/**
 *  Copyright (c) 2017 by Contributors
 * @file random.cc
 * @brief Random number generator interfaces
 */

#include <dgl/array.h>
#include <dgl/random.h>
#include <dgl/runtime/packed_func.h>
#include <dgl/runtime/parallel_for.h>
#include <dgl/runtime/registry.h>
#include <dmlc/omp.h>

using namespace dgl::runtime;

namespace dgl {

DGL_REGISTER_GLOBAL("rng._CAPI_SetSeed")
    .set_body([](DGLArgs args, DGLRetValue *rv) {
      const int seed = args[0];

      runtime::parallel_for(0, omp_get_max_threads(), [&](size_t b, size_t e) {
        for (auto i = b; i < e; ++i) {
          RandomEngine::ThreadLocal()->SetSeed(seed);
        }
      });
    });

DGL_REGISTER_GLOBAL("rng._CAPI_Choice")
    .set_body([](DGLArgs args, DGLRetValue *rv) {
      const int64_t num = args[0];
      const int64_t population = args[1];
      const NDArray prob = args[2];
      const bool replace = args[3];
      const int bits = args[4];
      CHECK(bits == 32 || bits == 64)
          << "Supported bit widths are 32 and 64, but got " << bits << ".";
      if (aten::IsNullArray(prob)) {
        if (bits == 32) {
          *rv = RandomEngine::ThreadLocal()->UniformChoice<int32_t>(
              num, population, replace);
        } else {
          *rv = RandomEngine::ThreadLocal()->UniformChoice<int64_t>(
              num, population, replace);
        }
      } else {
        if (bits == 32) {
          ATEN_FLOAT_TYPE_SWITCH(prob->dtype, FloatType, "probability", {
            *rv = RandomEngine::ThreadLocal()->Choice<int32_t, FloatType>(
                num, prob, replace);
          });
        } else {
          ATEN_FLOAT_TYPE_SWITCH(prob->dtype, FloatType, "probability", {
            *rv = RandomEngine::ThreadLocal()->Choice<int64_t, FloatType>(
                num, prob, replace);
          });
        }
      }
    });

};  // namespace dgl