/*
 * 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 org.apache.hudi.table.format.cow;

import org.apache.flink.formats.parquet.vector.reader.ColumnReader;
import org.apache.flink.table.data.ColumnarRowData;
import org.apache.flink.table.data.vector.ColumnVector;
import org.apache.flink.table.data.vector.VectorizedColumnBatch;
import org.apache.flink.table.data.vector.writable.WritableColumnVector;
import org.apache.flink.table.types.logical.LogicalType;
import org.apache.flink.table.types.logical.LogicalTypeRoot;
import org.apache.flink.util.FlinkRuntimeException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.parquet.column.ColumnDescriptor;
import org.apache.parquet.column.page.PageReadStore;
import org.apache.parquet.filter2.compat.FilterCompat;
import org.apache.parquet.hadoop.ParquetFileReader;
import org.apache.parquet.hadoop.metadata.BlockMetaData;
import org.apache.parquet.hadoop.metadata.ParquetMetadata;
import org.apache.parquet.schema.GroupType;
import org.apache.parquet.schema.MessageType;
import org.apache.parquet.schema.Type;
import org.apache.parquet.schema.Types;

import java.io.Closeable;
import java.io.IOException;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.stream.IntStream;

import static org.apache.hudi.table.format.cow.ParquetSplitReaderUtil.createColumnReader;
import static org.apache.hudi.table.format.cow.ParquetSplitReaderUtil.createWritableColumnVector;
import static org.apache.parquet.filter2.compat.RowGroupFilter.filterRowGroups;
import static org.apache.parquet.format.converter.ParquetMetadataConverter.range;
import static org.apache.parquet.hadoop.ParquetFileReader.readFooter;
import static org.apache.parquet.hadoop.ParquetInputFormat.getFilter;

/**
 * This reader is used to read a {@link VectorizedColumnBatch} from input split.
 *
 * <p>Note: Reference Flink release 1.11.2
 * {@code org.apache.flink.formats.parquet.vector.ParquetColumnarRowSplitReader}
 * because it is package scope.
 */
public class ParquetColumnarRowSplitReader implements Closeable {

  private final boolean utcTimestamp;

  private final MessageType fileSchema;

  private final LogicalType[] requestedTypes;

  private final MessageType requestedSchema;

  /**
   * The total number of rows this RecordReader will eventually read. The sum of the rows of all
   * the row groups.
   */
  private final long totalRowCount;

  private final WritableColumnVector[] writableVectors;

  private final VectorizedColumnBatch columnarBatch;

  private final ColumnarRowData row;

  private final int batchSize;

  private ParquetFileReader reader;

  /**
   * For each request column, the reader to read this column. This is NULL if this column is
   * missing from the file, in which case we populate the attribute with NULL.
   */
  private ColumnReader[] columnReaders;

  /**
   * The number of rows that have been returned.
   */
  private long rowsReturned;

  /**
   * The number of rows that have been reading, including the current in flight row group.
   */
  private long totalCountLoadedSoFar;

  // the index of the next row to return
  private int nextRow;

  // the number of rows in the current batch
  private int rowsInBatch;

  public ParquetColumnarRowSplitReader(
      boolean utcTimestamp,
      boolean caseSensitive,
      Configuration conf,
      LogicalType[] selectedTypes,
      String[] selectedFieldNames,
      ColumnBatchGenerator generator,
      int batchSize,
      Path path,
      long splitStart,
      long splitLength) throws IOException {
    this.utcTimestamp = utcTimestamp;
    this.batchSize = batchSize;
    // then we need to apply the predicate push down filter
    ParquetMetadata footer = readFooter(conf, path, range(splitStart, splitStart + splitLength));
    MessageType fileSchema = footer.getFileMetaData().getSchema();
    FilterCompat.Filter filter = getFilter(conf);
    List<BlockMetaData> blocks = filterRowGroups(filter, footer.getBlocks(), fileSchema);

    this.fileSchema = footer.getFileMetaData().getSchema();

