using UnityEngine;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System;
using UnityEngine.ProBuilder;
using UnityEngine.ProBuilder.KdTree;
using UnityEngine.ProBuilder.KdTree.Math;

namespace UnityEngine.ProBuilder.MeshOperations
{
    /// <summary>
    /// Methods for merging and splitting common (or shared) vertices.
    /// </summary>
    public static class VertexEditing
    {
        /// <summary>
        /// Collapses all specified indices to a single shared index.
        ///
        /// This is equivalent to the [Collapse Vertices](../manual/Vert_Collapse.html) action.
        /// </summary>
        /// <remarks>
        /// Retains vertex normals.
        /// </remarks>
        /// <param name="mesh">Target mesh.</param>
        /// <param name="indexes">The indexes to merge to a single shared vertex.</param>
        /// <param name="collapseToFirst">True to collapse the vertices onto the first vertex position; false to merge all vertices to the average position.</param>
        /// <returns>The first available local index created as a result of the merge, or -1 if action failed.</returns>
        public static int MergeVertices(this ProBuilderMesh mesh, int[] indexes, bool collapseToFirst = false)
        {
            if (mesh == null)
                throw new ArgumentNullException("mesh");

            if (indexes == null)
                throw new ArgumentNullException("indexes");

            Vertex[] vertices = mesh.GetVertices();
            Vertex cen = collapseToFirst ? vertices[indexes[0]] : Vertex.Average(vertices, indexes);
            mesh.SetVerticesCoincident(indexes);
            UVEditing.SplitUVs(mesh, indexes);
            int sharedVertexHandle = mesh.GetSharedVertexHandle(indexes[0]);
            mesh.SetSharedVertexValues(sharedVertexHandle, cen);

            SharedVertex merged = mesh.sharedVerticesInternal[sharedVertexHandle];
            List<int> removedIndexes = new List<int>();

            MeshValidation.RemoveDegenerateTriangles(mesh, removedIndexes);

            // get a non-deleted index to work with
            int ind = -1;
            for (int i = 0; i < merged.Count; i++)
                if (!removedIndexes.Contains(merged[i]))
                    ind = merged[i];

            int res = ind;

            for (int i = 0; i < removedIndexes.Count; i++)
                if (ind > removedIndexes[i])
                    res--;

            return res;
        }

        /// <summary>
        /// Splits the vertices referenced by edge from their shared indices so that each vertex moves independently.
        ///
        /// This corresponds to the [Split Vertices](../manual/Vert_Split.html) action.
        /// </summary>
        /// <remarks>
        /// This is equivalent to calling `SplitVertices(mesh, new int[] { edge.x, edge.y });`.
        /// </remarks>
        /// <param name="mesh">The source mesh.</param>
        /// <param name="edge">The edge to query for vertex indexes.</param>
        /// <seealso cref="SplitVertices(UnityEngine.ProBuilder.ProBuilderMesh,System.Collections.Generic.IEnumerable{int})"/>
        public static void SplitVertices(this ProBuilderMesh mesh, Edge edge)
        {
            SplitVertices(mesh, new int[] { edge.a, edge.b });
        }

        /// <summary>
        /// Splits vertices from their shared indices so that each vertex moves independently.
        ///
        /// This corresponds to the [Split Vertices](../manual/Vert_Split.html) action.
        /// </summary>
        /// <param name="mesh">The source mesh.</param>
        /// <param name="vertices">A list of vertex indices to split.</param>
        /// <seealso cref="ProBuilderMesh.sharedVertices"/>
        public static void SplitVertices(this ProBuilderMesh mesh, IEnumerable<int> vertices)
        {
            if (mesh == null)
                throw new ArgumentNullException("mesh");

            if (vertices == null)
                throw new ArgumentNullException("vertices");

            // ToDictionary always sets the universal indexes in ascending order from 0+.
            Dictionary<int, int> lookup = mesh.sharedVertexLookup;
            int max = lookup.Count;
            foreach (int i in vertices)
                lookup[i] = ++max;
            mesh.SetSharedVertices(lookup);
        }

