package com.juick.database;

import org.apache.commons.io.IOUtils;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.support.TransactionTemplate;
import org.springframework.util.Assert;

import javax.annotation.PostConstruct;
import java.io.InputStream;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.List;
import java.util.function.Supplier;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import static org.springframework.transaction.TransactionDefinition.PROPAGATION_REQUIRED;

/**
 * Created by aalexeev on 12/13/16.
 */
public class MySqlUpdater {
    private static final Pattern UPDATE_PATTERN = Pattern.compile(
            "update\\s+(version|`version`)\\s+set\\s+(version|`version`)\\s+=\\s*(\\d+)",
            Pattern.CASE_INSENSITIVE);

    private final Logger logger = LoggerFactory.getLogger(getClass());

    private final JdbcTemplate jdbcTemplate;
    private final TransactionTemplate transactionTemplate;
    private final String updateSqlResource;


    public MySqlUpdater(JdbcTemplate jdbcTemplate, PlatformTransactionManager transactionManager, String updateSqlResource) {
        Assert.notNull(jdbcTemplate);
        Assert.notNull(transactionManager);
        Assert.notNull(updateSqlResource);

        this.jdbcTemplate = jdbcTemplate;
        this.transactionTemplate = new TransactionTemplate(transactionManager);
        this.updateSqlResource = updateSqlResource;
    }

    @PostConstruct
    public void init() {
        try (
                InputStream is = Thread.currentThread().getContextClassLoader().getResourceAsStream(updateSqlResource);
        ) {
            if (is != null) {
                String content = IOUtils.toString(is, StandardCharsets.UTF_8);
                if (StringUtils.isNotEmpty(content)) {
                    String[] sqlArray = content.split(";");
                    if (sqlArray.length > 0) {
                        List<String> sqlList = new ArrayList<>(sqlArray.length);
                        for (String sql : sqlArray)
                            if (!sql.isEmpty()) {
                                String sqlTrimmed = sql.trim();
                                if (!sqlTrimmed.isEmpty())
                                    sqlList.add(sqlTrimmed);
                            }
                        if (!sqlList.isEmpty())
                            processingSql(sqlList);
                    }
                }
            }
        } catch (Exception e) {
            logger.error("MySqlUpdater initialization exception", e);
        }
    }

    private void processingSql(final List<String> sqls) {
        long currentDbVersion = getSingleResult(this::getVersionRaw);
        long actualVersion;

        List<String> changesSql = new ArrayList<>();

        for (String sql : sqls) {
            changesSql.add(sql);

            Matcher m = UPDATE_PATTERN.matcher(sql);
            if (m.matches()) {
                actualVersion = Long.valueOf(m.group(3));

                if (actualVersion > currentDbVersion) {
                    updateInTransaction(changesSql);
                    currentDbVersion = actualVersion;
                }
                changesSql.clear();
            }
        }
    }

    private void updateInTransaction(final List<String> sqls) {
        transactionTemplate.setReadOnly(false);
        transactionTemplate.setPropagationBehavior(PROPAGATION_REQUIRED);
        transactionTemplate.execute(status -> {
            for (String sql : sqls)
                jdbcTemplate.execute(sql);
            return 0;
        });
    }

    private <T> T getSingleResult(Supplier<T> supplier) {
        transactionTemplate.setReadOnly(true);
        transactionTemplate.setPropagationBehavior(PROPAGATION_REQUIRED);

        return transactionTemplate.execute(status -> supplier.get());
    }

    private long getVersionRaw() {
        int cnt = jdbcTemplate.query(
                "SELECT count(*) FROM information_schema.tables WHERE table_schema = ? AND table_name = ?",
                rs -> {
                    int result = 0;
                    if (rs.next())
                        result = rs.getInt(1);
                    return result;
                },
                "juick", "version");

        long version = 0l;

        if (cnt == 1) {
            List<Long> list = jdbcTemplate.queryForList("select version from version", Long.class);
            if (!list.isEmpty())
                version = list.get(0);
        }

        return version;
    }
}