schema.go

package graphql

import (
	"fmt"
)

type SchemaConfig struct {
	Query        *Object
	Mutation     *Object
	Subscription *Object
	Directives   []*Directive
}

type TypeMap map[string]Type

//Schema Definition
//A Schema is created by supplying the root types of each type of operation,
//query, mutation (optional) and subscription (optional). A schema definition is then supplied to the
//validator and executor.
//Example:
//    myAppSchema, err := NewSchema(SchemaConfig({
//      Query: MyAppQueryRootType,
//      Mutation: MyAppMutationRootType,
//      Subscription: MyAppSubscriptionRootType,
//    });
type Schema struct {
	typeMap    TypeMap
	directives []*Directive

	queryType        *Object
	mutationType     *Object
	subscriptionType *Object
}

func NewSchema(config SchemaConfig) (Schema, error) {
	var err error

	schema := Schema{}

	err = invariant(config.Query != nil, "Schema query must be Object Type but got: nil.")
	if err != nil {
		return schema, err
	}

	// if schema config contains error at creation time, return those errors
	if config.Query != nil && config.Query.err != nil {
		return schema, config.Query.err
	}
	if config.Mutation != nil && config.Mutation.err != nil {
		return schema, config.Mutation.err
	}

	schema.queryType = config.Query
	schema.mutationType = config.Mutation
	schema.subscriptionType = config.Subscription

	// Provide `@include() and `@skip()` directives by default.
	schema.directives = config.Directives
	if len(schema.directives) == 0 {
		schema.directives = []*Directive{
			IncludeDirective,
			SkipDirective,
		}
	}

	// Build type map now to detect any errors within this schema.
	typeMap := TypeMap{}
	objectTypes := []*Object{
		schema.QueryType(),
		schema.MutationType(),
		schema.SubscriptionType(),
		typeType,
		schemaType,
	}
	for _, objectType := range objectTypes {
		if objectType == nil {
			continue
		}
		if objectType.err != nil {
			return schema, objectType.err
		}
		typeMap, err = typeMapReducer(typeMap, objectType)
		if err != nil {
			return schema, err
		}
	}
	schema.typeMap = typeMap
	// Enforce correct interface implementations
	for _, ttype := range typeMap {
		switch ttype := ttype.(type) {
		case *Object:
			for _, iface := range ttype.Interfaces() {
				err := assertObjectImplementsInterface(ttype, iface)
				if err != nil {
					return schema, err
				}
			}
		}
	}

	return schema, nil
}

func (gq *Schema) QueryType() *Object {
	return gq.queryType
}

func (gq *Schema) MutationType() *Object {
	return gq.mutationType
}

func (gq *Schema) SubscriptionType() *Object {
	return gq.subscriptionType
}

func (gq *Schema) Directives() []*Directive {
	return gq.directives
}

func (gq *Schema) Directive(name string) *Directive {
	for _, directive := range gq.Directives() {
		if directive.Name == name {
			return directive
		}
	}
	return nil
}

func (gq *Schema) TypeMap() TypeMap {
	return gq.typeMap
}

func (gq *Schema) Type(name string) Type {
	return gq.TypeMap()[name]
}

func typeMapReducer(typeMap TypeMap, objectType Type) (TypeMap, error) {
	var err error
	if objectType == nil || objectType.Name() == "" {
		return typeMap, nil
	}

	switch objectType := objectType.(type) {
	case *List:
		if objectType.OfType != nil {
			return typeMapReducer(typeMap, objectType.OfType)
		}
	case *NonNull:
		if objectType.OfType != nil {
			return typeMapReducer(typeMap, objectType.OfType)
		}
	case *Object:
		if objectType.err != nil {
			return typeMap, objectType.err
		}
	}

