[TTS] Extract tapped text before showing UI.

chrome/android/java/src/org/chromium/chrome/browser/contextualsearch/ContextualSearchContext.java

Index: chrome/android/java/src/org/chromium/chrome/browser/contextualsearch/ContextualSearchContext.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/contextualsearch/ContextualSearchContext.java b/chrome/android/java/src/org/chromium/chrome/browser/contextualsearch/ContextualSearchContext.java
index b1ac520fc8828c0d12afd85e0946fc5e3038a2a8..0f56a3639b7c9bdc60cbc83e4cf677e5f9c6005c 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/contextualsearch/ContextualSearchContext.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/contextualsearch/ContextualSearchContext.java
@@ -4,45 +4,61 @@
 
 package org.chromium.chrome.browser.contextualsearch;
 
+import android.text.TextUtils;
+
+import org.chromium.base.Log;
 import org.chromium.base.annotations.CalledByNative;
 
+import javax.annotation.Nullable;
+
 /**
  * Provides a context in which to search, and links to the native ContextualSearchContext.
  * Includes the selection, selection offsets, surrounding page content, etc.
+ * Requires an override of #onSelectionChanged to call when a non-empty selection is established
+ * or changed.
  */
-public class ContextualSearchContext {
-    // The initial selection that established this context, or null.
-    private final String mSelection;
+public abstract class ContextualSearchContext {
+    static final int INVALID_SELECTION_OFFSET = -1;
+    private static final String TAG = "ContextualSearch";
 
     // Pointer to the native instance of this class.
     private long mNativePointer;
 
-    // Whether this context can Resolve a Search Term.
-    private boolean mCanResolve;
+    // Whether this context has had the required properties set so it can Resolve a Search Term.
+    private boolean mHasSetResolveProperties;
+
+    // A shortened version of the actual text content surrounding the selection, or null if not yet
+    // established.
+    private String mSurroundingText;
+
+    // The start and end offsets of the selection within the text content.
+    private int mSelectionStartOffset = INVALID_SELECTION_OFFSET;
+    private int mSelectionEndOffset = INVALID_SELECTION_OFFSET;
+
+    // The initial word selected by a Tap, or null.
+    private String mInitialSelectedWord;
+
+    // The original encoding of the base page.
+    private String mEncoding;
 
     /**
-     * Constructs a context that cannot resolve a search term and has a small amount of
-     * page content.
+     * Constructs a context that tracks the selection and some amount of page content.
      */
     ContextualSearchContext() {
         mNativePointer = nativeInit();
-        mSelection = null;
-        mCanResolve = false;
+        mHasSetResolveProperties = false;
     }
 
     /**
-     * Constructs a context that can resolve a search term and has a large amount of
+     * Updates a context to be able to resolve a search term and have a large amount of
      * page content.
-     * @param selection The current selection.
      * @param homeCountry The country where the user usually resides, or an empty string if not
      *        known.
      * @param maySendBasePageUrl Whether policy allows sending the base-page URL to the server.
      */
-    ContextualSearchContext(String selection, String homeCountry, boolean maySendBasePageUrl) {
-        mNativePointer = nativeInit();
-        mSelection = selection;
-        mCanResolve = true;
-        nativeSetResolveProperties(getNativePointer(), selection, homeCountry, maySendBasePageUrl);
+    void setResolveProperties(String homeCountry, boolean maySendBasePageUrl) {
+        mHasSetResolveProperties = true;
+        nativeSetResolveProperties(getNativePointer(), homeCountry, maySendBasePageUrl);
     }
 
     /**
@@ -53,23 +69,153 @@ public class ContextualSearchContext {
         assert mNativePointer != 0;
         nativeDestroy(mNativePointer);
         mNativePointer = 0;
+
+        // Also zero out private data that may be sizable.
+        mSurroundingText = null;
+    }
+
+    /**
+     * Sets the surrounding text and selection offsets.
+     * @param encoding The original encoding of the base page.
+     * @param surroundingText The text from the base page surrounding the selection.
+     * @param startOffset The offset of start the selection.
+     * @param endOffset The offset of the end of the selection
+     */
+    void setSurroundingText(
+            String encoding, String surroundingText, int startOffset, int endOffset) {
+        mEncoding = encoding;
+        mSurroundingText = surroundingText;
+        mSelectionStartOffset = startOffset;
+        mSelectionEndOffset = endOffset;
+        // Notify of an initial selection if it's not empty.
+        if (endOffset > startOffset) onSelectionChanged();
     }
 
     /**
-     * @return the original selection.
+     * @return The text that surrounds the selection, or {@code null} if none yet known.
      */
-    String getSelection() {
-        return mSelection;
+    @Nullable
+    String getSurroundingText() {
+        return mSurroundingText;
     }
 
