#ifndef STAN_MATH_REV_MAT_FUN_DOT_PRODUCT_HPP
#define STAN_MATH_REV_MAT_FUN_DOT_PRODUCT_HPP

#include <stan/math/prim/mat/fun/Eigen.hpp>
#include <stan/math/prim/mat/fun/typedefs.hpp>
#include <stan/math/prim/mat/err/check_vector.hpp>
#include <stan/math/prim/arr/err/check_matching_sizes.hpp>
#include <stan/math/prim/scal/fun/value_of.hpp>
#include <stan/math/rev/core.hpp>
#include <stan/math/rev/mat/fun/typedefs.hpp>
#include <stan/math/rev/scal/fun/value_of.hpp>
#include <boost/utility/enable_if.hpp>
#include <boost/type_traits.hpp>
#include <vector>

namespace stan {
  namespace math {

    namespace {
      template<typename T>
      struct dot_product_store_type;

      template<>
      struct dot_product_store_type<var> {
        typedef vari** type;
      };

      template<>
      struct dot_product_store_type<double> {
        typedef double* type;
      };

      template<typename T1, typename T2>
      class dot_product_vari : public vari {
      protected:
        typename dot_product_store_type<T1>::type v1_;
        typename dot_product_store_type<T2>::type v2_;
        size_t length_;

        inline static double var_dot(vari** v1, vari** v2,
                                     size_t length) {
          Eigen::VectorXd vd1(length), vd2(length);
          for (size_t i = 0; i < length; i++) {
            vd1[i] = v1[i]->val_;
            vd2[i] = v2[i]->val_;
          }
          return vd1.dot(vd2);
        }

        inline static double var_dot(const T1* v1, const T2* v2,
                                     size_t length) {
          Eigen::VectorXd vd1(length), vd2(length);
          for (size_t i = 0; i < length; i++) {
            vd1[i] = value_of(v1[i]);
            vd2[i] = value_of(v2[i]);
          }
          return vd1.dot(vd2);
        }

        template<typename Derived1, typename Derived2>
        inline static double var_dot(const Eigen::DenseBase<Derived1> &v1,
                                     const Eigen::DenseBase<Derived2> &v2) {
          Eigen::VectorXd vd1(v1.size()), vd2(v1.size());
          for (int i = 0; i < v1.size(); i++) {
            vd1[i] = value_of(v1[i]);
            vd2[i] = value_of(v2[i]);
          }
          return vd1.dot(vd2);
        }
        inline void chain(vari** v1, vari** v2) {
          for (size_t i = 0; i < length_; i++) {
            v1[i]->adj_ += adj_ * v2_[i]->val_;
            v2[i]->adj_ += adj_ * v1_[i]->val_;
          }
        }
        inline void chain(double* v1, vari** v2) {
          for (size_t i = 0; i < length_; i++) {
            v2[i]->adj_ += adj_ * v1_[i];
          }
        }
        inline void chain(vari** v1, double* v2) {
          for (size_t i = 0; i < length_; i++) {
            v1[i]->adj_ += adj_ * v2_[i];
          }
        }
        inline void initialize(vari** &mem_v, const var *inv,
                               vari **shared = NULL) {
          if (shared == NULL) {
            mem_v = reinterpret_cast<vari**>(ChainableStack::memalloc_
                                             .alloc(length_*sizeof(vari*)));
            for (size_t i = 0; i < length_; i++)
              mem_v[i] = inv[i].vi_;
          } else {
            mem_v = shared;
          }
        }
        template<typename Derived>
        inline void initialize(vari** &mem_v,
                               const Eigen::DenseBase<Derived> &inv,
                               vari **shared = NULL) {
          if (shared == NULL) {
            mem_v = reinterpret_cast<vari**>(ChainableStack::memalloc_
                                             .alloc(length_*sizeof(vari*)));
            for (size_t i = 0; i < length_; i++)
              mem_v[i] = inv(i).vi_;
          } else {
            mem_v = shared;
          }
        }

        inline void initialize(double* &mem_d, const double *ind,
                               double *shared = NULL) {
          if (shared == NULL) {
            mem_d = reinterpret_cast<double*>(ChainableStack::memalloc_
                                              .alloc(length_*sizeof(double)));
            for (size_t i = 0; i < length_; i++)
              mem_d[i] = ind[i];
          } else {
            mem_d = shared;
          }
        }
        template<typename Derived>
        inline void initialize(double* &mem_d,
                               const Eigen::DenseBase<Derived> &ind,
                               double *shared = NULL) {
          if (shared == NULL) {
            mem_d = reinterpret_cast<double*>
              (ChainableStack::memalloc_.alloc(length_*sizeof(double)));
            for (size_t i = 0; i < length_; i++)
              mem_d[i] = ind(i);
          } else {
            mem_d = shared;
          }
        }

