package console

// The console's reads through the S3 change index (S3 change-index design
// §4.6, discussion #336). Armed only by CARLOS_CHANGE_INDEX=read, which
// cmd/console turns into a record view handed to SetRecordView; unarmed,
// recordView stays nil and every sweep walks the bucket as before.

import (
	"context"
	"log"

	"github.com/carlosframework/platform/internal/provision"
	"github.com/carlosframework/platform/internal/release"
)

// SetRecordView arms the run and seed sweeps' record reads with v. serve
// calls it once, before it starts any worker; nil leaves them disarmed.
func (s *Server) SetRecordView(v *provision.RecordView) { s.recordView = v }

// The viewUse states; zero is none yet.
const (
	viewUseView int32 = 1 + iota
	viewUseWalk
)

// recordWalkStore is the store a sweep's record walk reads: the armed view's
// snapshot over live, refreshed first, when the refresh returned nil and the
// snapshot is Complete. Otherwise ok is false and the store is live, so the
// sweep walks the bucket as it did before the index (spec §3.4).
//
// Only record walks take it (provision.ListAllRecords*). The snapshot's
// ListDirs of apps/<a>/ names only apps with record-family state, so it must
// never reach an app enumerator, and every write and every non-record read
// (runs/, seeds/) stays on live. ctx bounds the refresh, so a stuck index
// poll or walk cannot hold the view, or the sweep, for good.
func (s *Server) recordWalkStore(ctx context.Context, live release.Store) (release.Store, bool) {
	v := s.recordView
	if v == nil || live == nil {
		return live, false
	}
	err := v.Refresh(ctx)
	sn := v.Snapshot()
	switch {
	case err != nil:
		s.noteViewUse(false, "the record view's refresh failed: "+err.Error())
		return live, false
	case sn == nil || !sn.Complete:
		s.noteViewUse(false, "the record view's snapshot is incomplete")
		return live, false
	}
	s.noteViewUse(true, "")
	return sn.Store(live), true
}

// noteViewUse logs a switch between reading the view and walking the bucket,
// once per change rather than on every pass.
func (s *Server) noteViewUse(ok bool, why string) {
	state := viewUseWalk
	if ok {
		state = viewUseView
	}
	if s.viewUse.Swap(state) == state {
		return
	}
	if ok {
		log.Printf("console: record view: the sweeps' record walks read the view")
		return
	}
	log.Printf("console: record view: %s; the sweeps' record walks read the bucket until it can vouch again", why)
}