    Type[] types = clipParquetSchema(fileSchema, selectedFieldNames, caseSensitive);
    int[] requestedIndices = IntStream.range(0, types.length).filter(i -> types[i] != null).toArray();
    Type[] readTypes = Arrays.stream(requestedIndices).mapToObj(i -> types[i]).toArray(Type[]::new);

    this.requestedTypes = Arrays.stream(requestedIndices).mapToObj(i -> selectedTypes[i]).toArray(LogicalType[]::new);
    this.requestedSchema = Types.buildMessage().addFields(readTypes).named("flink-parquet");
    this.reader = new ParquetFileReader(
        conf, footer.getFileMetaData(), path, blocks, requestedSchema.getColumns());

    long totalRowCount = 0;
    for (BlockMetaData block : blocks) {
      totalRowCount += block.getRowCount();
    }
    this.totalRowCount = totalRowCount;
    this.nextRow = 0;
    this.rowsInBatch = 0;
    this.rowsReturned = 0;

    checkSchema();

    this.writableVectors = createWritableVectors();
    ColumnVector[] columnVectors = patchedVector(selectedFieldNames.length, createReadableVectors(), requestedIndices);
    this.columnarBatch = generator.generate(columnVectors);
    this.row = new ColumnarRowData(columnarBatch);
  }

  /**
   * Patches the given vectors with nulls.
   * The vector position that is not requested (or read from file) is patched as null.
   *
   * @param fields  The total selected fields number
   * @param vectors The readable vectors
   * @param indices The requested indices from the selected fields
   */
  private static ColumnVector[] patchedVector(int fields, ColumnVector[] vectors, int[] indices) {
    ColumnVector[] patched = new ColumnVector[fields];
    for (int i = 0; i < indices.length; i++) {
      patched[indices[i]] = vectors[i];
    }
    return patched;
  }

  /**
   * Clips `parquetSchema` according to `fieldNames`.
   */
  private static Type[] clipParquetSchema(
      GroupType parquetSchema, String[] fieldNames, boolean caseSensitive) {
    Type[] types = new Type[fieldNames.length];
    if (caseSensitive) {
      for (int i = 0; i < fieldNames.length; ++i) {
        String fieldName = fieldNames[i];
        types[i] = parquetSchema.containsField(fieldName) ? parquetSchema.getType(fieldName) : null;
      }
    } else {
      Map<String, Type> caseInsensitiveFieldMap = new HashMap<>();
      for (Type type : parquetSchema.getFields()) {
        caseInsensitiveFieldMap.compute(type.getName().toLowerCase(Locale.ROOT),
            (key, previousType) -> {
              if (previousType != null) {
                throw new FlinkRuntimeException(
                    "Parquet with case insensitive mode should have no duplicate key: " + key);
              }
              return type;
            });
      }
      for (int i = 0; i < fieldNames.length; ++i) {
        Type type = caseInsensitiveFieldMap.get(fieldNames[i].toLowerCase(Locale.ROOT));
        // TODO clip for array,map,row types.
        types[i] = type;
      }
    }

    return types;
  }

  private WritableColumnVector[] createWritableVectors() {
    WritableColumnVector[] columns = new WritableColumnVector[requestedTypes.length];
    for (int i = 0; i < requestedTypes.length; i++) {
      columns[i] = createWritableColumnVector(
          batchSize,
          requestedTypes[i],
          requestedSchema.getColumns().get(i).getPrimitiveType());
    }
    return columns;
  }

  /**
   * Create readable vectors from writable vectors.
   * Especially for decimal, see {@link org.apache.flink.formats.parquet.vector.ParquetDecimalVector}.
   */
  private ColumnVector[] createReadableVectors() {
    ColumnVector[] vectors = new ColumnVector[writableVectors.length];
    for (int i = 0; i < writableVectors.length; i++) {
      vectors[i] = requestedTypes[i].getTypeRoot() == LogicalTypeRoot.DECIMAL
          ? new ParquetDecimalVector(writableVectors[i])
          : writableVectors[i];
    }
    return vectors;
  }

  private void checkSchema() throws IOException, UnsupportedOperationException {
    /*
     * Check that the requested schema is supported.
     */
    for (int i = 0; i < requestedSchema.getFieldCount(); ++i) {
      Type t = requestedSchema.getFields().get(i);
      if (!t.isPrimitive() || t.isRepetition(Type.Repetition.REPEATED)) {
        throw new UnsupportedOperationException("Complex types not supported.");
      }

