/*
 *      Copyright (C) 2012-2015 DataStax 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.datastax.driver.examples.json;

import com.datastax.driver.core.*;
import com.datastax.driver.extras.codecs.json.JacksonJsonCodec;
import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;

import static com.datastax.driver.core.querybuilder.QueryBuilder.*;

/**
 * Illustrates how to map an entire table row to a Java object using
 * the <a href="http://wiki.fasterxml.com/JacksonHome">Jackson</a> library,
 * and leveraging the {@code SELECT JSON} and {@code INSERT JSON} syntaxes
 * introduced in Cassandra 2.2.
 * <p/>
 * This example makes usage of a custom {@link TypeCodec codec},
 * {@link JacksonJsonCodec}, which is declared in the driver-extras module.
 * If you plan to follow this example, make sure to include the following
 * Maven dependencies in your project:
 * <pre>{@code
 * <dependency>
 *     <groupId>com.datastax.cassandra</groupId>
 *     <artifactId>cassandra-driver-extras</artifactId>
 *     <version>${driver.version}</version>
 * </dependency>
 *
 * <dependency>
 *     <groupId>com.fasterxml.jackson.core</groupId>
 *     <artifactId>jackson-databind</artifactId>
 *     <version>${jackson.version}</version>
 * </dependency>
 * }</pre>
 * This example also uses the {@link com.datastax.driver.core.querybuilder.QueryBuilder QueryBuilder};
 * for examples using the "core" API, see {@link PlainTextJson} (they are easily translatable to the
 * queries in this class).
 * <p/>
 * Preconditions:
 * - a Cassandra 2.2+ cluster is running and accessible through the contacts points identified by CONTACT_POINTS and PORT;
 * <p/>
 * Side effects:
 * - creates a new keyspace "examples" in the cluster. If a keyspace with this name already exists, it will be reused;
 * - creates a table "examples.json_jackson_row". If it already exists, it will be reused;
 * - inserts data in the table.
 *
 * @see <a href="http://www.datastax.com/dev/blog/whats-new-in-cassandra-2-2-json-support">What’s New in Cassandra 2.2: JSON Support</a>
 */
public class JacksonJsonRow {

    static String[] CONTACT_POINTS = {"127.0.0.1"};
    static int PORT = 9042;

    public static void main(String[] args) {
        Cluster cluster = null;
        try {

            // A codec to convert JSON payloads into User instances;
            // this codec is declared in the driver-extras module
            TypeCodec<User> userCodec = new JacksonJsonCodec<User>(User.class);

            cluster = Cluster.builder()
                    .addContactPoints(CONTACT_POINTS).withPort(PORT)
                    .withCodecRegistry(new CodecRegistry().register(userCodec))
                    .build();

            Session session = cluster.connect();

            createSchema(session);
            insertJsonRow(session);
            selectJsonRow(session);

        } finally {
            if (cluster != null) cluster.close();
        }
    }

    private static void createSchema(Session session) {
        session.execute("CREATE KEYSPACE IF NOT EXISTS examples " +
                "WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 1}");
        session.execute("CREATE TABLE IF NOT EXISTS examples.json_jackson_row(" +
                "id int PRIMARY KEY, name text, age int)");
    }

    // Mapping a User instance to a table row using INSERT JSON
    private static void insertJsonRow(Session session) {
        // Build and execute a simple statement
        Statement stmt = insertInto("examples", "json_jackson_row")
                .json(new User(1, "alice", 30));
        session.execute(stmt);

        // The JSON object can be a bound value if the statement is prepared
        // (we use a local variable here for the sake of example, but in a real application you would cache and reuse
        // the prepared statement)
        PreparedStatement pst = session.prepare(
                insertInto("examples", "json_jackson_row").json(bindMarker("user")));
        session.execute(pst.bind()
                .set("user", new User(2, "bob", 35), User.class));
    }

    // Retrieving User instances from table rows using SELECT JSON
    private static void selectJsonRow(Session session) {

        // Reading the whole row as a JSON object
        Statement stmt = select().json()
                .from("examples", "json_jackson_row")
                .where(in("id", 1, 2));

        ResultSet rows = session.execute(stmt);

        for (Row row : rows) {
            // SELECT JSON returns only one column for each row, of type VARCHAR,
            // containing the row as a JSON payload
            User user = row.get(0, User.class);
            System.out.printf("Retrieved user: %s%n", user);
        }
    }

    @SuppressWarnings("unused")
    public static class User {

        private final int id;

        private final String name;

        private final int age;

        @JsonCreator
        public User(@JsonProperty("id") int id, @JsonProperty("name") String name, @JsonProperty("age") int age) {
            this.id = id;
            this.name = name;
            this.age = age;
        }

        public int getId() {
            return id;
        }

        public String getName() {
            return name;
        }

        public int getAge() {
            return age;
        }

        @Override
        public String toString() {
            return String.format("%s (id %d, age %d)", name, id, age);
        }
    }
}