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<?php
namespace YOOtheme\GraphQL\Utils;
use YOOtheme\GraphQL\Type\Schema;
use YOOtheme\GraphQL\Type\Definition\AbstractType;
use YOOtheme\GraphQL\Type\Definition\CompositeType;
use YOOtheme\GraphQL\Type\Definition\ListOfType;
use YOOtheme\GraphQL\Type\Definition\NonNull;
use YOOtheme\GraphQL\Type\Definition\ObjectType;
use YOOtheme\GraphQL\Type\Definition\Type;
class TypeComparators
{
/**
* Provided two types, return true if the types are equal (invariant).
*
* @param Type $typeA
* @param Type $typeB
* @return bool
*/
public static function isEqualType(Type $typeA, Type $typeB)
{
// Equivalent types are equal.
if ($typeA === $typeB) {
return true;
}
// If either type is non-null, the other must also be non-null.
if ($typeA instanceof NonNull && $typeB instanceof NonNull) {
return self::isEqualType($typeA->getWrappedType(), $typeB->getWrappedType());
}
// If either type is a list, the other must also be a list.
if ($typeA instanceof ListOfType && $typeB instanceof ListOfType) {
return self::isEqualType($typeA->getWrappedType(), $typeB->getWrappedType());
}
// Otherwise the types are not equal.
return false;
}
/**
* Provided a type and a super type, return true if the first type is either
* equal or a subset of the second super type (covariant).
*
* @param Schema $schema
* @param Type $maybeSubType
* @param Type $superType
* @return bool
*/
static function isTypeSubTypeOf(Schema $schema, $maybeSubType, $superType)
{
// Equivalent type is a valid subtype
if ($maybeSubType === $superType) {
return true;
}
// If superType is non-null, maybeSubType must also be nullable.
if ($superType instanceof NonNull) {
if ($maybeSubType instanceof NonNull) {
return self::isTypeSubTypeOf($schema, $maybeSubType->getWrappedType(), $superType->getWrappedType());
}
return false;
} else if ($maybeSubType instanceof NonNull) {
// If superType is nullable, maybeSubType may be non-null.
return self::isTypeSubTypeOf($schema, $maybeSubType->getWrappedType(), $superType);
}
// If superType type is a list, maybeSubType type must also be a list.
if ($superType instanceof ListOfType) {
if ($maybeSubType instanceof ListOfType) {
return self::isTypeSubTypeOf($schema, $maybeSubType->getWrappedType(), $superType->getWrappedType());
}
return false;
} else if ($maybeSubType instanceof ListOfType) {
// If superType is not a list, maybeSubType must also be not a list.
return false;
}
// If superType type is an abstract type, maybeSubType type may be a currently
// possible object type.
if (Type::isAbstractType($superType) && $maybeSubType instanceof ObjectType && $schema->isPossibleType($superType, $maybeSubType)) {
return true;
}
// Otherwise, the child type is not a valid subtype of the parent type.
return false;
}
/**
* Provided two composite types, determine if they "overlap". Two composite
* types overlap when the Sets of possible concrete types for each intersect.
*
* This is often used to determine if a fragment of a given type could possibly
* be visited in a context of another type.
*
* This function is commutative.
*
* @param Schema $schema
* @param CompositeType $typeA
* @param CompositeType $typeB
* @return bool
*/
static function doTypesOverlap(Schema $schema, CompositeType $typeA, CompositeType $typeB)
{
// Equivalent types overlap
if ($typeA === $typeB) {
return true;
}
if ($typeA instanceof AbstractType) {
if ($typeB instanceof AbstractType) {
// If both types are abstract, then determine if there is any intersection
// between possible concrete types of each.
foreach ($schema->getPossibleTypes($typeA) as $type) {
if ($schema->isPossibleType($typeB, $type)) {
return true;
}
}
return false;
}
/** @var $typeB ObjectType */
// Determine if the latter type is a possible concrete type of the former.
return $schema->isPossibleType($typeA, $typeB);
}
if ($typeB instanceof AbstractType) {
/** @var $typeA ObjectType */
// Determine if the former type is a possible concrete type of the latter.
return $schema->isPossibleType($typeB, $typeA);
}
// Otherwise the types do not overlap.
return false;
}
}