// Copyright 2014 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 "components/dom_distiller/content/dom_distiller_viewer_source.h"

#include <sstream>
#include <string>
#include <vector>

#include "base/memory/ref_counted_memory.h"
#include "base/memory/scoped_ptr.h"
#include "base/message_loop/message_loop.h"
#include "base/strings/utf_string_conversions.h"
#include "components/dom_distiller/core/task_tracker.h"
#include "components/dom_distiller/core/url_constants.h"
#include "components/dom_distiller/core/viewer.h"
#include "content/public/browser/navigation_details.h"
#include "content/public/browser/navigation_entry.h"
#include "content/public/browser/render_frame_host.h"
#include "content/public/browser/render_view_host.h"
#include "content/public/browser/web_contents.h"
#include "content/public/browser/web_contents_observer.h"
#include "net/base/url_util.h"
#include "net/url_request/url_request.h"

namespace dom_distiller {

// Handles receiving data asynchronously for a specific entry, and passing
// it along to the data callback for the data source. Lifetime matches that of
// the current main frame's page in the Viewer instance.
class DomDistillerViewerSource::RequestViewerHandle
    : public ViewRequestDelegate,
      public content::WebContentsObserver {
 public:
  explicit RequestViewerHandle(
      content::WebContents* web_contents,
      const std::string& expected_scheme,
      const std::string& expected_request_path,
      const content::URLDataSource::GotDataCallback& callback);
  virtual ~RequestViewerHandle();

  // ViewRequestDelegate implementation.
  virtual void OnArticleReady(
      const DistilledArticleProto* article_proto) OVERRIDE;

  virtual void OnArticleUpdated(
      ArticleDistillationUpdate article_update) OVERRIDE;

  void TakeViewerHandle(scoped_ptr<ViewerHandle> viewer_handle);

  // WebContentsObserver:
  virtual void DidNavigateMainFrame(
      const content::LoadCommittedDetails& details,
      const content::FrameNavigateParams& params) OVERRIDE;
  virtual void RenderProcessGone(base::TerminationStatus status) OVERRIDE;
  virtual void WebContentsDestroyed() OVERRIDE;
  virtual void DidFinishLoad(
      int64 frame_id,
      const GURL& validated_url,
      bool is_main_frame,
      content::RenderViewHost* render_view_host) OVERRIDE;

 private:
  // Sends JavaScript to the attached Viewer, buffering data if the viewer isn't
  // ready.
  void SendJavaScript(const std::string& buffer);

  // Cancels the current view request. Once called, no updates will be
  // propagated to the view, and the request to DomDistillerService will be
  // cancelled.
  void Cancel();

  // The handle to the view request towards the DomDistillerService. It
  // needs to be kept around to ensure the distillation request finishes.
  scoped_ptr<ViewerHandle> viewer_handle_;

  // WebContents associated with the Viewer's render process.
  content::WebContents* web_contents_;

  // The scheme hosting the current view request;
  std::string expected_scheme_;

  // The query path for the current view request.
  std::string expected_request_path_;

  // Holds the callback to where the data retrieved is sent back.
  content::URLDataSource::GotDataCallback callback_;

  // Number of pages of the distilled article content that have been rendered by
  // the viewer.
  int page_count_;

  // Whether the page is sufficiently initialized to handle updates from the
  // distiller.
  bool waiting_for_page_ready_;

  // Temporary store of pending JavaScript if the page isn't ready to receive
  // data from distillation.
  std::string buffer_;
};

DomDistillerViewerSource::RequestViewerHandle::RequestViewerHandle(
    content::WebContents* web_contents,
    const std::string& expected_scheme,
    const std::string& expected_request_path,
    const content::URLDataSource::GotDataCallback& callback)
    : web_contents_(web_contents),
      expected_scheme_(expected_scheme),
      expected_request_path_(expected_request_path),
      callback_(callback),
      page_count_(0),
      waiting_for_page_ready_(true) {
  content::WebContentsObserver::Observe(web_contents_);
}