      public:
        dot_product_vari(typename dot_product_store_type<T1>::type v1,
                         typename dot_product_store_type<T2>::type v2,
                         size_t length)
          : vari(var_dot(v1, v2, length)), v1_(v1), v2_(v2), length_(length) {}

        dot_product_vari(const T1* v1, const T2* v2, size_t length,
                         dot_product_vari<T1, T2>* shared_v1 = NULL,
                         dot_product_vari<T1, T2>* shared_v2 = NULL) :
          vari(var_dot(v1, v2, length)), length_(length) {
          if (shared_v1 == NULL) {
            initialize(v1_, v1);
          } else {
            initialize(v1_, v1, shared_v1->v1_);
          }
          if (shared_v2 == NULL) {
            initialize(v2_, v2);
          } else {
            initialize(v2_, v2, shared_v2->v2_);
          }
        }
        template<typename Derived1, typename Derived2>
        dot_product_vari(const Eigen::DenseBase<Derived1> &v1,
                         const Eigen::DenseBase<Derived2> &v2,
                         dot_product_vari<T1, T2>* shared_v1 = NULL,
                         dot_product_vari<T1, T2>* shared_v2 = NULL) :
          vari(var_dot(v1, v2)), length_(v1.size()) {
          if (shared_v1 == NULL) {
            initialize(v1_, v1);
          } else {
            initialize(v1_, v1, shared_v1->v1_);
          }
          if (shared_v2 == NULL) {
            initialize(v2_, v2);
          } else {
            initialize(v2_, v2, shared_v2->v2_);
          }
        }
        template<int R1, int C1, int R2, int C2>
        dot_product_vari(const Eigen::Matrix<T1, R1, C1> &v1,
                         const Eigen::Matrix<T2, R2, C2> &v2,
                         dot_product_vari<T1, T2>* shared_v1 = NULL,
                         dot_product_vari<T1, T2>* shared_v2 = NULL) :
          vari(var_dot(v1, v2)), length_(v1.size()) {
          if (shared_v1 == NULL) {
            initialize(v1_, v1);
          } else {
            initialize(v1_, v1, shared_v1->v1_);
          }
          if (shared_v2 == NULL) {
            initialize(v2_, v2);
          } else {
            initialize(v2_, v2, shared_v2->v2_);
          }
        }
        virtual void chain() {
          chain(v1_, v2_);
        }
      };
    }

    /**
     * Returns the dot product.
     *
     * @param[in] v1 First column vector.
     * @param[in] v2 Second column vector.
     * @return Dot product of the vectors.
     * @throw std::domain_error if length of v1 is not equal to length of v2.
     */
    template<typename T1, int R1, int C1, typename T2, int R2, int C2>
    inline
    typename boost::enable_if_c<boost::is_same<T1, var>::value ||
    boost::is_same<T2, var>::value, var>::type
      dot_product(const Eigen::Matrix<T1, R1, C1>& v1,
                  const Eigen::Matrix<T2, R2, C2>& v2) {
      check_vector("dot_product", "v1", v1);
      check_vector("dot_product", "v2", v2);
      check_matching_sizes("dot_product",
                           "v1", v1,
                           "v2", v2);
      return var(new dot_product_vari<T1, T2>(v1, v2));
    }
    /**
     * Returns the dot product.
     *
     * @param[in] v1 First array.
     * @param[in] v2 Second array.
     * @param[in] length Length of both arrays.
     * @return Dot product of the arrays.
     */
    template<typename T1, typename T2>
    inline
    typename boost::enable_if_c<boost::is_same<T1, var>::value ||
    boost::is_same<T2, var>::value, var>::type
      dot_product(const T1* v1, const T2* v2, size_t length) {
      return var(new dot_product_vari<T1, T2>(v1, v2, length));
    }

    /**
     * Returns the dot product.
     *
     * @param[in] v1 First vector.
     * @param[in] v2 Second vector.
     * @return Dot product of the vectors.
     * @throw std::domain_error if sizes of v1 and v2 do not match.
     */
    template<typename T1, typename T2>
    inline
    typename boost::enable_if_c<boost::is_same<T1, var>::value ||
    boost::is_same<T2, var>::value, var>::type
      dot_product(const std::vector<T1>& v1,
                  const std::vector<T2>& v2) {
      check_matching_sizes("dot_product",
                           "v1", v1,
                           "v2", v2);
      return var(new dot_product_vari<T1, T2>(&v1[0], &v2[0], v1.size()));
    }

  }
}
#endif
