feat(read): switched to promises

BREAKING CHANGE: Switches to a Promise-based API and removes callback stuff

lib/content/read.js

@@ -1,47 +1,50 @@
 'use strict'
 
-var checksumStream = require('checksum-stream')
-var contentPath = require('./path')
-var dezalgo = require('dezalgo')
-var fs = require('graceful-fs')
-var pipe = require('mississippi').pipe
+const Promise = require('bluebird')
+
+const checksumStream = require('checksum-stream')
+const contentPath = require('./path')
+const fs = require('graceful-fs')
+const pipe = require('mississippi').pipe
+
+Promise.promisifyAll(fs)
 
 module.exports.readStream = readStream
 function readStream (cache, address, opts) {
   opts = opts || {}
-  var stream = checksumStream({
+  const stream = checksumStream({
     digest: address,
     algorithm: opts.hashAlgorithm || 'sha1'
   })
-  var cpath = contentPath(cache, address)
-  hasContent(cache, address, function (err, exists) {
-    if (err) { return stream.emit('error', err) }
+  const cpath = contentPath(cache, address)
+  hasContent(cache, address).then(exists => {
     if (!exists) {
-      err = new Error('content not found')
+      const err = new Error('content not found')
       err.code = 'ENOENT'
       err.cache = cache
       err.digest = address
       return stream.emit('error', err)
     } else {
       pipe(fs.createReadStream(cpath), stream)
     }
+  }).catch(err => {
+    stream.emit('error', err)
   })
   return stream
 }
 
 module.exports.hasContent = hasContent
 function hasContent (cache, address, cb) {
-  cb = dezalgo(cb)
-  if (!address) { return cb(null, false) }
-  fs.lstat(contentPath(cache, address), function (err) {
+  if (!address) { return Promise.resolve(false) }
+  return fs.lstatAsync(
+    contentPath(cache, address)
+  ).then(() => true).catch(err => {
     if (err && err.code === 'ENOENT') {
-      return cb(null, false)
+      return Promise.resolve(false)
     } else if (err && process.platform === 'win32' && err.code === 'EPERM') {
-      return cb(null, false)
-    } else if (err) {
-      return cb(err)
+      return Promise.resolve(false)
     } else {
-      return cb(null, true)
+      throw err
     }
   })
 }