using System;
using System.Threading;
using System.Threading.Tasks;
using System.Windows;

namespace AIStudio.Wpf.DiagramDesigner.Layout
{
    /// <summary>
    /// Reposition the nodes in a network using a physics-based approach.
    /// The nodes are interpreted as point masses, and the connections are represented
    /// by springs. This system, along with a few additional forces such as friction and a
    /// horizontal force, is then simulated to calculate the new position of the nodes.
    /// </summary>
    public class ForceDirectedLayouter
    {
        /// <summary>
        /// Layout the nodes in the network.
        /// </summary>
        /// <param name="config">The configuration to use.</param>
        /// <param name="maxIterations">The maximum amount of iterations after which the physics simulation ends.</param>
        public void Layout(Configuration config, int maxIterations)
        {
            var engine = new Engine();
            var state = new BufferedState();

            // Move each node so no two nodes have the exact same position.
            engine.ApplyRandomShift(config.Network);

            int deltaT = (int)Math.Ceiling(10.0 / (double)config.UpdatesPerIteration);
            for (int i = 0; i < maxIterations * config.UpdatesPerIteration; i++)
            {
                engine.Update(deltaT, state, config);
            }

            foreach (var newNodePosition in state.NodePositions)
            {
                newNodePosition.Key.Position = new Point(newNodePosition.Value.X, newNodePosition.Value.Y);
            }
        }

        /// <summary>
        /// Layout the nodes in the network, updating the user interface at each iteration.
        /// This method, contrary to Layout(), lets users see the simulation as it happens.
        /// The cancellation token should be used to end the simulation.
        /// </summary>
        /// <param name="config">The configuration to use.</param>
        /// <param name="token">A cancellation token to end the layout process.</param>
        /// <returns>The async task</returns>
        public async Task LayoutAsync(Configuration config, CancellationToken token)
        {
            var engine = new Engine();
            var state = new LiveState();

            // Move each node so no two nodes have the exact same position.
            engine.ApplyRandomShift(config.Network);

            DateTime start = DateTime.Now;
            TimeSpan t = TimeSpan.Zero;
            do
            {
                // Current real time
                var newT = DateTime.Now - start;
                var deltaT = newT - t;

                // Current modified time
                //int virtT = (int)(t.Milliseconds * Settings.TimeModifier);
                int virtDeltaT = (int)(deltaT.Milliseconds * config.TimeModifier);
                int virtDeltaTPerUpdate = virtDeltaT / config.UpdatesPerIteration;
                for (int i = 0; i < config.UpdatesPerIteration; i++)
                {
                    // Modified time in this update step
                    engine.Update(virtDeltaTPerUpdate, state, config);
                }

                t = newT;

                await Task.Delay(14, token);
            } while (!token.IsCancellationRequested);
        }
    }
}