// Copyright 2021 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "chrome/browser/preloading/prefetch/zero_suggest_prefetch/zero_suggest_prefetch_tab_helper.h"

#include "chrome/browser/ui/browser_window/public/browser_window_interface.h"
#include "chrome/browser/ui/browser_window/public/global_browser_collection.h"
#include "chrome/browser/ui/omnibox/omnibox_controller.h"
#include "chrome/browser/ui/search/omnibox_utils.h"
#include "chrome/browser/ui/tabs/tab_strip_model.h"
#include "components/omnibox/browser/autocomplete_controller.h"
#include "components/omnibox/browser/autocomplete_input.h"
#include "components/omnibox/browser/base_search_provider.h"
#include "components/omnibox/common/omnibox_features.h"
#include "content/public/browser/navigation_handle.h"
#include "content/public/browser/web_contents.h"

ZeroSuggestPrefetchTabHelper::ZeroSuggestPrefetchTabHelper(
    content::WebContents* web_contents)
    : content::WebContentsObserver(web_contents) {}

ZeroSuggestPrefetchTabHelper::~ZeroSuggestPrefetchTabHelper() = default;

void ZeroSuggestPrefetchTabHelper::DidFinishLoad(
    content::RenderFrameHost* render_frame_host,
    const GURL& validated_url) {
  if (!render_frame_host->IsInPrimaryMainFrame()) {
    return;
  }

  // Make sure to observe the TabStripModel, if not already, in order to get
  // notified when a New Tab Page is switched to.
  // Note that this is done here, i.e., after the New Tab Page is navigated to,
  // as opposed to the tab helper constructor which would have allowed us to get
  // notified when a new tab is opened in the foreground in the same
  // TabStripModelObserver callback. We are however not interested to start
  // prefetching that early since the AutocompleteController machinery gets
  // started and stopped multiple times since a new tab is opened and until the
  // New Tab Page is navigated to; invalidating prefetch requests prematurely.
  auto* browser = GlobalBrowserCollection::GetInstance()->FindBrowserWithTab(
      web_contents());
  if (browser && !TabStripModelObserver::IsObservingAny(this)) {
    browser->GetTabStripModel()->AddObserver(this);
  }

  StartPrefetch();
}

void ZeroSuggestPrefetchTabHelper::OnTabStripModelChanged(
    TabStripModel* tab_strip_model,
    const TabStripModelChange& change,
    const TabStripSelectionChange& selection) {
  if (!selection.active_tab_changed() ||
      web_contents() != selection.new_contents) {
    return;
  }

  // We get here when a New Tab Page is brought to foreground (aka switched to).
  StartPrefetch();
}

void ZeroSuggestPrefetchTabHelper::StartPrefetch() {
  auto* omnibox_controller = search::GetOmniboxController(web_contents());
  if (!omnibox_controller) {
    return;
  }

  omnibox_controller->StartZeroSuggestPrefetch();
}