// 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/omnibox/keyword_provider.h"

#include <algorithm>
#include <vector>

#include "base/strings/string16.h"
#include "base/strings/string_util.h"
#include "base/strings/utf_string_conversions.h"
#include "components/metrics/proto/omnibox_input_type.pb.h"
#include "components/omnibox/autocomplete_match.h"
#include "components/omnibox/autocomplete_provider_listener.h"
#include "components/omnibox/keyword_extensions_delegate.h"
#include "components/search_engines/template_url.h"
#include "components/search_engines/template_url_service.h"
#include "grit/components_strings.h"
#include "net/base/escape.h"
#include "net/base/net_util.h"
#include "ui/base/l10n/l10n_util.h"

namespace {

// Helper functor for Start(), for sorting keyword matches by quality.
class CompareQuality {
 public:
  // A keyword is of higher quality when a greater fraction of it has been
  // typed, that is, when it is shorter.
  //
  // TODO(pkasting): Most recent and most frequent keywords are probably
  // better rankings than the fraction of the keyword typed.  We should
  // always put any exact matches first no matter what, since the code in
  // Start() assumes this (and it makes sense).
  bool operator()(const TemplateURL* t_url1, const TemplateURL* t_url2) const {
    return t_url1->keyword().length() < t_url2->keyword().length();
  }
};

// Helper for KeywordProvider::Start(), for ending keyword mode unless
// explicitly told otherwise.
class ScopedEndExtensionKeywordMode {
 public:
  explicit ScopedEndExtensionKeywordMode(KeywordExtensionsDelegate* delegate);
  ~ScopedEndExtensionKeywordMode();

  void StayInKeywordMode();

 private:
  KeywordExtensionsDelegate* delegate_;

  DISALLOW_COPY_AND_ASSIGN(ScopedEndExtensionKeywordMode);
};

ScopedEndExtensionKeywordMode::ScopedEndExtensionKeywordMode(
    KeywordExtensionsDelegate* delegate)
    : delegate_(delegate) {
}

ScopedEndExtensionKeywordMode::~ScopedEndExtensionKeywordMode() {
  if (delegate_)
    delegate_->MaybeEndExtensionKeywordMode();
}

void ScopedEndExtensionKeywordMode::StayInKeywordMode() {
  delegate_ = NULL;
}

}  // namespace

KeywordProvider::KeywordProvider(
    AutocompleteProviderListener* listener,
    TemplateURLService* model)
    : AutocompleteProvider(AutocompleteProvider::TYPE_KEYWORD),
      listener_(listener),
      model_(model) {
}

// static
base::string16 KeywordProvider::SplitKeywordFromInput(
    const base::string16& input,
    bool trim_leading_whitespace,
    base::string16* remaining_input) {
  // Find end of first token.  The AutocompleteController has trimmed leading
  // whitespace, so we need not skip over that.
  const size_t first_white(input.find_first_of(base::kWhitespaceUTF16));
  DCHECK_NE(0U, first_white);
  if (first_white == base::string16::npos)
    return input;  // Only one token provided.

  // Set |remaining_input| to everything after the first token.
  DCHECK(remaining_input != NULL);
  const size_t remaining_start = trim_leading_whitespace ?
      input.find_first_not_of(base::kWhitespaceUTF16, first_white) :
      first_white + 1;

  if (remaining_start < input.length())
    remaining_input->assign(input.begin() + remaining_start, input.end());

  // Return first token as keyword.
  return input.substr(0, first_white);
}

// static
base::string16 KeywordProvider::SplitReplacementStringFromInput(
    const base::string16& input,
    bool trim_leading_whitespace) {
  // The input may contain leading whitespace, strip it.
  base::string16 trimmed_input;
  base::TrimWhitespace(input, base::TRIM_LEADING, &trimmed_input);

  // And extract the replacement string.
  base::string16 remaining_input;
  SplitKeywordFromInput(trimmed_input, trim_leading_whitespace,
      &remaining_input);
  return remaining_input;
}

// static
const TemplateURL* KeywordProvider::GetSubstitutingTemplateURLForInput(
    TemplateURLService* model,
    AutocompleteInput* input) {
  if (!input->allow_exact_keyword_match())
    return NULL;

  base::string16 keyword, remaining_input;
  if (!ExtractKeywordFromInput(*input, &keyword, &remaining_input))
    return NULL;

