/*
* Farseer Physics Engine:
* Copyright (c) 2012 Ian Qvist
* 
* Original source Box2D:
* Copyright (c) 2006-2011 Erin Catto http://www.box2d.org 
* 
* This software is provided 'as-is', without any express or implied 
* warranty.  In no event will the authors be held liable for any damages 
* arising from the use of this software. 
* Permission is granted to anyone to use this software for any purpose, 
* including commercial applications, and to alter it and redistribute it 
* freely, subject to the following restrictions: 
* 1. The origin of this software must not be misrepresented; you must not 
* claim that you wrote the original software. If you use this software 
* in a product, an acknowledgment in the product documentation would be 
* appreciated but is not required. 
* 2. Altered source versions must be plainly marked as such, and must not be 
* misrepresented as being the original software. 
* 3. This notice may not be removed or altered from any source distribution. 
*/
//#define USE_IGNORE_CCD_CATEGORIES

using System;
using System.Collections.Generic;
using System.Diagnostics;

namespace TrueSync.Physics2D
{
    [Flags]
    public enum Category
    {
        None = 0,
        All = int.MaxValue,
        Cat1 = 1,
        Cat2 = 2,
        Cat3 = 4,
        Cat4 = 8,
        Cat5 = 16,
        Cat6 = 32,
        Cat7 = 64,
        Cat8 = 128,
        Cat9 = 256,
        Cat10 = 512,
        Cat11 = 1024,
        Cat12 = 2048,
        Cat13 = 4096,
        Cat14 = 8192,
        Cat15 = 16384,
        Cat16 = 32768,
        Cat17 = 65536,
        Cat18 = 131072,
        Cat19 = 262144,
        Cat20 = 524288,
        Cat21 = 1048576,
        Cat22 = 2097152,
        Cat23 = 4194304,
        Cat24 = 8388608,
        Cat25 = 16777216,
        Cat26 = 33554432,
        Cat27 = 67108864,
        Cat28 = 134217728,
        Cat29 = 268435456,
        Cat30 = 536870912,
        Cat31 = 1073741824
    }

    /// <summary>
    /// This proxy is used internally to connect fixtures to the broad-phase.
    /// </summary>
    public struct FixtureProxy
    {
        public AABB AABB;
        public int ChildIndex;
        public Fixture Fixture;
        public int ProxyId;
    }

    /// <summary>
    /// A fixture is used to attach a Shape to a body for collision detection. A fixture
    /// inherits its transform from its parent. Fixtures hold additional non-geometric data
    /// such as friction, collision filters, etc.
    /// Fixtures are created via Body.CreateFixture.
    /// Warning: You cannot reuse fixtures.
    /// </summary>
    public class Fixture : IDisposable
    {
        [ThreadStatic]
        internal static int _fixtureIdCounter;
        private bool _isSensor;
        private FP _friction;
        private FP _restitution;

        internal Category _collidesWith;
        internal Category _collisionCategories;
        internal short _collisionGroup;
        internal HashSet<int> _collisionIgnores;

        public FixtureProxy[] Proxies;
        public int ProxyCount;
        public Category IgnoreCCDWith;

        /// <summary>
        /// Fires after two shapes has collided and are solved. This gives you a chance to get the impact force.
        /// </summary>
        public AfterCollisionEventHandler AfterCollision;

        /// <summary>
        /// Fires when two fixtures are close to each other.
        /// Due to how the broadphase works, this can be quite inaccurate as shapes are approximated using AABBs.
        /// </summary>
        public BeforeCollisionEventHandler BeforeCollision;

        /// <summary>
        /// Fires when two shapes collide and a contact is created between them.
        /// Note that the first fixture argument is always the fixture that the delegate is subscribed to.
        /// </summary>
        public OnCollisionEventHandler OnCollision;

        /// <summary>
        /// Fires when two shapes separate and a contact is removed between them.
        /// Note: This can in some cases be called multiple times, as a fixture can have multiple contacts.
        /// Note The first fixture argument is always the fixture that the delegate is subscribed to.
        /// </summary>
        public OnSeparationEventHandler OnSeparation;

        internal Fixture()
        {
            FixtureId = _fixtureIdCounter++;

            _collisionCategories = Settings.DefaultFixtureCollisionCategories;
            _collidesWith = Settings.DefaultFixtureCollidesWith;
            _collisionGroup = 0;
            _collisionIgnores = new HashSet<int>();

            IgnoreCCDWith = Settings.DefaultFixtureIgnoreCCDWith;

