package namespace

import (
	"context"

	"github.com/authzed/spicedb/pkg/datastore"
	"github.com/authzed/spicedb/pkg/genutil/mapz"
	core "github.com/authzed/spicedb/pkg/proto/core/v1"
)

// ReadNamespaceAndRelation checks that the specified namespace and relation exist in the
// datastore.
//
// Returns NamespaceNotFoundError if the namespace cannot be found.
// Returns RelationNotFoundError if the relation was not found in the namespace.
// Returns the direct downstream error for all other unknown error.
func ReadNamespaceAndRelation(
	ctx context.Context,
	namespace string,
	relation string,
	ds datastore.Reader,
) (*core.NamespaceDefinition, *core.Relation, error) {
	config, _, err := ds.ReadNamespaceByName(ctx, namespace)
	if err != nil {
		return nil, nil, err
	}

	for _, rel := range config.Relation {
		if rel.Name == relation {
			return config, rel, nil
		}
	}

	return nil, nil, NewRelationNotFoundErr(namespace, relation)
}

// TypeAndRelationToCheck is a single check of a namespace+relation pair.
type TypeAndRelationToCheck struct {
	// NamespaceName is the namespace name to ensure exists.
	NamespaceName string

	// RelationName is the relation name to ensure exists under the namespace.
	RelationName string

	// AllowEllipsis, if true, allows for the ellipsis as the RelationName.
	AllowEllipsis bool
}

// CheckNamespaceAndRelations ensures that the given namespace+relation checks all succeed. If any fail, returns an error.
//
// Returns NamespaceNotFoundError if the namespace cannot be found.
// Returns RelationNotFoundError if the relation was not found in the namespace.
// Returns the direct downstream error for all other unknown error.
func CheckNamespaceAndRelations(ctx context.Context, checks []TypeAndRelationToCheck, ds datastore.Reader) error {
	nsNames := mapz.NewSet[string]()
	for _, toCheck := range checks {
		nsNames.Insert(toCheck.NamespaceName)
	}

	if nsNames.IsEmpty() {
		return nil
	}

	namespaces, err := ds.LookupNamespacesWithNames(ctx, nsNames.AsSlice())
	if err != nil {
		return err
	}

	mappedNamespaces := make(map[string]*core.NamespaceDefinition, len(namespaces))
	for _, namespace := range namespaces {
		mappedNamespaces[namespace.Definition.Name] = namespace.Definition
	}

	for _, toCheck := range checks {
		nsDef, ok := mappedNamespaces[toCheck.NamespaceName]
		if !ok {
			return NewNamespaceNotFoundErr(toCheck.NamespaceName)
		}

		if toCheck.AllowEllipsis && toCheck.RelationName == datastore.Ellipsis {
			continue
		}

		foundRelation := false
		for _, rel := range nsDef.Relation {
			if rel.Name == toCheck.RelationName {
				foundRelation = true
				break
			}
		}

		if !foundRelation {
			return NewRelationNotFoundErr(toCheck.NamespaceName, toCheck.RelationName)
		}
	}

	return nil
}

// CheckNamespaceAndRelation checks that the specified namespace and relation exist in the
// datastore.
//
// Returns datastore.NamespaceNotFoundError if the namespace cannot be found.
// Returns RelationNotFoundError if the relation was not found in the namespace.
// Returns the direct downstream error for all other unknown error.
func CheckNamespaceAndRelation(
	ctx context.Context,
	namespace string,
	relation string,
	allowEllipsis bool,
	ds datastore.Reader,
) error {
	config, _, err := ds.ReadNamespaceByName(ctx, namespace)
	if err != nil {
		return err
	}

	if allowEllipsis && relation == datastore.Ellipsis {
		return nil
	}

	for _, rel := range config.Relation {
		if rel.Name == relation {
			return nil
		}
	}

	return NewRelationNotFoundErr(namespace, relation)
}

// ListReferencedNamespaces returns the names of all namespaces referenced in the
// given namespace definitions. This includes the namespaces themselves, as well as
// any found in type information on relations.
func ListReferencedNamespaces(nsdefs []*core.NamespaceDefinition) []string {
	referencedNamespaceNamesSet := mapz.NewSet[string]()
	for _, nsdef := range nsdefs {
		referencedNamespaceNamesSet.Insert(nsdef.Name)

		for _, relation := range nsdef.Relation {
			if relation.GetTypeInformation() != nil {
				for _, allowedRel := range relation.GetTypeInformation().AllowedDirectRelations {
					referencedNamespaceNamesSet.Insert(allowedRel.GetNamespace())
				}
			}
		}
	}
	return referencedNamespaceNamesSet.AsSlice()
}