1 /*
2 * Copyright (C) 2018 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include "annotator/strip-unpaired-brackets.h"
18
19 #include <iterator>
20
21 #include "utils/base/logging.h"
22 #include "utils/utf8/unicodetext.h"
23
24 namespace libtextclassifier3 {
25 namespace {
26
27 // Returns true if given codepoint is contained in the given span in context.
IsCodepointInSpan(const char32 codepoint,const UnicodeText & context_unicode,const CodepointSpan span)28 bool IsCodepointInSpan(const char32 codepoint,
29 const UnicodeText& context_unicode,
30 const CodepointSpan span) {
31 auto begin_it = context_unicode.begin();
32 std::advance(begin_it, span.first);
33 auto end_it = context_unicode.begin();
34 std::advance(end_it, span.second);
35
36 return std::find(begin_it, end_it, codepoint) != end_it;
37 }
38
39 // Returns the first codepoint of the span.
FirstSpanCodepoint(const UnicodeText & context_unicode,const CodepointSpan span)40 char32 FirstSpanCodepoint(const UnicodeText& context_unicode,
41 const CodepointSpan span) {
42 auto it = context_unicode.begin();
43 std::advance(it, span.first);
44 return *it;
45 }
46
47 // Returns the last codepoint of the span.
LastSpanCodepoint(const UnicodeText & context_unicode,const CodepointSpan span)48 char32 LastSpanCodepoint(const UnicodeText& context_unicode,
49 const CodepointSpan span) {
50 auto it = context_unicode.begin();
51 std::advance(it, span.second - 1);
52 return *it;
53 }
54
55 } // namespace
56
StripUnpairedBrackets(const std::string & context,CodepointSpan span,const UniLib & unilib)57 CodepointSpan StripUnpairedBrackets(const std::string& context,
58 CodepointSpan span, const UniLib& unilib) {
59 const UnicodeText context_unicode =
60 UTF8ToUnicodeText(context, /*do_copy=*/false);
61 return StripUnpairedBrackets(context_unicode, span, unilib);
62 }
63
64 // If the first or the last codepoint of the given span is a bracket, the
65 // bracket is stripped if the span does not contain its corresponding paired
66 // version.
StripUnpairedBrackets(const UnicodeText & context_unicode,CodepointSpan span,const UniLib & unilib)67 CodepointSpan StripUnpairedBrackets(const UnicodeText& context_unicode,
68 CodepointSpan span, const UniLib& unilib) {
69 if (context_unicode.empty() || !ValidNonEmptySpan(span)) {
70 return span;
71 }
72
73 const char32 begin_char = FirstSpanCodepoint(context_unicode, span);
74 const char32 paired_begin_char = unilib.GetPairedBracket(begin_char);
75 if (paired_begin_char != begin_char) {
76 if (!unilib.IsOpeningBracket(begin_char) ||
77 !IsCodepointInSpan(paired_begin_char, context_unicode, span)) {
78 ++span.first;
79 }
80 }
81
82 if (span.first == span.second) {
83 return span;
84 }
85
86 const char32 end_char = LastSpanCodepoint(context_unicode, span);
87 const char32 paired_end_char = unilib.GetPairedBracket(end_char);
88 if (paired_end_char != end_char) {
89 if (!unilib.IsClosingBracket(end_char) ||
90 !IsCodepointInSpan(paired_end_char, context_unicode, span)) {
91 --span.second;
92 }
93 }
94
95 // Should not happen, but let's make sure.
96 if (span.first > span.second) {
97 TC3_LOG(WARNING) << "Inverse indices result: " << span.first << ", "
98 << span.second;
99 span.second = span.first;
100 }
101
102 return span;
103 }
104
105 } // namespace libtextclassifier3
106