Implement the heuristic for auto-commit.

Bug: 9059617
Change-Id: I066abf018df5aaeabf415425dd822ebe233e6008

java/src/com/android/inputmethod/latin/BinaryDictionary.java

@@ -44,9 +44,9 @@ public final class BinaryDictionary extends Dictionary {
     private static final int MAX_WORD_LENGTH = Constants.DICTIONARY_MAX_WORD_LENGTH;
     // Must be equal to MAX_RESULTS in native/jni/src/defines.h
     private static final int MAX_RESULTS = 18;
-    // Required space count for auto commit.
-    // TODO: Remove this heuristic.
-    private static final int SPACE_COUNT_FOR_AUTO_COMMIT = 3;
+    // The cutoff returned by native for auto-commit confidence.
+    // Must be equal to CONFIDENCE_TO_AUTO_COMMIT in native/jni/src/defines.h
+    private static final int CONFIDENCE_TO_AUTO_COMMIT = 1000000;
 
     @UsedForTesting
     public static final String UNIGRAM_COUNT_QUERY = "UNIGRAM_COUNT";
@@ -343,18 +343,7 @@ public final class BinaryDictionary extends Dictionary {
 
     @Override
     public boolean shouldAutoCommit(final SuggestedWordInfo candidate) {
-        // TODO: actually use the confidence rather than use this completely broken heuristic
-        final String word = candidate.mWord;
-        final int length = word.length();
-        int remainingSpaces = SPACE_COUNT_FOR_AUTO_COMMIT;
-        for (int i = 0; i < length; ++i) {
-            // This is okay because no low-surrogate and no high-surrogate can ever match the
-            // space character, so we don't need to take care of iterating on code points.
-            if (Constants.CODE_SPACE == word.charAt(i)) {
-                if (0 >= --remainingSpaces) return true;
-            }
-        }
-        return false;
+        return candidate.mAutoCommitFirstWordConfidence > CONFIDENCE_TO_AUTO_COMMIT;
     }
 
     @Override

native/jni/src/defines.h

@@ -298,9 +298,19 @@ static inline void prof_out(void) {
 #define NOT_AN_INDEX (-1)
 #define NOT_A_PROBABILITY (-1)
 #define NOT_A_DICT_POS (S_INT_MIN)
+
 // A special value to mean the first word confidence makes no sense in this case,
 // e.g. this is not a multi-word suggestion.
-#define NOT_A_FIRST_WORD_CONFIDENCE (S_INT_MIN)
+#define NOT_A_FIRST_WORD_CONFIDENCE (S_INT_MAX)
+// How high the confidence needs to be for us to auto-commit. Arbitrary.
+// This needs to be the same as CONFIDENCE_FOR_AUTO_COMMIT in BinaryDictionary.java
+#define CONFIDENCE_FOR_AUTO_COMMIT (1000000)
+// 80% of the full confidence
+#define DISTANCE_WEIGHT_FOR_AUTO_COMMIT (80 * CONFIDENCE_FOR_AUTO_COMMIT / 100)
+// 100% of the full confidence
+#define LENGTH_WEIGHT_FOR_AUTO_COMMIT (CONFIDENCE_FOR_AUTO_COMMIT)
+// 80% of the full confidence
+#define SPACE_COUNT_WEIGHT_FOR_AUTO_COMMIT (80 * CONFIDENCE_FOR_AUTO_COMMIT / 100)
 
 #define KEYCODE_SPACE ' '
 #define KEYCODE_SINGLE_QUOTE '\''

native/jni/src/suggest/core/dicnode/dic_node.h

@@ -321,6 +321,16 @@ class DicNode {
         DUMP_WORD_AND_SCORE("OUTPUT");
     }
 
+    // "Total" in this context (and other methods in this class) means the whole suggestion. When
+    // this represents a multi-word suggestion, the referenced PtNode (in mDicNodeState) is only
+    // the one that corresponds to the last word of the suggestion, and all the previous words
+    // are concatenated together in mPrevWord - which contains a space at the end.
+    int getTotalNodeSpaceCount() const {
+        if (isFirstWord()) return 0;
+        return CharUtils::getSpaceCount(mDicNodeState.mDicNodeStatePrevWord.mPrevWord,
+                mDicNodeState.mDicNodeStatePrevWord.getPrevWordLength());
+    }
+
     int getSecondWordFirstInputIndex(const ProximityInfoState *const pInfoState) const {
         const int inputIndex = mDicNodeState.mDicNodeStatePrevWord.getSecondWordFirstInputIndex();
         if (inputIndex == NOT_AN_INDEX) {

native/jni/src/suggest/core/suggest.cpp

@@ -166,7 +166,11 @@ int Suggest::outputSuggestions(DicTraverseSession *traverseSession, int *frequen
     // TODO: have partial commit work even with multiple pointers.
     const bool outputSecondWordFirstLetterInputIndex =
             traverseSession->isOnlyOnePointerUsed(0 /* pointerId */);
-    outputAutoCommitFirstWordConfidence[0] = computeFirstWordConfidence();
+    if (terminalSize > 0) {
+        // If we have no suggestions, don't write this
+        outputAutoCommitFirstWordConfidence[0] =
+                computeFirstWordConfidence(&terminals[0]);
+    }
 
