Add sh.wget() for downloading files into the fs, with tests and docs

README.md

@@ -1133,6 +1133,7 @@ var sh = fs.Shell();
 * [sh.rm(path, [options], callback)](#rm)
 * [sh.tempDir(callback)](#tempDir)
 * [sh.mkdirp(path, callback)](#mkdirp)
+* [sh.wget(path, [options], callback)](#wget)
 
 #### sh.cd(path, callback)<a name="cd"></a>
 
@@ -1338,3 +1339,27 @@ sh.mkdirp('/test/mkdirp', function(err) {
   // the root '/' now contains a directory 'test' containing the directory 'mkdirp'
 });
 ```
+
+#### sh.wget(url, [options], callback)<a name="wget"></a>
+
+Downloads the file at `url` and saves it to the filesystem.
+The file is saved to a file named with the current date/time
+unless the `options.filename` is present, in which case that
+filename is used instead. The callback receives `(error, path)`,
+where `path` is the full path to the downloaded file.
+
+Example:
+
+```javascript
+// Download the file at /files/file.json
+sh.wget('/files/file.json', function(err, path) {
+  if(err) throw err;
+  // /file-134134513 is now saved to the fs
+});
+
+// Download the file at /files/file.json, specifying a filename
+sh.wget('/files/file.json', {filename: 'file.json'}, function(err, path) {
+  if(err) throw err;
+  // /file.json is now saved to the fs
+});
+```

src/shell/shell.js

@@ -421,6 +421,46 @@ define(function(require) {
     _mkdirp(path, callback);
   };
 
+  /**
+   * Downloads the file at `url` and saves it to the filesystem.
+   * The file is saved to a file named with the current date/time
+   * unless the `options.filename` is present, in which case that
+   * filename is used instead. The callback receives (error, path).
+   */
+  Shell.prototype.wget = function(url, options, callback) {
+    var fs = this.fs;
+    if(typeof options === 'function') {
+      callback = options;
+      options = {};
+    }
+    options = options || {};
+    callback = callback || function(){};
+
+    if(!url) {
+      callback(new Errors.EINVAL('missing url argument'));
+      return;
+    }
+
+    var path = options.filename || ('file-' + Date.now());
+    path = Path.resolve(fs.cwd, path);
+
+    var request = new XMLHttpRequest();
+    request.addEventListener("load", function() {
+      var data = new Uint8Array(request.response);
+      fs.writeFile(path, data, function(err) {
+        if(err) {
+          callback(err);
+        } else {
+          callback(null, path);
+        }
+      });
+    }, false);
+    request.addEventListener("error", function(err) { callback(err); }, false);
+    request.open("GET", url);
+    request.responseType = "arraybuffer";
+    request.send();
+  };
+
   return Shell;
 
 });

tests/spec/shell/wget.spec.js

@@ -0,0 +1,66 @@
+define(["Filer", "util"], function(Filer, util) {
+
+  describe('FileSystemShell.wget', function() {
+    beforeEach(util.setup);
+    afterEach(util.cleanup);
+
+    it('should be a function', function() {
+      var shell = util.shell();
+      expect(shell.wget).to.be.a('function');
+    });
+
+    it('should fail when url argument is absent', function(done) {
+      var fs = util.fs();
+      var shell = fs.Shell();
+
+      shell.wget(null, function(err, data) {
+        expect(err).to.exist;
+        expect(data).not.to.exist;
+        done();
+      });
+    });
+
+    it('should download the contents of a file from a url to default filename', function(done) {
+      var fs = util.fs();
+      var shell = fs.Shell();
+      var url = "test-file.txt";
+      var contents = "This is a test file used in some of the tests.\n";
+
+      shell.wget(url, function(err, path) {
+        if(err) throw err;
+
+        // The filename should be something like /file-13424512341
+        expect(path).to.match(/^\/file\-\d+$/);
+
+        fs.readFile(path, 'utf8', function(err, data) {
+          if(err) throw err;
+
+          expect(data).to.equal(contents);
+          done();
+        });
+      });
+    });
+
+    it('should download the contents of a file from a url to specified filename', function(done) {
+      var fs = util.fs();
+      var shell = fs.Shell();
+      var url = "test-file.txt";
+      var contents = "This is a test file used in some of the tests.\n";
+
+      shell.wget(url, { filename: 'test-file.txt' }, function(err, path) {
+        if(err) throw err;
+
+        // The filename should be something like /file-13424512341
+        expect(path).to.equal('/test-file.txt');
+
+        fs.readFile(path, 'utf8', function(err, data) {
+          if(err) throw err;
+
+          expect(data).to.equal(contents);
+          done();
+        });
+      });
+    });
+
+  });
+});

tests/test-file.txt

@@ -0,0 +1 @@
+This is a test file used in some of the tests.

tests/test-manifest.js

@@ -57,6 +57,7 @@ define([
   "spec/shell/rm.spec",
   "spec/shell/env.spec",
   "spec/shell/mkdirp.spec",
+  "spec/shell/wget.spec",
 
   // Ported node.js tests (filenames match names in https://github.com/joyent/node/tree/master/test)
   "spec/node-js/simple/test-fs-mkdir",