            //Fixture defaults
            Friction = 0.2f;
            Restitution = 0;
        }

        internal Fixture(Body body, Shape shape, object userData = null)
            : this()
        {
#if DEBUG
            if (shape.ShapeType == ShapeType.Polygon)
                ((PolygonShape)shape).Vertices.AttachedToBody = true;
#endif

            Body = body;
            UserData = userData;
            Shape = shape.Clone();

            RegisterFixture();
        }

        /// <summary>
        /// Defaults to 0
        /// 
        /// If Settings.UseFPECollisionCategories is set to false:
        /// Collision groups allow a certain group of objects to never collide (negative)
        /// or always collide (positive). Zero means no collision group. Non-zero group
        /// filtering always wins against the mask bits.
        /// 
        /// If Settings.UseFPECollisionCategories is set to true:
        /// If 2 fixtures are in the same collision group, they will not collide.
        /// </summary>
        public short CollisionGroup
        {
            set
            {
                if (_collisionGroup == value)
                    return;

                _collisionGroup = value;
                Refilter();
            }
            get { return _collisionGroup; }
        }

        /// <summary>
        /// Defaults to Category.All
        /// 
        /// The collision mask bits. This states the categories that this
        /// fixture would accept for collision.
        /// Use Settings.UseFPECollisionCategories to change the behavior.
        /// </summary>
        public Category CollidesWith
        {
            get { return _collidesWith; }

            set
            {
                if (_collidesWith == value)
                    return;

                _collidesWith = value;
                Refilter();
            }
        }

        /// <summary>
        /// The collision categories this fixture is a part of.
        /// 
        /// If Settings.UseFPECollisionCategories is set to false:
        /// Defaults to Category.Cat1
        /// 
        /// If Settings.UseFPECollisionCategories is set to true:
        /// Defaults to Category.All
        /// </summary>
        public Category CollisionCategories
        {
            get { return _collisionCategories; }

            set
            {
                if (_collisionCategories == value)
                    return;

                _collisionCategories = value;
                Refilter();
            }
        }

        /// <summary>
        /// Get the child Shape. You can modify the child Shape, however you should not change the
        /// number of vertices because this will crash some collision caching mechanisms.
        /// </summary>
        /// <value>The shape.</value>
        public Shape Shape { get; internal set; }

        /// <summary>
        /// Gets or sets a value indicating whether this fixture is a sensor.
        /// </summary>
        /// <value><c>true</c> if this instance is a sensor; otherwise, <c>false</c>.</value>
        public bool IsSensor
        {
            get { return _isSensor; }
            set
            {
                if (Body != null)
                    Body.Awake = true;

                _isSensor = value;
            }
        }

        /// <summary>
        /// Get the parent body of this fixture. This is null if the fixture is not attached.
        /// </summary>
        /// <value>The body.</value>
        public Body Body { get; internal set; }

        /// <summary>
        /// Set the user data. Use this to store your application specific data.
        /// </summary>
        /// <value>The user data.</value>
        public object UserData { get; set; }

        /// <summary>
        /// Set the coefficient of friction. This will _not_ change the friction of
        /// existing contacts.
        /// </summary>
        /// <value>The friction.</value>
        public FP Friction
        {
            get { return _friction; }
            set
            {
                Debug.Assert(!FP.IsNaN(value));

                _friction = value;
            }
        }

        /// <summary>
        /// Set the coefficient of restitution. This will not change the restitution of
        /// existing contacts.
        /// </summary>
        /// <value>The restitution.</value>
        public FP Restitution
        {
            get { return _restitution; }
            set
            {
                Debug.Assert(!FP.IsNaN(value));

                _restitution = value;
            }
        }

        /// <summary>
        /// Gets a unique ID for this fixture.
        /// </summary>
        /// <value>The fixture id.</value>
        public int FixtureId { get; internal set; }

        #region IDisposable Members

        public bool IsDisposed { get; set; }

        public void Dispose()
        {
            if (!IsDisposed)
            {
                Body.DestroyFixture(this);
                IsDisposed = true;
                GC.SuppressFinalize(this);
            }
        }

        #endregion

        /// <summary>
        /// Restores collisions between this fixture and the provided fixture.
        /// </summary>
        /// <param name="fixture">The fixture.</param>
        public void RestoreCollisionWith(Fixture fixture)
        {
            if (_collisionIgnores.Contains(fixture.FixtureId))
            {
                _collisionIgnores.Remove(fixture.FixtureId);
                Refilter();
            }
        }

