feat: convert to async/await (#21)

* feat: convert to async/await

* chore: readme update

* chore: fix linting

* feat: convert internals to be async/await

* test: increase test coverage

* chore: remove uncessary await

* feat: add export depth and recursive exports

* chore: address PR comments

* chore: update ipld formats

* chore: PR comments

* chore: standardise error codes

.aegir.js

@@ -0,0 +1,7 @@
+'use strict'
+
+module.exports = {
+  karma: {
+    browserNoActivityTimeout: 1000 * 1000,
+  }
+}

README.md

@@ -19,13 +19,22 @@
 
 ## Table of Contents
 
-- [Install](#install)
-- [Usage](#usage)
-  - [Example](#example)
-  - [API](#api)
-  - [exporter(cid, ipld)](#exportercid-ipld-options)
-- [Contribute](#contribute)
-- [License](#license)
+- [ipfs-unixfs-exporter](#ipfs-unixfs-exporter)
+  - [Lead Maintainer](#lead-maintainer)
+  - [Table of Contents](#table-of-contents)
+  - [Install](#install)
+  - [Usage](#usage)
+    - [Example](#example)
+      - [API](#api)
+    - [`exporter(cid, ipld)`](#exportercid-ipld)
+      - [UnixFS V1 entries](#unixfs-v1-entries)
+      - [Raw entries](#raw-entries)
+      - [CBOR entries](#cbor-entries)
+      - [`entry.content({ offset, length })`](#entrycontent-offset-length)
+    - [`exporter.path(cid, ipld)`](#exporterpathcid-ipld)
+    - [`exporter.recursive(cid, ipld)`](#exporterrecursivecid-ipld)
+  - [Contribute](#contribute)
+  - [License](#license)
 
 ## Install
 
@@ -38,29 +47,41 @@
 ### Example
 
 ```js
-// Create an export source pull-stream cid or ipfs path you want to export and a
-// <dag or ipld-resolver instance> to fetch the file from
+// import a file and export it again
+const importer = require('ipfs-unixfs-importer')
 const exporter = require('ipfs-unixfs-exporter')
-const pull = require('pull-stream/pull')
-const { stdout } = require('pull-stdio')
-
-const options = {}
-
-pull(
-  exporter(cid, ipld, options),
-  collect((error, files) => {
-    if (error) {
-      // ...handle error
-    }
-
-    // Set up a pull stream that sends the file content to process.stdout
-    pull(
-      // files[0].content is a pull-stream that contains the bytes of the file
-      files[0].content,
-      stdout()
-    )
-  })
-)
+
+const files = []
+
+for await (const file of importer([{
+  path: '/foo/bar.txt',
+  content: Buffer.from(0, 1, 2, 3)
+}], ipld)) {
+  files.push(file)
+}
+
+console.info(files[0].cid) // Qmbaz
+
+const entry = await exporter(files[0].cid, ipld)
+
+console.info(entry.cid) // Qmqux
+console.info(entry.path) // Qmbaz/foo/bar.txt
+console.info(entry.name) // bar.txt
+console.info(entry.unixfs.fileSize()) // 4
+
+// stream content from unixfs node
+const bytes = []
+
+for await (const buf of entry.content({
+  offset: 0, // optional offset
+  length: 4 // optional length
+})) {
+  bytes.push(buf)
+}
+
+const content = Buffer.concat(bytes)
+
+console.info(content) // 0, 1, 2, 3
 ```
 
 #### API
@@ -69,124 +90,146 @@ pull(
 const exporter = require('ipfs-unixfs-exporter')
 ```
 
-### exporter(cid, ipld, options)
+### `exporter(cid, ipld)`
 
-Uses the given [dag API][] or an [ipld-resolver instance][] to fetch an IPFS [UnixFS][] object(s) by their CID.
+Uses the given [js-ipld instance][] to fetch an IPFS node by it's CID.
 
-Creates a new pull stream that outputs objects of the form
+Returns a Promise which resolves to an `entry`.
 
-```js
+#### UnixFS V1 entries
+
+Entries with a `dag-pb` codec `CID` return UnixFS V1 entries:
+
+```javascript
 {
-  path: 'a name',
-  content: <pull stream>
+  name: 'foo.txt',
+  path: 'Qmbar/foo.txt',
+  cid: CID, // see https://github.com/multiformats/js-cid
+  node: DAGNode, // see https://github.com/ipld/js-ipld-dag-pb
+  content: function, // returns an async iterator
+  unixfs: UnixFS // see https://github.com/ipfs/js-ipfs-unixfs
 }
 ```
 
-#### `offset` and `length`
+If the entry is a file, `entry.content()` returns an async iterator that yields one or more buffers containing the file content:
 
-`offset` and `length` arguments can optionally be passed to the exporter function.  These will cause the returned stream to only emit bytes starting at `offset` and with length of `length`.
+```javascript
+if (entry.unixfs.type === 'file') {
+  for await (const chunk of entry.content()) {
+    // chunk is a Buffer
+  }
+}
+```
 
-See [the tests](test/exporter.js) for examples of using these arguments.
+If the entry is a directory or hamt shard, `entry.content()` returns further `entry` objects:
 
