/*
 * Copyright (C) 2017 The Gson 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.google.gson.internal;

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Locale;

/** Provides DateFormats for US locale with patterns which were the default ones before Java 9. */
public class PreJava9DateFormatProvider {
  private PreJava9DateFormatProvider() {}

  /**
   * Returns the same DateFormat as {@code DateFormat.getDateTimeInstance(dateStyle, timeStyle,
   * Locale.US)} in Java 8 or below.
   */
  public static DateFormat getUsDateTimeFormat(int dateStyle, int timeStyle) {
    String pattern =
        getDatePartOfDateTimePattern(dateStyle) + " " + getTimePartOfDateTimePattern(timeStyle);
    return new SimpleDateFormat(pattern, Locale.US);
  }

  private static String getDatePartOfDateTimePattern(int dateStyle) {
    switch (dateStyle) {
      case DateFormat.SHORT:
        return "M/d/yy";
      case DateFormat.MEDIUM:
        return "MMM d, yyyy";
      case DateFormat.LONG:
        return "MMMM d, yyyy";
      case DateFormat.FULL:
        return "EEEE, MMMM d, yyyy";
      default:
        throw new IllegalArgumentException("Unknown DateFormat style: " + dateStyle);
    }
  }

  private static String getTimePartOfDateTimePattern(int timeStyle) {
    switch (timeStyle) {
      case DateFormat.SHORT:
        return "h:mm a";
      case DateFormat.MEDIUM:
        return "h:mm:ss a";
      case DateFormat.FULL:
      case DateFormat.LONG:
        return "h:mm:ss a z";
      default:
        throw new IllegalArgumentException("Unknown DateFormat style: " + timeStyle);
    }
  }
}
