package watch

import (
	"encoding/json"
	"time"
)

// ChecksBucket is the bucket of the checks the builders are running (mesh-controller internal/broker
// CheckRunningBucket).
const ChecksBucket = "mesh-controller_checks-running"

// checkRecord is the part of a running check's key the watchman reads, as the controller's builder writes it
// (mesh-controller internal/link/checks_nats.go CheckRunning): the head being checked.
type checkRecord struct {
	Head string `json:"head"`
}

// Check is a change in the checks-running bucket. The builder puts a check's key when the check starts and puts it
// again at every heartbeat while the check lives, and deletes it when the check ends. Each new revision of the key is
// the check moving: the pulse is deleted and written again with the full bound from that revision's time, so only a
// check whose builder stops heartbeating for the whole bound is stuck; the key deleted is the check ended. An aged-out
// key is the bucket's own expiry of a builder that died: the pulse is left to run out.
func (w *Watchman) Check(key string, value []byte, at time.Time, op Op) {
	w.mu.Lock()
	defer w.mu.Unlock()
	switch op {
	case Expired:
		return
	case Delete:
		w.moved(ChecksBucket, key)
		return
	}
	var rec checkRecord
	_ = json.Unmarshal(value, &rec)
	if at.IsZero() {
		at = w.now()
	}
	if _, stalled := w.ttl(w.now().Sub(at)); !stalled {
		w.stuckMoved(ChecksBucket, key)
	}
	w.mirror(ChecksBucket, key, describe("the check of %s to end", key), rec.Head, at, 0)
}