-```js
-const exporter = require('ipfs-unixfs-exporter')
-const pull = require('pull-stream')
-const drain = require('pull-stream/sinks/drain')
-
-pull(
-  exporter(cid, ipld, {
-    offset: 0,
-    length: 10
-  })
-  drain((file) => {
-    // file.content is a pull stream containing only the first 10 bytes of the file
-  })
-)
+```javascript
+if (entry.unixfs.type.includes('directory')) { // can be 'directory' or 'hamt-sharded-directory'
+  for await (const entry of dir.content()) {
+    console.info(entry.name)
+  }
+}
 ```
 
-### `fullPath`
+#### Raw entries
 
-If specified the exporter will emit an entry for every path component encountered.
+Entries with a `raw` codec `CID` return raw entries:
 
 ```javascript
-const exporter = require('ipfs-unixfs-exporter')
-const pull = require('pull-stream')
-const collect = require('pull-stream/sinks/collect')
-
-pull(
-  exporter('QmFoo.../bar/baz.txt', ipld, {
-    fullPath: true
-  })
-  collect((err, files) => {
-    console.info(files)
-
-    // [{
-    //   depth: 0,
-    //   name: 'QmFoo...',
-    //   path: 'QmFoo...',
-    //   size: ...
-    //   cid: CID
-    //   content: undefined
-    //   type: 'dir'
-    // }, {
-    //   depth: 1,
-    //   name: 'bar',
-    //   path: 'QmFoo.../bar',
-    //   size: ...
-    //   cid: CID
-    //   content: undefined
-    //   type: 'dir'
-    // }, {
-    //   depth: 2,
-    //   name: 'baz.txt',
-    //   path: 'QmFoo.../bar/baz.txt',
-    //   size: ...
-    //   cid: CID
-    //   content: <Pull stream>
-    //   type: 'file'
-    // }]
-    //
-  })
-)
+{
+  name: 'foo.txt',
+  path: 'Qmbar/foo.txt',
+  cid: CID, // see https://github.com/multiformats/js-cid
+  node: Buffer, // see https://nodejs.org/api/buffer.html
+  content: function, // returns an async iterator
+}
 ```
 
-### `maxDepth`
+`entry.content()` returns an async iterator that yields a buffer containing the node content:
 
-If specified the exporter will only emit entries up to the specified depth.
+```javascript
+for await (const chunk of entry.content()) {
+  // chunk is a Buffer
+}
+```
+
+Unless you an options object containing `offset` and `length` keys as an argument to `entry.content()`, `chunk` will be equal to `entry.node`.
+
+#### CBOR entries
+
+Entries with a `dag-cbor` codec `CID` return JavaScript object entries:
 
 ```javascript
-const exporter = require('ipfs-unixfs-exporter')
-const pull = require('pull-stream')
-const collect = require('pull-stream/sinks/collect')
-
-pull(
-  exporter('QmFoo.../bar/baz.txt', ipld, {
-    fullPath: true,
-    maxDepth: 1
-  })
-  collect((err, files) => {
-    console.info(files)
-
-    // [{
-    //   depth: 0,
-    //   name: 'QmFoo...',
-    //   path: 'QmFoo...',
-    //   size: ...
-    //   cid: CID
-    //   content: undefined
-    //   type: 'dir'
-    // }, {
-    //   depth: 1,
-    //   name: 'bar',
-    //   path: 'QmFoo.../bar',
-    //   size: ...
-    //   cid: CID
-    //   content: undefined
-    //   type: 'dir'
-    // }]
-    //
-  })
-)
+{
+  name: 'foo.txt',
+  path: 'Qmbar/foo.txt',
+  cid: CID, // see https://github.com/multiformats/js-cid
+  node: Object, // see https://github.com/ipld/js-ipld-dag-cbor
+}
+```
+
+There is no `content` function for a `CBOR` node.
+
+
+#### `entry.content({ offset, length })`
+
+When `entry` is a file or a `raw` node, `offset` and/or `length` arguments can be passed to `entry.content()` to return slices of data:
+
+```javascript
+const bufs = []
+
+for await (const chunk of entry.content({
+  offset: 0,
+  length: 5
+})) {
+  bufs.push(chunk)
+}
+
+// `data` contains the first 5 bytes of the file
+const data = Buffer.concat(bufs)
+```
+
+If `entry` is a directory or hamt shard, passing `offset` and/or `length` to `entry.content()` will limit the number of files returned from the directory.
+
+```javascript
+const entries = []
+
+for await (const entry of dir.content({
+  offset: 0,
+  length: 5
+})) {
+  entries.push(entry)
+}
+
+// `entries` contains the first 5 files/directories in the directory
+```
+
+### `exporter.path(cid, ipld)`
+
+`exporter.path` will return an async iterator that yields entries for all segments in a path:
+
+```javascript
+const entries = []
+
+for await (const entry of exporter.path('Qmfoo/foo/bar/baz.txt', ipld)) {
+  entries.push(entry)
+}
+
+// entries contains 4x `entry` objects
+```
+
+### `exporter.recursive(cid, ipld)`
+
+`exporter.recursive` will return an async iterator that yields all entries beneath a given CID or IPFS path, as well as the containing directory.
+
+```javascript
+const entries = []
+
+for await (const child of exporter.recursive('Qmfoo/foo/bar', ipld)) {
+  entries.push(entry)
+}
+
+// entries contains all children of the `Qmfoo/foo/bar` directory and it's children
 ```
 
 [dag API]: https://github.com/ipfs/interface-ipfs-core/blob/master/SPEC/DAG.md