/*-
 * #%L
 * HAPI FHIR Server - SQL Migration
 * %%
 * Copyright (C) 2014 - 2023 Smile CDR, 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.
 * #L%
 */
package ca.uhn.fhir.jpa.migrate.taskdef;

import org.apache.commons.lang3.builder.EqualsBuilder;
import org.apache.commons.lang3.builder.HashCodeBuilder;
import org.apache.commons.lang3.tuple.Pair;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.jdbc.core.JdbcTemplate;

import java.sql.SQLException;

/**
 * Fix for bad version of {@link ForceIdMigrationCopyTask}
 * The earlier migration had used at cast to char instead of varchar, which is space-padded on Oracle.
 * This migration includes the copy action, but also adds a trim() call to fixup the bad server-assigned ids.
 */
public class ForceIdMigrationFixTask extends BaseTask {
        private static final Logger ourLog = LoggerFactory.getLogger(ForceIdMigrationFixTask.class);

        public ForceIdMigrationFixTask(String theProductVersion, String theSchemaVersion) {
                super(theProductVersion, theSchemaVersion);
        }

        @Override
        public void validate() {
                // no-op
        }

        @Override
        protected void doExecute() throws SQLException {
                logInfo(ourLog, "Starting: migrate fhir_id from hfj_forced_id to hfj_resource.fhir_id");

                JdbcTemplate jdbcTemplate = newJdbcTemplate();

                Pair<Long, Long> range = jdbcTemplate.queryForObject(
                                "select min(RES_ID), max(RES_ID) from HFJ_RESOURCE",
                                (rs, rowNum) -> Pair.of(rs.getLong(1), rs.getLong(2)));

                if (range == null || range.getLeft() == null) {
                        logInfo(ourLog, "HFJ_RESOURCE is empty.  No work to do.");
                        return;
                }

                // run update in batches.
                int rowsPerBlock = 50; // hfj_resource has roughly 50 rows per 8k block.
                int batchSize = rowsPerBlock * 2000; // a few thousand IOPS gives a batch size around a second.
                ourLog.info(
                                "About to migrate ids from {} to {} in batches of size {}",
                                range.getLeft(),
                                range.getRight(),
                                batchSize);
                for (long batchStart = range.getLeft(); batchStart <= range.getRight(); batchStart = batchStart + batchSize) {
                        long batchEnd = batchStart + batchSize;
                        ourLog.info("Migrating client-assigned ids for pids: {}-{}", batchStart, batchEnd);

                        /*
                        We have several cases.  Two require no action:
                        1. client-assigned id, with correct value in fhir_id and row in hfj_forced_id
                        2. server-assigned id, with correct value in fhir_id, no row in hfj_forced_id
                        And three require action:
                        3. client-assigned id, no value in fhir_id, but row in hfj_forced_id
                        4. server-assigned id, no value in fhir_id, and row in hfj_forced_id
                        5. bad migration - server-assigned id, with wrong space-padded value in fhir_id, no row in hfj_forced_id
                         */

                        executeSql(
                                        "hfj_resource",
                                        "update hfj_resource " +
                                                        // coalesce is varargs and chooses the first non-null value, like ||
                                                        " set fhir_id = coalesce( "
                                                        +
                                                        // case 5.
                                                        " trim(fhir_id), "
                                                        +
                                                        // case 3
                                                        " (select f.forced_id from hfj_forced_id f where f.resource_pid = res_id), "
                                                        +
                                                        // case 4 - use pid as fhir_id
                                                        "   cast(res_id as varchar(64)) "
                                                        + "  ) "
                                                        +
                                                        // avoid useless updates on engines that don't check
                                                        // skip case 1, 2.  Only check 3,4,5
                                                        " where (fhir_id is null or fhir_id <> trim(fhir_id)) "
                                                        +
                                                        // chunk range.
                                                        " and res_id >= ? and res_id < ?",
                                        batchStart,
                                        batchEnd);
                }
        }

        @Override
        protected void generateHashCode(HashCodeBuilder theBuilder) {
                // no-op - this is a singleton.
        }

        @Override
        protected void generateEquals(EqualsBuilder theBuilder, BaseTask theOtherObject) {
                // no-op - this is a singleton.
        }
}