Permify / permify

import (

	"errors"

	"github.com/Permify/permify/pkg/dsl/utils"

	base "github.com/Permify/permify/pkg/pb/base/v1"

)

// Walker is a struct used for traversing a schema

type Walker struct {

	schema *base.SchemaDefinition

	// map used to track visited nodes and avoid infinite recursion

	visited map[string]struct{}

}

// NewWalker is a constructor for the Walker struct

func NewWalker(schema *base.SchemaDefinition) *Walker {

	return &Walker{

		schema:  schema,

		visited: make(map[string]struct{}),

	}

}

// Walk traverses the schema based on entity type and permission

func (w *Walker) Walk(

	entityType string,

	permission string,

) error {

	// Generate a unique key for the entityType and permission combination

	key := utils.Key(entityType, permission)

	// Check if the entity-permission combination has already been visited

	if _, ok := w.visited[key]; ok {

		// If already visited, exit early to avoid redundant processing or infinite recursion

		return nil

	}

	// Mark the entity-permission combination as visited

	w.visited[key] = struct{}{}

	// Lookup the entity definition in the schema

	def, ok := w.schema.EntityDefinitions[entityType]

	if !ok {

		// Error is returned if entity definition is not found

		return errors.New(base.ErrorCode_ERROR_CODE_ENTITY_DEFINITION_NOT_FOUND.String())

	}

	// Switch on the type of reference specified by the permission

	switch def.References[permission] {

	case base.EntityDefinition_REFERENCE_PERMISSION:

		// If the reference type is a permission, look up the permission

		permission, ok := def.Permissions[permission]

		if !ok {

			// Error is returned if permission is not found

			return errors.New(base.ErrorCode_ERROR_CODE_PERMISSION_NOT_FOUND.String())

		}

		// Check if the permission has a child element

		child := permission.GetChild()

		// If the child has a rewrite rule, walk the rewrite rule

		if child.GetRewrite() != nil {

			return w.WalkRewrite(entityType, child.GetRewrite())

		}

		// Otherwise, walk the leaf node

		return w.WalkLeaf(entityType, child.GetLeaf())

	case base.EntityDefinition_REFERENCE_RELATION:

		// If the reference type is a relation, nothing to do, return nil

		return nil

	case base.EntityDefinition_REFERENCE_ATTRIBUTE:

		// If the reference type is an attribute, not implemented, return error

		return ErrUnimplemented

	default:

		// For any other reference type, not implemented, return error

		return errors.New(base.ErrorCode_ERROR_CODE_UNDEFINED_CHILD_KIND.String())

	}

}

// WalkRewrite is a method that walks through the rewrite part of the schema

func (w *Walker) WalkRewrite(

	entityType string,

	rewrite *base.Rewrite,

) error {

	// Loop through each child in the rewrite

	for _, child := range rewrite.GetChildren() {

		// Switch on the type of the child

		switch child.GetType().(type) {

		case *base.Child_Rewrite:

			if err := w.WalkRewrite(entityType, child.GetRewrite()); err != nil {

				return err

			}

		case *base.Child_Leaf:

			if err := w.WalkLeaf(entityType, child.GetLeaf()); err != nil {

				return err

			}

		default:

			// For any other child type, return an error indicating an undefined child type

			return errors.New(base.ErrorCode_ERROR_CODE_UNDEFINED_CHILD_KIND.String())

		}

	}

	// If no errors occurred during the loop, return nil

	return nil

}

// WalkComputedUserSet walk the relation within the ComputedUserSet for the given entityType.

// WalkLeaf is a method that walks through the leaf part of the schema

func (w *Walker) WalkLeaf(

	entityType string,

	leaf *base.Leaf,

) error {

	// Switch on the type of the leaf

	switch t := leaf.GetType().(type) {

	case *base.Leaf_TupleToUserSet:

		// Handle case where the leaf is a tuple to user set

		tupleSet := t.TupleToUserSet.GetTupleSet().GetRelation()

		computedUserSet := t.TupleToUserSet.GetComputed()

		// Look up the entity definition

		entityDefinitions, exists := w.schema.EntityDefinitions[entityType]

		if !exists {

			// Return error if entity definition is not found

			return errors.New(base.ErrorCode_ERROR_CODE_ENTITY_DEFINITION_NOT_FOUND.String())

		}

		// Look up the relations in the entity definition

		relations, exists := entityDefinitions.Relations[tupleSet]

		if !exists {

			// Return error if relations is not found

			return errors.New(base.ErrorCode_ERROR_CODE_UNDEFINED_RELATION_REFERENCE.String())

		}

		// Walk each relation reference

		for _, rel := range relations.GetRelationReferences() {

			return w.WalkComputedUserSet(rel.GetType(), computedUserSet)

		}

		// If no errors occur, return nil

		return nil

	case *base.Leaf_ComputedUserSet:

		// Handle case where the leaf is a computed user set

		// Walk the entity type and relation

		return w.WalkComputedUserSet(entityType, t.ComputedUserSet)

	case *base.Leaf_ComputedAttribute:

		// Handle case where the leaf is a computed attribute

		// This is currently unimplemented, so return an error

		return ErrUnimplemented

	case *base.Leaf_Call:

		// Handle case where the leaf is a call

		// This is currently unimplemented, so return an error

		return ErrUnimplemented

	default:

		// Handle any other type of leaf

		// Return an error indicating the leaf type is undefined

		return ErrUndefinedLeafType

	}

}