using System;

namespace AIStudio.Wpf.DiagramDesigner.Layout
{
    public class Configuration
    {
        /// <summary>
        /// The network whose nodes are to be repositioned.
        /// </summary>
        public DiagramViewModel Network
        {
            get; set;
        }

        /// <summary>
        /// A time modifier that is used to speed up, or slow down, time during the simulation.
        /// A greater time modifier speeds up the physics simulation, at the cost of accuracy and stability.
        /// </summary>
        public float TimeModifier { get; set; } = 3.5f;

        /// <summary>
        /// Number of updates per iteration.
        /// Increasing this number increases the accuracy of the physics simulation at the cost of performance.
        /// </summary>
        public int UpdatesPerIteration { get; set; } = 1;

        /// <summary>
        /// How strongly should nodes push eachother away?
        /// A greater NodeRepulsionForce increases the distance between nodes.
        /// </summary>
        public float NodeRepulsionForce { get; set; } = 100;

        /// <summary>
        /// A function that maps each connection onto the equilibrium distance of its corresponding spring.
        /// A greater equilibrium distance increases the distance between the two connected endpoints.
        /// </summary>
        public Func<ConnectionViewModel, double> EquilibriumDistance { get; set; } = conn => 100;

        /// <summary>
        /// A function that maps each connection onto the springiness/stiffness constant of its corresponding spring.
        /// (c.f. Hooke's law)
        /// </summary>
        public Func<ConnectionViewModel, double> SpringConstant { get; set; } = conn => 1;

        /// <summary>
        /// A function that maps each connection onto the strength of its row force.
        /// Since inputs/outputs are on the left/right of a node, networks tend to be layed out horizontally.
        /// The row force is added onto the endpoints of the connection to make the nodes end up in a more horizontal layout.
        /// </summary>
        public Func<ConnectionViewModel, double> RowForce { get; set; } = conn => 100;

        /// <summary>
        /// A function that maps each node onto its mass in the physics simulation.
        /// Greater mass makes the node harder to move.
        /// </summary>
        public Func<DesignerItemViewModelBase, float> NodeMass { get; set; } = node => 10;

        /// <summary>
        /// The friction coefficient is used to control friction forces in the simulation.
        /// Greater friction makes the simulation converge faster, as it slows nodes down when
        /// they are swinging around. If the friction is too high, the nodes will stop moving before
        /// they reach their optimal position or might not even move at all.
        /// </summary>
        public Func<DesignerItemViewModelBase, float> FrictionCoefficient { get; set; } = node => 2.5f;

        /// <summary>
        /// A predicate function that specifies whether or not a node is fixed.
        /// Fixed nodes do not get moved in the simulation.
        /// </summary>
        public Func<DesignerItemViewModelBase, bool> IsFixedNode { get; set; } = node => false;
    }
}
