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/*
 Copyright 2013 Red Hat, Inc. and/or its affiliates.

 This file is part of lightblue.

 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with this program.  If not, see .
 */
package com.redhat.lightblue.assoc;

import java.io.Serializable;

/**
 * A simple connection matrix implementation
 */
public class ConnMx implements Serializable {

    private static final long serialVersionUID = 1l;

    private static final int[] I0 = new int[0];

    /**
     * Connection matrix. connMx[i][j] is true if there is an edge from i to j
     */
    private final boolean[][] connMx;

    public ConnMx(int nNodes) {
        connMx = new boolean[nNodes][];
        for (int i = 0; i < nNodes; i++) {
            connMx[i] = new boolean[nNodes];
        }
    }

    /**
     * Copy constructor.
     */
    public ConnMx(ConnMx source) {
        connMx = new boolean[source.connMx.length][];
        for (int i = 0; i < source.connMx.length; i++) {
            connMx[i] = source.connMx[i].clone();
        }
    }

    /**
     * Returns the sources of the given node
     */
    public int[] getSources(int node) {
        int[] sources = new int[connMx.length];
        int nSources = 0;
        for (int i = 0; i < connMx.length; i++) {
            if (connMx[i][node]) {
                sources[nSources++] = i;
            }
        }
        return trunc(sources, nSources);
    }

    /**
     * Returns the destinations of the given node
     */
    public int[] getDestinations(int node) {
        int[] dests = new int[connMx.length];
        int nDests = 0;
        for (int i = 0; i < connMx.length; i++) {
            if (connMx[node][i]) {
                dests[nDests++] = i;
            }
        }
        return trunc(dests, nDests);
    }

    /**
     * Returns an array of source nodes, nodes with no incoming edges.
     */
    public int[] getSources() {
        // Source nodes are those with no incoming edges.
        int[] sources = new int[connMx.length];
        int n = 0;
        for (int node = 0; node < connMx.length; node++) {
            boolean incomingExists = false;
            for (int from = 0; from < connMx.length; from++) {
                if (connMx[from][node]) {
                    incomingExists = true;
                    break;
                }
            }
            if (!incomingExists) {
                sources[n++] = node;
            }
        }
        return trunc(sources, n);
    }

    /**
     * Flips the direction of a node.
     */
    public void flip(int x, int y) {
        if (connMx[x][y]) {
            connMx[x][y] = false;
            connMx[y][x] = true;
        } else if (connMx[y][x]) {
            connMx[y][x] = false;
            connMx[x][y] = true;
        }
    }

    /**
     * Returns if there exists a directed edge between the nodes, directed from
     * from to to
     */
    public boolean isDirectedConnected(int from,
                                       int to) {
        return connMx[from][to];
    }

    /**
     * Returns if there exists an edge between the two nodes, pointing either
     * way
     */
    public boolean isUndirectedConnected(int from,
                                         int to) {
        return connMx[from][to] || connMx[to][from];
    }

    @Override
    public String toString() {
        StringBuilder bld = new StringBuilder(128);
        for (int i = 0; i < connMx.length; i++) {
            for (int j = 0; j < connMx.length; j++) {
                bld.append(connMx[i][j] ? '1' : '0').append(' ');
            }
            bld.append('\n');
        }
        return bld.toString();
    }

    /**
     * Adds an edge from node from to node to
     */
    public void connect(int from, int to) {
        connMx[from][to] = true;
    }

    private int[] trunc(int[] arr, int n) {
        if (n == arr.length) {
            return arr;
        } else if (n == 0) {
            return I0;
        } else {
            int[] ret = new int[n];
            System.arraycopy(arr, 0, ret, 0, n);
            return ret;
        }
    }

}