// SPDX-License-Identifier: Apache-2.0
//
// Copyright 2008-2016 Conrad Sanderson (http://conradsanderson.id.au)
// Copyright 2008-2016 National ICT Australia (NICTA)
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// ------------------------------------------------------------------------

//! \addtogroup glue_intersect
//! @{

template <typename T1, typename T2>
inline void glue_intersect::apply(Mat<typename T1::elem_type>& out,
                                  const Glue<T1, T2, glue_intersect>& X) {
  arma_debug_sigprint();

  uvec iA;
  uvec iB;

  glue_intersect::apply(out, iA, iB, X.A, X.B, false);
}

template <typename T1, typename T2>
inline void glue_intersect::apply(Mat<typename T1::elem_type>& out, uvec& iA, uvec& iB,
                                  const Base<typename T1::elem_type, T1>& A_expr,
                                  const Base<typename T1::elem_type, T2>& B_expr,
                                  const bool calc_indx) {
  arma_debug_sigprint();

  typedef typename T1::elem_type eT;

  const quasi_unwrap<T1> UA(A_expr.get_ref());
  const quasi_unwrap<T2> UB(B_expr.get_ref());

  if (UA.M.is_empty() || UB.M.is_empty()) {
    out.reset();
    iA.reset();
    iB.reset();
    return;
  }

  uvec A_uniq_indx;
  uvec B_uniq_indx;

  Mat<eT> A_uniq;
  Mat<eT> B_uniq;

  if (calc_indx) {
    A_uniq_indx = find_unique(UA.M);
    B_uniq_indx = find_unique(UB.M);

    A_uniq = UA.M.elem(A_uniq_indx);
    B_uniq = UB.M.elem(B_uniq_indx);
  } else {
    A_uniq = unique(UA.M);
    B_uniq = unique(UB.M);
  }

  const uword C_n_elem = A_uniq.n_elem + B_uniq.n_elem;

  Col<eT> C(C_n_elem, arma_nozeros_indicator());

  arrayops::copy(C.memptr(), A_uniq.memptr(), A_uniq.n_elem);
  arrayops::copy(C.memptr() + A_uniq.n_elem, B_uniq.memptr(), B_uniq.n_elem);

  uvec C_sorted_indx;
  Col<eT> C_sorted;

  if (calc_indx) {
    C_sorted_indx = stable_sort_index(C);
    C_sorted = C.elem(C_sorted_indx);
  } else {
    C_sorted = sort(C);
  }

  const eT* C_sorted_mem = C_sorted.memptr();

  uvec jj(C_n_elem, arma_nozeros_indicator());  // worst case length

  uword* jj_mem = jj.memptr();
  uword jj_count = 0;

  for (uword i = 0; i < (C_n_elem - 1); ++i) {
    if (C_sorted_mem[i] == C_sorted_mem[i + 1]) {
      jj_mem[jj_count] = i;
      ++jj_count;
    }
  }

  if (jj_count == 0) {
    out.reset();
    iA.reset();
    iB.reset();
    return;
  }

  const uvec ii(jj.memptr(), jj_count, false);

  if (UA.M.is_rowvec() && UB.M.is_rowvec()) {
    out.set_size(1, ii.n_elem);

    Mat<eT> out_alias(out.memptr(), ii.n_elem, 1, false, true);

    // NOTE: this relies on .elem() not changing the size of the output and not
    // reallocating memory for the output
    out_alias = C_sorted.elem(ii);
  } else {
    out = C_sorted.elem(ii);
  }

  if (calc_indx) {
    iA = A_uniq_indx.elem(C_sorted_indx.elem(ii));
    iB = B_uniq_indx.elem(C_sorted_indx.elem(ii + 1) - A_uniq.n_elem);
  }
}

//! @}