	if mappedObjectType, ok := typeMap[objectType.Name()]; ok {
		err := invariant(
			mappedObjectType == objectType,
			fmt.Sprintf(`Schema must contain unique named types but contains multiple types named "%v".`, objectType.Name()),
		)
		if err != nil {
			return typeMap, err
		}
		return typeMap, err
	}
	if objectType.Name() == "" {
		return typeMap, nil
	}

	typeMap[objectType.Name()] = objectType

	switch objectType := objectType.(type) {
	case *Union:
		types := objectType.PossibleTypes()
		if objectType.err != nil {
			return typeMap, objectType.err
		}
		for _, innerObjectType := range types {
			if innerObjectType.err != nil {
				return typeMap, innerObjectType.err
			}
			typeMap, err = typeMapReducer(typeMap, innerObjectType)
			if err != nil {
				return typeMap, err
			}
		}
	case *Interface:
		types := objectType.PossibleTypes()
		if objectType.err != nil {
			return typeMap, objectType.err
		}
		for _, innerObjectType := range types {
			if innerObjectType.err != nil {
				return typeMap, innerObjectType.err
			}
			typeMap, err = typeMapReducer(typeMap, innerObjectType)
			if err != nil {
				return typeMap, err
			}
		}
	case *Object:
		interfaces := objectType.Interfaces()
		if objectType.err != nil {
			return typeMap, objectType.err
		}
		for _, innerObjectType := range interfaces {
			if innerObjectType.err != nil {
				return typeMap, innerObjectType.err
			}
			typeMap, err = typeMapReducer(typeMap, innerObjectType)
			if err != nil {
				return typeMap, err
			}
		}
	}

	switch objectType := objectType.(type) {
	case *Object:
		fieldMap := objectType.Fields()
		if objectType.err != nil {
			return typeMap, objectType.err
		}
		for _, field := range fieldMap {
			for _, arg := range field.Args {
				typeMap, err = typeMapReducer(typeMap, arg.Type)
				if err != nil {
					return typeMap, err
				}
			}
			typeMap, err = typeMapReducer(typeMap, field.Type)
			if err != nil {
				return typeMap, err
			}
		}
	case *Interface:
		fieldMap := objectType.Fields()
		if objectType.err != nil {
			return typeMap, objectType.err
		}
		for _, field := range fieldMap {
			for _, arg := range field.Args {
				typeMap, err = typeMapReducer(typeMap, arg.Type)
				if err != nil {
					return typeMap, err
				}
			}
			typeMap, err = typeMapReducer(typeMap, field.Type)
			if err != nil {
				return typeMap, err
			}
		}
	case *InputObject:
		fieldMap := objectType.Fields()
		if objectType.err != nil {
			return typeMap, objectType.err
		}
		for _, field := range fieldMap {
			typeMap, err = typeMapReducer(typeMap, field.Type)
			if err != nil {
				return typeMap, err
			}
		}
	}
	return typeMap, nil
}

func assertObjectImplementsInterface(object *Object, iface *Interface) error {
	objectFieldMap := object.Fields()
	ifaceFieldMap := iface.Fields()

	// Assert each interface field is implemented.
	for fieldName := range ifaceFieldMap {
		objectField := objectFieldMap[fieldName]
		ifaceField := ifaceFieldMap[fieldName]

		// Assert interface field exists on object.
		err := invariant(
			objectField != nil,
			fmt.Sprintf(`"%v" expects field "%v" but "%v" does not `+
				`provide it.`, iface, fieldName, object),
		)
		if err != nil {
			return err
		}

		// Assert interface field type is satisfied by object field type, by being
		// a valid subtype. (covariant)
		err = invariant(
			isTypeSubTypeOf(objectField.Type, ifaceField.Type),
			fmt.Sprintf(`%v.%v expects type "%v" but `+
				`%v.%v provides type "%v".`,
				iface, fieldName, ifaceField.Type,
				object, fieldName, objectField.Type),
		)
		if err != nil {
			return err
		}

