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// Copyright 2019 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 "third_party/blink/renderer/core/page/scrolling/text_fragment_finder.h"
#include <memory>
#include "third_party/blink/public/platform/web_string.h"
#include "third_party/blink/renderer/core/dom/document.h"
#include "third_party/blink/renderer/core/dom/range.h"
#include "third_party/blink/renderer/core/editing/ephemeral_range.h"
#include "third_party/blink/renderer/core/editing/finder/find_buffer.h"
#include "third_party/blink/renderer/core/editing/finder/find_options.h"
#include "third_party/blink/renderer/core/editing/iterators/character_iterator.h"
#include "third_party/blink/renderer/core/editing/position.h"
#include "third_party/blink/renderer/core/page/scrolling/text_fragment_selector.h"
#include "third_party/blink/renderer/platform/text/text_boundaries.h"
namespace blink {
namespace {
const char kNoContext[] = "";
// Determines whether the start and end positions of |range| are on word
// boundaries.
// TODO(crbug/924965): Determine how this should check node boundaries. This
// treats node boundaries as word boundaries, for example "o" is a whole word
// match in "f<i>o</i>o".
bool IsWholeWordMatch(EphemeralRangeInFlatTree range) {
wtf_size_t start_position = range.StartPosition().OffsetInContainerNode();
if (start_position != 0) {
String start_text = range.StartPosition().AnchorNode()->textContent();
start_text.Ensure16Bit();
wtf_size_t word_start = FindWordStartBoundary(
start_text.Characters16(), start_text.length(), start_position);
if (word_start != start_position)
return false;
}
wtf_size_t end_position = range.EndPosition().OffsetInContainerNode();
String end_text = range.EndPosition().AnchorNode()->textContent();
if (end_position != end_text.length()) {
end_text.Ensure16Bit();
// We expect end_position to be a word boundary, and FindWordEndBoundary
// finds the next word boundary, so start from end_position - 1.
wtf_size_t word_end = FindWordEndBoundary(
end_text.Characters16(), end_text.length(), end_position - 1);
if (word_end != end_position)
return false;
}
return true;
}
EphemeralRangeInFlatTree FindMatchInRange(String search_text,
PositionInFlatTree search_start,
PositionInFlatTree search_end) {
while (search_start < search_end) {
const EphemeralRangeInFlatTree search_range(search_start, search_end);
EphemeralRangeInFlatTree potential_match = FindBuffer::FindMatchInRange(
search_range, search_text, kCaseInsensitive);
if (potential_match.IsNull() || IsWholeWordMatch(potential_match))
return potential_match;
search_start = potential_match.EndPosition();
}
return EphemeralRangeInFlatTree();
}
PositionInFlatTree NextTextPosition(PositionInFlatTree position,
PositionInFlatTree end_position) {
const TextIteratorBehavior options =
TextIteratorBehavior::Builder().SetEmitsSpaceForNbsp(true).Build();
CharacterIteratorInFlatTree char_it(position, end_position, options);
for (; char_it.length(); char_it.Advance(1)) {
if (!IsSpaceOrNewline(char_it.CharacterAt(0)))
return char_it.StartPosition();
}
return end_position;
}
// Find and return the range of |search_text| if the first text in the search
// range is |search_text|, skipping over whitespace and element boundaries.
EphemeralRangeInFlatTree FindImmediateMatch(String search_text,
PositionInFlatTree search_start,
PositionInFlatTree search_end) {
if (search_text.IsEmpty())
return EphemeralRangeInFlatTree();
search_start = NextTextPosition(search_start, search_end);
if (search_start == search_end)
return EphemeralRangeInFlatTree();
FindBuffer buffer(EphemeralRangeInFlatTree(search_start, search_end));
// TODO(nburris): FindBuffer will search the rest of the document for a match,
// but we only need to check for an immediate match, so we should stop
// searching if there's no immediate match.
