	Requirements func(ctx context.Context, name string) ([]string, error)
}

// FloorOf names what a floor is asked for: the name on its seat, and the repository and tag prefix of its git tags.
type FloorOf struct{ Seat, Name, Repository, Prefix string }

// Ask asks the three sources of a name; a source that errs, or is not wired, is named in Silent with its error in why.
func (s FloorSources) Ask(ctx context.Context, of FloorOf) (Floor, map[string]string) {
	seat, name := of.Seat, of.Name
	var f Floor
	why := map[string]string{}
	ask := func(source string, call func() ([]string, error), into *[]string) {
		if call == nil {
			f.Silent, why[source] = append(f.Silent, source), "not asked: the builder has no path to it"
			return
		}
		got, err := call()
		if err != nil {
			f.Silent, why[source] = append(f.Silent, source), err.Error()
			return
		}
		*into = got
	}
	var seatCall, tagsCall, reqCall func() ([]string, error)
	if s.Seat != nil {
		seatCall = func() ([]string, error) { return s.Seat(ctx, seat, name) }
	}
	if s.Tags != nil {
		tagsCall = func() ([]string, error) { return s.Tags(ctx, of.Repository, of.Prefix) }
	}
	if s.Requirements != nil {
		reqCall = func() ([]string, error) { return s.Requirements(ctx, name) }
	}
	ask(SourceSeat, seatCall, &f.Seat)
	ask(SourceTags, tagsCall, &f.Tags)
	ask(SourceRequirements, reqCall, &f.Requirements)
	return f, why
}

// What wakes a name waiting on its floor, never a timer (design 51, DLV-B3b): the source that was silent saying
// something, or its module's health condition clearing.
const (
	// WakePublished is the holder's `published` on the builder's durable consumer of `<seat>.events`.
	WakePublished = "published"
	// WakeForge is the forge bridge's next message on its stream `forge`.
	WakeForge = "forge"
	// WakeAccepted is the indexer's next `manifest-accepted`.
	WakeAccepted = "manifest-accepted"
	// WakeCleared is the condition keeper's clear of a silent module's health condition on `mesh-conditions`.
	WakeCleared = "condition-cleared"
	// WakeByHand is builder_floor_again, a hand act.
	WakeByHand = "by hand"
)

// sourceOfWake is the floor source each event says something of; a clear names the source by its module.
var sourceOfWake = map[string]string{WakePublished: SourceSeat, WakeForge: SourceTags, WakeAccepted: SourceRequirements}

// ModuleOfSource is the module whose health condition's clear wakes a silent source.
var ModuleOfSource = map[string]string{
	SourceTags:         "mesh-delivery-forge-bridge",
	SourceRequirements: "mesh-delivery-indexer",
}

// FloorWait is one name waiting on its floor: the sources still silent and why, since when; the finding the builder
// writes names them, cleared once all three answer.
type FloorWait struct {
	Name   string            `json:"name"`
	Seat   string            `json:"seat"`
	Silent []string          `json:"silent"`
	Why    map[string]string `json:"why,omitempty"`
	Since  time.Time         `json:"since"`
	// Holder is the module holding the name's seat: its condition's clear wakes the seat source.
	Holder string `json:"holder,omitempty"`
}

// Finding is the floor finding's words.
func (w FloorWait) Finding() string {
	var parts []string
	for _, s := range w.Silent {
		p := s
		if why := w.Why[s]; why != "" {
			p += " (" + why + ")"
		}
		parts = append(parts, p)
	}
	return fmt.Sprintf("the floor of %s is not known since %s: %s did not answer; nothing of it is numbered until all three answer",
		w.Name, w.Since.UTC().Format(time.RFC3339), strings.Join(parts, ", "))
}

// FloorWaits are the names waiting on their floor. Wake answers which names to ask again for an event, Answered drops
// a name once all three answered; the builder's finding for each is the wait's Finding.
type FloorWaits struct {
	mu    sync.Mutex
	waits map[string]FloorWait
}

// Wait records that name's floor is not known.
func (fw *FloorWaits) Wait(name, seat, holder string, f Floor, why map[string]string, now time.Time) FloorWait {
	fw.mu.Lock()
	defer fw.mu.Unlock()
	if fw.waits == nil {
		fw.waits = map[string]FloorWait{}
	}
	w, had := fw.waits[name]
	if !had {
		w.Since = now
	}
	w.Name, w.Seat, w.Holder, w.Silent, w.Why = name, seat, holder, slices.Clone(f.Silent), why
	fw.waits[name] = w
	return w
}

// Answered drops name: its floor is known. It says whether the name waited, so its finding is cleared.
func (fw *FloorWaits) Answered(name string) bool {
	fw.mu.Lock()
	defer fw.mu.Unlock()
	_, had := fw.waits[name]
	delete(fw.waits, name)
	return had
}

// Wake answers the names to ask their floor again on an event: kind one of the Wake constants; seat the seat a
// `published` came on; module the module whose condition cleared. A name is woken only when the event says something
// of a source it waits on; WakeByHand with a name wakes that name alone.
func (fw *FloorWaits) Wake(kind, seat, module, name string) []string {
	fw.mu.Lock()
	defer fw.mu.Unlock()
	var out []string
	for n, w := range fw.waits {
		switch kind {
		case WakeByHand:
			if n == name {
				out = append(out, n)
			}
		case WakeCleared:
			for _, s := range w.Silent {
				if ModuleOfSource[s] == module || (s == SourceSeat && w.Holder != "" && w.Holder == module) {
					out = append(out, n)
					break
				}
			}
		default:
			src := sourceOfWake[kind]
			if slices.Contains(w.Silent, src) && (kind != WakePublished || seat == "" || seat == w.Seat) {
				out = append(out, n)
			}
		}
	}
	sort.Strings(out)
	return out
}

// Waiting is every wait, by name.
func (fw *FloorWaits) Waiting() []FloorWait {
	fw.mu.Lock()
	defer fw.mu.Unlock()
	out := make([]FloorWait, 0, len(fw.waits))
	for _, w := range fw.waits {
		out = append(out, w)
	}
	sort.Slice(out, func(i, j int) bool { return out[i].Name < out[j].Name })
	return out
}