package hostguard

import (
	"bytes"
	"context"
)

// SettleRootInventory completes only the already persisted installation intent.
// The callback may finish its journal after independently proving its effects;
// it must not create effects or infer an intention from service state.
func (g Guard) SettleRootInventory(ctx context.Context, host string, intent []byte, settle func(RootInstallation) error) error {
	if g.Root == nil || settle == nil {
		return ErrInvalidInput
	}
	return g.readLocked(ctx, host, func(d *recordDir) error {
		r, err := d.read(host)
		if err != nil {
			return err
		}
		if r.pendingInstallation == nil || !bytes.Equal(r.pendingInventory, intent) {
			return ErrInvalidInput
		}
		in := *r.pendingInstallation
		if r.installation.Incarnation != in.Incarnation || r.installation.Stamp != in.Stamp || r.installation.InventoryRevision+1 != in.InventoryRevision || r.ActiveStamp != in.Stamp {
			return ErrRecordIncarnation
		}
		if err := settle(in); err != nil {
			return err
		}
		r.installation = in
		r.pendingInventory, r.pendingInstallation = nil, nil
		return d.write(r)
	})
}