		// Assert each interface field arg is implemented.
		for _, ifaceArg := range ifaceField.Args {
			argName := ifaceArg.PrivateName
			var objectArg *Argument
			for _, arg := range objectField.Args {
				if arg.PrivateName == argName {
					objectArg = arg
					break
				}
			}
			// Assert interface field arg exists on object field.
			err = invariant(
				objectArg != nil,
				fmt.Sprintf(`%v.%v expects argument "%v" but `+
					`%v.%v does not provide it.`,
					iface, fieldName, argName,
					object, fieldName),
			)
			if err != nil {
				return err
			}

			// Assert interface field arg type matches object field arg type.
			// (invariant)
			err = invariant(
				isEqualType(ifaceArg.Type, objectArg.Type),
				fmt.Sprintf(
					`%v.%v(%v:) expects type "%v" `+
						`but %v.%v(%v:) provides `+
						`type "%v".`,
					iface, fieldName, argName, ifaceArg.Type,
					object, fieldName, argName, objectArg.Type),
			)
			if err != nil {
				return err
			}
		}
		// Assert additional arguments must not be required.
		for _, objectArg := range objectField.Args {
			argName := objectArg.PrivateName
			var ifaceArg *Argument
			for _, arg := range ifaceField.Args {
				if arg.PrivateName == argName {
					ifaceArg = arg
					break
				}
			}

			if ifaceArg == nil {
				_, ok := objectArg.Type.(*NonNull)
				err = invariant(
					!ok,
					fmt.Sprintf(`%v.%v(%v:) is of required type `+
						`"%v" but is not also provided by the interface %v.%v.`,
						object, fieldName, argName,
						objectArg.Type, iface, fieldName),
				)
				if err != nil {
					return err
				}
			}
		}
	}
	return nil
}

func isEqualType(typeA Type, typeB Type) bool {
	// Equivalent type is a valid subtype
	if typeA == typeB {
		return true
	}
	// If either type is non-null, the other must also be non-null.
	if typeA, ok := typeA.(*NonNull); ok {
		if typeB, ok := typeB.(*NonNull); ok {
			return isEqualType(typeA.OfType, typeB.OfType)
		}
	}
	// If either type is a list, the other must also be a list.
	if typeA, ok := typeA.(*List); ok {
		if typeB, ok := typeB.(*List); ok {
			return isEqualType(typeA.OfType, typeB.OfType)
		}
	}
	// 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).
 */
func isTypeSubTypeOf(maybeSubType Type, superType Type) bool {
	// Equivalent type is a valid subtype
	if maybeSubType == superType {
		return true
	}

	// If superType is non-null, maybeSubType must also be nullable.
	if superType, ok := superType.(*NonNull); ok {
		if maybeSubType, ok := maybeSubType.(*NonNull); ok {
			return isTypeSubTypeOf(maybeSubType.OfType, superType.OfType)
		}
		return false
	}
	if maybeSubType, ok := maybeSubType.(*NonNull); ok {
		// If superType is nullable, maybeSubType may be non-null.
		return isTypeSubTypeOf(maybeSubType.OfType, superType)
	}

	// If superType type is a list, maybeSubType type must also be a list.
	if superType, ok := superType.(*List); ok {
		if maybeSubType, ok := maybeSubType.(*List); ok {
			return isTypeSubTypeOf(maybeSubType.OfType, superType.OfType)
		}
		return false
	} else if _, ok := maybeSubType.(*List); ok {
		// 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 superType, ok := superType.(*Interface); ok {
		if maybeSubType, ok := maybeSubType.(*Object); ok && superType.IsPossibleType(maybeSubType) {
			return true
		}
	}
	if superType, ok := superType.(*Union); ok {
		if maybeSubType, ok := maybeSubType.(*Object); ok && superType.IsPossibleType(maybeSubType) {
			return true
		}
	}

	// Otherwise, the child type is not a valid subtype of the parent type.
	return false
}