DevTools: implement proxy server for hosted mode

third_party/WebKit/Source/devtools/hosted_mode/protocol_files_proxy.js

+// Copyright (c) 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+var request = require("./request");
+
+var protocolFileToPath = {
+    "/front_end/sdk/protocol/js_protocol.json": "core/inspector/browser_protocol.json",
+    "/front_end/sdk/protocol/browser_protocol.json": "platform/v8_inspector/js_protocol.json"
+};
+var protocolFiles = Object.keys(protocolFileToPath);
+
+function proxy(filePath, sendResponse)
+{
+    if (protocolFiles.indexOf(filePath) === -1)

[lushnikov, 2016/07/22 21:06:04]

if (!(filePath in protocolFileToPath))
    return null;

[chenwilliam, 2016/07/22 23:20:31]

Done.

+        return null;
+    return request("http://localhost:9222/json/version")
+        .then(onBrowserMetadata)
+        .then(data => sendResponse(200, data))
+        .catch(err => console.log(`Error getting ${protocolFile}:`, err));
+
+    function onBrowserMetadata(metadata)
+    {
+        metadata = JSON.parse(metadata);

[lushnikov, 2016/07/22 21:06:04]

let's make a separate variable for the parsed json (it's good to avoid
polymorphic variables)

[chenwilliam, 2016/07/22 23:20:31]

Done.

+        var match = metadata["WebKit-Version"].match(/\s\(@(\b[0-9a-f]{5,40}\b)/);
+        var commitHash = match[1];
+        protocolFileCache.setVersion(commitHash);
+        if (protocolFileCache.hasFile(filePath))
+            return protocolFileCache.getFile(filePath);
+        return request(getURL(filePath, commitHash))

[lushnikov, 2016/07/22 21:06:04]

I would use this url as a cache keys

[chenwilliam, 2016/07/22 23:20:31]

Done.

+            .then(text => new Buffer(text, "base64").toString("binary"))
+            .then(data => {

[lushnikov, 2016/07/22 21:06:04]

style: we don't use multiline arrow functions, let's extract into a named
function

[chenwilliam, 2016/07/22 23:20:31]

Done.

+                protocolFileCache.cacheFile(filePath, data);
+                return data;
+            });
+    }
+}
+
+function getURL(protocolFile, commitHash)
+{
+    var path = protocolFileToPath[protocolFile];
+    return `https://chromium.googlesource.com/chromium/src/+/${commitHash}/third_party/WebKit/Source/${path}?format=TEXT`;
+}
+
+var Cache = function()

[lushnikov, 2016/07/22 21:06:04]

you don't need this Cache at all - just inline it altogether

I would also inline everything into server.js - you would have just 3 small top
level functions: requestHandler, fetch and proxy

[chenwilliam, 2016/07/22 23:20:31]

Done.

+{
+    this._data = new Map();
+    this._version = null;
+};
+
+Cache.prototype = {
+
+    setVersion: function(version)
+    {
+        this._version = version;
+    },
+
+    hasFile: function(file)
+    {
+        return this._data.has(this._getKey(file));
+    },
+
+    getFile: function(file)
+    {
+        return this._data.get(this._getKey(file));
+    },
+
+    cacheFile: function(file, data)
+    {
+        this._data.set(this._getKey(file), data);
+    },
+
+    _getKey: function(file)
+    {
+        return `${file}__version:${this._version}`;
+    }
+};
+
+var protocolFileCache = new Cache();
+
+module.exports = {
+    proxy
+};