  DCHECK(model);
  const TemplateURL* template_url = model->GetTemplateURLForKeyword(keyword);
  if (template_url &&
      template_url->SupportsReplacement(model->search_terms_data())) {
    // Adjust cursor position iff it was set before, otherwise leave it as is.
    size_t cursor_position = base::string16::npos;
    // The adjustment assumes that the keyword was stripped from the beginning
    // of the original input.
    if (input->cursor_position() != base::string16::npos &&
        !remaining_input.empty() &&
        EndsWith(input->text(), remaining_input, true)) {
      int offset = input->text().length() - input->cursor_position();
      // The cursor should never be past the last character or before the
      // first character.
      DCHECK_GE(offset, 0);
      DCHECK_LE(offset, static_cast<int>(input->text().length()));
      if (offset <= 0) {
        // Normalize the cursor to be exactly after the last character.
        cursor_position = remaining_input.length();
      } else {
        // If somehow the cursor was before the remaining text, set it to 0,
        // otherwise adjust it relative to the remaining text.
        cursor_position = offset > static_cast<int>(remaining_input.length()) ?
            0u : remaining_input.length() - offset;
      }
    }
    input->UpdateText(remaining_input, cursor_position, input->parts());
    return template_url;
  }

  return NULL;
}

base::string16 KeywordProvider::GetKeywordForText(
    const base::string16& text) const {
  const base::string16 keyword(TemplateURLService::CleanUserInputKeyword(text));

  if (keyword.empty())
    return keyword;

  TemplateURLService* url_service = GetTemplateURLService();
  if (!url_service)
    return base::string16();

  // Don't provide a keyword if it doesn't support replacement.
  const TemplateURL* const template_url =
      url_service->GetTemplateURLForKeyword(keyword);
  if (!template_url ||
      !template_url->SupportsReplacement(url_service->search_terms_data()))
    return base::string16();

  // Don't provide a keyword for inactive/disabled extension keywords.
  if ((template_url->GetType() == TemplateURL::OMNIBOX_API_EXTENSION) &&
      extensions_delegate_ &&
      !extensions_delegate_->IsEnabledExtension(template_url->GetExtensionId()))
    return base::string16();

  return keyword;
}

AutocompleteMatch KeywordProvider::CreateVerbatimMatch(
    const base::string16& text,
    const base::string16& keyword,
    const AutocompleteInput& input) {
  // A verbatim match is allowed to be the default match.
  return CreateAutocompleteMatch(
      GetTemplateURLService()->GetTemplateURLForKeyword(keyword), input,
      keyword.length(), SplitReplacementStringFromInput(text, true), true, 0);
}

void KeywordProvider::Start(const AutocompleteInput& input,
                            bool minimal_changes) {
  // This object ensures we end keyword mode if we exit the function without
  // toggling keyword mode to on.
  ScopedEndExtensionKeywordMode keyword_mode_toggle(extensions_delegate_.get());

  matches_.clear();

  if (!minimal_changes) {
    done_ = true;

    // Input has changed. Increment the input ID so that we can discard any
    // stale extension suggestions that may be incoming.
    if (extensions_delegate_)
      extensions_delegate_->IncrementInputId();
  }

  // Split user input into a keyword and some query input.
  //
  // We want to suggest keywords even when users have started typing URLs, on
  // the assumption that they might not realize they no longer need to go to a
  // site to be able to search it.  So we call CleanUserInputKeyword() to strip
  // any initial scheme and/or "www.".  NOTE: Any heuristics or UI used to
  // automatically/manually create keywords will need to be in sync with
  // whatever we do here!
  //
  // TODO(pkasting): http://crbug/347744 If someday we remember usage frequency
  // for keywords, we might suggest keywords that haven't even been partially
  // typed, if the user uses them enough and isn't obviously typing something
  // else.  In this case we'd consider all input here to be query input.
  base::string16 keyword, remaining_input;
  if (!ExtractKeywordFromInput(input, &keyword, &remaining_input))
    return;

  // Get the best matches for this keyword.
  //
  // NOTE: We could cache the previous keywords and reuse them here in the
  // |minimal_changes| case, but since we'd still have to recalculate their
  // relevances and we can just recreate the results synchronously anyway, we
  // don't bother.
  TemplateURLService::TemplateURLVector matches;
  GetTemplateURLService()->FindMatchingKeywords(
      keyword, !remaining_input.empty(), &matches);

  for (TemplateURLService::TemplateURLVector::iterator i(matches.begin());
       i != matches.end(); ) {
    const TemplateURL* template_url = *i;

    // Prune any extension keywords that are disallowed in incognito mode (if
    // we're incognito), or disabled.
    if (template_url->GetType() == TemplateURL::OMNIBOX_API_EXTENSION &&
        extensions_delegate_ &&
        !extensions_delegate_->IsEnabledExtension(
            template_url->GetExtensionId())) {
      i = matches.erase(i);
      continue;
    }