DomDistillerViewerSource::RequestViewerHandle::~RequestViewerHandle() {
  // Balanced with constructor although can be a no-op if frame navigated away.
  content::WebContentsObserver::Observe(NULL);
}

void DomDistillerViewerSource::RequestViewerHandle::SendJavaScript(
    const std::string& buffer) {
  if (waiting_for_page_ready_) {
    buffer_ += buffer;
  } else {
    if (web_contents_) {
      web_contents_->GetMainFrame()->ExecuteJavaScript(
          base::UTF8ToUTF16(buffer));
    }
  }
}

void DomDistillerViewerSource::RequestViewerHandle::DidNavigateMainFrame(
    const content::LoadCommittedDetails& details,
    const content::FrameNavigateParams& params) {
  const GURL& navigation = details.entry->GetURL();
  if (details.is_in_page || (
      navigation.SchemeIs(expected_scheme_.c_str()) &&
      expected_request_path_ == navigation.query())) {
    // In-page navigations, as well as the main view request can be ignored.
    return;
  }

  Cancel();

}

void DomDistillerViewerSource::RequestViewerHandle::RenderProcessGone(
    base::TerminationStatus status) {
  Cancel();
}

void DomDistillerViewerSource::RequestViewerHandle::WebContentsDestroyed() {
  Cancel();
}

void DomDistillerViewerSource::RequestViewerHandle::Cancel() {
  // Ensure we don't send any incremental updates to the Viewer.
  web_contents_ = NULL;

  // No need to listen for notifications.
  content::WebContentsObserver::Observe(NULL);

  // Schedule the Viewer for deletion. Ensures distillation is cancelled, and
  // any pending data stored in |buffer_| is released.
  base::MessageLoop::current()->DeleteSoon(FROM_HERE, this);
}

void DomDistillerViewerSource::RequestViewerHandle::DidFinishLoad(
     int64 frame_id,
     const GURL& validated_url,
     bool is_main_frame,
     content::RenderViewHost* render_view_host)  {
  if (!is_main_frame || web_contents_ == NULL) {
    return;
  }
  waiting_for_page_ready_ = false;
  if (buffer_.empty()) {
    return;
  }
  if (web_contents_) {
    web_contents_->GetMainFrame()->ExecuteJavaScript(
        base::UTF8ToUTF16(buffer_));
  }
  buffer_.clear();
}

void DomDistillerViewerSource::RequestViewerHandle::OnArticleReady(
    const DistilledArticleProto* article_proto) {
  if (page_count_ == 0) {
    // This is a single-page article.
    std::string unsafe_page_html = viewer::GetUnsafeArticleHtml(article_proto);
    callback_.Run(base::RefCountedString::TakeString(&unsafe_page_html));
  } else if (page_count_ == article_proto->pages_size()) {
    // We may still be showing the "Loading" indicator.
    SendJavaScript(viewer::GetToggleLoadingIndicatorJs(true));
  } else {
    // It's possible that we didn't get some incremental updates from the
    // distiller. Ensure all remaining pages are flushed to the viewer.
    for (;page_count_ < article_proto->pages_size(); page_count_++) {
      const DistilledPageProto& page = article_proto->pages(page_count_);
      SendJavaScript(
          viewer::GetUnsafeIncrementalDistilledPageJs(
              &page,
              page_count_ == article_proto->pages_size()));
    }
  }
  // No need to hold on to the ViewerHandle now that distillation is complete.
  viewer_handle_.reset();
}

void DomDistillerViewerSource::RequestViewerHandle::OnArticleUpdated(
    ArticleDistillationUpdate article_update) {
  for (;page_count_ < static_cast<int>(article_update.GetPagesSize());
       page_count_++) {
    const DistilledPageProto& page =
        article_update.GetDistilledPage(page_count_);
    if (page_count_ == 0) {
      // This is the first page, so send Viewer page scaffolding too.
      std::string unsafe_page_html = viewer::GetUnsafePartialArticleHtml(&page);
      callback_.Run(base::RefCountedString::TakeString(&unsafe_page_html));
    } else {
      SendJavaScript(
          viewer::GetUnsafeIncrementalDistilledPageJs(&page, false));
    }
  }
}

void DomDistillerViewerSource::RequestViewerHandle::TakeViewerHandle(
    scoped_ptr<ViewerHandle> viewer_handle) {
  viewer_handle_ = viewer_handle.Pass();
}