        /// <summary>
        /// Ignores collisions between this fixture and the provided fixture.
        /// </summary>
        /// <param name="fixture">The fixture.</param>
        public void IgnoreCollisionWith(Fixture fixture)
        {
            if (!_collisionIgnores.Contains(fixture.FixtureId))
            {
                _collisionIgnores.Add(fixture.FixtureId);
                Refilter();
            }
        }

        /// <summary>
        /// Determines whether collisions are ignored between this fixture and the provided fixture.
        /// </summary>
        /// <param name="fixture">The fixture.</param>
        /// <returns>
        /// 	<c>true</c> if the fixture is ignored; otherwise, <c>false</c>.
        /// </returns>
        public bool IsFixtureIgnored(Fixture fixture)
        {
            return _collisionIgnores.Contains(fixture.FixtureId);
        }

        /// <summary>
        /// Contacts are persistant and will keep being persistant unless they are
        /// flagged for filtering.
        /// This methods flags all contacts associated with the body for filtering.
        /// </summary>
        private void Refilter()
        {
            // Flag associated contacts for filtering.
            ContactEdge edge = Body.ContactList;
            while (edge != null)
            {
                Contact contact = edge.Contact;
                Fixture fixtureA = contact.FixtureA;
                Fixture fixtureB = contact.FixtureB;
                if (fixtureA == this || fixtureB == this)
                {
                    contact.FilterFlag = true;
                }

                edge = edge.Next;
            }

            World world = Body._world;

            if (world == null)
            {
                return;
            }

            // Touch each proxy so that new pairs may be created
            IBroadPhase broadPhase = world.ContactManager.BroadPhase;
            for (int i = 0; i < ProxyCount; ++i)
            {
                broadPhase.TouchProxy(Proxies[i].ProxyId);
            }
        }

        private void RegisterFixture()
        {
            // Reserve proxy space
            Proxies = new FixtureProxy[Shape.ChildCount];
            ProxyCount = 0;

            if (Body.Enabled)
            {
                IBroadPhase broadPhase = Body._world.ContactManager.BroadPhase;
                CreateProxies(broadPhase, ref Body._xf);
            }

            Body.FixtureList.Add(this);

            // Adjust mass properties if needed.
            if (Shape._density > 0.0f)
            {
                Body.ResetMassData();
            }

            // Let the world know we have a new fixture. This will cause new contacts
            // to be created at the beginning of the next time step.
            Body._world._worldHasNewFixture = true;

            if (Body._world.FixtureAdded != null)
            {
                Body._world.FixtureAdded(this);
            }
        }

        /// <summary>
        /// Test a point for containment in this fixture.
        /// </summary>
        /// <param name="point">A point in world coordinates.</param>
        /// <returns></returns>
        public bool TestPoint(ref TSVector2 point)
        {
            return Shape.TestPoint(ref Body._xf, ref point);
        }

        /// <summary>
        /// Cast a ray against this Shape.
        /// </summary>
        /// <param name="output">The ray-cast results.</param>
        /// <param name="input">The ray-cast input parameters.</param>
        /// <param name="childIndex">Index of the child.</param>
        /// <returns></returns>
        public bool RayCast(out RayCastOutput output, ref RayCastInput input, int childIndex)
        {
            return Shape.RayCast(out output, ref input, ref Body._xf, childIndex);
        }

        /// <summary>
        /// Get the fixture's AABB. This AABB may be enlarge and/or stale.
        /// If you need a more accurate AABB, compute it using the Shape and
        /// the body transform.
        /// </summary>
        /// <param name="aabb">The aabb.</param>
        /// <param name="childIndex">Index of the child.</param>
        public void GetAABB(out AABB aabb, int childIndex)
        {
            Debug.Assert(0 <= childIndex && childIndex < ProxyCount);
            aabb = Proxies[childIndex].AABB;
        }

        internal void Destroy()
        {
#if DEBUG
            if (Shape.ShapeType == ShapeType.Polygon)
                ((PolygonShape)Shape).Vertices.AttachedToBody = false;
#endif

            // The proxies must be destroyed before calling this.
            Debug.Assert(ProxyCount == 0);

            // Free the proxy array.
            Proxies = null;
            Shape = null;

            //FPE: We set the userdata to null here to help prevent bugs related to stale references in GC
            UserData = null;

