Remove PrevWordsInfo.getBigramsIteratorForPrediction().

This changes the behavior of predictions for some rare cases.
For example, let's consider the case of the prev word is
"ABC", "ABC" and "abc" is in the dict, "ABC" doesn't have
any bigrams, and "abc" has bigrams.
Without this change, "abc"'s bigrams are used for
prediction. But, with this change, "abc"'s bigrams are not
used for prediction. This strategy is the same as the the
current way of bigram probability computation during
traversal (for suggestion).

Bug: 14425059
Change-Id: I857ff39aa70aea265efa651451a63b759bb47d48

3 files changed, 16 insertions, 51 deletions

diff --git a/native/jni/src/suggest/core/dictionary/dictionary.cpp b/native/jni/src/suggest/core/dictionary/dictionary.cpp
index 92f5c1713..d62573970 100644
--- a/native/jni/src/suggest/core/dictionary/dictionary.cpp
+++ b/native/jni/src/suggest/core/dictionary/dictionary.cpp
@@ -92,7 +92,11 @@ void Dictionary::getPredictions(const PrevWordsInfo *const prevWordsInfo,
     TimeKeeper::setCurrentTime();
     NgramListenerForPrediction listener(prevWordsInfo, outSuggestionResults,
             mDictionaryStructureWithBufferPolicy.get());
-    mDictionaryStructureWithBufferPolicy->iterateNgramEntries(prevWordsInfo, &listener);
+    int prevWordsPtNodePos[MAX_PREV_WORD_COUNT_FOR_N_GRAM];
+    prevWordsInfo->getPrevWordsTerminalPtNodePos(
+            mDictionaryStructureWithBufferPolicy.get(), prevWordsPtNodePos,
+            true /* tryLowerCaseSearch */);
+    mDictionaryStructureWithBufferPolicy->iterateNgramEntries(prevWordsPtNodePos, &listener);
 }
 
 int Dictionary::getProbability(const int *word, int length) const {
@@ -111,7 +115,15 @@ int Dictionary::getNgramProbability(const PrevWordsInfo *const prevWordsInfo, co
     int nextWordPos = mDictionaryStructureWithBufferPolicy->getTerminalPtNodePositionOfWord(word,
             length, false /* forceLowerCaseSearch */);
     if (NOT_A_DICT_POS == nextWordPos) return NOT_A_PROBABILITY;
-    return getDictionaryStructurePolicy()->getProbabilityOfPtNode(prevWordsInfo, nextWordPos);
+    if (!prevWordsInfo) {
+        return getDictionaryStructurePolicy()->getProbabilityOfPtNode(
+                nullptr /* prevWordsPtNodePos */, nextWordPos);
+    }
+    int prevWordsPtNodePos[MAX_PREV_WORD_COUNT_FOR_N_GRAM];
+    prevWordsInfo->getPrevWordsTerminalPtNodePos(
+            mDictionaryStructureWithBufferPolicy.get(), prevWordsPtNodePos,
+            true /* tryLowerCaseSearch */);
+    return getDictionaryStructurePolicy()->getProbabilityOfPtNode(prevWordsPtNodePos, nextWordPos);
 }
 
 bool Dictionary::addUnigramEntry(const int *const word, const int length,
diff --git a/native/jni/src/suggest/core/policy/dictionary_structure_with_buffer_policy.h b/native/jni/src/suggest/core/policy/dictionary_structure_with_buffer_policy.h
index 81e38f78e..7e3bf3ff6 100644
--- a/native/jni/src/suggest/core/policy/dictionary_structure_with_buffer_policy.h
+++ b/native/jni/src/suggest/core/policy/dictionary_structure_with_buffer_policy.h
@@ -59,10 +59,10 @@ class DictionaryStructureWithBufferPolicy {
     virtual int getProbability(const int unigramProbability,
             const int bigramProbability) const = 0;
 
-    virtual int getProbabilityOfPtNode(const PrevWordsInfo *const prevWordsInfo,
+    virtual int getProbabilityOfPtNode(const int *const prevWordsPtNodePos,
             const int nodePos) const = 0;
 
