// Package health defines the technical-health domain types owned by
// Runtime Manager.
//
// EventType matches the `event_type` enum frozen in
// `galaxy/rtmanager/api/runtime-health-asyncapi.yaml`. SnapshotStatus
// matches the SQL CHECK on `health_snapshots.status` and is intentionally
// narrower than EventType (the snapshot table collapses
// `container_started → healthy` and drops `probe_recovered` per
// `galaxy/rtmanager/README.md §Health Monitoring`).
package health

import (
	"encoding/json"
	"fmt"
	"strings"
	"time"
)

// EventType identifies one entry on the `runtime:health_events` Redis
// Stream. Used by the health-event publishers and consumers.
type EventType string

const (
	// EventTypeContainerStarted reports a successful container start.
	EventTypeContainerStarted EventType = "container_started"

	// EventTypeContainerExited reports a non-zero Docker `die` event.
	EventTypeContainerExited EventType = "container_exited"

	// EventTypeContainerOOM reports a Docker `oom` event.
	EventTypeContainerOOM EventType = "container_oom"

	// EventTypeContainerDisappeared reports that the listener observed
	// a `destroy` event for a record Runtime Manager did not initiate.
	EventTypeContainerDisappeared EventType = "container_disappeared"

	// EventTypeInspectUnhealthy reports an unexpected outcome of the
	// periodic Docker inspect (RestartCount growth, unexpected status,
	// declared HEALTHCHECK reporting unhealthy).
	EventTypeInspectUnhealthy EventType = "inspect_unhealthy"

	// EventTypeProbeFailed reports that the active HTTP probe crossed
	// the configured failure threshold.
	EventTypeProbeFailed EventType = "probe_failed"

	// EventTypeProbeRecovered reports the first probe success after a
	// `probe_failed` event was published.
	EventTypeProbeRecovered EventType = "probe_recovered"
)

// IsKnown reports whether eventType belongs to the frozen event-type
// vocabulary.
func (eventType EventType) IsKnown() bool {
	switch eventType {
	case EventTypeContainerStarted,
		EventTypeContainerExited,
		EventTypeContainerOOM,
		EventTypeContainerDisappeared,
		EventTypeInspectUnhealthy,
		EventTypeProbeFailed,
		EventTypeProbeRecovered:
		return true
	default:
		return false
	}
}

// AllEventTypes returns the frozen list of every event-type value.
func AllEventTypes() []EventType {
	return []EventType{
		EventTypeContainerStarted,
		EventTypeContainerExited,
		EventTypeContainerOOM,
		EventTypeContainerDisappeared,
		EventTypeInspectUnhealthy,
		EventTypeProbeFailed,
		EventTypeProbeRecovered,
	}
}

// SnapshotStatus identifies one latest-observation status value stored
// in the `health_snapshots.status` column. Distinct from EventType: the
// table collapses `container_started → healthy` and never persists
// `probe_recovered` (it is conveyed only as a `runtime:health_events`
// entry with status=healthy in the next observation).
type SnapshotStatus string

const (
	// SnapshotStatusHealthy reports that the most recent observation
	// found the container live and the engine probe responsive.
	SnapshotStatusHealthy SnapshotStatus = "healthy"

	// SnapshotStatusProbeFailed reports that the active probe crossed
	// the failure threshold.
	SnapshotStatusProbeFailed SnapshotStatus = "probe_failed"

	// SnapshotStatusExited reports that the container exited.
	SnapshotStatusExited SnapshotStatus = "exited"

	// SnapshotStatusOOM reports that the container was killed by the
	// OOM killer.
	SnapshotStatusOOM SnapshotStatus = "oom"

	// SnapshotStatusInspectUnhealthy reports that the periodic inspect
	// observed an unexpected state.
	SnapshotStatusInspectUnhealthy SnapshotStatus = "inspect_unhealthy"