            BeforeCollision = null;
            OnCollision = null;
            OnSeparation = null;
            AfterCollision = null;

            if (Body._world.FixtureRemoved != null)
            {
                Body._world.FixtureRemoved(this);
            }

            Body._world.FixtureAdded = null;
            Body._world.FixtureRemoved = null;
            OnSeparation = null;
            OnCollision = null;
        }

        // These support body activation/deactivation.
        internal void CreateProxies(IBroadPhase broadPhase, ref Transform xf)
        {
            Debug.Assert(ProxyCount == 0);

            // Create proxies in the broad-phase.
            ProxyCount = Shape.ChildCount;

            for (int i = 0; i < ProxyCount; ++i)
            {
                FixtureProxy proxy = new FixtureProxy();
                Shape.ComputeAABB(out proxy.AABB, ref xf, i);
                proxy.Fixture = this;
                proxy.ChildIndex = i;

                //FPE note: This line needs to be after the previous two because FixtureProxy is a struct
                proxy.ProxyId = broadPhase.AddProxy(ref proxy);

                Proxies[i] = proxy;
            }
        }

        internal void DestroyProxies(IBroadPhase broadPhase)
        {
            // Destroy proxies in the broad-phase.
            for (int i = 0; i < ProxyCount; ++i)
            {
                broadPhase.RemoveProxy(Proxies[i].ProxyId);
                Proxies[i].ProxyId = -1;
            }

            ProxyCount = 0;
        }

        internal void Synchronize(IBroadPhase broadPhase, ref Transform transform1, ref Transform transform2)
        {
            if (ProxyCount == 0)
            {
                return;
            }

            for (int i = 0; i < ProxyCount; ++i)
            {
                FixtureProxy proxy = Proxies[i];

                // Compute an AABB that covers the swept Shape (may miss some rotation effect).
                AABB aabb1, aabb2;
                Shape.ComputeAABB(out aabb1, ref transform1, proxy.ChildIndex);
                Shape.ComputeAABB(out aabb2, ref transform2, proxy.ChildIndex);

                proxy.AABB.Combine(ref aabb1, ref aabb2);

                TSVector2 displacement = transform2.p - transform1.p;

                broadPhase.MoveProxy(proxy.ProxyId, ref proxy.AABB, displacement);
            }
        }

        /// <summary>
        /// Only compares the values of this fixture, and not the attached shape or body.
        /// This is used for deduplication in serialization only.
        /// </summary>
        internal bool CompareTo(Fixture fixture)
        {
            return (_collidesWith == fixture._collidesWith &&
                    _collisionCategories == fixture._collisionCategories &&
                    _collisionGroup == fixture._collisionGroup &&
                    Friction == fixture.Friction &&
                    IsSensor == fixture.IsSensor &&
                    Restitution == fixture.Restitution &&
                    UserData == fixture.UserData &&
                    IgnoreCCDWith == fixture.IgnoreCCDWith &&
                    SequenceEqual(_collisionIgnores, fixture._collisionIgnores));
        }

        private bool SequenceEqual<T>(HashSet<T> first, HashSet<T> second)
        {
            if (first.Count != second.Count)
                return false;

            using (IEnumerator<T> enumerator1 = first.GetEnumerator())
            {
                using (IEnumerator<T> enumerator2 = second.GetEnumerator())
                {
                    while (enumerator1.MoveNext())
                    {
                        if (!enumerator2.MoveNext() || !Equals(enumerator1.Current, enumerator2.Current))
                            return false;
                    }

                    if (enumerator2.MoveNext())
                        return false;
                }
            }

            return true;
        }

        /// <summary>
        /// Clones the fixture and attached shape onto the specified body.
        /// </summary>
        /// <param name="body">The body you wish to clone the fixture onto.</param>
        /// <returns>The cloned fixture.</returns>
        public Fixture CloneOnto(Body body)
        {
            Fixture fixture = new Fixture();
            fixture.Body = body;
            fixture.Shape = Shape.Clone();
            fixture.UserData = UserData;
            fixture.Restitution = Restitution;
            fixture.Friction = Friction;
            fixture.IsSensor = IsSensor;
            fixture._collisionGroup = _collisionGroup;
            fixture._collisionCategories = _collisionCategories;
            fixture._collidesWith = _collidesWith;
            fixture.IgnoreCCDWith = IgnoreCCDWith;

            foreach (int ignore in _collisionIgnores)
            {
                fixture._collisionIgnores.Add(ignore);
            }

            fixture.RegisterFixture();
            return fixture;
        }
    }
}