Helper function for checking whether an AFS has been committed to

README.md

@@ -64,12 +64,14 @@ The contracts in this repository are currently deployed on [Ara Privatenet](http
 * [async registry.deployNewStandard(opts)](#newstandard)
 
 ### Library
+
 * [async library.getLibrary(requesterDid)](#getlibrary)
 * [async library.getLibrarySize(requesterDid)](#librarysize)
 * [async library.getLibraryItem(opts)](#libraryitem)
 * [async library.hasPurchased(opts)](#haspurchased)
 
 ### Rewards
+
 * [async rewards.submit(opts)](#submit)
 * [async rewards.allocate(opts)](#allocate)
 * [async rewards.redeem(opts)](#redeem)

storage.js

@@ -1,7 +1,14 @@
-const { web3: { tx, call, isAddress } } = require('ara-util')
 const { abi } = require('./build/contracts/AFS.json')
 const isBuffer = require('is-buffer')
 
+const {
+  web3: {
+    isAddress,
+    call,
+    tx
+  }
+} = require('ara-util')
+
 async function read(opts) {
   _validateOpts(opts)
   const { address, fileIndex, offset } = opts
@@ -91,6 +98,30 @@ async function hasBuffer(opts) {
   })
 }
 
+async function isEmpty(address = '') {
+  if (!address || 'string' !== typeof address) {
+    throw new TypeError('Expecting address to be non-empty string')
+  }
+
+  if (!isAddress(address)) {
+    throw new Error(`${address} is not a valid Ethereum address`)
+  }
+
+  let empty = true
+  try {
+    // only need to check first header
+    const buf = await read({
+      fileIndex: 0,
+      offset: 0,
+      address
+    })
+    empty = null === buf
+  } catch (err) {
+    throw err
+  }
+  return empty
+}
+
 function _validateOpts(opts) {
   if (!opts || 'object' !== typeof opts) {
     throw new TypeError('Expecting opts to be of type object')
@@ -107,6 +138,7 @@ function _validateOpts(opts) {
 
 module.exports = {
   hasBuffer,
+  isEmpty,
   write,
   read
 }

test/storage.js

@@ -150,6 +150,11 @@ test.serial("hasBuffer(opts) buffer does not exist", async (t) => {
   t.true(false === Boolean(exists))
 })
 
+test.serial("isEmpty(did) empty", async (t) => {
+  const { address } = t.context
+  t.is(true, await storage.isEmpty(address))
+})
+
 test.serial("hasBuffer(opts) buffer exists", async (t) => {
   const { address } = t.context
 
@@ -196,6 +201,11 @@ test.serial("hasBuffer(opts) buffer exists", async (t) => {
   t.true(true === Boolean(exists))
 })
 
+test.serial("isEmpty(did) not empty", async (t) => {
+  const { address } = t.context
+  t.is(false, await storage.isEmpty(address))
+})
+
 test.serial("write(opts) read(opts) append", async (t) => {
   const { address } = t.context
 
@@ -235,3 +245,9 @@ test.serial("write(opts) read(opts) append", async (t) => {
   t.is(result, msBuffer)
 })
 
+test.serial("isEmpty(did) invalid did", async (t) => {
+  await t.throwsAsync(storage.isEmpty())
+  await t.throwsAsync(storage.isEmpty({ }))
+  await t.throwsAsync(storage.isEmpty(null))
+  await t.throwsAsync(storage.isEmpty('0x1234'))
+})