mesh-delivery/modules/mesh-delivery-sdk/steprun/askers.go

package steprun

import (
	"encoding/json"
	"fmt"
	"slices"
	"strings"
	"sync/atomic"

	buildrun "git.novox.be/novox/mesh-delivery/modules/mesh-delivery-sdk/buildrun"
	sdkstep "git.novox.be/novox/mesh-delivery/modules/mesh-delivery-sdk/buildstep"
	stdio "git.novox.be/novox/mesh-sdk/go"
	"git.novox.be/novox/mesh-sdk/go/seatdef"
	"git.novox.be/novox/mesh-sdk/go/seatlist"
)

// **A holder refuses a kind its asker may not ask** (design 47 G §543, A-163, A-170). An ask rides
// `mesh.seat.<seat>.accept.<queue>.<asker>`, the asker the asking seat's own name, and its kind stays in its body. The
// holder takes the asker from the subject and checks the kind against the callers the seat's definition lists for it (read
// from the seat list); on main's subject, which names no asker, it takes only a build and a run.

// KindOf is the word the seat definition gives an ask's kind: run for a run or a compose, else the ask's own kind.
func KindOf(ask sdkstep.StepAsk) string {
	if ask.Run != nil || ask.Compose != nil {
		return "run"
	}
	return ask.Kind
}

// CallersFromDefinitions is a Puller.Callers: the seats the definition of language's build seat lists as callers of an
// accepted kind, from the seat list's definitions (seatlist.Reader.Definitions). found is false when the definition or the
// kind is not held yet. A caller entry is `seat:<name>`.
func CallersFromDefinitions(language string, definitions func() map[string]seatdef.Definition) func(kind string) (callers []string, found bool) {
	return func(kind string) ([]string, bool) {
		seat, err := sdkstep.BuildSeat(language)
		if err != nil {
			return nil, false
		}
		def, ok := definitions()[seat]
		if !ok {
			return nil, false
		}
		var out []string
		found := false
		for _, m := range def.Accepts {
			if m.Name != kind {
				continue
			}
			found = true
			if m.Callers != nil {
				for _, e := range m.Callers.List {
					if name, ok := strings.CutPrefix(e, "seat:"); ok {
						out = append(out, name)
					}
				}
			}
		}
		return out, found
	}
}

// askerRefusal is why an ask must not be taken from its subject's asker: "" when it may be, and judged false when the seat
// list does not say yet (the ask is given back, not refused).
func (p *Puller) askerRefusal(msg *Pulled, ask sdkstep.StepAsk) (why string, judged bool) {
	if msg.Subject == "" {
		return "", true // a source that gives no subject (a test's)
	}
	_, _, asker, err := sdkstep.ParseAskSubjectBy(msg.Subject)
	if err != nil {
		return fmt.Sprintf("the ask came on %s, which is no accept subject of this seat", msg.Subject), true
	}
	kind := KindOf(ask)
	if asker == "" {
		if (ask.Build != nil && ask.Kind == sdkstep.AskDelivery) || kind == "run" {
			return "", true
		}
		return fmt.Sprintf("the kind %s is not taken on main's subject, which takes only a build and a run (asker: none named)", kind), true
	}
	if p.Callers == nil {
		return "", true
	}
	callers, found := p.Callers(kind)
	if !found {
		return "", false
	}
	if !slices.Contains(callers, asker) {
		return fmt.Sprintf("the kind %s is not one %s may ask: its callers are %s", kind, asker, strings.Join(callers, ", ")), true
	}
	return "", true
}

// refuseAsker ends an ask whose asker may not ask its kind: its step key says failed with the reason, naming the kind and the
// asker, step-ended says failed, and the message is dropped.
func (p *Puller) refuseAsker(msg *Pulled, ask sdkstep.StepAsk, why string) {
	key, err := sdkstep.AskStepKey(p.Node, ask.ID)
	if err == nil {
		at := now().UTC()
		step := sdkstep.Step{ID: ask.ID, Tool: ask.Kind + " ask", Node: p.Node, State: sdkstep.StepFailed, Started: at, Ended: at,
			Reason: "error: " + why, Owner: buildrun.Owner, Run: int(msg.Delivered)}
		err = writeEnd(p.Put, key, step)
	}
	if err != nil {
		p.logf("the ask %s of the wrong asker cannot be answered on %s, so it is given back: %v", ask.ID, p.Node, err)
		_ = msg.Nak()
		return
	}
	p.logf("the ask %s is refused on %s: %s", ask.ID, p.Node, why)
	if ask.Step == nil {
		p.sayEnded(msg, ask, sdkstep.OutcomeFailed, why, nil)
	} else if end, err := sdkstep.EndOf(ask, p.Node, sdkstep.OutcomeFailed); err == nil {
		// A pipeline step's end names its pipeline, step, commit and fingerprint (its own form, §602).
		end.Said, end.At, end.Asker = why, now().UTC(), askerOf(msg, ask)
		if body, err := sdkstep.EncodeStepEnded(end); err == nil {
			p.say("step-ended", json.RawMessage(body), "step-ended."+ask.ID)
		}
	}
	_ = msg.Term()
}

// giveBack hands an ask back to be judged again a little later, once the seat list says more.
func (p *Puller) giveBack(msg *Pulled, ask sdkstep.StepAsk) {
	p.logf("the ask %s is given back on %s: the seat list holds no definition of its kind yet", ask.ID, p.Node)
	if msg.NakAfter != nil && msg.NakAfter(DefaultPullWait) == nil {
		return
	}
	_ = msg.Nak()
}

// SeatListCallers is a Puller.Callers that follows the seat list: it starts the reader once the runtime serves
// (seatlist.Start through the runtime's own way in) and answers from its definitions, found false until it has read them.
// A reader that cannot start is said and the asks are given back until it can (design 47 G §543, A-163).
func SeatListCallers(language string, logf func(format string, args ...any)) func(kind string) ([]string, bool) {
	var reader atomic.Pointer[seatlist.Reader]
	go func() {
		<-stdio.Served()
		r, err := seatlist.Start(seatlist.Config{Bus: seatlist.StdioBus(), Bootstrap: seatlist.Bootstrapped()})
		if err != nil && logf != nil {
			logf("following the seat list: %v", err)
		}
		reader.Store(r)
	}()
	return func(kind string) ([]string, bool) {
		r := reader.Load()
		if r == nil {
			return nil, false
		}
		return CallersFromDefinitions(language, r.Definitions)(kind)
	}
}