[Payment Request] Add classes to fetch information on native apps from iTunes

These two new files are mostly a copy of json_response_fetcher.cc and
json_response_fetcher.h from chrome/browser/ui/app_list/search/common/ 
(https://cs.chromium.org/chromium/src/chrome/browser/ui/app_list/search/common/?q=chrome/browser/ui/app_list/search/common&sq=package:chromium&dr).
The main differences are that 1) The namespace is changed from app_list to
payment_request_util 2) Instead of using SafeJsonParser, a basic parser is used
instead since iOS does not currently support SafeJsonParser.

Bug: 602666
Change-Id: Ibf619f1c53a32eb53654e00959fbcba61720c8a5
Reviewed-on: https://chromium-review.googlesource.com/562581
Commit-Queue: Randall Raymond <rayraymond@google.com>
Reviewed-by: Jean-François Geyelin <jif@chromium.org>
Reviewed-by: mahmadi <mahmadi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#485122}

ios/chrome/browser/payments/BUILD.gn

@@ -9,6 +9,8 @@ source_set("payments") {
   sources = [
     "ios_can_make_payment_query_factory.cc",
     "ios_can_make_payment_query_factory.h",
+    "itunes_json_request.cc",
+    "itunes_json_request.h",
     "payment_request.h",
     "payment_request.mm",
     "payment_request_util.h",
@@ -27,7 +29,9 @@ source_set("payments") {
     "//ios/chrome/browser/browser_state",
     "//ios/chrome/browser/signin",
     "//ios/web",
+    "//net",
     "//ui/base",
+    "//url",
   ]
   libs = [ "UIKit.framework" ]
 }

ios/chrome/browser/payments/itunes_json_request.cc

+// Copyright 2017 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.
+
+#include "ios/chrome/browser/payments/itunes_json_request.h"
+
+#include <utility>
+
+#include "base/bind.h"
+#include "base/json/json_reader.h"
+#include "base/memory/ptr_util.h"
+#include "base/values.h"
+#include "net/base/load_flags.h"
+#include "net/http/http_status_code.h"
+#include "net/url_request/url_fetcher.h"
+#include "net/url_request/url_request_status.h"
+#include "url/gurl.h"
+
+namespace payment_request_util {
+
+const char kBadResponse[] = "Bad iTunes Store search response";
+const char kITunesStoreLookupPrefix[] = "https://itunes.apple.com/lookup?";
+const char kITunesStoreSearchPrefix[] = "https://itunes.apple.com/search?";
+
+ITunesJsonRequest::ITunesJsonRequest(
+    const Callback& callback,
+    net::URLRequestContextGetter* context_getter)
+    : callback_(callback),
+      context_getter_(context_getter),
+      weak_factory_(this) {
+  DCHECK(!callback_.is_null());
+}
+
+ITunesJsonRequest::~ITunesJsonRequest() {}
+
+void ITunesJsonRequest::Start(ITunesStoreRequestType request_type,
+                              const std::string& request_query) {
+  Stop();
+
+  std::string complete_query;
+  switch (request_type) {
+    case LOOKUP:
+      complete_query = kITunesStoreLookupPrefix + request_query;
+    case SEARCH:
+      complete_query = kITunesStoreSearchPrefix + request_query;
+  }
+
+  fetcher_ =
+      net::URLFetcher::Create(GURL(complete_query), net::URLFetcher::GET, this);
+  fetcher_->SetRequestContext(context_getter_);
+  fetcher_->SetLoadFlags(net::LOAD_MAYBE_USER_GESTURE |
+                         net::LOAD_DO_NOT_SAVE_COOKIES |
+                         net::LOAD_VERIFY_EV_CERT);
+  fetcher_->Start();
+}
+
+void ITunesJsonRequest::Stop() {
+  fetcher_.reset();
+  weak_factory_.InvalidateWeakPtrs();
+}
+
+void ITunesJsonRequest::ParseJson(
+    const std::string& json,
+    const payment_request_util::ITunesJsonRequest::SuccessCallback&
+        success_callback,
+    const payment_request_util::ITunesJsonRequest::ErrorCallback&
+        error_callback) {
+  DCHECK(!success_callback.is_null());
+  DCHECK(!error_callback.is_null());
+
+  base::JSONReader json_reader;
+  std::unique_ptr<base::Value> value = json_reader.ReadToValue(json);
+  if (value) {
+    success_callback.Run(std::move(value));
+  } else {
+    error_callback.Run(json_reader.GetErrorMessage());
+  }
+}
+
+void ITunesJsonRequest::OnJsonParseSuccess(
+    std::unique_ptr<base::Value> parsed_json) {
+  if (!parsed_json->IsType(base::Value::Type::DICTIONARY)) {
+    OnJsonParseError(kBadResponse);
+    return;
+  }
+
+  callback_.Run(base::WrapUnique(
+      static_cast<base::DictionaryValue*>(parsed_json.release())));
+}
+
+void ITunesJsonRequest::OnJsonParseError(const std::string& error) {
+  callback_.Run(std::unique_ptr<base::DictionaryValue>());
+}
+
+void ITunesJsonRequest::OnURLFetchComplete(const net::URLFetcher* source) {
+  CHECK_EQ(fetcher_.get(), source);
+
+  std::unique_ptr<net::URLFetcher> fetcher(std::move(fetcher_));
+
+  if (!fetcher->GetStatus().is_success() ||
+      fetcher->GetResponseCode() != net::HTTP_OK) {
+    OnJsonParseError(kBadResponse);
+    return;
+  }
+
+  std::string json_data;
+  fetcher->GetResponseAsString(&json_data);
+
+  // The parser will call us back via one of the callbacks.
+  ParseJson(json_data,
+            base::Bind(&ITunesJsonRequest::OnJsonParseSuccess,
+                       weak_factory_.GetWeakPtr()),
+            base::Bind(&ITunesJsonRequest::OnJsonParseError,
+                       weak_factory_.GetWeakPtr()));
+}
+
+}  // namespace payment_request_util

