async-graphql/async-graphql-derive/src/subscription.rs

use crate::args;
use crate::utils::{build_value_repr, check_reserved_name, get_crate_name};
use inflector::Inflector;
use proc_macro::TokenStream;
use quote::quote;
use syn::{Error, FnArg, ImplItem, ItemImpl, Pat, Result, ReturnType, Type, TypeImplTrait};

pub fn generate(object_args: &args::Object, item_impl: &mut ItemImpl) -> Result<TokenStream> {
    let crate_name = get_crate_name(object_args.internal);
    let (self_ty, self_name) = match item_impl.self_ty.as_ref() {
        Type::Path(path) => (
            path,
            path.path
                .segments
                .last()
                .map(|s| s.ident.to_string())
                .unwrap(),
        ),
        _ => return Err(Error::new_spanned(&item_impl.self_ty, "Invalid type")),
    };
    let generics = &item_impl.generics;

    let gql_typename = object_args
        .name
        .clone()
        .unwrap_or_else(|| self_name.clone());
    check_reserved_name(&gql_typename, object_args.internal)?;

    let desc = object_args
        .desc
        .as_ref()
        .map(|s| quote! {Some(#s)})
        .unwrap_or_else(|| quote! {None});

    let mut create_stream = Vec::new();
    let mut schema_fields = Vec::new();

    for item in &mut item_impl.items {
        if let ImplItem::Method(method) = item {
            if let Some(field) = args::Field::parse(&method.attrs)? {
                let ident = &method.sig.ident;
                let field_name = field
                    .name
                    .clone()
                    .unwrap_or_else(|| method.sig.ident.to_string().to_camel_case());
                let field_desc = field
                    .desc
                    .as_ref()
                    .map(|s| quote! {Some(#s)})
                    .unwrap_or_else(|| quote! {None});
                let field_deprecation = field
                    .deprecation
                    .as_ref()
                    .map(|s| quote! {Some(#s)})
                    .unwrap_or_else(|| quote! {None});

                if method.sig.asyncness.is_none() {
                    return Err(Error::new_spanned(
                        &method.sig.asyncness,
                        "The subscription stream function must be asynchronous",
                    ));
                }

                match &method.sig.inputs[0] {
                    FnArg::Receiver(_) => {}
                    _ => {
                        return Err(Error::new_spanned(
                            &method.sig.inputs[0],
                            "The first argument must be self receiver",
                        ));
                    }
                }

                let mut args = Vec::new();

                for arg in method.sig.inputs.iter_mut().skip(1) {
                    if let FnArg::Typed(pat) = arg {
                        match (&*pat.pat, &*pat.ty) {
                            (Pat::Ident(arg_ident), Type::Path(arg_ty)) => {
                                args.push((
                                    arg_ident,
                                    arg_ty,
                                    args::Argument::parse(&crate_name, &pat.attrs)?,
                                ));
                                pat.attrs.clear();
                            }
                            _ => {
                                return Err(Error::new_spanned(arg, "Incorrect argument type"));
                            }
                        }
                    } else {
                        return Err(Error::new_spanned(arg, "Incorrect argument type"));
                    }
                }

                let mut schema_args = Vec::new();
                let mut use_params = Vec::new();
                let mut get_params = Vec::new();

                for (
                    ident,
                    ty,
                    args::Argument {
                        name,
                        desc,
                        default,
                        validator,
                    },
                ) in args
                {
                    let name = name
                        .clone()
                        .unwrap_or_else(|| ident.ident.to_string().to_camel_case());
                    let desc = desc
                        .as_ref()
                        .map(|s| quote! {Some(#s)})
                        .unwrap_or_else(|| quote! {None});
                    let schema_default = default
                        .as_ref()
                        .map(|v| {
                            let s = v.to_string();
                            quote! {Some(#s)}
                        })
                        .unwrap_or_else(|| quote! {None});

                    schema_args.push(quote! {
                        args.insert(#name, #crate_name::registry::InputValue {
                            name: #name,
                            description: #desc,
                            ty: <#ty as #crate_name::Type>::create_type_info(registry),
                            default_value: #schema_default,
                            validator: #validator,
                        });
                    });

                    use_params.push(quote! { #ident });

                    let default = match &default {
                        Some(default) => {
                            let repr = build_value_repr(&crate_name, &default);
                            quote! {|| #repr }
                        }
                        None => quote! { || #crate_name::Value::Null },
                    };

