/*
 * Copyright (C) 2011 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.common.format;

import android.text.SpannableString;
import android.text.style.CharacterStyle;
import android.text.style.StyleSpan;
import android.widget.TextView;

/** Highlights the text in a text field. */
public class TextHighlighter {

  private int mTextStyle;

  private CharacterStyle mTextStyleSpan;

  public TextHighlighter(int textStyle) {
    mTextStyle = textStyle;
    mTextStyleSpan = getStyleSpan();
  }

  /**
   * Sets the text on the given text view, highlighting the word that matches the given prefix.
   *
   * @param view the view on which to set the text
   * @param text the string to use as the text
   * @param prefix the prefix to look for
   */
  public void setPrefixText(TextView view, String text, String prefix) {
    view.setText(applyPrefixHighlight(text, prefix));
  }

  private CharacterStyle getStyleSpan() {
    return new StyleSpan(mTextStyle);
  }

  /**
   * Applies highlight span to the text.
   *
   * @param text Text sequence to be highlighted.
   * @param start Start position of the highlight sequence.
   * @param end End position of the highlight sequence.
   */
  public void applyMaskingHighlight(SpannableString text, int start, int end) {
    /** Sets text color of the masked locations to be highlighted. */
    text.setSpan(getStyleSpan(), start, end, 0);
  }

  /**
   * Returns a CharSequence which highlights the given prefix if found in the given text.
   *
   * @param text the text to which to apply the highlight
   * @param prefix the prefix to look for
   */
  public CharSequence applyPrefixHighlight(CharSequence text, String prefix) {
    if (prefix == null) {
      return text;
    }

    // Skip non-word characters at the beginning of prefix.
    int prefixStart = 0;
    while (prefixStart < prefix.length()
        && !Character.isLetterOrDigit(prefix.charAt(prefixStart))) {
      prefixStart++;
    }
    final String trimmedPrefix = prefix.substring(prefixStart);

    int index = indexOfWordPrefix(text, trimmedPrefix);
    if (index != -1) {
      final SpannableString result = new SpannableString(text);
      result.setSpan(mTextStyleSpan, index, index + trimmedPrefix.length(), 0 /* flags */);
      return result;
    } else {
      return text;
    }
  }

  /**
   * Finds the index of the first word that starts with the given prefix.
   *
   * <p>If not found, returns -1.
   *
   * @param text the text in which to search for the prefix
   * @param prefix the text to find, in upper case letters
   */
  public static int indexOfWordPrefix(CharSequence text, String prefix) {
    if (prefix == null || text == null) {
      return -1;
    }

    int textLength = text.length();
    int prefixLength = prefix.length();

    if (prefixLength == 0 || textLength < prefixLength) {
      return -1;
    }

    int i = 0;
    while (i < textLength) {
      // Skip non-word characters
      while (i < textLength && !Character.isLetterOrDigit(text.charAt(i))) {
        i++;
      }

      if (i + prefixLength > textLength) {
        return -1;
      }

      // Compare the prefixes
      int j;
      for (j = 0; j < prefixLength; j++) {
        if (Character.toUpperCase(text.charAt(i + j)) != prefix.charAt(j)) {
          break;
        }
      }
      if (j == prefixLength) {
        return i;
      }

      // Skip this word
      while (i < textLength && Character.isLetterOrDigit(text.charAt(i))) {
        i++;
      }
    }

    return -1;
  }
}