package host

import (
	"context"

	"github.com/carlosframework/platform/internal/hostbox"
	"github.com/carlosframework/platform/internal/hostguard"
)

type servingParkDisposition uint8

const (
	servingParkRefuse servingParkDisposition = iota
	servingParkArtifactFree
	servingParkDiscard
	servingParkRetain
)

// servingGenerationParkDisposition is a root-side decision made after source
// capture and stop authentication. The database must exist to own the slot.
// A prelaunch record alone proves no tenant started. Once a main-role launch
// was intended, missing start evidence is ambiguous: StartedUnit is recorded
// after the process may have run. Preserve that source and refuse retirement.
// Task 0R's filesystem driver must persist this decision with its source
// identities before either replacing the slot or discarding a restore.
func servingGenerationParkDisposition(ctx context.Context, journal *hostbox.LaunchJournal, prior servingArtifactIdentity, receipts []hostguard.FenceReceipt, databasePresent bool) (servingParkDisposition, error) {
	if ctx == nil || journal == nil || prior.Host == "" || prior.Box == "" || prior.Region == "" || prior.Incarnation == "" || prior.Generation == "" || prior.Stamp == 0 || prior.Session == 0 || len(receipts) == 0 {
		return servingParkRefuse, hostbox.ErrChanged
	}
	launched := false
	for _, receipt := range receipts {
		t := receipt.Target
		if t.Host != prior.Host || t.Box != prior.Box || t.Region != prior.Region || t.Incarnation != prior.Incarnation || t.Stamp != prior.Stamp || t.Session != prior.Session || t.Op != "" || t.Phase != "" || t.ObligationID != "" || verifyRetirementReceipt(ctx, receipt) != nil {
			return servingParkRefuse, ErrClaimStopReceipt
		}
	}
	if databasePresent {
		t := receipts[0].Target
		records, err := journal.RootSessionLaunches(ctx, prior.Host, prior.Incarnation, prior.Stamp, prior.Session, prior.Box, t.Enrollment)
		if err != nil {
			return servingParkRefuse, err
		}
		if len(records) != 1 {
			return servingParkRefuse, hostbox.ErrChanged
		}
		record := records[0]
		matched := false
		for _, receipt := range receipts {
			matched = matched || hostbox.SameLaunchOwner(record.Target, receipt.Target)
		}
		if !matched {
			return servingParkRefuse, hostbox.ErrChanged
		}
		seen := make(map[string]bool)
		for _, reservation := range record.Reservations {
			if reservation.Role != "main" {
				continue
			}
			if reservation.ID == "" || seen[reservation.ID] || !hostbox.SameLaunchOwner(reservation.Target, record.Target) {
				return servingParkRefuse, hostbox.ErrChanged
			}
			seen[reservation.ID] = true
			if reservation.NeverIntended && record.WritersClosed && reservation.State == hostbox.UnitSettled && reservation.PID == 0 && reservation.ProcessStart == "" && reservation.Group.InvocationID == "" && reservation.Group.Device == 0 && reservation.Group.Inode == 0 {
				continue
			}
			if !hostbox.IsUnitReservation(reservation) || reservation.State != hostbox.UnitSettled || reservation.PID <= 0 || reservation.ProcessStart == "" || reservation.Group.InvocationID == "" || reservation.Group.Device == 0 || reservation.Group.Inode == 0 || reservation.Executable.Device == 0 || reservation.Executable.Inode == 0 {
				return servingParkRefuse, hostbox.ErrChanged
			}
			launched = true
		}
	}
	if !databasePresent {
		return servingParkArtifactFree, nil
	}
	if launched {
		return servingParkRetain, nil
	}
	return servingParkDiscard, nil
}