package moves

import "time"

// The steps of a StoppedReport, in §5.3's order. StepTree to StepLease
// are what stopevidence.Reconstruct observes from the box's durable state;
// StepReplica is the caller's (the cut's step 5: the final checkpoint and
// the digests), set after the checkpoint.
const (
	// StepTree: the host's cgroup was killed and drained (or never existed).
	StepTree = "tree"
	// StepStray: the agent's own cgroup leaf holds only the agent.
	StepStray = "stray"
	// StepFDs: no visible process holds the database, its WAL or its SHM.
	StepFDs = "fds"
	// StepLease: the host's lock.json is absent, released, or expired by
	// more than the lease's renewal margin.
	StepLease = "lease"
	// StepReplica: the final checkpoint reached the replica.
	StepReplica = "replica"
)

// treeSteps are §5.3 steps 1 to 4, what `stopping` needs before the final
// checkpoint. allSteps adds the replica.
var (
	treeSteps = [...]string{StepTree, StepStray, StepFDs, StepLease}
	allSteps  = [...]string{StepTree, StepStray, StepFDs, StepLease, StepReplica}
)

// StoppedReport is a role's stop evidence for one move operation (§5.3),
// written to moves/<acct>/<app>/<host>/<op id>/stopped-<role>.json. Every
// observation is from durable, observable state, so a restarted agent
// writes the same report. Steps holds one Check per step id; a step that
// never ran is absent, and an absent step is not OK. Stray lists the pids
// StepStray found in the agent's leaf besides the agent, for the alert. A 0
// in it marks members the box could not identify (not visible in its pid
// namespace).
type StoppedReport struct {
	V            int              `json:"v"`
	Role         string           `json:"role"`
	Box          string           `json:"box"`
	Incarnation  string           `json:"incarnation"`
	ClaimGen     uint64           `json:"claim_gen"`
	Host         string           `json:"host"`
	OpID         string           `json:"op_id"`
	Steps        map[string]Check `json:"steps"`
	Stray        []int            `json:"stray,omitempty"`
	FinalTXID    uint64           `json:"final_txid"`
	DBSHA256     string           `json:"db_sha256"`
	FilesPlain   string           `json:"files_plain"`
	TimersSHA256 string           `json:"timers_sha256"`
	CheckedAt    time.Time        `json:"checked_at"`
}

// TreeStopped reports §5.3 steps 1 to 4 all present and OK: the writer has
// fully stopped, so the final checkpoint may run.
func (r StoppedReport) TreeStopped() bool {
	return r.stepsOK(treeSteps[:])
}

// Complete reports every step OK, StepReplica included. It fails closed on
// any other step recorded in the report and not OK, so a step a later
// version adds cannot be ignored by an older reader.
func (r StoppedReport) Complete() bool {
	if !r.stepsOK(allSteps[:]) {
		return false
	}
	for _, c := range r.Steps {
		if !c.OK {
			return false
		}
	}
	return true
}

func (r StoppedReport) stepsOK(ids []string) bool {
	for _, id := range ids {
		if c, ok := r.Steps[id]; !ok || !c.OK {
			return false
		}
	}
	return true
}