// Shatter Toolkit
// Copyright 2015 Gustav Olsson
using System.Collections.Generic;
using UnityEngine;

namespace ShatterToolkit
{
    [RequireComponent(typeof(MeshFilter))]
    public class ShatterTool : MonoBehaviour
    {
        [SerializeField]
        protected int generation = 1;
        
        [SerializeField]
        protected int generationLimit = 3;
        
        [SerializeField]
        protected int cuts = 2;
        
        [SerializeField]
        protected bool fillCut = true;
        
        [SerializeField]
        protected bool sendPreSplitMessage = false;
        
        [SerializeField]
        protected bool sendPostSplitMessage = false;
        
        [SerializeField]
        protected HullType internalHullType = HullType.FastHull;
        
        protected bool isIntact = true;
        protected IHull hull;
        protected Vector3 center;
        
        /// <summary>
        /// Gets or sets the current generation of this ShatterTool instance.
        /// By default, a game object is of generation 1. When a game object
        /// is shattered using ShatterTool.Shatter() all new game objects
        /// will be considered of generation 2, and so on.
        /// For example, this value can be used to vary the color of a
        /// game object depending on how many times it has been shattered.
        /// </summary>
        public int Generation
        {
            get { return generation; }
            set { generation = Mathf.Max(value, 1); }
        }
        
        /// <summary>
        /// Gets or sets the generation limit of this ShatterTool instance.
        /// This value restricts how many times a game object may be shattered
        /// using ShatterTool.Shatter(). A game object will only be able to shatter
        /// if ShatterTool.Generation is less than ShatterTool.GenerationLimit.
        /// </summary>
        public int GenerationLimit
        {
            get { return generationLimit; }
            set { generationLimit = Mathf.Max(value, 1); }
        }
        
        /// <summary>
        /// Gets or sets the number of times the game object will be cut when ShatterTool.Shatter() occurs.
        /// </summary>
        public int Cuts
        {
            get { return cuts; }
            set { cuts = Mathf.Max(value, 1); }
        }
        
        /// <summary>
        /// Gets or sets whether the cut region should be triangulated.
        /// If true, the connected UvMapper component will control the vertex properties of the filled area.
        /// When the ShatterTool is used on double-sided meshes with zero thickness, such as planes, this value
        /// should be false.
        /// </summary>
        public bool FillCut
        {
            get { return fillCut; }
            set { fillCut = value; }
        }
        
        /// <summary>
        /// Gets or sets whether a PreSplit(Plane[] planes) message should be sent to the original game object prior to a split occurs.
        /// The supplied object will be the array of Planes that will be used to split the game object.
        /// </summary>
        public bool SendPreSplitMessage
        {
            get { return sendPreSplitMessage; }
            set { sendPreSplitMessage = value; }
        }
        
        /// <summary>
        /// Gets or sets whether a PostSplit(GameObject[] newGameObjects) message should be sent to the original game object
        /// after a split has occured. The message will be sent before destroying the original game object.
        /// The supplied object will be an array of all new GameObjects created during the split.
        /// </summary>
        public bool SendPostSplitMessage
        {
            get { return sendPostSplitMessage; }
            set { sendPostSplitMessage = value; }
        }
        
        /// <summary>
        /// Gets or sets the type of the internal hull used to shatter the mesh. The FastHull implementation is roughly 20-50% faster
        /// than the LegacyHull implementation and requires no time to startup. The LegacyHull implementation is more robust in extreme
        /// cases and is provided for backwards compatibility. This setting can't be changed during runtime.
        /// </summary>
        public HullType InternalHullType
        {
            get { return internalHullType; }
            set { internalHullType = value; }
        }
        
        /// <summary>
        /// Determines whether this game object is of the first generation. (Generation == 1)
        /// </summary>
        public bool IsFirstGeneration
        {
            get { return generation == 1; }
        }
        
        /// <summary>
        /// Determines whether this game object is of the last generation. (Generation >= GenerationLimit)
        /// </summary>
        public bool IsLastGeneration
        {
            get { return generation >= generationLimit; }
        }
        
        /// <summary>
        /// Gets the worldspace center of the game object. Only works during runtime.
        /// </summary>
        public Vector3 Center
        {
            get { return transform.TransformPoint(center); }
        }
        
        protected void CalculateCenter()
        {
            // Get the localspace center of the mesh bounds
            center = GetComponent<MeshFilter>().sharedMesh.bounds.center;
        }
        
        public void Start()
        {
            Mesh sharedMesh = GetComponent<MeshFilter>().sharedMesh;
            
            // Initialize the first generation hull
            if (hull == null)
            {
                if (internalHullType == HullType.FastHull)
                {
                    hull = new FastHull(sharedMesh);
                }
                else if (internalHullType == HullType.LegacyHull)
                {
                    hull = new LegacyHull(sharedMesh);
                }
            }
            
            // Update properties
            CalculateCenter();
        }
        
        /// <summary>
        /// Shatters the game object at a point, instantiating the pieces as new
        /// game objects (clones of the original) and destroying the original game object when finished.
        /// If the game object has reached the generation limit, nothing will happen.
        /// Apart from taking the generation into account, this is equivalent to calling
        /// ShatterTool.Split() using randomly generated planes passing through the point.
        /// </summary>
        /// <param name="point">
        /// The world-space point.
        /// </param>
        public void Shatter(Vector3 point)
        {
            if (!IsLastGeneration)
            {
                // Increase generation
                generation++;
                
                // Split the hull using randomly generated planes passing through the point
                Plane[] planes = new Plane[cuts];
                
                for (int i = 0; i < planes.Length; i++)
                {
                    planes[i] = new Plane(Random.onUnitSphere, point);
                }
                
