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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 io.delta.flink.internal.table;

import java.util.List;
import java.util.Map.Entry;

import io.delta.flink.internal.table.DeltaFlinkJobSpecificOptions.QueryMode;
import io.delta.flink.source.DeltaSource;
import io.delta.flink.source.internal.builder.DeltaSourceBuilderBase;
import org.apache.flink.core.fs.Path;
import org.apache.flink.table.connector.ChangelogMode;
import org.apache.flink.table.connector.source.DynamicTableSource;
import org.apache.flink.table.connector.source.ScanTableSource;
import org.apache.flink.table.connector.source.SourceProvider;
import org.apache.flink.table.data.RowData;
import org.apache.hadoop.conf.Configuration;

/**
 * Implementation of {@link ScanTableSource} interface for Table/SQL support for Delta Source
 * connector.
 */
public class DeltaDynamicTableSource implements ScanTableSource {

    private final Configuration hadoopConf;

    private final QueryOptions queryOptions;

    private final List columns;

    /**
     * Constructor for creating Source of Flink dynamic table to Delta table.
     *
     * @param hadoopConf   Hadoop's configuration.
     * @param queryOptions Query options returned by Catalog and resolved query plan.
     * @param columns      Table's columns to extract from Delta table.
     */
    public DeltaDynamicTableSource(
            Configuration hadoopConf,
            QueryOptions queryOptions,
            List columns) {

        this.hadoopConf = hadoopConf;
        this.queryOptions = queryOptions;
        this.columns = columns;
    }

    @Override
    public ChangelogMode getChangelogMode() {
        return ChangelogMode.insertOnly();
    }

    @Override
    public ScanRuntimeProvider getScanRuntimeProvider(ScanContext runtimeProviderContext) {

        QueryMode mode = queryOptions.getQueryMode();
        String tablePath = queryOptions.getDeltaTablePath();

        DeltaSourceBuilderBase sourceBuilder;

        switch (mode) {
            case BATCH:
                sourceBuilder = DeltaSource.forBoundedRowData(new Path(tablePath), hadoopConf);
                break;
            case STREAMING:
                sourceBuilder = DeltaSource.forContinuousRowData(new Path(tablePath), hadoopConf);
                break;
            default:
                throw new RuntimeException(
                    String.format(
                        "Unrecognized table mode %s used for Delta table %s",
                        mode, tablePath
                    ));
        }

        // Since currently DeltaDynamicTableSource does not implement SupportsProjectionPushDown,
        // one may say that passing columns (which currently represents full table schema)
        // to the DeltaSourceBuilder seems useless since DeltaSourceBuilder will discover full table
        // schema if no user columns are specified. However, with this we can play extra safe and
        // ensure that source will use exact the same schema that is specified in Delta Catalog
        // which should match exactly _delta_log schema for this table. With this, TableAPI is
        // fully relying on Delta catalog as the source of truth.
        sourceBuilder.columnNames(columns);

        for (Entry queryOption : queryOptions.getJobSpecificOptions().entrySet()) {
            sourceBuilder.option(queryOption.getKey(), queryOption.getValue());
        }

        return SourceProvider.of(sourceBuilder.build());
    }

    @Override
    public DynamicTableSource copy() {
        return new DeltaDynamicTableSource(this.hadoopConf, this.queryOptions, this.columns);
    }

    @Override
    public String asSummaryString() {
        return "DeltaSource";
    }

}