import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

/**
 * 只读探针：把一个库的结构摘要打到标准输出，用于合并前比对目标库与本机开发库。
 *
 * <p>不含任何写入语句。用法：java SchemaDigest &lt;jdbc-url&gt;
 */
public class SchemaDigest {

    public static void main(String[] args) throws Exception {
        String url = args[0];
        try (Connection connection = DriverManager.getConnection(url, "root", "123456")) {
            String database = connection.getCatalog();
            System.out.println("== SERVER ==");
            try (Statement statement = connection.createStatement();
                 ResultSet rows = statement.executeQuery("select version()")) {
                rows.next();
                System.out.println("  " + rows.getString(1));
            }
            System.out.println("== DATABASE " + database + " ==");

            System.out.println("== FLYWAY ==");
            try (Statement statement = connection.createStatement();
                 ResultSet rows = statement.executeQuery(
                         "select version, description, success from flyway_schema_history order by installed_rank")) {
                while (rows.next()) {
                    System.out.println("  " + rows.getString(1) + " | " + rows.getString(2)
                            + " | success=" + rows.getBoolean(3));
                }
            } catch (SQLException exception) {
                System.out.println("  (没有 flyway_schema_history：" + exception.getMessage() + ")");
            }

            System.out.println("== TABLES ==");
            try (PreparedStatement statement = connection.prepareStatement("""
                    select table_name, table_rows, table_comment from information_schema.tables
                    where table_schema = ? order by table_name
                    """)) {
                statement.setString(1, database);
                try (ResultSet rows = statement.executeQuery()) {
                    while (rows.next()) {
                        System.out.println("  " + rows.getString(1) + " rows~" + rows.getLong(2)
                                + " [" + rows.getString(3) + "]");
                    }
                }
            }

            System.out.println("== COLUMNS ==");
            try (PreparedStatement statement = connection.prepareStatement("""
                    select table_name, column_name, column_type, is_nullable, coalesce(column_default, '')
                    from information_schema.columns where table_schema = ?
                    order by table_name, ordinal_position
                    """)) {
                statement.setString(1, database);
                try (ResultSet rows = statement.executeQuery()) {
                    while (rows.next()) {
                        System.out.println("  " + rows.getString(1) + "." + rows.getString(2)
                                + " " + rows.getString(3) + " null=" + rows.getString(4)
                                + " default=" + rows.getString(5));
                    }
                }
            }

            System.out.println("== INDEXES ==");
            try (PreparedStatement statement = connection.prepareStatement("""
                    select table_name, index_name, non_unique, seq_in_index, column_name
                    from information_schema.statistics where table_schema = ?
                    order by table_name, index_name, seq_in_index
                    """)) {
                statement.setString(1, database);
                try (ResultSet rows = statement.executeQuery()) {
                    while (rows.next()) {
                        System.out.println("  " + rows.getString(1) + " " + rows.getString(2)
                                + " unique=" + (rows.getInt(3) == 0) + " seq=" + rows.getInt(4)
                                + " col=" + rows.getString(5));
                    }
                }
            }
        }
    }
}