/**
 * Copyright (c) 2011, The University of Southampton and the individual contributors.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 *   *  Redistributions of source code must retain the above copyright notice,
 *      this list of conditions and the following disclaimer.
 *
 *   *  Redistributions in binary form must reproduce the above copyright notice,
 *      this list of conditions and the following disclaimer in the documentation
 *      and/or other materials provided with the distribution.
 *
 *   *  Neither the name of the University of Southampton nor the names of its
 *      contributors may be used to endorse or promote products derived from this
 *      software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.openimaj.math.matrix;

import ch.akuhn.matrix.Matrix;
import ch.akuhn.matrix.Vector;

/**
 * @author Sina Samangooei (ss@ecs.soton.ac.uk)
 *
 */
public class DiagonalMatrix extends Matrix{

        private double[] vals;

        /**
         * New empty matrix with 0s down the diagonals
         * @param rowcol
         */
        public DiagonalMatrix(int rowcol) {
                this.vals = new double[rowcol];
        }
        
        /**
         * New empty matrix with val down the diagonals
         * @param rowcol
         * @param val 
         */
        public DiagonalMatrix(int rowcol, double val) {
                this.vals = new double[rowcol];
                for (int i = 0; i < vals.length; i++) {
                        vals[i] = val;
                }
        }

        /**
         * Diagonal version of the matrix handed
         * @param arr
         */
        public DiagonalMatrix(double[][] arr) {
                this(Math.min(arr.length, arr[0].length));
                for (int i = 0; i < vals.length; i++) {
                        this.vals[i] = arr[i][i];
                }
        }
        
        /**
         * @param mat
         */
        public DiagonalMatrix(Matrix mat) {
                this(Math.min(mat.rowCount(), mat.columnCount()));
                for (int i = 0; i < vals.length; i++) {
                        this.vals[i] = mat.get(i, i);
                }
        }
        
        @Override
        public Vector mult(Vector x) {
                double[] y = new double[this.columnCount()];
                for (int i = 0; i < y.length; i++) {
                        y[i] = this.vals[i] * x.get(i);
                }
                return Vector.wrap(y);
        }
        
        @Override
        public Vector transposeMultiply(Vector x) {
                return mult(x);
        }
        
        @Override
        public Vector transposeNonTransposeMultiply(Vector x) {
                double[] y = new double[this.columnCount()];
                for (int i = 0; i < y.length; i++) {
                        y[i] = this.vals[i] * this.vals[i] * x.get(i);
                }
                return Vector.wrap(y);
        }
        
        @Override
        public int columnCount() {
                return this.vals.length;
        }

        @Override
        public double get(int row, int column) {
                if(row!=column) return 0;
                else return vals[row];
        }

        @Override
        public double put(int row, int column, double value) {
                if(row == column)
                        return vals[row] = value;
                return 0;
        }

        @Override
        public int rowCount() {
                return vals.length;
        }

        @Override
        public int used() {
                return vals.length;
        }


        /**
         * @param rowcol
         * @return a matrix of ones in the diagonal
         */
        public static DiagonalMatrix zeros(int rowcol) {
                return fill(rowcol,0.);
        }

        /**
         * @param rowcol
         * @return a matrix of ones in the diagonal
         */
        public static DiagonalMatrix ones(int rowcol) {
                return fill(rowcol,1.);
        }

        /**
         * @param rowcol
         * @param d
         * @return a matrix with d in the diagonal
         */
        public static DiagonalMatrix fill(int rowcol, double d) {
                DiagonalMatrix ret = new DiagonalMatrix(rowcol);
                for (int i = 0; i < rowcol; i++) {
                        ret.vals[i] = d;
                }
                return ret;
        }

        /**
         * @return the diagonals
         */
        public double[] getVals() {
                return this.vals;
        }

        @Override
        public Matrix newInstance(int rows, int cols) {
                return new DiagonalMatrix(rows);
        }
}