feat: implement ipfs refs

Author: dirkmc

src/cli/commands/refs.js

@@ -0,0 +1,104 @@
+'use strict'
+
+const { print } = require('../utils')
+
+// Default formats
+const Format = {
+  default: '<dst>',
+  edges: '<src> -> <dst>'
+}
+
+module.exports = {
+  command: 'refs <key>',
+
+  describe: 'List links (references) from an object',
+
+  builder: {
+    r: {
+      alias: 'recursive',
+      desc: 'Recursively list links of child nodes.',
+      type: 'boolean',
+      default: false
+    },
+    format: {
+      desc: 'Output edges with given format. Available tokens: <src> <dst> <linkname>.',
+      type: 'string',
+      default: Format.default
+    },
+    e: {
+      alias: 'edges',
+      desc: 'Output edge format: `<from> -> <to>`',
+      type: 'boolean',
+      default: false
+    },
+    u: {
+      alias: 'unique',
+      desc: 'Omit duplicate refs from output.',
+      type: 'boolean',
+      default: false
+    },
+    'max-depth': {
+      desc: 'Only for recursive refs, limits fetch and listing to the given depth.',
+      type: 'number'
+    }
+  },
+
+  handler ({ getIpfs, key, recursive, format, e, u, resolve, maxDepth }) {
+    resolve((async () => {
+      if (format !== Format.default && e) {
+        throw new Error('Cannot set edges to true and also specify format')
+      }
+
+      if (maxDepth === 0) {
+        return
+      }
+
+      const ipfs = await getIpfs()
+      let links = await ipfs.refs(key, { recursive, maxDepth })
+      if (!links.length) {
+        return
+      }
+
+      const linkDAG = getLinkDAG(links)
+      format = e ? Format.edges : format || Format.default
+      printLinks(linkDAG, links[0], format, u && new Set())
+    })())
+  }
+}
+
+// Get links as a DAG Object
+// { <linkName1>: [link2, link3, link4], <linkName2>: [...] }
+function getLinkDAG (links) {
+  const linkNames = {}
+  for (const link of links) {
+    linkNames[link.name] = link
+  }
+
+  const linkDAG = {}
+  for (const link of links) {
+    const parentName = link.path.substring(0, link.path.lastIndexOf('/'))
+    linkDAG[parentName] = linkDAG[parentName] || []
+    linkDAG[parentName].push(link)
+  }
+  return linkDAG
+}
+
+// Print children of a link
+function printLinks (linkDAG, link, format, uniques) {
+  const children = linkDAG[link.path] || []
+  for (const child of children) {
+    if (!uniques || !uniques.has(child.hash)) {
+      uniques && uniques.add(child.hash)
+      printLink(link, child, format)
+      printLinks(linkDAG, child, format, uniques)
+    }
+  }
+}
+
+// Print formatted link
+function printLink (src, dst, format) {
+  let out = format.replace(/<src>/g, src.hash)
+  out = out.replace(/<dst>/g, dst.hash)
+  out = out.replace(/<linkname>/g, dst.name)
+  print(out)
+}

src/core/components/files-regular/index.js

@@ -15,5 +15,7 @@ module.exports = self => ({
   getReadableStream: require('./get-readable-stream')(self),
   ls: require('./ls')(self),
   lsPullStream: require('./ls-pull-stream')(self),
-  lsReadableStream: require('./ls-readable-stream')(self)
+  lsReadableStream: require('./ls-readable-stream')(self),
+  refs: require('./refs')(self),
+  refsPullStream: require('./refs-pull-stream')(self)
 })

src/core/components/files-regular/refs-pull-stream.js

@@ -0,0 +1,38 @@
+'use strict'
+
+const exporter = require('ipfs-unixfs-exporter')
+const pull = require('pull-stream')
+const { normalizePath } = require('./utils')
+
+module.exports = function (self) {
+  return function (ipfsPath, options = {}) {
+    const path = normalizePath(ipfsPath)
+    const pathComponents = path.split('/')
+
+    // eg QmHash/linkName => 2
+    const pathDepth = pathComponents.length
+
+    // The exporter returns a depth for each node, eg:
+    // Qmhash.../linkName/linkName/linkName/block
+    //    0         1         2        3      4
+    if (options.maxDepth === undefined) {
+      options.maxDepth = options.recursive ? global.Infinity : pathDepth
+    } else {
+      options.maxDepth = options.maxDepth + pathDepth - 1
+    }
+
+    if (options.preload !== false) {
+      self._preload(pathComponents[0])
+    }
+
+    return pull(
+      exporter(ipfsPath, self._ipld, options),
+      pull.map(node => {
+        node.hash = node.cid.toString()
+        delete node.cid
+        delete node.content
+        return node
+      })
+    )
+  }
+}

src/core/components/files-regular/refs.js

@@ -0,0 +1,25 @@
+'use strict'
+
+const promisify = require('promisify-es6')
+const pull = require('pull-stream')
+
+module.exports = function (self) {
+  return promisify((ipfsPath, options, callback) => {
+    if (typeof options === 'function') {
+      callback = options
+      options = {}
+    }
+
+    options = options || {}
+
+    pull(
+      self.refsPullStream(ipfsPath, options),
+      pull.collect((err, values) => {
+        if (err) {
+          return callback(err)
+        }
+        callback(null, values)
+      })
+    )
+  })
+}