API Subscriptions (#62)

* Upgrades

* Add getHead & newHead

* Handle pubsub interfaces

* Flow fixes

packages/api-jsonrpc/src/chain/getHead.js

@@ -0,0 +1,20 @@
+// Copyright 2017-2018 Jaco Greeff
+// This software may be modified and distributed under the terms
+// of the ISC license. See the LICENSE file for details.
+// @flow
+
+import type { InterfaceMethodDefinition } from '../types';
+
+/**
+  @name getHead
+  @signature chain_getHead (): HeaderHash
+  @summary Retrieves the best headerHash.
+  @description
+    Return the block hash for the lastest/best.
+*/
+module.exports = ({
+  inputs: [],
+  output: {
+    type: 'HeaderHash'
+  }
+}: InterfaceMethodDefinition);

packages/api-jsonrpc/src/chain/index.js

@@ -5,13 +5,17 @@
 
 import type { InterfaceDefinition } from '../types';
 
+const getHead = require('./getHead');
 const getHeader = require('./getHeader');
+const newHead = require('./newHead');
 
 /**
   @summary Methods to retrieve chain data.
 */
 module.exports = ({
   methods: {
-    getHeader
+    getHead,
+    getHeader,
+    newHead
   }
 }: InterfaceDefinition);

packages/api-jsonrpc/src/chain/newHead.js

@@ -0,0 +1,21 @@
+// Copyright 2017-2018 Jaco Greeff
+// This software may be modified and distributed under the terms
+// of the ISC license. See the LICENSE file for details.
+// @flow
+
+import type { InterfaceMethodDefinition } from '../types';
+
+/**
+  @name getHead
+  @signature chain_newHead (): HeaderHash
+  @summary Retrieves the best headerHash via subscription.
+  @description
+    Return the block hash for the lastest/best.
+*/
+module.exports = ({
+  isSubscription: true,
+  inputs: [],
+  output: {
+    type: 'HeaderHash'
+  }
+}: InterfaceMethodDefinition);

packages/api-jsonrpc/src/types.js

@@ -7,7 +7,7 @@ export type InterfaceTypes = 'author' | 'chain' | 'extra' | 'state';
 
 export type FormatInputType = 'Bytes' | 'H256' | 'HeaderHash' | 'String';
 
-export type FormatOutputType = 'BlockNumber' | 'Bytes' | 'Header' | 'U64';
+export type FormatOutputType = 'BlockNumber' | 'Bytes' | 'Header' | 'HeaderHash' | 'U64';
 
 export type InterfaceInputType = {
   name: string,
@@ -18,8 +18,14 @@ export type InterfaceOutputType = {
   type: FormatOutputType
 };
 
+export type InterfaceMethodDefinition$Subscribe = {
+  subscribe: string,
+  unsubscribe: string
+}
+
 export type InterfaceMethodDefinition = {
-  deprecated?: boolean,
+  isDeprecated?: boolean,
+  isSubscription?: boolean,
   inputs: Array<InterfaceInputType>,
   output: InterfaceOutputType
 };