mesh-tools/node-tools/internal/firstview/approval.go

package firstview

import (
	"context"
	"strconv"
	"time"

	"git.novox.be/novox/mesh-delivery/contracts/go/clients/meshcatalogclient"
	catalogseat "git.novox.be/novox/mesh-delivery/contracts/go/seats/meshcatalog"
	"git.novox.be/novox/mesh-sdk/go/seatdef"

	"github.com/novox/mesh-tools/node-tools/internal/approval"
)

// Findings is the runner's held finding writer, the one the gate writes its findings through too (design 46 7-approval-mark
// §4, §16, §19); nil when it was not made.
func (v *Views) Findings() approval.FindingWriter {
	if v.deps.Findings == nil {
		return nil
	}
	return v.deps.Findings
}

// ApprovalCatalog is the catalog half as the gate reads its marks (design 46 7-approval-mark §5): the entries the branch
// follower holds, an entry by fingerprint asked of `mesh-catalog.entry` when no branch lists it, and the seat definitions
// the seat list holds (defs).
func (v *Views) ApprovalCatalog(defs func() map[string]seatdef.Definition) approval.Catalog {
	return approvalCatalog{v: v, defs: defs}
}

type approvalCatalog struct {
	v    *Views
	defs func() map[string]seatdef.Definition
}

func (c approvalCatalog) Ready() error {
	if c.v.branches == nil {
		return errNotFollowed
	}
	return c.v.branches.Ready()
}

func (c approvalCatalog) Revision() string {
	if c.v.branches == nil {
		return ""
	}
	for _, branch := range c.v.branches.Followed() {
		if cat, ok := c.v.branches.Catalog(branch); ok {
			if half, ok := cat.View(); ok {
				return strconv.FormatInt(half.Revision.Revision, 10)
			}
		}
	}
	return ""
}

func (c approvalCatalog) Served(fingerprint string) (catalogseat.CatalogEntry, bool, string) {
	if c.v.branches == nil {
		return catalogseat.CatalogEntry{}, false, errNotFollowed.Error()
	}
	e, state := c.v.branches.Resolve(context.Background(), fingerprint)
	return e, state == meshcatalogclient.EntryAnswered, string(state)
}

func (c approvalCatalog) Newest(module string) (catalogseat.CatalogEntry, bool) {
	if c.v.branches == nil {
		return catalogseat.CatalogEntry{}, false
	}
	e, ok, err := c.v.branches.Entry(module)
	return e, ok && err == nil
}

func (c approvalCatalog) Definitions() map[string]seatdef.Definition {
	if c.defs == nil {
		return nil
	}
	return c.defs()
}

type notFollowed struct{}

func (notFollowed) Error() string { return "the catalog half is not followed by this runner" }

var errNotFollowed error = notFollowed{}

// heardOne wakes every wait on the picture.
func (v *Views) heardOne() {
	v.mu.Lock()
	defer v.mu.Unlock()
	if v.heard != nil {
		close(v.heard)
	}
	v.heard = make(chan struct{})
}

// heardNext is closed at the next event heard.
func (v *Views) heardNext() <-chan struct{} {
	v.mu.Lock()
	defer v.mu.Unlock()
	if v.heard == nil {
		v.heard = make(chan struct{})
	}
	return v.heard
}

// WaitCatalog waits within the bound for the catalog half's first view of every watched branch (design 46 7-approval-mark
// §19), waking at each event the runner hears and at each first view answered; nil once it is read, else why not.
func (v *Views) WaitCatalog(within time.Duration) error {
	c := approvalCatalog{v: v}
	timer := time.NewTimer(within)
	defer timer.Stop()
	for {
		next := v.heardNext()
		err := c.Ready()
		if err == nil {
			return nil
		}
		var ready []<-chan struct{}
		if v.branches != nil {
			for _, branch := range v.branches.Followed() {
				if cat, ok := v.branches.Catalog(branch); ok {
					select {
					case <-cat.Ready(): // read already: waits on nothing
					default:
						ready = append(ready, cat.Ready())
					}
				}
			}
		}
		if !waitAny(next, timer.C, ready) {
			return c.Ready()
		}
	}
}

// waitAny waits for next or one of ready, true, or for the bound, false.
func waitAny(next <-chan struct{}, bound <-chan time.Time, ready []<-chan struct{}) bool {
	woke := make(chan struct{}, 1)
	stop := make(chan struct{})
	defer close(stop)
	for _, r := range ready {
		go func(r <-chan struct{}) {
			select {
			case <-r:
				woke <- struct{}{}
			case <-stop:
			}
		}(r)
	}
	select {
	case <-next:
	case <-woke:
	case <-bound:
		return false
	}
	return true
}