package host

import (
	"context"

	"github.com/carlosframework/platform/internal/hostclaim"
	"github.com/carlosframework/platform/internal/moves"
	"github.com/carlosframework/platform/internal/park"
	"github.com/carlosframework/platform/internal/provision"
)

// CommittedLandingRecords is hostclaim.CommittedLandingGuard over the
// authoritative instance record: the move named by the claim's op has
// committed for this incarnation (provision.MoveCommitted, no rollback),
// and the regions and park scopes are the commit's (moves.CommitScopes),
// the regions as engine regions.
type CommittedLandingRecords struct{ Records MovesRecordReader }

var _ hostclaim.CommittedLandingGuard = CommittedLandingRecords{}

func (g CommittedLandingRecords) CheckLandingCommitted(ctx context.Context, o hostclaim.Observed, opID string) (hostclaim.CommittedLanding, error) {
	c := o.Claim
	if g.Records == nil || c == nil || c.Holder == nil || c.Op.ID != opID {
		return hostclaim.CommittedLanding{}, hostclaim.ErrWrongState
	}
	rec, err := g.Records(ctx, c.Holder.Account, c.Holder.App, o.Host)
	if err != nil {
		return hostclaim.CommittedLanding{}, err
	}
	if rec == nil || rec.Move == nil {
		return hostclaim.CommittedLanding{}, hostclaim.ErrWrongState
	}
	m := rec.Move
	if m.ID != opID || m.Incarnation != c.Holder.Incarnation || m.State != provision.MoveCommitted || m.Rollback != nil || m.CommittedAt == nil {
		return hostclaim.CommittedLanding{}, hostclaim.ErrWrongState
	}
	source, staging, err := moves.CommitScopes(c, m.FlippedAt)
	if err != nil {
		return hostclaim.CommittedLanding{}, err
	}
	// The record's From and To are placement codes. The commit's parks are
	// queued in engine regions, as moves' commitClaim queues them
	// (park.PlacementRegion, so the home is park.HomeRegion, never ""); a
	// code that is no placement refuses.
	from, to := park.PlacementRegion(m.From), park.PlacementRegion(m.To)
	if from == "" || to == "" {
		return hostclaim.CommittedLanding{}, hostclaim.ErrWrongState
	}
	return hostclaim.CommittedLanding{FromRegion: from, ToRegion: to, SourceScope: source, StagingScope: staging}, nil
}