/*
 * Copyright (c) 2017. Developed by Hedgecode.
 *
 * 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 org.hedgecode.snooker.gson;

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

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.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;

/**
 * GSON Adapter for Date including a check for an empty string.
 *
 * @author Dmitry Samoshin aka gotty
 */
public final class EmptyDateTypeAdapter extends TypeAdapter<Date> {

    public static final TypeAdapterFactory FACTORY = new TypeAdapterFactory() {
        @SuppressWarnings("unchecked")
        @Override
        public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> typeToken) {
            return typeToken.getRawType() == Date.class
                    ? (TypeAdapter<T>) new EmptyDateTypeAdapter()
                    : null;
        }
    };

    private final DateFormat enUsFormat =
            DateFormat.getDateTimeInstance(
                    DateFormat.DEFAULT, DateFormat.DEFAULT, Locale.US
            );
    private final DateFormat localFormat =
            DateFormat.getDateTimeInstance(
                    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) {
        if (json.isEmpty())
            return null;
        try {
            return localFormat.parse(json);
        } catch (ParseException ignored) {
        }
        try {
            return enUsFormat.parse(json);
        } catch (ParseException ignored) {
        }
        try {
            return ISO8601Utils.parse(json, new ParsePosition(0));
        } catch (ParseException ignored) {
        }
        try {
            return new Date(Long.parseLong(json));
        } catch (Exception e) {
            throw new JsonSyntaxException(json, e);
        }
    }

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

}