DomDistillerViewerSource::DomDistillerViewerSource(
    DomDistillerServiceInterface* dom_distiller_service,
    const std::string& scheme)
    : scheme_(scheme), dom_distiller_service_(dom_distiller_service) {
}

DomDistillerViewerSource::~DomDistillerViewerSource() {
}

std::string DomDistillerViewerSource::GetSource() const {
  return scheme_ + "://";
}

void DomDistillerViewerSource::StartDataRequest(
    const std::string& path,
    int render_process_id,
    int render_frame_id,
    const content::URLDataSource::GotDataCallback& callback) {
  content::RenderFrameHost* render_frame_host =
      content::RenderFrameHost::FromID(render_process_id, render_frame_id);
  DCHECK(render_frame_host);
  content::RenderViewHost* render_view_host =
      render_frame_host->GetRenderViewHost();
  DCHECK(render_view_host);
  CHECK_EQ(0, render_view_host->GetEnabledBindings());

  if (kViewerCssPath == path) {
    std::string css = viewer::GetCss();
    callback.Run(base::RefCountedString::TakeString(&css));
    return;
  }
  if (kViewerJsPath == path) {
    std::string js = viewer::GetJavaScript();
    callback.Run(base::RefCountedString::TakeString(&js));
    return;
  }
  content::WebContents* web_contents =
      content::WebContents::FromRenderFrameHost(
          content::RenderFrameHost::FromID(render_process_id,
                                           render_frame_id));
  DCHECK(web_contents);
  // An empty |path| is invalid, but guard against it. If not empty, assume
  // |path| starts with '?', which is stripped away.
  const std::string path_after_query_separator =
      path.size() > 0 ? path.substr(1) : "";
  RequestViewerHandle* request_viewer_handle = new RequestViewerHandle(
      web_contents, scheme_, path_after_query_separator, callback);
  scoped_ptr<ViewerHandle> viewer_handle = viewer::CreateViewRequest(
      dom_distiller_service_, path, request_viewer_handle);

  if (viewer_handle) {
    // The service returned a |ViewerHandle| and guarantees it will call
    // the |RequestViewerHandle|, so passing ownership to it, to ensure the
    // request is not cancelled. The |RequestViewerHandle| will delete itself
    // after receiving the callback.
    request_viewer_handle->TakeViewerHandle(viewer_handle.Pass());
  } else {
    // The service did not return a |ViewerHandle|, which means the
    // |RequestViewerHandle| will never be called, so clean up now.
    delete request_viewer_handle;

    std::string error_page_html = viewer::GetErrorPageHtml();
    callback.Run(base::RefCountedString::TakeString(&error_page_html));
  }
};

std::string DomDistillerViewerSource::GetMimeType(
    const std::string& path) const {
  if (kViewerCssPath == path) {
    return "text/css";
  }
  if (kViewerJsPath == path) {
    return "text/javascript";
  }
  return "text/html";
}

bool DomDistillerViewerSource::ShouldServiceRequest(
    const net::URLRequest* request) const {
  return request->url().SchemeIs(scheme_.c_str());
}

// TODO(nyquist): Start tracking requests using this method.
void DomDistillerViewerSource::WillServiceRequest(
    const net::URLRequest* request,
    std::string* path) const {
}

std::string DomDistillerViewerSource::GetContentSecurityPolicyObjectSrc()
    const {
  return "object-src 'none'; style-src 'self';";
}

}  // namespace dom_distiller