/*!
 *  Copyright (c) 2018 by Contributors
 * \file dgl/sampler.h
 * \brief DGL sampler header.
 */
#ifndef DGL_SAMPLER_H_
#define DGL_SAMPLER_H_

#include <vector>
#include <string>
#include <cstdlib>
#include <ctime>
#include "graph_interface.h"
#include "nodeflow.h"

namespace dgl {

class ImmutableGraph;

class SamplerOp {
 public:
  /*!
   * \brief Sample a graph from the seed vertices with neighbor sampling.
   * The neighbors are sampled with a uniform distribution.
   *
   * \param graphs A graph for sampling.
   * \param seeds the nodes where we should start to sample.
   * \param edge_type the type of edges we should sample neighbors.
   * \param num_hops the number of hops to sample neighbors.
   * \param expand_factor the max number of neighbors to sample.
   * \param add_self_loop whether to add self loop to the sampled subgraph
   * \param probability the transition probability (float/double).
   * \return a NodeFlow graph.
   */
  template<typename ValueType>
  static NodeFlow NeighborSample(const ImmutableGraph *graph,
                                 const std::vector<dgl_id_t>& seeds,
                                 const std::string &edge_type,
                                 int num_hops, int expand_factor,
                                 const bool add_self_loop,
                                 const ValueType *probability);

  /*!
   * \brief Sample a graph from the seed vertices with layer sampling.
   * The layers are sampled with a uniform distribution.
   *
   * \param graphs A graph for sampling.
   * \param seeds the nodes where we should start to sample.
   * \param edge_type the type of edges we should sample neighbors.
   * \param layer_sizes The size of layers.
   * \return a NodeFlow graph.
   */
  static NodeFlow LayerUniformSample(const ImmutableGraph *graph,
                                     const std::vector<dgl_id_t>& seeds,
                                     const std::string &neigh_type,
                                     IdArray layer_sizes);
};

}  // namespace dgl

#endif  // DGL_SAMPLER_H_
