feat(dat): support dat dependency as an experimental feature

lib/install/installer.js

@@ -3,6 +3,7 @@ const mkdirp = require('mkdirp')
 const path = require('path')
 const nm = require('../utils/nm')
 const bin = require('./installer/bin')
+const dat = require('./installer/dat')
 const git = require('./installer/git')
 const local = require('./installer/local')
 const remote = require('./installer/remote')
@@ -20,7 +21,12 @@ const installer = (dep, deps, base, resolve, reject) => {
   const pkg = deps[dep]
   var fetch
 
+  if (pkg.type === 'git') console.log('\n\n\n\n123\n\n\n\n')
+
   switch (pkg.type) {
+    case 'dat':
+      fetch = dat(pkg, target)
+      break
     case 'git':
       fetch = git(pkg, target)
       break
@@ -31,7 +37,6 @@ const installer = (dep, deps, base, resolve, reject) => {
       fetch = local(pkg, target)
       break
     case 'registry':
-    default:
       fetch = registry(pkg, target)
       break
   }

lib/install/installer/dat.js

@@ -0,0 +1,19 @@
+const Dat = require('dat-node')
+
+module.exports = (pkg, cwd) => {
+  return new Promise((resolve, reject) => {
+    Dat(cwd, {key: pkg.url, sparse: true}, function (e, dat) {
+      if (e) return reject(e)
+      dat.joinNetwork()
+      dat.archive.readFile('/package.json', function (e, content) {
+        if (e) {
+          dat.leaveNetwork()
+          reject(e)
+        }
+        if (!content || !content.toString()) return
+        dat.leaveNetwork()
+        resolve()
+      })
+    })
+  })
+}

lib/install/resolver/fetcher.js

@@ -1,4 +1,5 @@
 const npa = require('npm-package-arg')
+const dat = require('./fetchers/dat')
 const git = require('./fetchers/git')
 const local = require('./fetchers/local')
 const remote = require('./fetchers/remote')
@@ -7,11 +8,25 @@ const registry = require('./fetchers/registry')
 module.exports = (name, spec) => {
   var result
   try {
-    result = npa.resolve(name, spec, process.cwd())
+    if (spec.startsWith('dat:')) {
+      result = {
+        type: 'dat',
+        fetchSpec: spec
+      }
+    } else {
+      result = npa.resolve(name, spec, process.cwd())
+    }
   } catch (e) { throw new Error(e) }
 
   switch (result.type) {
     // type git
+    case 'dat':
+      process.stdout.write(
+        'Using dat as deps is an experimental feature.\n' +
+        'It could be changed at any time.\n\n'
+      )
+      return dat(name, result.fetchSpec, result)
+    // type git
     case 'git':
       return git(name, result.fetchSpec, result)
     // type remote

lib/install/resolver/fetchers/dat.js

@@ -0,0 +1,31 @@
+const os = require('os')
+const path = require('path')
+const Dat = require('dat-node')
+
+module.exports = (name, spec, result) => {
+  return new Promise((resolve, reject) => {
+    Dat(path.join(os.tmpdir(), encodeURIComponent(spec)), {key: spec, sparse: true}, function (e, dat) {
+      if (e) return reject(e)
+      dat.joinNetwork()
+      dat.archive.readFile('/package.json', function (e, content) {
+        if (e) {
+          dat.leaveNetwork()
+          reject(e)
+        }
+        if (!content) return
+        dat.leaveNetwork()
+        try {
+          const pkg = JSON.parse(content.toString())
+          resolve({
+            type: 'dat',
+            version: pkg.version,
+            dependencies: pkg.dependencies,
+            url: spec
+          })
+        } catch (e) {
+          reject(e)
+        }
+      })
+    })
+  })
+}