ios/chrome/browser/payments/itunes_json_request.h

+// Copyright 2017 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.
+
+#ifndef IOS_CHROME_BROWSER_PAYMENTS_ITUNES_JSON_REQUEST_H_
+#define IOS_CHROME_BROWSER_PAYMENTS_ITUNES_JSON_REQUEST_H_
+
+#include <memory>
+#include <string>
+
+#include "base/callback.h"
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "net/url_request/url_fetcher_delegate.h"
+
+namespace base {
+class DictionaryValue;
+class Value;
+}  // namespace base
+
+namespace net {
+class URLFetcher;
+class URLRequestContextGetter;
+}  // namespace net
+
+namespace payment_request_util {
+
+// A class that fetches a JSON formatted response from the iTunes Store using
+// the iTunes Search API and a basic JSON parser to parse the response as a
+// DictionaryValue.
+class ITunesJsonRequest : public net::URLFetcherDelegate {
+ public:
+  // Callback to pass back the parsed json dictionary returned from iTunes.
+  // Invoked with NULL if there is an error.
+  typedef base::Callback<void(std::unique_ptr<base::DictionaryValue>)> Callback;
+
+  ITunesJsonRequest(const Callback& callback,
+                    net::URLRequestContextGetter* context_getter);
+  ~ITunesJsonRequest() override;
+
+  // Used to express the type of request. Please view the following for info:
+  // https://affiliate.itunes.apple.com/resources/documentation/itunes-store-web-service-search-api/
+  enum ITunesStoreRequestType {
+    LOOKUP,
+    SEARCH,
+  };
+
+  // Starts to fetch results for the given |request_type| and |request_query|.
+  void Start(ITunesStoreRequestType request_type,
+             const std::string& request_query);
+  void Stop();
+
+ private:
+  // Callbacks for JSON parsing.
+  typedef base::Callback<void(std::unique_ptr<base::Value> result)>
+      SuccessCallback;
+  typedef base::Callback<void(const std::string& error)> ErrorCallback;
+
+  void ParseJson(const std::string& raw_json_string,
+                 const SuccessCallback& success_callback,
+                 const ErrorCallback& error_callback);
+
+  void OnJsonParseSuccess(std::unique_ptr<base::Value> parsed_json);
+  void OnJsonParseError(const std::string& error);
+
+  // net::URLFetcherDelegate overrides:
+  void OnURLFetchComplete(const net::URLFetcher* source) override;
+
+  Callback callback_;
+  net::URLRequestContextGetter* context_getter_;
+
+  std::unique_ptr<net::URLFetcher> fetcher_;
+  base::WeakPtrFactory<ITunesJsonRequest> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(ITunesJsonRequest);
+};
+
+}  // namespace payment_request_util
+
+#endif  // IOS_CHROME_BROWSER_PAYMENTS_ITUNES_JSON_REQUEST_H_