using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Azimuth;
using Annulus;
using Slipstream.StokesFlow;

namespace Slipstream.Testbed.Demos
{
    public class UniformFlowStokeslet : Demo
    {
        public static Vector PositionAtIndex(int index)
        {
            Scalar t = (Scalar)index / (count - 1);
            return new Vector(-panelLength/2 + panelLength * t, 0);
        }

        public const int count = 20;
        public const float panelLength = 10;
        AbstractBoundaryBody body;
        public override void Start(FluidWorld world)
        {
            var points = new List<Vector>();
            for (int i = 0; i < count; ++i)
            {
                points.Add(PositionAtIndex(i));
            }
            body = new StokesBoundaryBody(points, Vector.Zero, 0);

            world.AddBoundary(body);

            Random rand = new Random(1);
            for (int i = 0; i < 1000; ++i)
            {
                world.AddTracerParticle(new Vector(2 * rand.NextDouble() - 1, 2 * rand.NextDouble() - 1) * 100);
            }
        }

        Scalar cycleCount = 0;
        public override void Update(FluidWorld world)
        {
            cycleCount += 1.0 / 60.0;

            Scalar period = 10;
            Scalar angularVelocity = (1.0 / period) * (2 * Math.PI);

            var velocity = new Vector(0, 50 * angularVelocity * Math.Cos(angularVelocity * cycleCount));
            world.FluidBaseVelocity = velocity;

            Scalar totalEnergyCount;
            world.EnforceBoundaryConditions();
            world.IntegrateTracerParticles(1.0 / 60.0, out totalEnergyCount);
        }

        public override void Reset(FluidWorld world)
        {
            cycleCount = 0;
        }

        public override Blacklight.Core.Cel Draw(FluidWorld world)
        {
            var cel = new Blacklight.Core.Cel();
            var collage = new Blacklight.Core.Drawables.Collage();

            var ellipse = new Blacklight.Core.Drawables.Ellipse
            {
                InsideColor = new Blacklight.Core.Color(0.84, 0, 0),
                ShellColor = new Blacklight.Core.Color(0.25, 0, 0),
                ShellPixelThickness = 0,
                ShellModelSpaceThickness = 0.25,
                SmoothBorder = false,
            };

            for (int i = 0; i < count; ++i)
            {
                collage.AddDrawable(ellipse, AffineMatrix.BuildFromTranslation(PositionAtIndex(i)) *
                                             AffineMatrix.BuildFromScale(1));
            }

            cel.AddEntity(new Blacklight.Core.Entity
            {
                drawable = collage,
                modelToWorld = body.ModelToWorld,
            });

            return cel;
        }
    }
}