Remove unigram for v402 with historical info.

Bug: 15531638
Change-Id: If1b73ac693e45a80df987ea16b2dece5597697e8

native/jni/src/suggest/policyimpl/dictionary/structure/backward/v402/ver4_patricia_trie_node_writer.cpp

@@ -425,6 +425,18 @@ bool Ver4PatriciaTrieNodeWriter::updatePtNodeFlags(const int ptNodePos,
     return true;
 }
 
+bool Ver4PatriciaTrieNodeWriter::suppressUnigramEntry(const PtNodeParams *const ptNodeParams) {
+    if (!mHeaderPolicy->hasHistoricalInfoOfWords()) {
+        // Require historical info to suppress unigram entry.
+        return false;
+    }
+    const HistoricalInfo suppressedHistorycalInfo(0 /* timestamp */, 0 /* level */, 0 /* count */);
+    const ProbabilityEntry probabilityEntryToWrite =
+            ProbabilityEntry().createEntryWithUpdatedHistoricalInfo(&suppressedHistorycalInfo);
+    return mBuffers->getMutableProbabilityDictContent()->setProbabilityEntry(
+            ptNodeParams->getTerminalId(), &probabilityEntryToWrite);
+}
+
 } // namespace v402
 } // namespace backward
 } // namespace latinime

native/jni/src/suggest/policyimpl/dictionary/structure/backward/v402/ver4_patricia_trie_node_writer.h

@@ -111,6 +111,11 @@ class Ver4PatriciaTrieNodeWriter : public PtNodeWriter {
 
     bool updatePtNodeHasBigramsAndShortcutTargetsFlags(const PtNodeParams *const ptNodeParams);
 
+    // Suppress unigram not to use the word for generating suggestions. So, this method can be used
+    // only for dictionaries with historical info. Also, suppressed entries are included in unigram
+    // count. They will be removed from the dictionary during GC.
+    bool suppressUnigramEntry(const PtNodeParams *const ptNodeParams);
+
  private:
     DISALLOW_COPY_AND_ASSIGN(Ver4PatriciaTrieNodeWriter);
 

native/jni/src/suggest/policyimpl/dictionary/structure/backward/v402/ver4_patricia_trie_policy.cpp

@@ -258,6 +258,20 @@ bool Ver4PatriciaTriePolicy::addUnigramEntry(const int *const word, const int le
     }
 }
 
+bool Ver4PatriciaTriePolicy::removeUnigramEntry(const int *const word, const int length) {
+    if (!mBuffers->isUpdatable()) {
+        AKLOGI("Warning: removeUnigramEntry() is called for non-updatable dictionary.");
+        return false;
+    }
+    const int ptNodePos = getTerminalPtNodePositionOfWord(word, length,
+            false /* forceLowerCaseSearch */);
+    if (ptNodePos == NOT_A_DICT_POS) {
+        return false;
+    }
+    const PtNodeParams ptNodeParams = mNodeReader.fetchPtNodeParamsInBufferFromPtNodePos(ptNodePos);
+    return mNodeWriter.suppressUnigramEntry(&ptNodeParams);
+}
+
 bool Ver4PatriciaTriePolicy::addNgramEntry(const PrevWordsInfo *const prevWordsInfo,
         const BigramProperty *const bigramProperty) {
     if (!mBuffers->isUpdatable()) {

native/jni/src/suggest/policyimpl/dictionary/structure/backward/v402/ver4_patricia_trie_policy.h

@@ -108,10 +108,7 @@ class Ver4PatriciaTriePolicy : public DictionaryStructureWithBufferPolicy {
     bool addUnigramEntry(const int *const word, const int length,
             const UnigramProperty *const unigramProperty);
 
-    bool removeUnigramEntry(const int *const word, const int length) {
+    bool removeUnigramEntry(const int *const word, const int length);
-        // Removing unigram entry is not supported.
-        return false;
-    }
 
     bool addNgramEntry(const PrevWordsInfo *const prevWordsInfo,
             const BigramProperty *const bigramProperty);

tests/src/com/android/inputmethod/latin/BinaryDictionaryDecayingTests.java

@@ -689,4 +689,36 @@ public class BinaryDictionaryDecayingTests extends AndroidTestCase {
         binaryDictionary.close();
         dictFile.delete();
     }
+
+    public void testRemoveUnigrams() {
+        for (final int formatVersion : DICT_FORMAT_VERSIONS) {
+            testRemoveUnigrams(formatVersion);
+        }
+    }
+
+    private void testRemoveUnigrams(final int formatVersion) {
+        final int unigramInputCount = 20;
+        setCurrentTimeForTestMode(mCurrentTime);
+        File dictFile = null;
+        try {
+            dictFile = createEmptyDictionaryAndGetFile("TestBinaryDictionary", formatVersion);
+        } catch (IOException e) {
+            fail("IOException while writing an initial dictionary : " + e);
+        }
+        final BinaryDictionary binaryDictionary = new BinaryDictionary(dictFile.getAbsolutePath(),
+                0 /* offset */, dictFile.length(), true /* useFullEditDistance */,
+                Locale.getDefault(), TEST_LOCALE, true /* isUpdatable */);
+
+        addUnigramWord(binaryDictionary, "aaa", Dictionary.NOT_A_PROBABILITY);
+        assertFalse(binaryDictionary.isValidWord("aaa"));
+        for (int i = 0; i < unigramInputCount; i++) {
+            addUnigramWord(binaryDictionary, "aaa", Dictionary.NOT_A_PROBABILITY);
+        }
+        assertTrue(binaryDictionary.isValidWord("aaa"));
+        assertTrue(binaryDictionary.removeUnigramEntry("aaa"));
+        assertFalse(binaryDictionary.isValidWord("aaa"));
+
+        binaryDictionary.close();
+        dictFile.delete();
+    }
 }