/*
 * Copyright 2012-2014 Red Hat, Inc.
 *
 * This file is part of Thermostat.
 *
 * Thermostat is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published
 * by the Free Software Foundation; either version 2, or (at your
 * option) any later version.
 *
 * Thermostat is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Thermostat; see the file COPYING.  If not see
 * <http://www.gnu.org/licenses/>.
 *
 * Linking this code with other modules is making a combined work
 * based on this code.  Thus, the terms and conditions of the GNU
 * General Public License cover the whole combination.
 *
 * As a special exception, the copyright holders of this code give
 * you permission to link this code with independent modules to
 * produce an executable, regardless of the license terms of these
 * independent modules, and to copy and distribute the resulting
 * executable under terms of your choice, provided that you also
 * meet, for each linked independent module, the terms and conditions
 * of the license of that module.  An independent module is a module
 * which is not derived from or based on this code.  If you modify
 * this code, you may extend this exception to your version of the
 * library, but you are not obligated to do so.  If you do not wish
 * to do so, delete this exception statement from your version.
 */

package com.redhat.thermostat.web.common.typeadapters;

import java.io.IOException;
import java.lang.reflect.Field;

import com.google.gson.Gson;
import com.google.gson.TypeAdapter;
import com.google.gson.stream.JsonReader;
import com.google.gson.stream.JsonToken;
import com.google.gson.stream.JsonWriter;
import com.redhat.thermostat.storage.core.PreparedParameter;
import com.redhat.thermostat.storage.core.PreparedParameters;

class PreparedParametersTypeAdapter extends TypeAdapter<PreparedParameters> {

    private final Gson gson;
    private final Field paramsField;
    
    PreparedParametersTypeAdapter(Gson gson) {
        this.gson = gson;
        this.paramsField = getParametersField();
    }
    
    @Override
    public void write(JsonWriter out, PreparedParameters value)
            throws IOException {
        // handle null
        if (value == null) {
            out.nullValue();
            return;
        }
        
        TypeAdapter<PreparedParameter[]> paramsTa = gson.getAdapter(PreparedParameter[].class);
        paramsTa.write(out, value.getParams());
    }

    @Override
    public PreparedParameters read(JsonReader in) throws IOException {
        // handle null
        if (in.peek() == JsonToken.NULL) {
            in.nextNull();
            return null;
        }
        
        TypeAdapter<PreparedParameter[]> paramsTa = gson.getAdapter(PreparedParameter[].class);
        PreparedParameters params = new PreparedParameters(0);
        PreparedParameter[] payload = paramsTa.read(in);
        setParamenters(params, payload);
        return params;
    }

    private void setParamenters(PreparedParameters params, PreparedParameter[] payload) {
        // Set parameters via reflection in order to not be forced to
        // introduce a public setter.
        try {
            paramsField.set(params, payload);
        } catch (SecurityException | IllegalArgumentException | IllegalAccessException e) {
            throw new IllegalStateException("Failed to set params field");
        }
    }
    
    private Field getParametersField() {
        try {
            Field field = PreparedParameters.class.getDeclaredField("params");
            field.setAccessible(true);
            return field;
        } catch (NoSuchFieldException | SecurityException e) {
            throw new IllegalStateException("params field not found");
        }
    }

}