	// SnapshotStatusContainerDisappeared reports that Docker no longer
	// reports the container.
	SnapshotStatusContainerDisappeared SnapshotStatus = "container_disappeared"
)

// IsKnown reports whether status belongs to the frozen snapshot-status
// vocabulary.
func (status SnapshotStatus) IsKnown() bool {
	switch status {
	case SnapshotStatusHealthy,
		SnapshotStatusProbeFailed,
		SnapshotStatusExited,
		SnapshotStatusOOM,
		SnapshotStatusInspectUnhealthy,
		SnapshotStatusContainerDisappeared:
		return true
	default:
		return false
	}
}

// AllSnapshotStatuses returns the frozen list of every snapshot-status
// value.
func AllSnapshotStatuses() []SnapshotStatus {
	return []SnapshotStatus{
		SnapshotStatusHealthy,
		SnapshotStatusProbeFailed,
		SnapshotStatusExited,
		SnapshotStatusOOM,
		SnapshotStatusInspectUnhealthy,
		SnapshotStatusContainerDisappeared,
	}
}

// SnapshotSource identifies the observation source that produced one
// snapshot. Matches the SQL CHECK on `health_snapshots.source`.
type SnapshotSource string

const (
	// SnapshotSourceDockerEvent reports that the latest observation
	// arrived through the Docker events listener.
	SnapshotSourceDockerEvent SnapshotSource = "docker_event"

	// SnapshotSourceInspect reports that the latest observation arrived
	// through the periodic Docker inspect worker.
	SnapshotSourceInspect SnapshotSource = "inspect"

	// SnapshotSourceProbe reports that the latest observation arrived
	// through the active HTTP probe.
	SnapshotSourceProbe SnapshotSource = "probe"
)

// IsKnown reports whether source belongs to the frozen snapshot-source
// vocabulary.
func (source SnapshotSource) IsKnown() bool {
	switch source {
	case SnapshotSourceDockerEvent,
		SnapshotSourceInspect,
		SnapshotSourceProbe:
		return true
	default:
		return false
	}
}

// AllSnapshotSources returns the frozen list of every snapshot-source
// value.
func AllSnapshotSources() []SnapshotSource {
	return []SnapshotSource{
		SnapshotSourceDockerEvent,
		SnapshotSourceInspect,
		SnapshotSourceProbe,
	}
}

// HealthSnapshot stores the latest technical-health observation for one
// game. One row per game_id; later observations overwrite.
type HealthSnapshot struct {
	// GameID identifies the platform game.
	GameID string

	// ContainerID stores the Docker container id observed by the
	// snapshot source. Empty when the source could not associate a
	// container (e.g., reconciler dispose for a record whose container
	// is already gone).
	ContainerID string

	// Status stores the latest observed snapshot status.
	Status SnapshotStatus

	// Source stores the observation source that produced this entry.
	Source SnapshotSource

	// Details stores the source-specific JSON detail payload. Adapters
	// store and retrieve it verbatim. Empty / nil values are persisted
	// as the SQL default `{}`.
	Details json.RawMessage

	// ObservedAt stores the wall-clock at which the source captured the
	// observation.
	ObservedAt time.Time
}

// Validate reports whether snapshot satisfies the snapshot invariants
// implied by the SQL CHECK constraints.
func (snapshot HealthSnapshot) Validate() error {
	if strings.TrimSpace(snapshot.GameID) == "" {
		return fmt.Errorf("game id must not be empty")
	}
	if !snapshot.Status.IsKnown() {
		return fmt.Errorf("status %q is unsupported", snapshot.Status)
	}
	if !snapshot.Source.IsKnown() {
		return fmt.Errorf("source %q is unsupported", snapshot.Source)
	}
	if snapshot.ObservedAt.IsZero() {
		return fmt.Errorf("observed at must not be zero")
	}
	if len(snapshot.Details) > 0 && !json.Valid(snapshot.Details) {
		return fmt.Errorf("details must be valid JSON when non-empty")
	}

	return nil
}