FindBuffer::Results match_results =
buffer.FindMatches(search_text, kCaseInsensitive);
if (!match_results.IsEmpty() && match_results.front().start == 0u) {
FindBuffer::BufferMatchResult buffer_match = match_results.front();
EphemeralRangeInFlatTree match = buffer.RangeFromBufferIndex(
buffer_match.start, buffer_match.start + buffer_match.length);
if (IsWholeWordMatch(match))
return match;
}
return EphemeralRangeInFlatTree();
}
EphemeralRangeInFlatTree FindMatchInRangeWithContext(
const String& search_text,
const String& prefix,
const String& suffix,
PositionInFlatTree search_start,
PositionInFlatTree search_end) {
while (search_start != search_end) {
EphemeralRangeInFlatTree potential_match;
if (!prefix.IsEmpty()) {
EphemeralRangeInFlatTree prefix_match =
FindMatchInRange(prefix, search_start, search_end);
// No prefix_match in remaining range
if (prefix_match.IsNull())
return EphemeralRangeInFlatTree();
search_start = prefix_match.EndPosition();
potential_match =
FindImmediateMatch(search_text, search_start, search_end);
// No search_text match after current prefix_match
if (potential_match.IsNull())
continue;
} else {
potential_match = FindMatchInRange(search_text, search_start, search_end);
// No search_text match in remaining range
if (potential_match.IsNull())
return EphemeralRangeInFlatTree();
search_start = potential_match.EndPosition();
}
PositionInFlatTree suffix_start = potential_match.EndPosition();
DCHECK(potential_match.IsNotNull());
if (!suffix.IsEmpty()) {
EphemeralRangeInFlatTree suffix_match =
FindImmediateMatch(suffix, suffix_start, search_end);
// No suffix match after current potential_match
if (suffix_match.IsNull())
continue;
}
// If we reach here without a return or continue, we have a full match.
return potential_match;
}
return EphemeralRangeInFlatTree();
}
} // namespace
TextFragmentFinder::TextFragmentFinder(Client& client,
const TextFragmentSelector& selector)
: client_(client), selector_(selector) {
DCHECK(!selector_.Start().IsEmpty());
}
void TextFragmentFinder::FindMatch(Document& document) {
PositionInFlatTree search_start =
PositionInFlatTree::FirstPositionInNode(document);
auto forced_lock_scope = document.GetScopedForceActivatableLocks();
document.UpdateStyleAndLayout(DocumentUpdateReason::kFindInPage);
EphemeralRangeInFlatTree match =
FindMatchFromPosition(document, search_start);
if (match.IsNotNull()) {
client_.DidFindMatch(match);
// Continue searching to see if we have an ambiguous selector.
// TODO(crbug.com/919204): This is temporary and only for measuring
// ambiguous matching during prototyping.
EphemeralRangeInFlatTree ambiguous_match =
FindMatchFromPosition(document, match.EndPosition());
if (ambiguous_match.IsNotNull())
client_.DidFindAmbiguousMatch();
}
}
EphemeralRangeInFlatTree TextFragmentFinder::FindMatchFromPosition(
Document& document,
PositionInFlatTree search_start) {
PositionInFlatTree search_end;
if (document.documentElement() && document.documentElement()->lastChild()) {
search_end =
PositionInFlatTree::AfterNode(*document.documentElement()->lastChild());
} else {
search_end = PositionInFlatTree::LastPositionInNode(document);
}
// TODO(crbug.com/930156): Make FindMatch work asynchronously.
EphemeralRangeInFlatTree match;
if (selector_.Type() == TextFragmentSelector::kExact) {
match = FindMatchInRangeWithContext(selector_.Start(), selector_.Prefix(),
selector_.Suffix(), search_start,
search_end);
} else {
EphemeralRangeInFlatTree start_match =
FindMatchInRangeWithContext(selector_.Start(), selector_.Prefix(),
kNoContext, search_start, search_end);
if (start_match.IsNull())
return start_match;
// TODO(crbug.com/924964): Determine what we should do if the start text and
// end text are the same (and there are no context terms). This
// implementation continues searching for the next instance of the text,
// from the end of the first instance.
search_start = start_match.EndPosition();
EphemeralRangeInFlatTree end_match = FindMatchInRangeWithContext(
selector_.End(), kNoContext, selector_.Suffix(), search_start,
search_end);
if (end_match.IsNotNull()) {
match = EphemeralRangeInFlatTree(start_match.StartPosition(),
end_match.EndPosition());
}
}
return match;
}
} // namespace blink
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