/*
 * Copyright (C) 2011 Google Inc.
 *
 * 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.bind;

import com.google.gson.Gson;
import com.google.gson.JsonSyntaxException;
import com.google.gson.TypeAdapter;
import com.google.gson.TypeAdapterFactory;
import com.google.gson.internal.JavaVersion;
import com.google.gson.internal.PreJava9DateFormatProvider;
import com.google.gson.internal.bind.util.ISO8601Utils;
import com.google.gson.reflect.TypeToken;
import com.google.gson.stream.JsonReader;
import com.google.gson.stream.JsonToken;
import com.google.gson.stream.JsonWriter;

import java.io.IOException;
import java.text.DateFormat;
import java.text.ParseException;
import java.text.ParsePosition;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import java.util.Locale;

Adapter for Date. Although this class appears stateless, it is not.
DateFormat captures its time zone and locale when it is created, which gives
this class state. DateFormat isn't thread safe either, so this class has
to synchronize its read and write methods.
/**
 * Adapter for Date. Although this class appears stateless, it is not.
 * DateFormat captures its time zone and locale when it is created, which gives
 * this class state. DateFormat isn't thread safe either, so this class has
 * to synchronize its read and write methods.
 */
public final class DateTypeAdapter extends TypeAdapter<Date> {
  public static final TypeAdapterFactory FACTORY = new TypeAdapterFactory() {
    @SuppressWarnings("unchecked") // we use a runtime check to make sure the 'T's equal
    @Override public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> typeToken) {
      return typeToken.getRawType() == Date.class ? (TypeAdapter<T>) new DateTypeAdapter() : null;
    }
  };

  
List of 1 or more different date formats used for de-serialization attempts.
The first of them (default US format) is used for serialization as well.
/**
   * List of 1 or more different date formats used for de-serialization attempts.
   * The first of them (default US format) is used for serialization as well.
   */
  private final List<DateFormat> dateFormats = new ArrayList<DateFormat>();

  public DateTypeAdapter() {
    dateFormats.add(DateFormat.getDateTimeInstance(DateFormat.DEFAULT, DateFormat.DEFAULT, Locale.US));
    if (!Locale.getDefault().equals(Locale.US)) {
      dateFormats.add(DateFormat.getDateTimeInstance(DateFormat.DEFAULT, DateFormat.DEFAULT));
    }
    if (JavaVersion.isJava9OrLater()) {
      dateFormats.add(PreJava9DateFormatProvider.getUSDateTimeFormat(DateFormat.DEFAULT, DateFormat.DEFAULT));
    }
  }

  @Override public Date read(JsonReader in) throws IOException {
    if (in.peek() == JsonToken.NULL) {
      in.nextNull();
      return null;
    }
    return deserializeToDate(in.nextString());
  }

  private synchronized Date deserializeToDate(String json) {
    for (DateFormat dateFormat : dateFormats) {
      try {
        return dateFormat.parse(json);
      } catch (ParseException ignored) {}
    }
    try {
    	return ISO8601Utils.parse(json, new ParsePosition(0));
    } catch (ParseException e) {
      throw new JsonSyntaxException(json, e);
    }
  }

  @Override public synchronized void write(JsonWriter out, Date value) throws IOException {
    if (value == null) {
      out.nullValue();
      return;
    }
    String dateFormatAsString = dateFormats.get(0).format(value);
    out.value(dateFormatAsString);
  }
  
  
}