                Split(planes);
            }
        }
        
        /// <summary>
        /// Splits the game object using an array of planes, instantiating the pieces as new
        /// game objects (clones of the original) and destroying the original game object when finished.
        /// </summary>
        /// <param name="planes">
        /// An array of world-space planes with unit-length normals.
        /// </param>
        public void Split(Plane[] planes)
        {
            if (planes != null && planes.Length > 0 && isIntact && hull != null && !hull.IsEmpty)
            {
                UvMapper uvMapper = GetComponent<UvMapper>();
                ColorMapper colorMapper = GetComponent<ColorMapper>();
                
                if (sendPreSplitMessage)
                {
                    SendMessage("PreSplit", planes, SendMessageOptions.DontRequireReceiver);
                }
                
                Vector3[] points, normals;
                ConvertPlanesToLocalspace(planes, out points, out normals);
                
                IList<IHull> newHulls;
                CreateNewHulls(uvMapper, colorMapper, points, normals, out newHulls);
                
                GameObject[] newGameObjects;
                CreateNewGameObjects(newHulls, out newGameObjects);
                
                if (sendPostSplitMessage)
                {
                    SendMessage("PostSplit", newGameObjects, SendMessageOptions.DontRequireReceiver);
                }
                
                Destroy(gameObject);
                
                isIntact = false;
            }
        }
        
        protected void ConvertPlanesToLocalspace(Plane[] planes, out Vector3[] points, out Vector3[] normals)
        {
            points = new Vector3[planes.Length];
            normals = new Vector3[planes.Length];
            
            for (int i = 0; i < planes.Length; i++)
            {
                Plane plane = planes[i];
                
                Vector3 localPoint = transform.InverseTransformPoint(plane.normal * -plane.distance);
                Vector3 localNormal = transform.InverseTransformDirection(plane.normal);
                
                localNormal.Scale(transform.localScale);
                localNormal.Normalize();
                
                points[i] = localPoint;
                normals[i] = localNormal;
            }
        }
        
        protected void CreateNewHulls(UvMapper uvMapper, ColorMapper colorMapper, Vector3[] points, Vector3[] normals, out IList<IHull> newHulls)
        {
            newHulls = new List<IHull>();
            
            // Add the starting hull
            newHulls.Add(hull);
            
            for (int j = 0; j < points.Length; j++)
            {
                int previousHullCount = newHulls.Count;
                
                for (int i = 0; i < previousHullCount; i++)
                {
                    IHull previousHull = newHulls[0];
                    
                    // Split the previous hull
                    IHull a, b;
                    
                    previousHull.Split(points[j], normals[j], fillCut, uvMapper, colorMapper, out a, out b);
                    
                    // Update the list
                    newHulls.Remove(previousHull);
                    
                    if (!a.IsEmpty)
                    {
                        newHulls.Add(a);
                    }
                    
                    if (!b.IsEmpty)
                    {
                        newHulls.Add(b);
                    }
                }
            }
        }
        
        protected void CreateNewGameObjects(IList<IHull> newHulls, out GameObject[] newGameObjects)
        {
            // Get new meshes
            Mesh[] newMeshes = new Mesh[newHulls.Count];
            float[] newVolumes = new float[newHulls.Count];
            
            float totalVolume = 0.0f;
            
            for (int i = 0; i < newHulls.Count; i++)
            {
                Mesh mesh = newHulls[i].GetMesh();
                Vector3 size = mesh.bounds.size;
                float volume = size.x * size.y * size.z;
                
                newMeshes[i] = mesh;
                newVolumes[i] = volume;
                
                totalVolume += volume;
            }

            MeshFilter meshFilter = GetComponent<MeshFilter>();
            MeshCollider meshCollider = GetComponent<MeshCollider>();
            Rigidbody rigidbody = GetComponent<Rigidbody>();

            // Remove mesh references to speed up instantiation
            meshFilter.sharedMesh = null;

            if (meshCollider != null)
            {
                meshCollider.sharedMesh = null;
            }
            
            // Create new game objects
            newGameObjects = new GameObject[newHulls.Count];
            
            for (int i = 0; i < newHulls.Count; i++)
            {
                IHull newHull = newHulls[i];
                Mesh newMesh = newMeshes[i];
                float volume = newVolumes[i];
                
                GameObject newGameObject = (GameObject)Instantiate(gameObject);
                
                // Set shatter tool
                ShatterTool newShatterTool = newGameObject.GetComponent<ShatterTool>();
                
                if (newShatterTool != null)
                {
                    newShatterTool.hull = newHull;
                }
                
                // Set mesh filter
                MeshFilter newMeshFilter = newGameObject.GetComponent<MeshFilter>();
                
                if (newMeshFilter != null)
                {
                    newMeshFilter.sharedMesh = newMesh;
                }
                
                // Set mesh collider
                MeshCollider newMeshCollider = newGameObject.GetComponent<MeshCollider>();
                
                if (newMeshCollider != null)
                {
                    newMeshCollider.sharedMesh = newMesh;
                }
                
                // Set rigidbody
                Rigidbody newRigidbody = newGameObject.GetComponent<Rigidbody>();
                
                if (rigidbody != null && newRigidbody != null)
                {
                    newRigidbody.mass = rigidbody.mass * (volume / totalVolume);
                    
                    if (!newRigidbody.isKinematic)
                    {
                        newRigidbody.velocity = rigidbody.GetPointVelocity(newRigidbody.worldCenterOfMass);
                        
                        newRigidbody.angularVelocity = rigidbody.angularVelocity;
                    }
                }
                
                // Update properties
                newShatterTool.CalculateCenter();
                
                newGameObjects[i] = newGameObject;
            }
        }
    }
}