    // Prune any substituting keywords if there is no substitution.
    if (template_url->SupportsReplacement(
            GetTemplateURLService()->search_terms_data()) &&
        remaining_input.empty() &&
        !input.allow_exact_keyword_match()) {
      i = matches.erase(i);
      continue;
    }

    ++i;
  }
  if (matches.empty())
    return;
  std::sort(matches.begin(), matches.end(), CompareQuality());

  // Limit to one exact or three inexact matches, and mark them up for display
  // in the autocomplete popup.
  // Any exact match is going to be the highest quality match, and thus at the
  // front of our vector.
  if (matches.front()->keyword() == keyword) {
    const TemplateURL* template_url = matches.front();
    const bool is_extension_keyword =
        template_url->GetType() == TemplateURL::OMNIBOX_API_EXTENSION;

    // Only create an exact match if |remaining_input| is empty or if
    // this is an extension keyword.  If |remaining_input| is a
    // non-empty non-extension keyword (i.e., a regular keyword that
    // supports replacement and that has extra text following it),
    // then SearchProvider creates the exact (a.k.a. verbatim) match.
    if (!remaining_input.empty() && !is_extension_keyword)
      return;

    // TODO(pkasting): We should probably check that if the user explicitly
    // typed a scheme, that scheme matches the one in |template_url|.

    // When creating an exact match (either for the keyword itself, no
    // remaining query or an extension keyword, possibly with remaining
    // input), allow the match to be the default match.
    matches_.push_back(CreateAutocompleteMatch(
        template_url, input, keyword.length(), remaining_input, true, -1));

    if (is_extension_keyword && extensions_delegate_) {
      if (extensions_delegate_->Start(input, minimal_changes, template_url,
                                      remaining_input))
        keyword_mode_toggle.StayInKeywordMode();
    }
  } else {
    if (matches.size() > kMaxMatches)
      matches.erase(matches.begin() + kMaxMatches, matches.end());
    for (TemplateURLService::TemplateURLVector::const_iterator i(
         matches.begin()); i != matches.end(); ++i) {
      matches_.push_back(CreateAutocompleteMatch(
          *i, input, keyword.length(), remaining_input, false, -1));
    }
  }
}

void KeywordProvider::Stop(bool clear_cached_results) {
  done_ = true;
  if (extensions_delegate_)
    extensions_delegate_->MaybeEndExtensionKeywordMode();
}

KeywordProvider::~KeywordProvider() {}

// static
bool KeywordProvider::ExtractKeywordFromInput(const AutocompleteInput& input,
                                              base::string16* keyword,
                                              base::string16* remaining_input) {
  if ((input.type() == metrics::OmniboxInputType::INVALID) ||
      (input.type() == metrics::OmniboxInputType::FORCED_QUERY))
    return false;

  *keyword = TemplateURLService::CleanUserInputKeyword(
      SplitKeywordFromInput(input.text(), true, remaining_input));
  return !keyword->empty();
}

// static
int KeywordProvider::CalculateRelevance(metrics::OmniboxInputType::Type type,
                                        bool complete,
                                        bool supports_replacement,
                                        bool prefer_keyword,
                                        bool allow_exact_keyword_match) {
  // This function is responsible for scoring suggestions of keywords
  // themselves and the suggestion of the verbatim query on an
  // extension keyword.  SearchProvider::CalculateRelevanceForKeywordVerbatim()
  // scores verbatim query suggestions for non-extension keywords.
  // These two functions are currently in sync, but there's no reason
  // we couldn't decide in the future to score verbatim matches
  // differently for extension and non-extension keywords.  If you
  // make such a change, however, you should update this comment to
  // describe it, so it's clear why the functions diverge.
  if (!complete)
    return (type == metrics::OmniboxInputType::URL) ? 700 : 450;
  if (!supports_replacement || (allow_exact_keyword_match && prefer_keyword))
    return 1500;
  return (allow_exact_keyword_match &&
          (type == metrics::OmniboxInputType::QUERY)) ?
      1450 : 1100;
}

AutocompleteMatch KeywordProvider::CreateAutocompleteMatch(
    const TemplateURL* template_url,
    const AutocompleteInput& input,
    size_t prefix_length,
    const base::string16& remaining_input,
    bool allowed_to_be_default_match,
    int relevance) {
  DCHECK(template_url);
  const bool supports_replacement =
      template_url->url_ref().SupportsReplacement(
          GetTemplateURLService()->search_terms_data());