                    get_params.push(quote! {
                        let #ident: #ty = ctx.param_value(#name, ctx.position, #default)?;
                    });
                }

                let stream_ty = match &method.sig.output {
                    ReturnType::Default => {
                        return Err(Error::new_spanned(
                            &method.sig.output,
                            "Must be return a stream type",
                        ))
                    }
                    ReturnType::Type(_, ty) => {
                        if let Type::ImplTrait(TypeImplTrait { bounds, .. }) = ty.as_ref() {
                            quote! { #bounds }
                        } else {
                            quote! { #ty }
                        }
                    }
                };

                schema_fields.push(quote! {
                    fields.insert(#field_name.to_string(), #crate_name::registry::Field {
                        name: #field_name.to_string(),
                        description: #field_desc,
                        args: {
                            let mut args = std::collections::HashMap::new();
                            #(#schema_args)*
                            args
                        },
                        ty: <#stream_ty as #crate_name::futures::stream::Stream>::Item::create_type_info(registry),
                        deprecation: #field_deprecation,
                        cache_control: Default::default(),
                    });
                });

                create_stream.push(quote! {
                    if ctx.name.as_str() == #field_name {
                        let field_name = ctx.result_name().to_string();
                        #(#get_params)*
                        let field_selection_set = std::sync::Arc::new(ctx.selection_set.clone());
                        let schema = schema.clone();
                        let pos = ctx.position;
                        let environment = environment.clone();
                        let stream = #crate_name::futures::stream::StreamExt::then(self.#ident(#(#use_params),*).await.fuse(), move |msg| {
                            let environment = environment.clone();
                            let field_selection_set = field_selection_set.clone();
                            let schema = schema.clone();
                            async move {
                                let resolve_id = std::sync::atomic::AtomicUsize::default();
                                let ctx_selection_set = environment.create_context(
                                    &*field_selection_set,
                                    Some(#crate_name::QueryPathNode {
                                        parent: None,
                                        segment: #crate_name::QueryPathSegment::Name("time"),
                                    }),
                                    &resolve_id,
                                    schema.registry(),
                                    schema.data(),
                                );
                                #crate_name::OutputValueType::resolve(&msg, &ctx_selection_set, pos).await
                            }
                        }).
                        filter_map(move |res| {
                            let res = res.ok().map(|value| {
                                #crate_name::serde_json::json!({ &field_name: value })
                            });
                            async move { res }
                        });
                        return Ok(Box::pin(stream));
                    }
                });

                method.attrs.clear();
            }
        }
    }

    let expanded = quote! {
        #item_impl

        impl #generics #crate_name::Type for #self_ty {
            fn type_name() -> std::borrow::Cow<'static, str> {
                std::borrow::Cow::Borrowed(#gql_typename)
            }

            #[allow(bare_trait_objects)]
            fn create_type_info(registry: &mut #crate_name::registry::Registry) -> String {
                registry.create_type::<Self, _>(|registry| #crate_name::registry::Type::Object {
                    name: #gql_typename.to_string(),
                    description: #desc,
                    fields: {
                        let mut fields = std::collections::HashMap::new();
                        #(#schema_fields)*
                        fields
                    },
                    cache_control: Default::default(),
                })
            }
        }

        #[#crate_name::async_trait::async_trait]
        impl #crate_name::SubscriptionType for SubscriptionRoot {
            #[allow(unused_variables)]
            #[allow(bare_trait_objects)]
            async fn create_field_stream<Query, Mutation>(
                &self,
                ctx: &#crate_name::Context<'_>,
                schema: &#crate_name::Schema<Query, Mutation, Self>,
                environment: std::sync::Arc<#crate_name::Environment>,
            ) -> #crate_name::Result<std::pin::Pin<Box<dyn futures::Stream<Item = #crate_name::serde_json::Value> + Send>>>
            where
                Query: #crate_name::ObjectType + Send + Sync + 'static,
                Mutation: #crate_name::ObjectType + Send + Sync + 'static,
                Self: Send + Sync + 'static + Sized,
            {
                #(#create_stream)*
                Err(#crate_name::QueryError::FieldNotFound {
                    field_name: ctx.name.clone(),
                    object: #gql_typename.to_string(),
                }.into_error(ctx.position))
            }
        }
    };
    Ok(expanded.into())
}