// Copyright (C) 2018-2021 Intel Corporation
// SPDX-License-Identifier: Apache-2.0
//

#pragma once

#include <memory>

#include "ngraph/descriptor/tensor.hpp"

namespace ngraph
{
    class Node;

    namespace descriptor
    {
        class Output;

        // Describes a tensor that is an input to an op, directly or indirectly via a tuple
        class NGRAPH_API Input
        {
            friend class ngraph::Node;

        public:
            /// \param node The node that owns this input
            /// \param index The position of this this tensor in all input tensors
            /// \param output The output that supplies a value for this input
            Input(Node* node, size_t index, Output& output);
            /// \brief Create an Input that is not connected to an output
            /// \param node The node that owns this input
            /// \param index The position of this this tensor in all input tensors
            Input(Node* node, size_t index);
            ~Input();

            /// \return the node that this is an input of
            std::shared_ptr<Node> get_node() const;

            /// \return the raw pointer to the node that this is an input of
            Node* get_raw_pointer_node() const { return m_node; }
            /// \return the position within all supplied tensors of this input
            size_t get_index() const { return m_index; }
            /// \return the connected output
            const Output& get_output() const { return *m_output; }
            /// \return the connected output
            Output& get_output() { return *m_output; }
            /// \return true if an output is connected to the input.
            bool has_output() const { return m_output != nullptr; }
            /// \return the tensor of the connected output
            const Tensor& get_tensor() const;

            /// \return the tensor of the connected output
            Tensor& get_tensor();

            /// \brief Replace the current output that supplies a value for this input with output i
            ///        of node
            void replace_output(std::shared_ptr<Node> node, size_t i);
            /// \brief Replace the current output that supplies a value for this input with output
            void replace_output(Output& output);
            /// \brief Remove the output from this input. The node will not be valid until another
            ///        output is supplied.
            void remove_output();

            /// \return true if the value of this input is relevant to the output shapes of the
            ///         corresponding node. (Usually this is false.)
            ///
            /// See Node::set_input_is_relevant_to_shape for more details.
            bool get_is_relevant_to_shape() const { return m_is_relevant_to_shape; }
            /// \return true if the value of this input is relevant to the output value of the
            ///         corresponding node. (Usually this is true.)
            ///
            /// See Node::set_input_is_relevant_to_value for more details.
            bool get_is_relevant_to_value() const { return m_is_relevant_to_value; }

        protected:
            /// \return the tensor for the connected output
            std::shared_ptr<const Tensor> get_tensor_ptr() const;

            /// \return the tensor for the connected output
            std::shared_ptr<Tensor> get_tensor_ptr();

        public:
            /// \return the shape of the connected output
            const Shape& get_shape() const;

            /// \return the partial shape of the connected output
            const PartialShape& get_partial_shape() const;

            /// \return the element type of the connected output
            const element::Type& get_element_type() const;

            Input(const Input&) = default;
            Input(Input&&) = default;
            Input& operator=(const Input&) = default;

        protected:
            // owner of an argument node (in lieu of m_arguments)
            std::shared_ptr<Node> m_src_node;
            Node* m_node;   // The node we are an input for
            size_t m_index; // Index into all input tensors
            Output* m_output;

        private:
            bool m_is_relevant_to_shape;
            bool m_is_relevant_to_value;
        };
    } // namespace descriptor
} // namespace ngraph
