package service

import (
	"context"

	"go.infratographer.com/x/events"
	"go.infratographer.com/x/gidx"
	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/trace"

	"go.equinixmetal.net/infra9-metal-bridge/internal/permissions"
)

// processRelationships determines the changes between what is wanted and what is live and executes on the differences.
// Relationship creations use events.
// Relationship deletions use the api, as delete events delete all related resources and not just the provided ones.
func (s *service) processRelationships(ctx context.Context, eventType string, relationships Relationships) int {
	ctx, span := tracer.Start(ctx, "processRelationships",
		trace.WithAttributes(
			attribute.String("resource.id", relationships.Resource.PrefixedID().String()),
			attribute.Int("resource.subject_relationships", len(relationships.SubjectRelationships)),
		),
	)

	defer span.End()

	rlogger := s.logger.With("resource.id", relationships.Resource.PrefixedID())

	wantParentRelationship, wantSubjectRelationships := s.mapRelationWants(relationships)

	liveParentRelationships, liveSubjectRelationships, err := s.getRelationshipMap(ctx, relationships.Resource, relationships.SubjectRelation)
	if err != nil {
		rlogger.Errorw("failed to get relationship map",
			"relationships.subject_relation", relationships.SubjectRelation,
			"error", err,
		)

		return 0
	}

	var (
		createParentRelationship  *Relation
		deleteParentRelationships []gidx.PrefixedID

		foundParent bool

		createSubjectRelationships []Relation
		deleteSubjectRelationships []Relation
	)

	if wantParentRelationship != nil {
		for subjID := range liveParentRelationships {
			if subjID == wantParentRelationship.Resource.PrefixedID() {
				foundParent = true

				continue
			}

			deleteParentRelationships = append(deleteParentRelationships, subjID)
		}

		if !foundParent {
			createParentRelationship = wantParentRelationship
		}
	} else {
		for subjID := range liveParentRelationships {
			deleteParentRelationships = append(deleteParentRelationships, subjID)
		}
	}

	for resID, relation := range wantSubjectRelationships {
		if _, ok := liveSubjectRelationships[resID]; ok {
			continue
		}

		createSubjectRelationships = append(createSubjectRelationships, Relation{
			Resource: prefixedID{resID},
			Relation: relation,
		})
	}

	for resID, relation := range liveSubjectRelationships {
		if _, ok := wantSubjectRelationships[resID]; ok {
			continue
		}

		deleteSubjectRelationships = append(deleteSubjectRelationships, Relation{
			Resource: prefixedID{resID},
			Relation: relation,
		})
	}

	var processEvents []events.ChangeMessage

	rlogger.Debugw("processing relationships",
		"parent.create", createParentRelationship != nil,
		"parent.delete", len(deleteParentRelationships),
		"subject.create", len(createSubjectRelationships),
		"subject.delete", len(deleteSubjectRelationships),
	)

	if createParentRelationship != nil {
		processEvents = append(processEvents, events.ChangeMessage{
			SubjectID: relationships.Resource.PrefixedID(),
			EventType: string(events.CreateChangeType),
			AdditionalSubjectIDs: []gidx.PrefixedID{
				createParentRelationship.Resource.PrefixedID(),
			},
		})
	}

	for _, relation := range createSubjectRelationships {
		processEvents = append(processEvents, events.ChangeMessage{
			SubjectID: relation.Resource.PrefixedID(),
			EventType: string(events.CreateChangeType),
			AdditionalSubjectIDs: []gidx.PrefixedID{
				relationships.Resource.PrefixedID(),
			},
		})
	}

	for _, relatedResourceID := range deleteParentRelationships {
		err = s.perms.DeleteResourceRelationship(ctx, relationships.Resource.PrefixedID(), string(RelateParent), relatedResourceID)
		if err != nil {
			rlogger.Errorw("error deleting parent relationship",
				"parent.resource.id", relatedResourceID.String(),
			)
		}
	}

	for _, relation := range deleteSubjectRelationships {
		err = s.perms.DeleteResourceRelationship(ctx, relation.Resource.PrefixedID(), string(relation.Relation), relationships.Resource.PrefixedID())
		if err != nil {
			rlogger.Errorw("error deleting relationship",
				"relation", relation.Relation,
				"subject.id", relation.Resource.PrefixedID().String(),
			)
		}
	}

	for _, event := range processEvents {
		err = s.publisher.PublishChange(ctx, eventType, event)

		if err != nil {
			rlogger.Errorw("error publishing change",
				"subject_type", eventType,
				"subject.id", event.SubjectID,
				"event.type", event.EventType,
				"additional_subject_ids", event.AdditionalSubjectIDs,
				"error", err,
			)
		}
	}

	rlogger.Debugw("relationships processed",
		"parent.create", createParentRelationship != nil,
		"parent.delete", len(deleteParentRelationships),
		"subject.create", len(createSubjectRelationships),
		"subject.delete", len(deleteSubjectRelationships),
	)

	changes := len(deleteParentRelationships) + len(createSubjectRelationships) + len(deleteSubjectRelationships)

	if createParentRelationship != nil {
		changes++
	}

	return changes
}

// mapRelationWants returns the parent relation if provided and a map of Subjects -> relation.
func (s *service) mapRelationWants(relationships Relationships) (*Relation, map[gidx.PrefixedID]RelationshipType) {
	var wantParent *Relation

	wantSubject := make(map[gidx.PrefixedID]RelationshipType)

	if relationships.Parent.Resource != nil {
		wantParent = &relationships.Parent
	}

	for _, relationship := range relationships.SubjectRelationships {
		wantSubject[relationship.Resource.PrefixedID()] = relationship.Relation
	}

	return wantParent, wantSubject
}

// getRelationshipMap fetches the provided resources relationships, as the source resource and the destination subject.
// Returned are two maps, the first maps Subject IDs -> Relationship
// The second map, maps Resource IDs -> relationship
func (s *service) getRelationshipMap(ctx context.Context, resource IDPrefixableResource, relation RelationshipType) (map[gidx.PrefixedID]RelationshipType, map[gidx.PrefixedID]RelationshipType, error) {
	liveResource, err := s.perms.ListResourceRelationshipsFrom(ctx, resource.PrefixedID())
	if err != nil {
		return nil, nil, err
	}

	var liveSubject []permissions.ResourceRelationship

	if relation != "" {
		liveSubject, err = s.perms.ListResourceRelationshipsTo(ctx, resource.PrefixedID())
		if err != nil {
			return nil, nil, err
		}
	}

	parents := make(map[gidx.PrefixedID]RelationshipType, len(liveResource))

	for _, relationship := range liveResource {
		if relationship.Relation != string(RelateParent) {
			continue
		}

		parents[relationship.SubjectID] = RelationshipType(relationship.Relation)
	}

	subject := make(map[gidx.PrefixedID]RelationshipType, len(liveSubject))

	for _, relationship := range liveSubject {
		if relationship.Relation != string(relation) {
			continue
		}

		subject[relationship.ResourceID] = RelationshipType(relationship.Relation)
	}

	return parents, subject, nil
}