Fixing the contacts indexer for UNICODE and last-name-first sorting.

This change may temporarily adversely affect the indexing in Japan.
If needed, I will take care of that in a separate CL.

Bug: 2407129
Change-Id: I2d96dab771243f68646edc49f0200d02e8c28bd9
diff --git a/src/com/android/contacts/ContactsSectionIndexer.java b/src/com/android/contacts/ContactsSectionIndexer.java
new file mode 100644
index 0000000..01d461f
--- /dev/null
+++ b/src/com/android/contacts/ContactsSectionIndexer.java
@@ -0,0 +1,96 @@
+/*
+ * Copyright (C) 2010 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.contacts;
+
+import android.widget.SectionIndexer;
+
+import java.util.Arrays;
+
+/**
+ * A section indexer that is configured with precomputed section titles and
+ * their respective counts.
+ */
+public class ContactsSectionIndexer implements SectionIndexer {
+
+    private final String[] mSections;
+    private final int[] mPositions;
+    private final int mCount;
+
+    /**
+     * Constructor.
+     *
+     * @param sections a non-null array
+     * @param counts a non-null array of the same size as <code>sections</code>
+     */
+    public ContactsSectionIndexer(String[] sections, int[] counts) {
+        if (sections == null || counts == null) {
+            throw new NullPointerException();
+        }
+
+        if (sections.length != counts.length) {
+            throw new IllegalArgumentException(
+                    "The sections and counts arrays must have the same length");
+        }
+
+        // TODO process sections/counts based on current locale and/or specific section titles
+
+        this.mSections = sections;
+        mPositions = new int[counts.length];
+        int position = 0;
+        for (int i = 0; i < counts.length; i++) {
+            if (mSections[i] == null) {
+                mSections[i] = " ";
+            } else {
+                mSections[i] = mSections[i].trim();
+            }
+
+            mPositions[i] = position;
+            position += counts[i];
+        }
+        mCount = position;
+    }
+
+    public Object[] getSections() {
+        return mSections;
+    }
+
+    public int getPositionForSection(int section) {
+        if (section < 0 || section >= mSections.length) {
+            return -1;
+        }
+
+        return mPositions[section];
+    }
+
+    public int getSectionForPosition(int position) {
+        if (position < 0 || position >= mCount) {
+            return -1;
+        }
+
+        int index = Arrays.binarySearch(mPositions, position);
+
+        /*
+         * Consider this example: section positions are 0, 3, 5; the supplied
+         * position is 4. The section corresponding to position 4 starts at
+         * position 3, so the expected return value is 1. Binary search will not
+         * find 4 in the array and thus will return -insertPosition-1, i.e. -3.
+         * To get from that number to the expected value of 1 we need to negate
+         * and subtract 2.
+         */
+        return index >= 0 ? index : -index - 2;
+    }
+}