#pragma once

#include <QMap>
#include <QSet>
#include <QVector>

#include <QtCore/QJsonObject>
#include <QtCore/QObject>
#include <QtCore/QVariant>

#include "global.h"


/**
 * The central class in the Model-View approach. It delivers all kinds
 * of information from the backing user data structures that represent
 * the graph. The class allows to modify the graph structure: create
 * and remove nodes and connections.
 *
 * We use two types of the unique ids for graph manipulations:
 *   - NodeId
 *   - ConnectionId
 */
class AbstractGraphModel : public QObject
{
    Q_OBJECT
public:
    /// Generates a new unique NodeId.
    virtual NodeId newNodeId() = 0;

    /// @brief Returns the full set of unique Node Ids.
    /**
   * Model creator is responsible for generating unique `unsigned int`
   * Ids for all the nodes in the graph. From an Id it should be
   * possible to trace back to the model's internal representation of
   * the node.
   */
    virtual QSet<NodeId> allNodeIds() const = 0;

    /**
   * A collection of all input and output connections for the given `nodeId`.
   */
    virtual QSet<ConnectionId> allConnectionIds(NodeId const nodeId) const = 0;

    /// @brief Returns all connected Node Ids for given port.
    /**
   * The returned set of nodes and port indices correspond to the type
   * opposite to the given `portType`.
   */
    virtual QSet<ConnectionId> connections(NodeId nodeId,
                                                         PortType portType,
                                                         PortIndex index) const
        = 0;

    /// Checks if two nodes with the given `connectionId` are connected.
    virtual bool connectionExists(ConnectionId const connectionId) const = 0;

    /// Creates a new node instance in the derived class.
    /**
   * The model is responsible for generating a unique `NodeId`.
   * @param[in] nodeType is free to be used and interpreted by the
   * model on its own, it helps to distinguish between possible node
   * types and create a correct instance inside.
   */
    virtual NodeId addNode(QString const nodeType = QString()) = 0;

    /// Model decides if a conection with a given connection Id possible.
    /**
   * The default implementation compares corresponding data types.
   *
   * It is possible to override the function and connect non-equal
   * data types.
   */
    virtual bool connectionPossible(ConnectionId const connectionId) const = 0;

    /// Defines if detaching the connection is possible.
    virtual bool detachPossible(ConnectionId const) const { return true; }

    /// Creates a new connection between two nodes.
    /**
   * Default implementation emits signal
   * `connectionCreated(connectionId)`
   *
   * In the derived classes user must emite the signal to notify the
   * scene about the changes.
   */
    virtual void addConnection(ConnectionId const connectionId) = 0;

    /**
   * @returns `true` if there is data in the model associated with the
   * given `nodeId`.
   */
    virtual bool nodeExists(NodeId const nodeId) const = 0;

    /// @brief Returns node-related data for requested NodeRole.
    /**
   * @returns Node Caption, Node Caption Visibility, Node Position etc.
   */
    virtual QVariant nodeData(NodeId nodeId, NodeRole role) const = 0;

    /**
   * A utility function that unwraps the `QVariant` value returned from the
   * standard `QVariant AbstractGraphModel::nodeData(NodeId, NodeRole)` function.
   */
    template<typename T>
    T nodeData(NodeId nodeId, NodeRole role) const
    {
        return nodeData(nodeId, role).value<T>();
    }

    virtual NodeFlags nodeFlags(NodeId nodeId) const
    {
        Q_UNUSED(nodeId);
        return NodeFlag::NoFlags;
    }

    /// @brief Sets node properties.
    /**
   * Sets: Node Caption, Node Caption Visibility,
   * Shyle, State, Node Position etc.
   * @see NodeRole.
   */
    virtual bool setNodeData(NodeId nodeId, NodeRole role, QVariant value) = 0;

    /// @brief Returns port-related data for requested NodeRole.
    /**
   * @returns Port Data Type, Port Data, Connection Policy, Port
   * Caption.
   */
    virtual QVariant portData(NodeId nodeId, PortType portType, PortIndex index, PortRole role) const
        = 0;

    /**
   * A utility function that unwraps the `QVariant` value returned from the
   * standard `QVariant AbstractGraphModel::portData(...)` function.
   */
    template<typename T>
    T portData(NodeId nodeId, PortType portType, PortIndex index, PortRole role) const
    {
        return portData(nodeId, portType, index, role).value<T>();
    }

    virtual bool setPortData(NodeId nodeId,
                             PortType portType,
                             PortIndex index,
                             QVariant const &value,
                             PortRole role = PortRole::Data)
        = 0;

    virtual bool deleteConnection(ConnectionId const connectionId) = 0;

    virtual bool deleteNode(NodeId const nodeId) = 0;

    /**
   * Reimplement the function if you want to store/restore the node's
   * inner state during undo/redo node deletion operations.
   */
    virtual QJsonObject saveNode(NodeId const) const { return {}; }

    /**
   * Reimplement the function if you want to support:
   *
   *   - graph save/restore operations,
   *   - undo/redo operations after deleting the node.
   *
   * QJsonObject must contain following fields:
   *
   *
   * ```
   * {
   *   id : 5,
   *   position : { x : 100, y : 200 },
   *   internal-data {
   *     "your model specific data here"
   *   }
   * }
   * ```
   *
   * The function must do almost exacly the same thing as the normal addNode().
   * The main difference is in a model-specific `inner-data` processing.
   */
    virtual void loadNode(QJsonObject const &) {}

public:
    /**
   * Function clears connections attached to the ports that are scheduled to be
   * deleted. It must be called right before the model removes its old port data.
   *
   * @param nodeId Defines the node to be modified
   * @param portType Is either PortType::In or PortType::Out
   * @param first Index of the first port to be removed
   * @param last Index of the last port to be removed
   */
    void portsAboutToBeDeleted(NodeId const nodeId,
                               PortType const portType,
                               PortIndex const first,
                               PortIndex const last);

    /**
   * Signal emitted when model no longer has the old data associated with the
   * given port indices and when the node must be repainted.
   */
    void portsDeleted();

    /**
   * Signal emitted when model is about to create new ports on the given node.
   * @param first Is the first index of the new port after insertion.
   * @param last Is the last index of the new port after insertion.
   *
   * Function caches existing connections that are located after the `last` port
   * index. For such connections the new "post-insertion" addresses are computed
   * and stored until the function AbstractGraphModel::portsInserted is called.
   */
    void portsAboutToBeInserted(NodeId const nodeId,
                                PortType const portType,
                                PortIndex const first,
                                PortIndex const last);

    /**
   * Function re-creates the connections that were shifted during the port
   * insertion. After that the node is updated.
   */
    void portsInserted();

Q_SIGNALS:
    void connectionCreated(ConnectionId const connectionId);

    void connectionDeleted(ConnectionId const connectionId);

    void nodeCreated(NodeId const nodeId);

    void nodeDeleted(NodeId const nodeId);

    void nodeUpdated(NodeId const nodeId);

    void nodeFlagsUpdated(NodeId const nodeId);

    void nodePositionUpdated(NodeId const nodeId);

    void modelReset();

private:
    QVector<ConnectionId> _shiftedByDynamicPortsConnections;
};