init commit

.gitignore

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+
+# Created by https://www.gitignore.io/api/osx,node
+
+### Node ###
+# Logs
+logs
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+
+# Runtime data
+pids
+*.pid
+*.seed
+*.pid.lock
+
+# Directory for instrumented libs generated by jscoverage/JSCover
+lib-cov
+
+# Coverage directory used by tools like istanbul
+coverage
+
+# nyc test coverage
+.nyc_output
+
+# Grunt intermediate storage (http://gruntjs.com/creating-plugins#storing-task-files)
+.grunt
+
+# Bower dependency directory (https://bower.io/)
+bower_components
+
+# node-waf configuration
+.lock-wscript
+
+# Compiled binary addons (http://nodejs.org/api/addons.html)
+build/Release
+
+# Dependency directories
+node_modules/
+jspm_packages/
+
+# Typescript v1 declaration files
+typings/
+
+# Optional npm cache directory
+.npm
+
+# Optional eslint cache
+.eslintcache
+
+# Optional REPL history
+.node_repl_history
+
+# Output of 'npm pack'
+*.tgz
+
+# Yarn Integrity file
+.yarn-integrity
+
+# dotenv environment variables file
+.env
+
+
+### OSX ###
+*.DS_Store
+.AppleDouble
+.LSOverride
+
+# Icon must end with two \r
+Icon
+
+
+# Thumbnails
+._*
+
+# Files that might appear in the root of a volume
+.DocumentRevisions-V100
+.fseventsd
+.Spotlight-V100
+.TemporaryItems
+.Trashes
+.VolumeIcon.icns
+.com.apple.timemachine.donotpresent
+
+# Directories potentially created on remote AFP share
+.AppleDB
+.AppleDesktop
+Network Trash Folder
+Temporary Items
+.apdisk
+
+# End of https://www.gitignore.io/api/osx,node

block-ref.js

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+module.exports = BlockRefRewriteMiddleware
+
+function BlockRefRewriteMiddleware({ blockTracker }) {
+  if (!blockTracker) {
+    throw Error('BlockRefRewriteMiddleware - mandatory "blockTracker" option is missing.')
+  }
+
+  let requestQueue = []
+  let currentHandler = null
+
+  if (blockTracker.getCurrentBlock()) {
+    // block tracker is already ready
+    currentHandler = handleRequest
+  } else {
+    // buffer all requests for first block
+    currentHandler = addToQueue
+    // after first block
+    blockTracker.once('latest', () => {
+      // update handler
+      currentHandler = handleRequest
+      // process backlog
+      requestQueue.forEach((args) => handleRequest.apply(null, args))
+      requestQueue = null
+    })
+  }
+
+  return (req, res, next, end) => {
+    currentHandler(req, res, next, end)
+  }
+
+  // add requst to queue if blockRef is "latest"
+  function addToQueue(req, res, next, end) {
+    const blockRefIndex = blockRefParamIndex(req.method)
+    const blockRef = req.params[blockRefIndex]
+    if (blockRef === 'latest') {
+      requestQueue.push([req, res, next, end])
+    } else {
+      next()
+    }
+  }
+
+  // if blockRef is "latest", rewrite to latest block number
+  function handleRequest(req, res, next, end) {
+    const blockRefIndex = blockRefParamIndex(req.method)
+    const blockRef = req.params[blockRefIndex]
+    if (blockRef === 'latest') {
+      let block = blockTracker.getCurrentBlock()
+      req.params[blockRefIndex] = block.number
+    }
+    next()
+  }
+}
+
+
+function blockRefParamIndex(rpcMethod) {
+  switch (rpcMethod) {
+    // blockRef is second param
+    case 'eth_getBalance':
+    case 'eth_getCode':
+    case 'eth_getTransactionCount':
+    case 'eth_getStorageAt':
+    case 'eth_call':
+    case 'eth_estimateGas':
+      return 1
+    // blockRef is first param
+    case 'eth_getBlockByNumber':
+      return 0
+    // there is no blockRef
+    default:
+      return undefined
+  }
+}

