/*
 * Copyright (C) 2011 The Libphonenumber Authors
 *
 * 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.i18n.phonenumbers;

import com.android.i18n.phonenumbers.Phonemetadata.PhoneMetadata;
import com.android.i18n.phonenumbers.Phonemetadata.PhoneNumberDesc;

import java.util.regex.Pattern;

/*
 * Utility for international short phone numbers, such as short codes and emergency numbers. Note
 * most commercial short numbers are not handled here, but by the PhoneNumberUtil.
 *
 * @author Shaopeng Jia
 */
public class ShortNumberUtil {

  private final PhoneNumberUtil phoneUtil;

  public ShortNumberUtil() {
    phoneUtil = PhoneNumberUtil.getInstance();
  }

  // @VisibleForTesting
  ShortNumberUtil(PhoneNumberUtil util) {
    phoneUtil = util;
  }

  /**
   * Returns true if the number might be used to connect to an emergency service in the given
   * region.
   *
   * This method takes into account cases where the number might contain formatting, or might have
   * additional digits appended (when it is okay to do that in the region specified).
   *
   * @param number  the phone number to test
   * @param regionCode  the region where the phone number is being dialed
   * @return  if the number might be used to connect to an emergency service in the given region.
   */
  public boolean connectsToEmergencyNumber(String number, String regionCode) {
    return matchesEmergencyNumberHelper(number, regionCode, true /* allows prefix match */);
  }

  /**
   * Returns true if the number exactly matches an emergency service number in the given region.
   *
   * This method takes into account cases where the number might contain formatting, but doesn't
   * allow additional digits to be appended.
   *
   * @param number  the phone number to test
   * @param regionCode  the region where the phone number is being dialed
   * @return  if the number exactly matches an emergency services number in the given region.
   */
  public boolean isEmergencyNumber(String number, String regionCode) {
    return matchesEmergencyNumberHelper(number, regionCode, false /* doesn't allow prefix match */);
  }

  private boolean matchesEmergencyNumberHelper(String number, String regionCode,
      boolean allowPrefixMatch) {
    number = PhoneNumberUtil.extractPossibleNumber(number);
    if (PhoneNumberUtil.PLUS_CHARS_PATTERN.matcher(number).lookingAt()) {
      // Returns false if the number starts with a plus sign. We don't believe dialing the country
      // code before emergency numbers (e.g. +1911) works, but later, if that proves to work, we can
      // add additional logic here to handle it.
      return false;
    }
    PhoneMetadata metadata = phoneUtil.getMetadataForRegion(regionCode);
    if (metadata == null || !metadata.hasEmergency()) {
      return false;
    }
    Pattern emergencyNumberPattern =
        Pattern.compile(metadata.getEmergency().getNationalNumberPattern());
    String normalizedNumber = PhoneNumberUtil.normalizeDigitsOnly(number);
    // In Brazil, it is impossible to append additional digits to an emergency number to dial the
    // number.
    return (!allowPrefixMatch || regionCode.equals("BR"))
        ? emergencyNumberPattern.matcher(normalizedNumber).matches()
        : emergencyNumberPattern.matcher(normalizedNumber).lookingAt();
  }
}