feat(subscriptions): added delegateSubscription method to base bindin…

…g class for static bindings (#10)

src/Binding.ts

@@ -1,14 +1,9 @@
+import { $$asyncIterator } from 'iterall'
 import { buildInfo } from './info'
 import { GraphQLResolveInfo, graphql, GraphQLSchema } from 'graphql'
 import { delegateToSchema } from 'graphql-tools'
 import { makeProxy, makeSubscriptionProxy } from './proxy'
-import {
-  QueryMap,
-  BindingOptions,
-  FragmentReplacements,
-  SubscriptionMap,
-  Operation,
-} from './types'
+import { QueryMap, BindingOptions, FragmentReplacements, SubscriptionMap, Operation } from './types'
 
 export class Binding {
   query: QueryMap
@@ -28,32 +23,27 @@ export class Binding {
       schema: this.schema,
       fragmentReplacements: this.fragmentReplacements,
       operation: 'query',
-      before: this.before,
+      before: this.before
     })
     this.mutation = makeProxy<QueryMap>({
       schema: this.schema,
       fragmentReplacements: this.fragmentReplacements,
       operation: 'mutation',
-      before: this.before,
+      before: this.before
     })
     this.subscription = makeSubscriptionProxy<SubscriptionMap>({
       schema: this.schema,
       fragmentReplacements: this.fragmentReplacements,
-      before: this.before,
+      before: this.before
     })
   }
 
-  async request<T = any>(
-    query: string,
-    variables?: { [key: string]: any },
-  ): Promise<T> {
+  public async request<T = any>(query: string, variables?: { [key: string]: any }): Promise<T> {
     this.before()
-    return graphql(this.schema, query, null, null, variables).then(
-      r => r.data![Object.keys(r.data!)[0]],
-    )
+    return graphql(this.schema, query, null, null, variables).then(r => r.data![Object.keys(r.data!)[0]])
   }
 
-  async delegate(
+  public async delegate(
     operation: Operation,
     fieldName: string,
     args: {
@@ -62,7 +52,7 @@ export class Binding {
     context: {
       [key: string]: any
     },
-    info?: GraphQLResolveInfo | string,
+    info?: GraphQLResolveInfo | string
   ) {
     this.before()
 
@@ -75,7 +65,44 @@ export class Binding {
       fieldName,
       args,
       context,
-      info,
+      info
+    )
+  }
+
+  public async delegateSubscription(
+    fieldName: string,
+    args?: { [key: string]: any },
+    infoOrQuery?: GraphQLResolveInfo | string
+  ): Promise<AsyncIterator<any>> {
+    this.before()
+
+    const info = buildInfo(fieldName, 'subscription', this.schema, infoOrQuery)
+
+    const iterator = await delegateToSchema(
+      this.schema,
+      this.fragmentReplacements,
+      'subscription',
+      fieldName,
+      args || {},
+      {},
+      info
     )
+
+    return {
+      async next() {
+        const { value } = await iterator.next()
+        const data = { [info.fieldName]: value.data[fieldName] }
+        return { value: data, done: false }
+      },
+      return() {
+        return Promise.resolve({ value: undefined, done: true })
+      },
+      throw(error) {
+        return Promise.reject(error)
+      },
+      [$$asyncIterator]() {
+        return this
+      }
+    }
   }
 }