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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 org.apache.mahout.math;

import com.google.common.base.Preconditions;
import org.apache.hadoop.io.Writable;
import org.apache.mahout.math.list.IntArrayList;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

public class MatrixWritable implements Writable {

  private static final int FLAG_DENSE = 0x01;
  private static final int FLAG_SEQUENTIAL = 0x02;
  private static final int FLAG_LABELS = 0x04;
  private static final int FLAG_SPARSE_ROW = 0x08;
  private static final int NUM_FLAGS = 4;

  private Matrix matrix;

  public MatrixWritable() {}

  public MatrixWritable(Matrix m) {
    this.matrix = m;
  }

  public Matrix get() {
    return matrix;
  }

  public void set(Matrix matrix) {
    this.matrix = matrix;
  }

  @Override
  public void write(DataOutput out) throws IOException {
    writeMatrix(out, matrix);
  }

  @Override
  public void readFields(DataInput in) throws IOException {
    matrix = readMatrix(in);
  }

  public static void readLabels(DataInput in,
                                Map columnLabelBindings,
                                Map rowLabelBindings) throws IOException {
    int colSize = in.readInt();
    if (colSize > 0) {
      for (int i = 0; i < colSize; i++) {
        columnLabelBindings.put(in.readUTF(), in.readInt());
      }
    }
    int rowSize = in.readInt();
    if (rowSize > 0) {
      for (int i = 0; i < rowSize; i++) {
        rowLabelBindings.put(in.readUTF(), in.readInt());
      }
    }
  }

  public static void writeLabelBindings(DataOutput out,
                                        Map columnLabelBindings,
                                        Map rowLabelBindings) throws IOException {
    if (columnLabelBindings == null) {
      out.writeInt(0);
    } else {
      out.writeInt(columnLabelBindings.size());
      for (Map.Entry stringIntegerEntry : columnLabelBindings.entrySet()) {
        out.writeUTF(stringIntegerEntry.getKey());
        out.writeInt(stringIntegerEntry.getValue());
      }
    }
    if (rowLabelBindings == null) {
      out.writeInt(0);
    } else {
      out.writeInt(rowLabelBindings.size());
      for (Map.Entry stringIntegerEntry : rowLabelBindings.entrySet()) {
        out.writeUTF(stringIntegerEntry.getKey());
        out.writeInt(stringIntegerEntry.getValue());
      }
    }
  }

  /** Reads a typed Matrix instance from the input stream */
  public static Matrix readMatrix(DataInput in) throws IOException {
    int flags = in.readInt();
    Preconditions.checkArgument(flags >> NUM_FLAGS == 0, "Unknown flags set: %d", Integer.toString(flags, 2));
    boolean dense = (flags & FLAG_DENSE) != 0;
    boolean sequential = (flags & FLAG_SEQUENTIAL) != 0;
    boolean hasLabels = (flags & FLAG_LABELS) != 0;
    boolean isSparseRowMatrix = (flags & FLAG_SPARSE_ROW) != 0;

    int rows = in.readInt();
    int columns = in.readInt();

    byte vectorFlags = in.readByte();

    Matrix matrix;

    if (dense) {
      matrix = new DenseMatrix(rows, columns);
      for (int row = 0; row < rows; row++) {
        matrix.assignRow(row, VectorWritable.readVector(in, vectorFlags, columns));
      }
    } else if (isSparseRowMatrix) {
      Vector[] rowVectors = new Vector[rows];
      for (int row = 0; row < rows; row++) {
        rowVectors[row] = VectorWritable.readVector(in, vectorFlags, columns);
      }
      matrix = new SparseRowMatrix(rows, columns, rowVectors, true, !sequential);
    } else {
      matrix = new SparseMatrix(rows, columns);
      int numNonZeroRows = in.readInt();
      int rowsRead = 0;
      while (rowsRead++ < numNonZeroRows) {
        int rowIndex = in.readInt();
        matrix.assignRow(rowIndex, VectorWritable.readVector(in, vectorFlags, columns));
      }
    }

    if (hasLabels) {
      Map columnLabelBindings = new HashMap<>();
      Map rowLabelBindings = new HashMap<>();
      readLabels(in, columnLabelBindings, rowLabelBindings);
      if (!columnLabelBindings.isEmpty()) {
        matrix.setColumnLabelBindings(columnLabelBindings);
      }
      if (!rowLabelBindings.isEmpty()) {
        matrix.setRowLabelBindings(rowLabelBindings);
      }
    }

    return matrix;
  }

  /** Writes a typed Matrix instance to the output stream */
  public static void writeMatrix(final DataOutput out, Matrix matrix) throws IOException {
    int flags = 0;
    Vector row = matrix.viewRow(0);
    boolean isDense = row.isDense();
    if (isDense) {
      flags |= FLAG_DENSE;
    }
    if (row.isSequentialAccess()) {
      flags |= FLAG_SEQUENTIAL;
    }
    if (matrix.getRowLabelBindings() != null || matrix.getColumnLabelBindings() != null) {
      flags |= FLAG_LABELS;
    }
    boolean isSparseRowMatrix = matrix instanceof SparseRowMatrix;
    if (isSparseRowMatrix) {
      flags |= FLAG_SPARSE_ROW;
    }

    out.writeInt(flags);
    out.writeInt(matrix.rowSize());
    out.writeInt(matrix.columnSize());

    // We only use vectors of the same type, so we write out the type information only once!
    byte vectorFlags = VectorWritable.flags(matrix.viewRow(0), false);
    out.writeByte(vectorFlags);

    if (isDense || isSparseRowMatrix) {
      for (int i = 0; i < matrix.rowSize(); i++) {
        VectorWritable.writeVectorContents(out, matrix.viewRow(i), vectorFlags);
      }
    } else {
      IntArrayList rowIndices = ((SparseMatrix) matrix).nonZeroRowIndices();
      int numNonZeroRows = rowIndices.size();
      out.writeInt(numNonZeroRows);
      for (int i = 0; i < numNonZeroRows; i++) {
        int rowIndex = rowIndices.getQuick(i);
        out.writeInt(rowIndex);
        VectorWritable.writeVectorContents(out, matrix.viewRow(rowIndex), vectorFlags);
      }
    }

    if ((flags & FLAG_LABELS) != 0) {
      writeLabelBindings(out, matrix.getColumnLabelBindings(), matrix.getRowLabelBindings());
    }
  }
}