feat(state channels): allow to pass metadata to transfer update (#755)

Author: mpowaga

es/channel/index.js

@@ -112,6 +112,7 @@ function id () {
  * @param {String} to - Receiver's public address
  * @param {Number} amount - Transaction amount
  * @param {Function} sign - Function which verifies and signs offchain transaction
+ * @param {Array<String>} metadata
  * @return {Promise<Object>}
  * @example channel.update(
  *   'ak_Y1NRjHuoc3CGMYMvCmdHSBpJsMDR6Ra2t5zjhRcbtMeXXLpLH',
@@ -124,7 +125,7 @@ function id () {
  *   }
  * )
  */
-function update (from, to, amount, sign) {
+function update (from, to, amount, sign, metadata) {
   return new Promise((resolve, reject) => {
     enqueueAction(
       this,
@@ -133,7 +134,7 @@ function update (from, to, amount, sign) {
         send(channel, {
           jsonrpc: '2.0',
           method: 'channels.update.new',
-          params: { from, to, amount }
+          params: { from, to, amount, meta: metadata }
         })
         return {
           handler: handlers.awaitingOffChainTx,

test/integration/channel.js

@@ -295,6 +295,27 @@ describe('Channel', function () {
     })
   })
 
+  it('can post update with metadata', async () => {
+    responderShouldRejectUpdate = true
+    const meta = 'meta 1'
+    const sign = sinon.spy(initiator.signTransaction.bind(initiator))
+    await initiatorCh.update(
+      await initiator.address(),
+      await responder.address(),
+      100,
+      sign,
+      [meta]
+    )
+    sign.firstCall.args[1].updates.should.eql([
+      sign.firstCall.args[1].updates[0],
+      { data: meta, op: 'OffChainMeta'}
+    ])
+    responderSign.firstCall.args[2].updates.should.eql([
+      responderSign.firstCall.args[2].updates[0],
+      { data: meta, op: 'OffChainMeta'}
+    ])
+  })
+
   it('can get proof of inclusion', async () => {
     const initiatorAddr = await initiator.address()
     const responderAddr = await responder.address()