#ifndef STAN_MATH_PRIM_MAT_FUN_APPEND_ROW_HPP
#define STAN_MATH_PRIM_MAT_FUN_APPEND_ROW_HPP

#include <stan/math/prim/mat/fun/Eigen.hpp>
#include <stan/math/prim/scal/meta/return_type.hpp>
#include <stan/math/prim/scal/err/check_size_match.hpp>
#include <vector>

namespace stan {

  namespace math {

    /**
     * Return the result of stacking the rows of the first argument
     * matrix on top of the second argument matrix.
     *
     * The inputs can be
     * (matrix, matrix),
     * (matrix, row_vector),
     * (row_vector, matrix), or
     * (row_vector, row_vector),
     * and the output is always a matrix.
     *
     * @tparam T1 Scalar type of first matrix.
     * @tparam T2 Scalar type of second matrix.
     * @tparam R1 Row specification of first matrix.
     * @tparam C1 Column specification of first matrix.
     * @tparam R2 Row specification of second matrix.
     * @tparam C2 Column specification of second matrix.
     * @param A First matrix.
     * @param B Second matrix.
     * @return Result of stacking first matrix on top of second.
     */
    template <typename T1, typename T2, int R1, int C1, int R2, int C2>
    inline Eigen::Matrix<typename return_type<T1, T2>::type,
                         Eigen::Dynamic, Eigen::Dynamic>
    append_row(const Eigen::Matrix<T1, R1, C1>& A,
               const Eigen::Matrix<T2, R2, C2>& B) {
      using Eigen::Dynamic;
      using Eigen::Matrix;

      int Arows = A.rows();
      int Brows = B.rows();
      int Acols = A.cols();
      int Bcols = B.cols();
      check_size_match("append_row",
                       "columns of A", Acols,
                       "columns of B", Bcols);

      Matrix<typename return_type<T1, T2>::type, Dynamic, Dynamic>
        result(Arows + Brows, Acols);
      for (int j = 0; j < Acols; j++) {
        for (int i = 0; i < Arows; i++)
          result(i, j) = A(i, j);
        for (int i = Arows, k = 0; k < Brows; i++, k++)
          result(i, j) = B(k, j);
      }
      return result;
    }


    /**
     * Return the result of stacking the first vector on top of the
     * second vector, with the result being a vector.
     *
     * This function applies to (vector, vector) and returns a vector.
     *
     * @tparam T1 Scalar type of first vector.
     * @tparam T2 Scalar type of second vector.
     * @tparam R1 Row specification of first vector.
     * @tparam R2 Row specification of second vector.
     * @param A First vector.
     * @param B Second vector
     * @return Result of stacking first vector on top of the second
     * vector.
     */
    template <typename T1, typename T2, int R1, int R2>
    inline Eigen::Matrix<typename return_type<T1, T2>::type,
                         Eigen::Dynamic, 1>
    append_row(const Eigen::Matrix<T1, R1, 1>& A,
               const Eigen::Matrix<T2, R2, 1>& B) {
      using Eigen::Dynamic;
      using Eigen::Matrix;

      int Asize = A.size();
      int Bsize = B.size();
      Matrix<typename return_type<T1, T2>::type, 1, Dynamic>
        result(Asize + Bsize);
      for (int i = 0; i < Asize; i++)
        result(i) = A(i);
      for (int i = 0, j = Asize; i < Bsize; i++, j++)
        result(j) = B(i);
      return result;
    }


    /**
     * Return the result of stacking the rows of the first argument
     * matrix on top of the second argument matrix.  This is an
     * overload for the case when the scalar types of the two input
     * matrix are the same.
     *
     * The inputs can be
     * (matrix, matrix),
     * (matrix, row_vector),
     * (row_vector, matrix), or
     * (row_vector, row_vector),
     * and the output is always a matrix.
     *
     * @tparam T Scalar type of both matrices.
     * @tparam R1 Row specification of first matrix.
     * @tparam C1 Column specification of first matrix.
     * @tparam R2 Row specification of second matrix.
     * @tparam C2 Column specification of second matrix.
     * @param A First matrix.
     * @param B Second matrix.
     * @return Result of stacking first matrix on top of second.
     */
    template <typename T, int R1, int C1, int R2, int C2>
    inline Eigen::Matrix<T, Eigen::Dynamic, Eigen::Dynamic>
    append_row(const Eigen::Matrix<T, R1, C1>& A,
               const Eigen::Matrix<T, R2, C2>& B) {
      using Eigen::Dynamic;
      using Eigen::Matrix;

      check_size_match("append_row",
                       "columns of A", A.cols(),
                       "columns of B", B.cols());

      Matrix<T, Dynamic, Dynamic>
        result(A.rows() + B.rows(), A.cols());
      result << A, B;
      return result;
    }


    /**
     * Return the result of stacking the first vector on top of the
     * second vector, with the result being a vector.  This is an
     * overloaded template function for the case where both inputs
     * have the same scalar type.
     *
     * This function applies to (vector, vector) and returns a vector.
     *
     * @tparam T Scalar type of both vectors.
     * @tparam R1 Row specification of first vector.
     * @tparam R2 Row specification of second vector.
     * @param A First vector.
     * @param B Second vector
     * @return Result of stacking first vector on top of the second
     * vector.
     */
    template <typename T, int R1, int R2>
    inline Eigen::Matrix<T, Eigen::Dynamic, 1>
    append_row(const Eigen::Matrix<T, R1, 1>& A,
               const Eigen::Matrix<T, R2, 1>& B) {
      using Eigen::Dynamic;
      using Eigen::Matrix;

      Matrix<T, Dynamic, 1>  result(A.size()+B.size());
      result << A, B;
      return result;
    }

  }

}

#endif
