// Copyright 2015 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/web_resource/web_resource_util.h"

#include "base/bind.h"
#include "base/json/json_reader.h"
#include "base/location.h"
#include "base/task_runner.h"
#include "base/task_runner_util.h"
#include "base/values.h"
#include "ios/web/public/web_thread.h"

namespace web_resource {

namespace {

const char kInvalidDataTypeError[] =
    "Data from web resource server is missing or not valid JSON.";

const char kUnexpectedJSONFormatError[] =
    "Data from web resource server does not have expected format.";

// Runs |error_callback| with |error| on |task_runner|.
void PostErrorTask(base::TaskRunner* task_runner,
                   const WebResourceService::ErrorCallback& error_callback,
                   const char error[]) {
  task_runner->PostTask(FROM_HERE,
                        base::Bind(error_callback, std::string(error)));
}

// Parses |data| as a JSON string and calls back on |task_runner|.
// Must not be called on the UI thread, for performance reasons.
void ParseJSONOnBackgroundThread(
    base::TaskRunner* task_runner,
    const std::string& data,
    const WebResourceService::SuccessCallback& success_callback,
    const WebResourceService::ErrorCallback& error_callback) {
  if (data.empty()) {
    PostErrorTask(task_runner, error_callback, kInvalidDataTypeError);
    return;
  }

  scoped_ptr<base::Value> value(base::JSONReader::Read(data));
  if (!value.get()) {
    // Page information not properly read, or corrupted.
    PostErrorTask(task_runner, error_callback, kInvalidDataTypeError);
    return;
  }

  if (!value->IsType(base::Value::TYPE_DICTIONARY)) {
    PostErrorTask(task_runner, error_callback, kUnexpectedJSONFormatError);
    return;
  }

  task_runner->PostTask(FROM_HERE,
                        base::Bind(success_callback, base::Passed(&value)));
}

// Starts the parsing of |data| as a JSON string asynchronously on a background
// thread. Can be called from the UI thread.
void StartParseJSONAsync(
    const std::string& data,
    const WebResourceService::SuccessCallback& success_callback,
    const WebResourceService::ErrorCallback& error_callback) {
  web::WebThread::PostBlockingPoolTask(
      FROM_HERE,
      base::Bind(&ParseJSONOnBackgroundThread,
                 base::RetainedRef(base::ThreadTaskRunnerHandle::Get()), data,
                 success_callback, error_callback));
}

}  // namespace

WebResourceService::ParseJSONCallback GetIOSChromeParseJSONCallback() {
  return base::Bind(&StartParseJSONAsync);
}

}  // namespace web_resource