     // Output suggestion results here
     for (int terminalIndex = 0; terminalIndex < terminalSize && outputWordIndex < MAX_RESULTS;
@@ -255,9 +259,55 @@ int Suggest::outputSuggestions(DicTraverseSession *traverseSession, int *frequen
     return outputWordIndex;
 }
 
-int Suggest::computeFirstWordConfidence() const {
-    // TODO: implement this.
-    return NOT_A_FIRST_WORD_CONFIDENCE;
+int Suggest::computeFirstWordConfidence(const DicNode *const terminalDicNode) const {
+    // Get the number of spaces in the first suggestion
+    const int spaceCount = terminalDicNode->getTotalNodeSpaceCount();
+    // Get the number of characters in the first suggestion
+    const int length = terminalDicNode->getTotalNodeCodePointCount();
+    // Get the distance for the first word of the suggestion
+    const float distance = terminalDicNode->getNormalizedCompoundDistanceAfterFirstWord();
+
+    // Arbitrarily, we give a score whose useful values range from 0 to 1,000,000.
+    // 1,000,000 will be the cutoff to auto-commit. It's fine if the number is under 0 or
+    // above 1,000,000 : under 0 just means it's very bad to commit, and above 1,000,000 means
+    // we are very confident.
+    // Expected space count is 1 ~ 5
+    static const int MIN_EXPECTED_SPACE_COUNT = 1;
+    static const int MAX_EXPECTED_SPACE_COUNT = 5;
+    // Expected length is about 4 ~ 30
+    static const int MIN_EXPECTED_LENGTH = 4;
+    static const int MAX_EXPECTED_LENGTH = 30;
+    // Expected distance is about 0.2 ~ 2.0, but consider 0.0 ~ 2.0
+    static const float MIN_EXPECTED_DISTANCE = 0.0;
+    static const float MAX_EXPECTED_DISTANCE = 2.0;
+    // This is not strict: it's where most stuff will be falling, but it's still fine if it's
+    // outside these values. We want to output a value that reflects all of these. Each factor
+    // contributes a bit.
+
+    // We need at least a space.
+    if (spaceCount < 1) return NOT_A_FIRST_WORD_CONFIDENCE;
+
+    // The smaller the edit distance, the higher the contribution. MIN_EXPECTED_DISTANCE means 0
+    // contribution, while MAX_EXPECTED_DISTANCE means full contribution according to the
+    // weight of the distance. Clamp to avoid overflows.
+    const float clampedDistance = distance < MIN_EXPECTED_DISTANCE ? MIN_EXPECTED_DISTANCE
+            : distance > MAX_EXPECTED_DISTANCE ? MAX_EXPECTED_DISTANCE : distance;
+    const int distanceContribution = DISTANCE_WEIGHT_FOR_AUTO_COMMIT
+            * (MAX_EXPECTED_DISTANCE - clampedDistance)
+            / (MAX_EXPECTED_DISTANCE - MIN_EXPECTED_DISTANCE);
+    // The larger the suggestion length, the larger the contribution. MIN_EXPECTED_LENGTH is no
+    // contribution, MAX_EXPECTED_LENGTH is full contribution according to the weight of the
+    // length. Length is guaranteed to be between 1 and 48, so we don't need to clamp.
+    const int lengthContribution = LENGTH_WEIGHT_FOR_AUTO_COMMIT
+            * (length - MIN_EXPECTED_LENGTH) / (MAX_EXPECTED_LENGTH - MIN_EXPECTED_LENGTH);
+    // The more spaces, the larger the contribution. MIN_EXPECTED_SPACE_COUNT space is no
+    // contribution, MAX_EXPECTED_SPACE_COUNT spaces is full contribution according to the
+    // weight of the space count.
+    const int spaceContribution = SPACE_COUNT_WEIGHT_FOR_AUTO_COMMIT
+            * (spaceCount - MIN_EXPECTED_SPACE_COUNT)
+            / (MAX_EXPECTED_SPACE_COUNT - MIN_EXPECTED_SPACE_COUNT);
+
+    return distanceContribution + lengthContribution + spaceContribution;
 }
 
 /**

native/jni/src/suggest/core/suggest.h

@@ -58,7 +58,7 @@ class Suggest : public SuggestInterface {
     int outputSuggestions(DicTraverseSession *traverseSession, int *frequencies,
             int *outputCodePoints, int *outputIndicesToPartialCommit, int *outputTypes,
             int *outputAutoCommitFirstWordConfidence) const;
-    int computeFirstWordConfidence() const;
+    int computeFirstWordConfidence(const DicNode *const terminalDicNode) const;
     void initializeSearch(DicTraverseSession *traverseSession, int commitPoint) const;
     void expandCurrentDicNodes(DicTraverseSession *traverseSession) const;
     void processTerminalDicNode(DicTraverseSession *traverseSession, DicNode *dicNode) const;

native/jni/src/utils/char_utils.h

@@ -75,6 +75,16 @@ class CharUtils {
         return c;
     }
 
+    static AK_FORCE_INLINE int getSpaceCount(const int *const codePointBuffer, const int length) {
+        int spaceCount = 0;
+        for (int i = 0; i < length; ++i) {
+            if (codePointBuffer[i] == KEYCODE_SPACE) {
+                ++spaceCount;
+            }
+        }
+        return spaceCount;
+    }
+
     static unsigned short latin_tolower(const unsigned short c);
 
  private: