using System;
using System.Drawing;
using Amphora;
using Azimuth;
using Blacklight.Core;
using Blacklight.Core.Drawables;
using Prism;
using UnitTestSharp;

namespace Konis.Blacklight.UnitTests
{
    public class ParticleSpriteWriterTests : TestFixture
    {
        private static SpriteSource Source()
        {
            return new SpriteSource(null, new Point(4, 6), new Size(16, 8));
        }

        private static StandardEmitterDef Def(
            Variation speed = default(Variation),
            double size = 1,
            Variation spin = default(Variation),
            Gradient tint = null,
            double rate = 1)
        {
            return new StandardEmitterDef
            {
                Capacity = 10,
                Rate = rate,
                Lifetime = 2,
                Speed = speed,
                Size = size,
                AngularVelocity = spin,
                TintOverLife = new GradientDef { Gradient = tint ?? Gradient.Constant(Colors.White) },
            };
        }

        private static StandardEmitter Born(StandardEmitterDef def, double secondsAfterBirth = 0)
        {
            var emitter = new StandardEmitter(def, new ScriptedGenerator());
            emitter.Update(1f);
            emitter.Update((float)secondsAfterBirth);
            return emitter;
        }

        private static bool Near(double expected, double actual)
        {
            return Math.Abs(expected - actual) < 1e-5;
        }

        public class WriteTests : TestFixture
        {
            public void AnEmptyEmitter_WritesNothingAndReturnsZero()
            {
                var emitter = new StandardEmitter(Def(), new ScriptedGenerator());
                var entries = new SpriteBatch.EntrySet();

                CheckEqual(0, ParticleSpriteWriter.Write(emitter, ViewProjection.TopDown, Source(), entries));
            }

            public void AddsTheTintAndTransformColumnsToASetThatLacksThem()
            {
                var entries = new SpriteBatch.EntrySet();

                ParticleSpriteWriter.Write(Born(Def()), ViewProjection.TopDown, Source(), entries);

                CheckEqual(
                    SpriteBatch.Varying.TintColor | SpriteBatch.Varying.Transform, entries.Columns);
            }

            public void LeavesAnotherColumnTheSetHadAlone()
            {
                var entries = new SpriteBatch.EntrySet(capacity: 4, columns: SpriteBatch.Varying.Additiveness);

                ParticleSpriteWriter.Write(Born(Def()), ViewProjection.TopDown, Source(), entries);

                CheckEqual(
                    SpriteBatch.Varying.Additiveness | SpriteBatch.Varying.TintColor | SpriteBatch.Varying.Transform,
                    entries.Columns);
            }

            public void ReturnsTheNumberOfLiveParticles()
            {
                var emitter = new StandardEmitter(Def(rate: 8), new ScriptedGenerator());
                emitter.Update(0.5f);
                var entries = new SpriteBatch.EntrySet();

                CheckEqual(4, ParticleSpriteWriter.Write(emitter, ViewProjection.TopDown, Source(), entries));
            }

            public void GrowsTheSetToHoldEveryParticle()
            {
                var emitter = new StandardEmitter(Def(rate: 8), new ScriptedGenerator());
                emitter.Update(1f);
                var entries = new SpriteBatch.EntrySet();

                ParticleSpriteWriter.Write(emitter, ViewProjection.TopDown, Source(), entries);

                CheckTrue(entries.Capacity >= 8);
                CheckEqual(entries.Capacity, entries.Transforms.Length);
                CheckEqual(entries.Capacity, entries.TintColors.Length);
            }

            public void LeavesEntriesPastTheCountAlone()
            {
                var entries = new SpriteBatch.EntrySet(capacity: 4, columns: SpriteBatch.Varying.Transform);
                entries.Transforms[3] = new AffineMatrix(0, new Vector(7, 8), 2);

                ParticleSpriteWriter.Write(Born(Def()), ViewProjection.TopDown, Source(), entries);

                CheckEqual(7.0, entries.Transforms[3].Translation.X.Value);
            }

            public void CopiesTheSourceRegionAndCentersTheDestinationOnIt()
            {
                var entries = new SpriteBatch.EntrySet();