-    virtual void iterateNgramEntries(const PrevWordsInfo *const prevWordsInfo,
+    virtual void iterateNgramEntries(const int *const prevWordsPtNodePos,
             NgramListener *const listener) const = 0;
 
     virtual int getShortcutPositionOfPtNode(const int nodePos) const = 0;
diff --git a/native/jni/src/suggest/core/session/prev_words_info.h b/native/jni/src/suggest/core/session/prev_words_info.h
index 76276f528..e44e876e9 100644
--- a/native/jni/src/suggest/core/session/prev_words_info.h
+++ b/native/jni/src/suggest/core/session/prev_words_info.h
@@ -90,13 +90,6 @@ class PrevWordsInfo {
         }
     }
 
-    BinaryDictionaryBigramsIterator getBigramsIteratorForPrediction(
-            const DictionaryStructureWithBufferPolicy *const dictStructurePolicy) const {
-        return getBigramsIteratorForWordWithTryingLowerCaseSearch(
-                dictStructurePolicy, mPrevWordCodePoints[0], mPrevWordCodePointCount[0],
-                mIsBeginningOfSentence[0]);
-    }
-
     // n is 1-indexed.
     const int *getNthPrevWordCodePoints(const int n) const {
         if (n <= 0 || n > MAX_PREV_WORD_COUNT_FOR_N_GRAM) {
@@ -154,46 +147,6 @@ class PrevWordsInfo {
                 codePoints, codePointCount, true /* forceLowerCaseSearch */);
     }
 
-    static BinaryDictionaryBigramsIterator getBigramsIteratorForWordWithTryingLowerCaseSearch(
-            const DictionaryStructureWithBufferPolicy *const dictStructurePolicy,
-            const int *const wordCodePoints, const int wordCodePointCount,
-            const bool isBeginningOfSentence) {
-        if (!dictStructurePolicy || !wordCodePoints || wordCodePointCount > MAX_WORD_LENGTH) {
-            return BinaryDictionaryBigramsIterator();
-        }
-        int codePoints[MAX_WORD_LENGTH];
-        int codePointCount = wordCodePointCount;
-        memmove(codePoints, wordCodePoints, sizeof(int) * codePointCount);
-        if (isBeginningOfSentence) {
-            codePointCount = CharUtils::attachBeginningOfSentenceMarker(codePoints,
-                    codePointCount, MAX_WORD_LENGTH);
-            if (codePointCount <= 0) {
-                return BinaryDictionaryBigramsIterator();
-            }
-        }
-        BinaryDictionaryBigramsIterator bigramsIt = getBigramsIteratorForWord(dictStructurePolicy,
-                codePoints, codePointCount, false /* forceLowerCaseSearch */);
-        // getBigramsIteratorForWord returns an empty iterator if this word isn't in the dictionary
-        // or has no bigrams.
-        if (bigramsIt.hasNext()) {
-            return bigramsIt;
-        }
-        // If no bigrams for this exact word, search again in lower case.
-        return getBigramsIteratorForWord(dictStructurePolicy, codePoints,
-                codePointCount, true /* forceLowerCaseSearch */);
-    }
-
-    static BinaryDictionaryBigramsIterator getBigramsIteratorForWord(
-            const DictionaryStructureWithBufferPolicy *const dictStructurePolicy,
-            const int *wordCodePoints, const int wordCodePointCount,
-            const bool forceLowerCaseSearch) {
-        if (!wordCodePoints || wordCodePointCount <= 0) return BinaryDictionaryBigramsIterator();
-        const int terminalPtNodePos = dictStructurePolicy->getTerminalPtNodePositionOfWord(
-                wordCodePoints, wordCodePointCount, forceLowerCaseSearch);
-        if (NOT_A_DICT_POS == terminalPtNodePos) return BinaryDictionaryBigramsIterator();
-        return dictStructurePolicy->getBigramsIteratorOfPtNode(terminalPtNodePos);
-    }
-
     void clear() {
         for (size_t i = 0; i < NELEMS(mPrevWordCodePoints); ++i) {
             mPrevWordCodePointCount[i] = 0;