// Package runtime defines the runtime-record domain model, status machine,
// and sentinel errors owned by Runtime Manager.
//
// The package mirrors the durable shape of the `runtime_records`
// PostgreSQL table (see
// `galaxy/rtmanager/internal/adapters/postgres/migrations/00001_init.sql`).
// Every status / transition / required-field rule already documented in
// `galaxy/rtmanager/README.md` lives here as code so adapter and service
// layers do not re-derive it.
package runtime

import (
	"fmt"
	"strings"
	"time"
)

// Status identifies one runtime-record lifecycle state.
type Status string

const (
	// StatusRunning reports that an engine container is live and bound to
	// the record. The associated container id and image ref are non-empty
	// and StartedAt is set.
	StatusRunning Status = "running"

	// StatusStopped reports that the engine container has exited (graceful
	// stop, observed Docker exit, or reconciled exit). The container is
	// still present in Docker until the cleanup worker removes it.
	StatusStopped Status = "stopped"

	// StatusRemoved reports that the container has been removed from
	// Docker (admin cleanup or reconcile_dispose). The record stays in
	// PostgreSQL for audit; there is no transition out of this state.
	StatusRemoved Status = "removed"
)

// IsKnown reports whether status belongs to the frozen runtime status
// vocabulary.
func (status Status) IsKnown() bool {
	switch status {
	case StatusRunning, StatusStopped, StatusRemoved:
		return true
	default:
		return false
	}
}

// IsTerminal reports whether status can no longer accept lifecycle
// transitions.
func (status Status) IsTerminal() bool {
	return status == StatusRemoved
}

// AllStatuses returns the frozen list of every runtime status value. The
// slice order is stable across calls and matches the README §Persistence
// Layout listing.
func AllStatuses() []Status {
	return []Status{
		StatusRunning,
		StatusStopped,
		StatusRemoved,
	}
}

// RuntimeRecord stores one durable runtime record owned by Runtime
// Manager. It mirrors one row of the `runtime_records` table.
//
// CurrentContainerID and CurrentImageRef are stored as plain strings; an
// empty value represents SQL NULL and is bridged at the adapter layer.
// StartedAt, StoppedAt, and RemovedAt are *time.Time so a missing value
// is unambiguous and aligns with the jet-generated model.
type RuntimeRecord struct {
	// GameID identifies the platform game owning this runtime record.
	GameID string

	// Status stores the current lifecycle state.
	Status Status

	// CurrentContainerID identifies the bound Docker container. Empty
	// when status is removed and after a reconciler observes
	// disappearance.
	CurrentContainerID string

	// CurrentImageRef stores the Docker reference of the currently-bound
	// engine image. Non-empty when status is running or stopped.
	CurrentImageRef string

	// EngineEndpoint stores the stable URL Game Master uses to reach the
	// engine container, in `http://galaxy-game-{game_id}:8080` form.
	EngineEndpoint string

	// StatePath stores the absolute host path of the bind-mounted engine
	// state directory.
	StatePath string

	// DockerNetwork stores the Docker network the container was attached
	// to at create time.
	DockerNetwork string

	// StartedAt stores the wall-clock at which the container became
	// running. Non-nil when status is running or stopped.
	StartedAt *time.Time

	// StoppedAt stores the wall-clock at which the container exited.
	// Non-nil when status is stopped or removed (when the record passed
	// through stopped before removal).
	StoppedAt *time.Time

	// RemovedAt stores the wall-clock at which the container was removed
	// from Docker. Non-nil when status is removed.
	RemovedAt *time.Time

	// LastOpAt stores the wall-clock of the most recent operation
	// affecting this record. Drives the cleanup TTL.
	LastOpAt time.Time

	// CreatedAt stores the wall-clock at which Runtime Manager first saw
	// this game.
	CreatedAt time.Time
}

// Validate reports whether record satisfies the runtime-record invariants
// implied by README §Lifecycles and the SQL CHECK on `runtime_records`.
func (record RuntimeRecord) Validate() error {
	if strings.TrimSpace(record.GameID) == "" {
		return fmt.Errorf("game id must not be empty")
	}
	if !record.Status.IsKnown() {
		return fmt.Errorf("status %q is unsupported", record.Status)
	}
	if strings.TrimSpace(record.EngineEndpoint) == "" {
		return fmt.Errorf("engine endpoint must not be empty")
	}
	if strings.TrimSpace(record.StatePath) == "" {
		return fmt.Errorf("state path must not be empty")
	}
	if strings.TrimSpace(record.DockerNetwork) == "" {
		return fmt.Errorf("docker network must not be empty")
	}
	if record.LastOpAt.IsZero() {
		return fmt.Errorf("last op at must not be zero")
	}
	if record.CreatedAt.IsZero() {
		return fmt.Errorf("created at must not be zero")
	}
	if record.LastOpAt.Before(record.CreatedAt) {
		return fmt.Errorf("last op at must not be before created at")
	}

	switch record.Status {
	case StatusRunning:
		if strings.TrimSpace(record.CurrentContainerID) == "" {
			return fmt.Errorf("current container id must not be empty for running records")
		}
		if strings.TrimSpace(record.CurrentImageRef) == "" {
			return fmt.Errorf("current image ref must not be empty for running records")
		}
		if record.StartedAt == nil {
			return fmt.Errorf("started at must not be nil for running records")
		}
		if record.StartedAt.IsZero() {
			return fmt.Errorf("started at must not be zero when present")
		}

	case StatusStopped:
		if strings.TrimSpace(record.CurrentImageRef) == "" {
			return fmt.Errorf("current image ref must not be empty for stopped records")
		}
		if record.StoppedAt == nil {
			return fmt.Errorf("stopped at must not be nil for stopped records")
		}
		if record.StoppedAt.IsZero() {
			return fmt.Errorf("stopped at must not be zero when present")
		}

	case StatusRemoved:
		if record.RemovedAt == nil {
			return fmt.Errorf("removed at must not be nil for removed records")
		}
		if record.RemovedAt.IsZero() {
			return fmt.Errorf("removed at must not be zero when present")
		}
	}

	if record.StartedAt != nil && record.StartedAt.Before(record.CreatedAt) {
		return fmt.Errorf("started at must not be before created at")
	}
	if record.StoppedAt != nil && record.StartedAt != nil && record.StoppedAt.Before(*record.StartedAt) {
		return fmt.Errorf("stopped at must not be before started at")
	}
	if record.RemovedAt != nil && record.RemovedAt.Before(record.CreatedAt) {
		return fmt.Errorf("removed at must not be before created at")
	}

	return nil
}