  // Create an edit entry of "[keyword] [remaining input]".  This is helpful
  // even when [remaining input] is empty, as the user can select the popup
  // choice and immediately begin typing in query input.
  const base::string16& keyword = template_url->keyword();
  const bool keyword_complete = (prefix_length == keyword.length());
  if (relevance < 0) {
    relevance =
        CalculateRelevance(input.type(), keyword_complete,
                           // When the user wants keyword matches to take
                           // preference, score them highly regardless of
                           // whether the input provides query text.
                           supports_replacement, input.prefer_keyword(),
                           input.allow_exact_keyword_match());
  }
  AutocompleteMatch match(this, relevance, false,
      supports_replacement ? AutocompleteMatchType::SEARCH_OTHER_ENGINE :
                             AutocompleteMatchType::HISTORY_KEYWORD);
  match.allowed_to_be_default_match = allowed_to_be_default_match;
  match.fill_into_edit = keyword;
  if (!remaining_input.empty() || supports_replacement)
    match.fill_into_edit.push_back(L' ');
  match.fill_into_edit.append(remaining_input);
  // If we wanted to set |result.inline_autocompletion| correctly, we'd need
  // CleanUserInputKeyword() to return the amount of adjustment it's made to
  // the user's input.  Because right now inexact keyword matches can't score
  // more highly than a "what you typed" match from one of the other providers,
  // we just don't bother to do this, and leave inline autocompletion off.

  // Create destination URL and popup entry content by substituting user input
  // into keyword templates.
  FillInURLAndContents(remaining_input, template_url, &match);

  match.keyword = keyword;
  match.transition = ui::PAGE_TRANSITION_KEYWORD;

  return match;
}

void KeywordProvider::FillInURLAndContents(
    const base::string16& remaining_input,
    const TemplateURL* element,
    AutocompleteMatch* match) const {
  DCHECK(!element->short_name().empty());
  const TemplateURLRef& element_ref = element->url_ref();
  DCHECK(element_ref.IsValid(GetTemplateURLService()->search_terms_data()));
  int message_id = (element->GetType() == TemplateURL::OMNIBOX_API_EXTENSION) ?
      IDS_EXTENSION_KEYWORD_COMMAND : IDS_KEYWORD_SEARCH;
  if (remaining_input.empty()) {
    // Allow extension keyword providers to accept empty string input. This is
    // useful to allow extensions to do something in the case where no input is
    // entered.
    if (element_ref.SupportsReplacement(
            GetTemplateURLService()->search_terms_data()) &&
        (element->GetType() != TemplateURL::OMNIBOX_API_EXTENSION)) {
      // No query input; return a generic, no-destination placeholder.
      match->contents.assign(
          l10n_util::GetStringFUTF16(message_id,
              element->AdjustedShortNameForLocaleDirection(),
              l10n_util::GetStringUTF16(IDS_EMPTY_KEYWORD_VALUE)));
      match->contents_class.push_back(
          ACMatchClassification(0, ACMatchClassification::DIM));
    } else {
      // Keyword that has no replacement text (aka a shorthand for a URL).
      match->destination_url = GURL(element->url());
      match->contents.assign(element->short_name());
      AutocompleteMatch::ClassifyLocationInString(0, match->contents.length(),
          match->contents.length(), ACMatchClassification::NONE,
          &match->contents_class);
    }
  } else {
    // Create destination URL by escaping user input and substituting into
    // keyword template URL.  The escaping here handles whitespace in user
    // input, but we rely on later canonicalization functions to do more
    // fixup to make the URL valid if necessary.
    DCHECK(element_ref.SupportsReplacement(
        GetTemplateURLService()->search_terms_data()));
    TemplateURLRef::SearchTermsArgs search_terms_args(remaining_input);
    search_terms_args.append_extra_query_params =
        element == GetTemplateURLService()->GetDefaultSearchProvider();
    match->destination_url = GURL(element_ref.ReplaceSearchTerms(
        search_terms_args, GetTemplateURLService()->search_terms_data()));
    std::vector<size_t> content_param_offsets;
    match->contents.assign(l10n_util::GetStringFUTF16(message_id,
                                                      element->short_name(),
                                                      remaining_input,
                                                      &content_param_offsets));
    DCHECK_EQ(2U, content_param_offsets.size());
    AutocompleteMatch::ClassifyLocationInString(content_param_offsets[1],
        remaining_input.length(), match->contents.length(),
        ACMatchClassification::NONE, &match->contents_class);
  }
}

TemplateURLService* KeywordProvider::GetTemplateURLService() const {
  // Make sure the model is loaded. This is cheap and quickly bails out if
  // the model is already loaded.
  model_->Load();
  return model_;
}