                ParticleSpriteWriter.Write(Born(Def()), ViewProjection.TopDown, Source(), entries);

                SpriteBatch.Entry entry = entries.Entries[0];
                CheckEqual(new Point(4, 6), entry.SourceOrigin);
                CheckEqual(new Size(16, 8), entry.SourceSize);
                CheckEqual(-8.0, entry.Destination.min.X.Value);
                CheckEqual(-4.0, entry.Destination.min.Y.Value);
                CheckEqual(8.0, entry.Destination.max.X.Value);
                CheckEqual(4.0, entry.Destination.max.Y.Value);
            }

            public void PositionsAParticleAtTheEmittersPositionPlusItsOwnProjected()
            {
                StandardEmitter emitter = Born(Def(speed: 4), secondsAfterBirth: 0.5);
                emitter.Position = new Vector3(10, 20, 0);
                var entries = new SpriteBatch.EntrySet();

                ParticleSpriteWriter.Write(emitter, ViewProjection.TopDown, Source(), entries);

                CheckTrue(Near(12, entries.Transforms[0].Translation.X.Value));
                CheckTrue(Near(20, entries.Transforms[0].Translation.Y.Value));
            }

            public void UnderATopDownView_IgnoresAltitude()
            {
                StandardEmitter emitter = Born(Def());
                emitter.Position = new Vector3(0, 0, 5);
                var entries = new SpriteBatch.EntrySet();

                ParticleSpriteWriter.Write(emitter, ViewProjection.TopDown, Source(), entries);

                CheckTrue(Near(0, entries.Transforms[0].Translation.Y.Value));
            }

            public void UnderAnAngledView_RaisesAParticleOnTheScreenWithAltitude()
            {
                StandardEmitter emitter = Born(Def());
                emitter.Position = new Vector3(0, 0, 5);
                var entries = new SpriteBatch.EntrySet();

                ParticleSpriteWriter.Write(emitter, ViewProjection.Dimetric2To1, Source(), entries);

                CheckTrue(entries.Transforms[0].Translation.Y.Value > 1);
            }

            public void ScalesByTheSizeOverTheSourceWidth()
            {
                var entries = new SpriteBatch.EntrySet();

                ParticleSpriteWriter.Write(Born(Def(size: 8)), ViewProjection.TopDown, Source(), entries);

                CheckTrue(Near(0.5, entries.Transforms[0].M00.Value));
                CheckTrue(Near(0.5, entries.Transforms[0].M11.Value));
            }

            public void TurnsByTheParticlesRotation()
            {
                StandardEmitter emitter = Born(Def(size: 16, spin: 0.5), secondsAfterBirth: 0.5);
                var entries = new SpriteBatch.EntrySet();

                ParticleSpriteWriter.Write(emitter, ViewProjection.TopDown, Source(), entries);

                CheckTrue(Near(0, entries.Transforms[0].M00.Value));
                CheckTrue(Near(1, entries.Transforms[0].M10.Value));
            }

            public void TintsByTheParticlesColor()
            {
                var entries = new SpriteBatch.EntrySet();

                ParticleSpriteWriter.Write(
                    Born(Def(tint: Gradient.Constant(Colors.Red))), ViewProjection.TopDown, Source(), entries);

                CheckEqual(Colors.Red.ToArgb(), entries.TintColors[0].ToArgb());
            }

            public void WritesEveryParticleInTheOrderTheEmitterKeepsThem()
            {
                var emitter = new StandardEmitter(Def(speed: 4), new ScriptedGenerator());
                emitter.Update(2f);
                var entries = new SpriteBatch.EntrySet();

                int count = ParticleSpriteWriter.Write(emitter, ViewProjection.TopDown, Source(), entries);

                CheckEqual(2, count);
                CheckTrue(Near(emitter.Store.Items[0].PositionX, entries.Transforms[0].Translation.X.Value));
                CheckTrue(Near(emitter.Store.Items[1].PositionX, entries.Transforms[1].Translation.X.Value));
            }
        }
    }
}