Add a WidgetsSearchBar(Launcher3) and a WidgetsSearchController.

- Make WidgetsSearchBar in Launcher3 initialize WidgetsSearchController with SimpleWidgetsSearchPipeline
- Modify SimpleWidgetsSearchPipeline to filter widgets entries on widgets/shortcut labels also.

Test: Tested prototype locally. Also added robolectric test.
Bug: b/157286785
Change-Id: I65f5fa0240ffb6d22023167e4e86d94d83bbd9f7

src/com/android/launcher3/search/StringMatcherUtility.java

@@ -0,0 +1,162 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.launcher3.search;
+
+import java.text.Collator;
+
+/**
+ * Utilities for matching query string to target string.
+ */
+public class StringMatcherUtility {
+
+    /**
+     * Returns {@code true} is {@code query} is a prefix substring of a complete word/phrase in
+     * {@code target}.
+     */
+    public static boolean matches(String query, String target, StringMatcher matcher) {
+        int queryLength = query.length();
+
+        int targetLength = target.length();
+
+        if (targetLength < queryLength || queryLength <= 0) {
+            return false;
+        }
+
+        if (requestSimpleFuzzySearch(query)) {
+            return target.toLowerCase().contains(query);
+        }
+
+        int lastType;
+        int thisType = Character.UNASSIGNED;
+        int nextType = Character.getType(target.codePointAt(0));
+
+        int end = targetLength - queryLength;
+        for (int i = 0; i <= end; i++) {
+            lastType = thisType;
+            thisType = nextType;
+            nextType = i < (targetLength - 1)
+                    ? Character.getType(target.codePointAt(i + 1)) : Character.UNASSIGNED;
+            if (isBreak(thisType, lastType, nextType)
+                    && matcher.matches(query, target.substring(i, i + queryLength))) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    /**
+     * Returns true if the current point should be a break point. Following cases
+     * are considered as break points:
+     *      1) Any non space character after a space character
+     *      2) Any digit after a non-digit character
+     *      3) Any capital character after a digit or small character
+     *      4) Any capital character before a small character
+     */
+    private static boolean isBreak(int thisType, int prevType, int nextType) {
+        switch (prevType) {
+            case Character.UNASSIGNED:
+            case Character.SPACE_SEPARATOR:
+            case Character.LINE_SEPARATOR:
+            case Character.PARAGRAPH_SEPARATOR:
+                return true;
+        }
+        switch (thisType) {
+            case Character.UPPERCASE_LETTER:
+                if (nextType == Character.UPPERCASE_LETTER) {
+                    return true;
+                }
+                // Follow through
+            case Character.TITLECASE_LETTER:
+                // Break point if previous was not a upper case
+                return prevType != Character.UPPERCASE_LETTER;
+            case Character.LOWERCASE_LETTER:
+                // Break point if previous was not a letter.
+                return prevType > Character.OTHER_LETTER || prevType <= Character.UNASSIGNED;
+            case Character.DECIMAL_DIGIT_NUMBER:
+            case Character.LETTER_NUMBER:
+            case Character.OTHER_NUMBER:
+                // Break point if previous was not a number
+                return !(prevType == Character.DECIMAL_DIGIT_NUMBER
+                        || prevType == Character.LETTER_NUMBER
+                        || prevType == Character.OTHER_NUMBER);
+            case Character.MATH_SYMBOL:
+            case Character.CURRENCY_SYMBOL:
+            case Character.OTHER_PUNCTUATION:
+            case Character.DASH_PUNCTUATION:
+                // Always a break point for a symbol
+                return true;
+            default:
+                return  false;
+        }
+    }
+
+    /**
+     * Performs locale sensitive string comparison using {@link Collator}.
+     */
+    public static class StringMatcher {
+
+        private static final char MAX_UNICODE = '\uFFFF';
+
+        private final Collator mCollator;
+
+        StringMatcher() {
+            // On android N and above, Collator uses ICU implementation which has a much better
+            // support for non-latin locales.
+            mCollator = Collator.getInstance();
+            mCollator.setStrength(Collator.PRIMARY);
+            mCollator.setDecomposition(Collator.CANONICAL_DECOMPOSITION);
+        }
+
+        /**
+         * Returns true if {@param query} is a prefix of {@param target}
+         */
+        public boolean matches(String query, String target) {
+            switch (mCollator.compare(query, target)) {
+                case 0:
+                    return true;
+                case -1:
+                    // The target string can contain a modifier which would make it larger than
+                    // the query string (even though the length is same). If the query becomes
+                    // larger after appending a unicode character, it was originally a prefix of
+                    // the target string and hence should match.
+                    return mCollator.compare(query + MAX_UNICODE, target) > -1;
+                default:
+                    return false;
+            }
+        }
+
+        public static StringMatcher getInstance() {
+            return new StringMatcher();
+        }
+    }
+
+    /**
+     * Matching optimization to search in Chinese.
+     */
+    private static boolean requestSimpleFuzzySearch(String s) {
+        for (int i = 0; i < s.length(); ) {
+            int codepoint = s.codePointAt(i);
+            i += Character.charCount(codepoint);
+            switch (Character.UnicodeScript.of(codepoint)) {
+                case HAN:
+                    //Character.UnicodeScript.HAN: use String.contains to match
+                    return true;
+            }
+        }
+        return false;
+    }
+}