grafbase_sdk_mock/

builder.rs

#![allow(clippy::panic)]

use std::collections::HashMap;

use async_graphql::{
    ServerError,
    dynamic::{FieldValue, ResolverContext},
};
use cynic_parser::{common::WrappingType, type_system as parser};
use serde::Deserialize;

use super::{
    GraphqlSubgraph,
    entity_resolver::{EntityResolver, EntityResolverContext},
    resolver::Resolver,
};

type ResolverMap = HashMap<(String, String), Box<dyn Resolver>>;
type EntityResolverMap = HashMap<String, Box<dyn EntityResolver>>;

/// A builder for dynamic GraphQL schemas.
pub struct GraphqlSubgraphBuilder {
    sdl: String,
    name: String,
    field_resolvers: ResolverMap,
    entity_resolvers: EntityResolverMap,
}

impl GraphqlSubgraphBuilder {
    pub(crate) fn new(sdl: String, name: String) -> Self {
        GraphqlSubgraphBuilder {
            sdl,
            name,
            field_resolvers: Default::default(),
            entity_resolvers: Default::default(),
        }
    }

    /// Specify the name of this subgraph.
    pub fn with_name(mut self, name: impl AsRef<str>) -> Self {
        self.name = name.as_ref().to_string();
        self
    }

    /// Adds a field resolver to this schema.
    ///
    /// # Arguments
    /// * `ty` - The name of the type that contains the field
    /// * `field` - The name of the field to resolve
    /// * `resolver` - A resolver implementation for the field
    pub fn with_resolver(mut self, ty: &str, field: &str, resolver: impl Resolver + 'static) -> Self {
        self.field_resolvers
            .insert((ty.into(), field.into()), Box::new(resolver));
        self
    }

    /// Adds an entity resolver to this schema.
    ///
    /// # Arguments
    /// * `entity` - The name of the entity type to resolve
    /// * `resolver` - A resolver implementation for the entity
    pub fn with_entity_resolver(mut self, entity: &str, resolver: impl EntityResolver + 'static) -> Self {
        self.entity_resolvers.insert(entity.into(), Box::new(resolver));
        self
    }

    /// Builds the GraphQL subgraph.
    pub fn build(self) -> GraphqlSubgraph {
        let Self {
            sdl,
            name,
            mut field_resolvers,
            entity_resolvers,
        } = self;

        let schema = cynic_parser::parse_type_system_document(&sdl)
            .map_err(|e| e.to_report(&sdl))
            .expect("a valid document");

        let (query_type, ..) = root_types(&schema);

        // Note: don't enable federation on this because we want to provide all that stuff ourselves
        let mut builder = schema_builder(&schema);
        builder = builder.register(service_type(&sdl));
        let entities = find_entities(&schema);

        if !entities.is_empty() {
            builder = builder.register(any_type());
            builder = builder.register(entity_type(&entities));
        }

        let mut entity_resolvers = Some(entity_resolvers);
        for definition in schema.definitions() {
            match definition {
                parser::Definition::Type(def) => {
                    let mut ty = convert_type(def, &mut field_resolvers);
                    if def.name() == query_type {
                        if let Some(entity_resolvers) = entity_resolvers.take() {
                            ty = add_federation_fields(ty, &entities, entity_resolvers);
                        }
                    }
                    builder = builder.register(ty);
                }
                parser::Definition::TypeExtension(_) => {
                    unimplemented!("this is just for tests, extensions aren't supported")
                }
                _ => {}
            }
        }

        if entity_resolvers.is_some() && !entities.is_empty() {
            let entity_resolvers = entity_resolvers.unwrap();
            builder = builder.register(add_federation_fields(
                async_graphql::dynamic::Object::new("Query").into(),
                &entities,
                entity_resolvers,
            ));
        }

        let executable_schema = builder.finish().unwrap();

        GraphqlSubgraph {
            executable_schema,
            schema: sdl,
            name,
        }
    }
}

fn find_entities(schema: &parser::TypeSystemDocument) -> Vec<&str> {
    schema
        .definitions()
        .filter_map(|def| match def {
            parser::Definition::Type(def) => Some(def),
            parser::Definition::TypeExtension(def) => Some(def),
            _ => None,
        })
        .filter(|def| def.directives().any(|directive| directive.name() == "key"))
        .map(|def| def.name())
        .collect()
}

fn convert_type(def: parser::TypeDefinition<'_>, resolvers: &mut ResolverMap) -> async_graphql::dynamic::Type {
    match def {
        parser::TypeDefinition::Scalar(def) => async_graphql::dynamic::Scalar::new(def.name()).into(),
        parser::TypeDefinition::Object(def) => convert_object(def, resolvers),
        parser::TypeDefinition::Interface(def) => convert_iface(def),
        parser::TypeDefinition::Union(def) => convert_union(def),
        parser::TypeDefinition::Enum(def) => convert_enum(def),
        parser::TypeDefinition::InputObject(def) => convert_input_object(def),
    }
}

fn convert_object(def: parser::ObjectDefinition<'_>, resolvers: &mut ResolverMap) -> async_graphql::dynamic::Type {
    use async_graphql::dynamic::*;

    let mut object = Object::new(def.name());

    for name in def.implements_interfaces() {
        object = object.implement(name);
    }

    for field_def in def.fields() {
        let type_ref = convert_type_ref(field_def.ty());
        let resolver = std::sync::Mutex::new(
            resolvers
                .remove(&(def.name().into(), field_def.name().into()))
                .unwrap_or_else(|| Box::new(default_field_resolver(field_def.name()))),
        );

        let mut field = Field::new(field_def.name(), type_ref, move |context| {
            let mut resolver = resolver.lock().expect("mutex to be unpoisoned");
            FieldFuture::Value(resolver.resolve(context).map(|value| {
                let value = async_graphql::Value::deserialize(value).unwrap();
                transform_into_field_value(value)
            }))
        });

        for argument in field_def.arguments() {
            field = field.argument(convert_input_value(argument));
        }

        object = object.field(field);
    }

    object.into()
}

fn transform_into_field_value(mut value: async_graphql::Value) -> FieldValue<'static> {
    match value {
        async_graphql::Value::Object(ref mut fields) => {
            if let Some(async_graphql::Value::String(ty)) = fields.swap_remove("__typename") {
                FieldValue::from(value).with_type(ty)
            } else {
                FieldValue::from(value)
            }
        }
        async_graphql::Value::List(values) => FieldValue::list(values.into_iter().map(transform_into_field_value)),
        value => FieldValue::from(value),
    }
}

fn convert_iface(def: parser::InterfaceDefinition<'_>) -> async_graphql::dynamic::Type {
    use async_graphql::dynamic::*;
    let mut interface = Interface::new(def.name());

    for field_def in def.fields() {
        let type_ref = convert_type_ref(field_def.ty());

        let mut field = InterfaceField::new(field_def.name(), type_ref);

        for argument in field_def.arguments() {
            field = field.argument(convert_input_value(argument));
        }

        interface = interface.field(field);
    }

    interface.into()
}

fn convert_union(def: parser::UnionDefinition<'_>) -> async_graphql::dynamic::Type {
    use async_graphql::dynamic::*;

    let mut output = Union::new(def.name());

    for member in def.members() {
        output = output.possible_type(member.name());
    }

    output.into()
}

fn convert_enum(def: parser::EnumDefinition<'_>) -> async_graphql::dynamic::Type {
    use async_graphql::dynamic::*;

    Enum::new(def.name())
        .items(def.values().map(|value| EnumItem::new(value.value())))
        .into()
}

fn convert_input_object(def: parser::InputObjectDefinition<'_>) -> async_graphql::dynamic::Type {
    use async_graphql::dynamic::*;

    let mut object = InputObject::new(def.name());

    for field_def in def.fields() {
        object = object.field(convert_input_value(field_def))
    }

    object.into()
}

fn convert_type_ref(ty: parser::Type<'_>) -> async_graphql::dynamic::TypeRef {
    use async_graphql::dynamic::TypeRef;

    let mut output = TypeRef::named(ty.name());

    for wrapper in ty.wrappers() {
        match wrapper {
            WrappingType::NonNull => {
                output = TypeRef::NonNull(Box::new(output));
            }
            WrappingType::List => {
                output = TypeRef::List(Box::new(output));
            }
        }
    }

    output
}

fn convert_input_value(value_def: parser::InputValueDefinition<'_>) -> async_graphql::dynamic::InputValue {
    use async_graphql::dynamic::InputValue;

    let mut value = InputValue::new(value_def.name(), convert_type_ref(value_def.ty()));

    if let Some(default) = value_def.default_value() {
        value = value.default_value(convert_value(default))
    }

    value
}

fn convert_value(value: cynic_parser::ConstValue<'_>) -> async_graphql::Value {
    match value {
        cynic_parser::ConstValue::Int(inner) => async_graphql::Value::Number(inner.as_i64().into()),
        cynic_parser::ConstValue::Float(inner) => {
            async_graphql::Value::Number(serde_json::Number::from_f64(inner.as_f64()).unwrap())
        }
        cynic_parser::ConstValue::String(inner) => async_graphql::Value::String(inner.as_str().into()),
        cynic_parser::ConstValue::Boolean(inner) => async_graphql::Value::Boolean(inner.as_bool()),
        cynic_parser::ConstValue::Null(_) => async_graphql::Value::Null,
        cynic_parser::ConstValue::Enum(inner) => async_graphql::Value::Enum(async_graphql::Name::new(inner.name())),
        cynic_parser::ConstValue::List(inner) => async_graphql::Value::List(inner.items().map(convert_value).collect()),
        cynic_parser::ConstValue::Object(inner) => async_graphql::Value::Object(
            inner
                .fields()
                .map(|field| (async_graphql::Name::new(field.name()), convert_value(field.value())))
                .collect(),
        ),
    }
}

fn schema_builder(schema: &cynic_parser::TypeSystemDocument) -> async_graphql::dynamic::SchemaBuilder {
    let (query_name, mutation_name, subscription_name) = root_types(schema);
    async_graphql::dynamic::Schema::build(query_name, mutation_name, subscription_name)
}

fn root_types(schema: &cynic_parser::TypeSystemDocument) -> (&str, Option<&str>, Option<&str>) {
    use parser::Definition;

    let mut query_name = "Query";
    let mut mutation_name = None;
    let mut subscription_name = None;
    let mut found_schema_def = false;
    let mut mutation_present = false;
    let mut subscription_present = false;
    for definition in schema.definitions() {
        if let Definition::Schema(_) = definition {
            found_schema_def = true;
        }
        match definition {
            Definition::Schema(schema) | Definition::SchemaExtension(schema) => {
                if let Some(def) = schema.query_type() {
                    query_name = def.named_type();
                }
                if let Some(def) = schema.mutation_type() {
                    mutation_name = Some(def.named_type());
                }
                if let Some(def) = schema.subscription_type() {
                    subscription_name = Some(def.named_type());
                }
            }
            Definition::Type(ty) | Definition::TypeExtension(ty) if ty.name() == "Mutation" => mutation_present = true,
            Definition::Type(ty) | Definition::TypeExtension(ty) if ty.name() == "Subscription" => {
                subscription_present = true
            }
            _ => {}
        }
    }
    if !found_schema_def {
        if mutation_present {
            mutation_name = Some("Mutation");
        }
        if subscription_present {
            mutation_name = Some("Subscription");
        }
    }

    (query_name, mutation_name, subscription_name)
}

fn default_field_resolver(field_name: &str) -> impl Resolver + 'static {
    let field_name = async_graphql::Name::new(field_name);

    move |context: ResolverContext<'_>| {
        if let Some(value) = context.parent_value.as_value() {
            return match value {
                async_graphql::Value::Object(map) => {
                    map.get(&field_name).map(|value| value.clone().into_json().unwrap())
                }
                _ => None,
            };
        }
        panic!("Unexpected parent value for tests: {:?}", context.parent_value)
    }
}

fn service_type(sdl: &str) -> async_graphql::dynamic::Type {
    use async_graphql::dynamic::*;
    let mut object = Object::new("_Service");

    let sdl = sdl.to_string();

    object = object.field(Field::new("sdl", TypeRef::named_nn("String"), move |_| {
        FieldFuture::from_value(Some(async_graphql::Value::String(sdl.clone())))
    }));

    object.into()
}

fn entity_type(entities: &[&str]) -> async_graphql::dynamic::Type {
    use async_graphql::dynamic::*;

    let mut ty = Union::new("_Entity");

    for entity in entities {
        ty = ty.possible_type(*entity);
    }

    ty.into()
}

fn any_type() -> async_graphql::dynamic::Type {
    use async_graphql::dynamic::*;

    Scalar::new("_Any").into()
}

fn add_federation_fields(
    query_ty: async_graphql::dynamic::Type,
    entities: &[&str],
    entity_resolvers: EntityResolverMap,
) -> async_graphql::dynamic::Type {
    use async_graphql::dynamic::*;

    let async_graphql::dynamic::Type::Object(mut obj) = query_ty else {
        panic!("this shouldn't happen probably")
    };
    obj = obj.field(Field::new("_service", TypeRef::named_nn("_Service"), |_| {
        // Doesnt matter what we return here hopefully?
        FieldFuture::from_value(Some(async_graphql::Value::Object([].into())))
    }));

    for entity in entity_resolvers.keys() {
        if !entities.contains(&entity.as_str()) {
            panic!("Tried to add an resolver for {entity}, but this entity doesnt exist");
        }
    }

    if !entities.is_empty() {
        let resolvers = std::sync::Mutex::new(entity_resolvers);

        let entity_field = Field::new("_entities", TypeRef::named_list_nn("_Entity"), move |context| {
            let mut resolvers = resolvers.lock().expect("mutex to be unpoisoned");
            let representations = context
                .args
                .get("representations")
                .expect("_entities needs representations");

            let reprs = representations
                .deserialize::<Vec<serde_json::Value>>()
                .expect("representations to be a list of objects");

            let entities = reprs.into_iter().map(|repr| {
                let context = EntityResolverContext::new(&context, repr);

                let typename = context.typename.clone();
                let Some(resolver) = resolvers.get_mut(&context.typename) else {
                    context.add_error(ServerError::new(format!("{} has no resolver", context.typename), None));
                    return FieldValue::NULL;
                };

                let json_value = resolver.resolve(context).unwrap_or_default();

                transform_into_field_value(async_graphql::Value::deserialize(json_value).unwrap()).with_type(typename)
            });

            FieldFuture::Value(Some(FieldValue::list(entities)))
        })
        .argument(InputValue::new("representations", TypeRef::named_nn_list_nn("_Any")));

        obj = obj.field(entity_field);
    }

    obj.into()
}