     /**
-     * @return Whether this context can "Resolve" the Search Term or is just used for a
-     *         non-resolving Tap gesture or a Long-press gesture.
+     * @return The offset into the surrounding text of the start of the selection, or
+     *         {@link #INVALID_SELECTION_OFFSET} if not yet established.
+     */
+    int getSelectionStartOffset() {
+        return mSelectionStartOffset;
+    }
+
+    /**
+     * @return The offset into the surrounding text of the end of the selection, or
+     *         {@link #INVALID_SELECTION_OFFSET} if not yet established.
+     */
+    int getSelectionEndOffset() {
+        return mSelectionEndOffset;
+    }
+
+    /**
+     * @return The original encoding of the base page.
+     */
+    String getEncoding() {
+        return mEncoding;
+    }
+
+    /**
+     * @return The initial word selected by a Tap.
+     */
+    String getInitialSelectedWord() {
+        return mInitialSelectedWord;
+    }
+
+    /**
+     * @return The text content that follows the selection (one side of the surrounding text).
+     */
+    String getTextContentFollowingSelection() {
+        if (mSurroundingText != null && mSelectionEndOffset > 0
+                && mSelectionEndOffset <= mSurroundingText.length()) {
+            return mSurroundingText.substring(mSelectionEndOffset);
+        } else {
+            return "";
+        }
+    }
+
+    /**
+     * @return Whether this context can Resolve the Search Term.
      */
     boolean canResolve() {
-        return mCanResolve;
+        return mHasSetResolveProperties && mSelectionStartOffset != INVALID_SELECTION_OFFSET
+                && mSelectionEndOffset != INVALID_SELECTION_OFFSET
+                && mSelectionEndOffset > mSelectionStartOffset;
     }
 
+    /**
+     * Notifies of an adjustment that has been applied to the start and end of the selection.
+     * @param startAdjust A signed value indicating the direction of the adjustment to the start of
+     *        the selection (typically a negative value when the selection expands).
+     * @param endAdjust A signed value indicating the direction of the adjustment to the end of
+     *        the selection (typically a positive value when the selection expands).
+     */
+    void onSelectionAdjusted(int startAdjust, int endAdjust) {
+        makeSelectionAdjustments(startAdjust, endAdjust);
+    }
+
+    /**
+     * Update the context based on the given selection.
+     * TODO(donnd): This method of finding the adjustment to the selection is unreliable!
+     * TODO(donnd): Replace by getting the selection adjustment directly from
+     *              {@link #onSelectionAdjusted} which is called by SelectWordAroundCaretAck
+     *              (since it knows how the selection was actually adjusted).
+     *              This method can be removed once SelectWordAroundCaretAck is in place.
+     *              See crbug.com/435778 for details.
+     * @param selection The new selection.
+     */
+    void updateContextFromSelection(String selection) {
+        mInitialSelectedWord = selection;
+        if (mSelectionStartOffset == INVALID_SELECTION_OFFSET
+                || mSelectionEndOffset == INVALID_SELECTION_OFFSET
+                || TextUtils.isEmpty(mSurroundingText) || TextUtils.isEmpty(selection)) {
+            return;
+        }
+
+        int selectionLength = selection.length();
+        for (int i = 0; i <= selectionLength; i++) {
+            int possibleStart = mSelectionStartOffset - i;
+            int possibleEnd = possibleStart + selectionLength;
+            if (possibleStart >= 0 && possibleEnd <= mSurroundingText.length()
+                    && selection.equals(mSurroundingText.substring(possibleStart, possibleEnd))) {
+                makeSelectionAdjustments(-i, selectionLength - i);
+                return;
+            }
+        }
+
+        Log.w(TAG, "Warning, unable to update context from the selection!");
+    }
+
+    /**
+     * Makes adjustments to the selection offsets.
+     * @param startAdjust A signed value indicating the direction of the adjustment to the start of
+     *        the selection (typically a negative value when the selection expands).
+     * @param endAdjust A signed value indicating the direction of the adjustment to the end of
+     *        the selection (typically a positive value when the selection expands).
+     */
+    private void makeSelectionAdjustments(int startAdjust, int endAdjust) {
+        nativeAdjustSelection(getNativePointer(), startAdjust, endAdjust);
+        // Fully track the selection as it changes.
+        mSelectionStartOffset += startAdjust;
+        mSelectionEndOffset += endAdjust;
+        // Notify of changes.
+        onSelectionChanged();
+    }
+
+    /**
+     * Notifies this instance that the selection has been changed.
+     */
+    abstract void onSelectionChanged();
+
+    // TODO(donnd): Add a test for this class!
+
     // ============================================================================================
     // Native callback support.
     // ============================================================================================
@@ -85,6 +231,8 @@ public class ContextualSearchContext {
     // ============================================================================================
     private native long nativeInit();
     private native void nativeDestroy(long nativeContextualSearchContext);
-    private native void nativeSetResolveProperties(long nativeContextualSearchContext,
-            String selection, String homeCountry, boolean maySendBasePageUrl);
+    private native void nativeSetResolveProperties(
+            long nativeContextualSearchContext, String homeCountry, boolean maySendBasePageUrl);
+    private native void nativeAdjustSelection(
+            long nativeContextualSearchContext, int startAdjust, int endAdjust);
 }