package.json

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+{
+  "name": "eth-json-rpc-middleware",
+  "version": "1.0.0",
+  "main": "block-ref.js",
+  "directories": {
+    "test": "test"
+  },
+  "scripts": {
+    "test": "node test/block-ref.js"
+  },
+  "author": "",
+  "license": "ISC",
+  "description": "",
+  "devDependencies": {
+    "eth-block-tracker": "^1.0.3",
+    "eth-query": "^2.1.0",
+    "json-rpc-engine": "^2.1.0",
+    "tape": "^4.6.3"
+  }
+}

scaffold.js

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+module.exports = ScaffoldMiddleware
+
+function ScaffoldMiddleware(handlers) {
+  return (req, res, next, end) => {
+    const handler = handlers[req.method]
+    // if no handler, return
+    if (handler === undefined) {
+      return next()
+    }
+    // if handler is fn, call as middleware
+    if (typeof handler === 'function') {
+      return handler(req, res, next, end)
+    }
+    // if handler is some other value, use as result
+    res.result = handler
+    end()
+  }
+}

test/block-ref.js

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+const test = require('tape')
+const JsonRpcEngine = require('json-rpc-engine')
+const asMiddleware = require('json-rpc-engine/lib/asMiddleware')
+const RpcBlockTracker = require('eth-block-tracker')
+const EthQuery = require('eth-query')
+const TestBlockMiddleware = require('eth-block-tracker/test/util/testBlockMiddleware')
+const BlockRefMiddleware = require('../block-ref')
+const ScaffoldMiddleware = require('../scaffold')
+
+test('contructor - no opts', (t) => {
+  t.plan(1)
+
+  t.throws(() => {
+    BlockRefMiddleware()
+  }, Error, 'Constructor without options fails')
+  t.end()
+})
+
+test('contructor - empty opts', (t) => {
+  t.plan(1)
+
+  t.throws(() => {
+    BlockRefMiddleware({})
+  }, Error, 'Constructor without empty options')
+  t.end()
+})
+
+test('provider not ready - shouldnt hang non-"latest" requests', (t) => {
+  t.plan(3)
+
+  const { engine, dataEngine, testBlockSource } = createTestSetup()
+
+  // add handler for `test_method`
+  dataEngine.push(ScaffoldMiddleware({
+    test_method: true,
+  }))
+
+  // fire request for `test_method`
+  engine.handle({ id: 1, method: 'test_method', params: [] }, (err, res) => {
+    t.notOk(err, 'No error in response')
+    t.ok(res, 'Has response')
+    t.equal(res.result, true, 'Response result is correct.')
+    t.end()
+  })
+
+})
+
+// util
+
+function createTestSetup() {
+  // raw data source
+  const { engine: dataEngine, testBlockSource } = createEngineForTestData()
+  const dataProvider = providerFromEngine(dataEngine)
+  // create block tracker
+  const blockTracker = new RpcBlockTracker({ provider: dataProvider })
+  // create higher level
+  const engine = new JsonRpcEngine()
+  const provider = providerFromEngine(engine)
+  // add block ref middleware
+  engine.push(BlockRefMiddleware({ blockTracker }))
+  // add data source
+  engine.push(asMiddleware(dataEngine))
+  const query = new EthQuery(provider)
+  return { engine, provider, dataEngine, dataProvider, query, blockTracker, testBlockSource }
+}
+
+function createEngineForTestData() {
+  const engine = new JsonRpcEngine()
+  const testBlockSource = new TestBlockMiddleware()
+  engine.push(testBlockSource.createMiddleware())
+  return { engine, testBlockSource }
+}
+
+function providerFromEngine(engine) {
+  const provider = { sendAsync: engine.handle.bind(engine) }
+  return provider
+}