// ==========================================================================
//                 SeqAn - The Library for Sequence Analysis
// ==========================================================================
// Copyright (c) 2006-2024, Knut Reinert, FU Berlin
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// ==========================================================================
// Author: Tobias Raussch <rausch@embl.de>
// ==========================================================================
// Implementation of Breadth-First-Search.
// ==========================================================================

#ifndef INCLUDE_SEQAN_GRAPH_ALGORITHMS_BREADTH_FIRST_SEARCH_H_
#define INCLUDE_SEQAN_GRAPH_ALGORITHMS_BREADTH_FIRST_SEARCH_H_

namespace seqan2 {

// ============================================================================
// Forwards
// ============================================================================

// ============================================================================
// Tags, Classes, Enums
// ============================================================================

// ============================================================================
// Metafunctions
// ============================================================================

// ============================================================================
// Functions
// ============================================================================

// ----------------------------------------------------------------------------
// Function breadthFirstSearch()
// ----------------------------------------------------------------------------

/*!
 * @fn breadthFirstSearch
 * @headerfile <seqan/graph_algorithms.h>
 * @brief Implements a breadth-first search on a graph.
 *
 * @signature void breadthFirstSearch(predecessor, distance, g, source);
 *
 * @param[out] predecessor A property map.  The predecessor map stores implicitly the breadth-first tree.
 * @param[out] distance    A property map.  The distance map indicates at what depth a vertex was discovered.
 * @param[in]  g           Undirected Graph, Directed Graph
 * @param[in]  source      A vertex descriptor.  The breadth-first search is started from this vertex.
 *                         Types: VertexDescriptor
 *
 * Breadth-first search computes the distance from source to all reachable vertices.  It also produces a breath-first
 * tree where each node has a predecessor/parent.
 *
 * @section Example
 *
 * @include demos/dox/graph_algorithms/breadth_first_search.cpp
 *
 * @include demos/dox/graph_algorithms/breadth_first_search.cpp.stdout
 *
 * @see depthFirstSearch
 */

template <typename TSpec, typename TVertexDescriptor, typename TPredecessorMap, typename TDistanceMap>
void breadthFirstSearch(TPredecessorMap & predecessor,
                        TDistanceMap & distance,
                        Graph<TSpec> const & g,
                        TVertexDescriptor const source)
{
    typedef Graph<TSpec> TGraph;
    typedef typename Iterator<TGraph, VertexIterator>::Type TVertexIterator;
    typedef typename Value<TPredecessorMap>::Type TPredVal;
    typedef typename Value<TDistanceMap>::Type TDistVal;

    // Initialization
    resizeVertexMap(predecessor, g);
    resizeVertexMap(distance, g);
    TPredVal nilPred = getNil<typename VertexDescriptor<TGraph>::Type>();
    TDistVal infDist = _getInfinityDistance(distance);

    String<bool> tokenMap;
    resizeVertexMap(tokenMap, g);
    TVertexIterator it(g);
    for(;!atEnd(it);goNext(it)) {
        assignProperty(tokenMap, getValue(it), false);
        assignProperty(distance, getValue(it), infDist);
        assignProperty(predecessor, getValue(it), nilPred);
    }
    assignProperty(tokenMap, source, true);
    assignProperty(distance, source, 0);
    assignProperty(predecessor, source, nilPred);
    std::deque<TVertexDescriptor> queue;
    queue.push_back(source);

    // Bfs
    while (!queue.empty()) {
        TVertexDescriptor u = queue.front();
        queue.pop_front();
        typedef typename Iterator<Graph<TSpec>, OutEdgeIterator>::Type TOutEdgeIterator;
        TOutEdgeIterator itout(g,u);
        for(;!atEnd(itout);goNext(itout)) {
            TVertexDescriptor v = targetVertex(itout);
            if (getProperty(tokenMap, v) == false) {
                assignProperty(tokenMap, v, true);
                assignProperty(distance, v, getProperty(distance,u) + 1);
                assignProperty(predecessor, v, u);
                queue.push_back(v);
            }
        }
    }
}

}  // namespace seqan2

#endif  // #ifndef INCLUDE_SEQAN_GRAPH_ALGORITHMS_BREADTH_FIRST_SEARCH_H_