      String[] colPath = requestedSchema.getPaths().get(i);
      if (fileSchema.containsPath(colPath)) {
        ColumnDescriptor fd = fileSchema.getColumnDescription(colPath);
        if (!fd.equals(requestedSchema.getColumns().get(i))) {
          throw new UnsupportedOperationException("Schema evolution not supported.");
        }
      } else {
        if (requestedSchema.getColumns().get(i).getMaxDefinitionLevel() == 0) {
          // Column is missing in data but the required data is non-nullable. This file is invalid.
          throw new IOException("Required column is missing in data file. Col: " + Arrays.toString(colPath));
        }
      }
    }
  }

  /**
   * Method used to check if the end of the input is reached.
   *
   * @return True if the end is reached, otherwise false.
   * @throws IOException Thrown, if an I/O error occurred.
   */
  public boolean reachedEnd() throws IOException {
    return !ensureBatch();
  }

  public ColumnarRowData nextRecord() {
    // return the next row
    row.setRowId(this.nextRow++);
    return row;
  }

  /**
   * Checks if there is at least one row left in the batch to return. If no more row are
   * available, it reads another batch of rows.
   *
   * @return Returns true if there is one more row to return, false otherwise.
   * @throws IOException throw if an exception happens while reading a batch.
   */
  private boolean ensureBatch() throws IOException {
    if (nextRow >= rowsInBatch) {
      // No more rows available in the Rows array.
      nextRow = 0;
      // Try to read the next batch if rows from the file.
      return nextBatch();
    }
    // there is at least one Row left in the Rows array.
    return true;
  }

  /**
   * Advances to the next batch of rows. Returns false if there are no more.
   */
  private boolean nextBatch() throws IOException {
    for (WritableColumnVector v : writableVectors) {
      v.reset();
    }
    columnarBatch.setNumRows(0);
    if (rowsReturned >= totalRowCount) {
      return false;
    }
    if (rowsReturned == totalCountLoadedSoFar) {
      readNextRowGroup();
    }

    int num = (int) Math.min(batchSize, totalCountLoadedSoFar - rowsReturned);
    for (int i = 0; i < columnReaders.length; ++i) {
      //noinspection unchecked
      columnReaders[i].readToVector(num, writableVectors[i]);
    }
    rowsReturned += num;
    columnarBatch.setNumRows(num);
    rowsInBatch = num;
    return true;
  }

  private void readNextRowGroup() throws IOException {
    PageReadStore pages = reader.readNextRowGroup();
    if (pages == null) {
      throw new IOException("expecting more rows but reached last block. Read "
          + rowsReturned + " out of " + totalRowCount);
    }
    List<ColumnDescriptor> columns = requestedSchema.getColumns();
    columnReaders = new ColumnReader[columns.size()];
    for (int i = 0; i < columns.size(); ++i) {
      columnReaders[i] = createColumnReader(
          utcTimestamp,
          requestedTypes[i],
          columns.get(i),
          pages.getPageReader(columns.get(i)));
    }
    totalCountLoadedSoFar += pages.getRowCount();
  }

  /**
   * Seek to a particular row number.
   */
  public void seekToRow(long rowCount) throws IOException {
    if (totalCountLoadedSoFar != 0) {
      throw new UnsupportedOperationException("Only support seek at first.");
    }

    List<BlockMetaData> blockMetaData = reader.getRowGroups();

    for (BlockMetaData metaData : blockMetaData) {
      if (metaData.getRowCount() > rowCount) {
        break;
      } else {
        reader.skipNextRowGroup();
        rowsReturned += metaData.getRowCount();
        totalCountLoadedSoFar += metaData.getRowCount();
        rowsInBatch = (int) metaData.getRowCount();
        nextRow = (int) metaData.getRowCount();
        rowCount -= metaData.getRowCount();
      }
    }
    for (int i = 0; i < rowCount; i++) {
      boolean end = reachedEnd();
      if (end) {
        throw new RuntimeException("Seek to many rows.");
      }
      nextRecord();
    }
  }

  @Override
  public void close() throws IOException {
    if (reader != null) {
      reader.close();
      reader = null;
    }
  }

  /**
   * Interface to gen {@link VectorizedColumnBatch}.
   */
  public interface ColumnBatchGenerator {
    VectorizedColumnBatch generate(ColumnVector[] readVectors);
  }
}

