package conditions

import "time"

// The events a condition's life emits (to-be 45 §2), as the mesh-controller seat's own: published on
// `mesh.seat.mesh-controller.event.<name>`, on the events stream, so a consumer that was away catches
// up. **This is a contract**: the operator-channel's holder is written against these names and the
// shape of Event, and the controller learns nothing about telling.
const (
	// EventRaised: a condition was raised — new, or the same fault again within ReopenWithin of its
	// clearing (Change says which). A reopened condition is not news: its key is the one the
	// first message was about.
	EventRaised = "condition-raised"
	// EventChanged: its severity, its resolver or its silence changed. Not every observation: a
	// condition observed again is written, and says nothing.
	EventChanged = "condition-changed"
	// EventCleared: an observation says it is resolved. The condition is removed from the store and
	// the transition kept in its history.
	EventCleared = "condition-cleared"
)

// Events is every event a condition's life emits.
var Events = []string{EventRaised, EventChanged, EventCleared}

// HeartbeatEvent is the self-check's heartbeat (to-be 45 §4, S10), said under the same seat at the end
// of every run: `{run, at, interval-seconds, counts: {passed, failed, failed-to-run, deferred}, probes,
// controller, why}`. mesh-watcher, on a machine that is not the control node, listens for it.
const HeartbeatEvent = "doctor-heartbeat"

// What changed, as an event's Change and a history entry's says it.
const (
	ChangeRaised     = "raised"
	ChangeReopened   = "reopened"
	ChangeSeverity   = "severity"
	ChangeResolver   = "resolver"
	ChangeSilenced   = "silenced"
	ChangeUnsilenced = "silence-ended"
	ChangeCleared    = "cleared"
)

// Event is the body of every condition event, and the shape a history entry keeps: **the condition
// itself, at the top level** — key, kind, subject, severity, summary, source, raised, last-observed,
// observations, resolver, silenced (null when not), epoch, and the evidence — with what happened to
// it beside. One object a consumer reads the same way whichever of the three it is.
type Event struct {
	// Condition is the condition after the transition — as it was last held, for a clearing.
	Condition
	// Event is the event's own name, so a body read without its subject still says what it is.
	Event string `json:"event"`
	// At is when the transition happened.
	At time.Time `json:"at"`
	// Change is what happened: raised, reopened, severity, resolver, silenced, silence-ended, cleared.
	Change string `json:"change"`
	// Was is the value before, for a severity or resolver change.
	Was string `json:"was,omitempty"`
	// Why says why it cleared, or why it was silenced.
	Why string `json:"why,omitempty"`
	// Cleared is when it cleared, on a clearing.
	Cleared *time.Time `json:"cleared,omitempty"`
	// Show is the verb that shows more.
	Show string `json:"show"`
}

// eventFor is the event a change is said under.
func eventFor(change string) string {
	switch change {
	case ChangeRaised, ChangeReopened:
		return EventRaised
	case ChangeCleared:
		return EventCleared
	}
	return EventChanged
}