        /// <summary>
        /// Similar to Merge vertices, expect that this method only collapses vertices within a specified distance
        /// of one another (typically `Mathf.Epsilon` is used).
        ///
        /// This is equivalent to the [Weld Vertices](../manual/Vert_Weld.html) action.
        /// </summary>
        /// <param name="mesh">The source mesh.</param>
        /// <param name="indexes">The vertex indices to consider. For example, to weld the entire object, set this value to the return value from `pb.faces.SelectMany(x => x.indexes)`.</param>
        /// <param name="neighborRadius">The minimum distance between vertices to consider them for welding.</param>
        /// <returns>The indices of any new vertices created by a weld.</returns>
        public static int[] WeldVertices(this ProBuilderMesh mesh, IEnumerable<int> indexes, float neighborRadius)
        {
            if (mesh == null)
                throw new ArgumentNullException("mesh");

            if (indexes == null)
                throw new ArgumentNullException("indexes");

            Vertex[] vertices = mesh.GetVertices();
            SharedVertex[] sharedIndexes = mesh.sharedVerticesInternal;

            HashSet<int> common = mesh.GetSharedVertexHandles(indexes);
            int vertexCount = common.Count;

            // Make assumption that there will rarely be a time when a single weld encompasses more than 32 vertices.
            // If a radial search returns neighbors matching the max count, the search is re-done and maxNearestNeighbors
            // is set to the resulting length. This will be slow, but in most cases shouldn't happen ever, or if it does,
            // should only happen once or twice.
            int maxNearestNeighbors = System.Math.Min(32, common.Count);

            // 3 dimensions, duplicate entries allowed
            KdTree<float, int> tree = new KdTree<float, int>(3, new FloatMath(), AddDuplicateBehavior.Collect);

            foreach (int i in common)
            {
                Vector3 v = vertices[sharedIndexes[i][0]].position;
                tree.Add(new float[] { v.x, v.y, v.z }, i);
            }

            float[] point = new float[3] { 0, 0, 0 };
            Dictionary<int, int> remapped = new Dictionary<int, int>();
            Dictionary<int, Vector3> averages = new Dictionary<int, Vector3>();
            int index = sharedIndexes.Length;

            foreach (int commonIndex in common)
            {
                // already merged with another
                if (remapped.ContainsKey(commonIndex))
                    continue;

                Vector3 v = vertices[sharedIndexes[commonIndex][0]].position;

                point[0] = v.x;
                point[1] = v.y;
                point[2] = v.z;

                // Radial search at each point
                KdTreeNode<float, int>[] neighbors = tree.RadialSearch(point, neighborRadius, maxNearestNeighbors);

                // if first radial search filled the entire allotment reset the max neighbor count to 1.5x.
                // the result hopefully preventing double-searches in the next iterations.
                if (maxNearestNeighbors < vertexCount && neighbors.Length >= maxNearestNeighbors)
                {
                    neighbors = tree.RadialSearch(point, neighborRadius, vertexCount);
                    maxNearestNeighbors = System.Math.Min(vertexCount, neighbors.Length + neighbors.Length / 2);
                }

                Vector3 avg = Vector3.zero;
                float count = 0;

                for (int neighborIndex = 0; neighborIndex < neighbors.Length; neighborIndex++)
                {
                    // common index of this neighbor
                    int c = neighbors[neighborIndex].Value;

                    // if it's already been added to another, skip it
                    if (remapped.ContainsKey(c))
                        continue;

                    avg.x += neighbors[neighborIndex].Point[0];
                    avg.y += neighbors[neighborIndex].Point[1];
                    avg.z += neighbors[neighborIndex].Point[2];

                    remapped.Add(c, index);

                    count++;

                    if (neighbors[neighborIndex].Duplicates != null)
                    {
                        for (int duplicateIndex = 0; duplicateIndex < neighbors[neighborIndex].Duplicates.Count; duplicateIndex++)
                            remapped.Add(neighbors[neighborIndex].Duplicates[duplicateIndex], index);
                    }
                }

                avg.x /= count;
                avg.y /= count;
                avg.z /= count;

                averages.Add(index, avg);

                index++;
            }

            var welds = new int[remapped.Count];
            int n = 0;
            var lookup = mesh.sharedVertexLookup;

            foreach (var kvp in remapped)
            {
                SharedVertex tris = sharedIndexes[kvp.Key];

                welds[n++] = tris[0];

                for (int i = 0; i < tris.Count; i++)
                {
                    lookup[tris[i]] = kvp.Value;
                    vertices[tris[i]].position = averages[kvp.Value];
                }
            }

            mesh.SetSharedVertices(lookup);
            mesh.SetVertices(vertices);
            return welds;
        }

        /// <summary>
        /// Split a common index on a face into two vertices and slide each vertex backwards along it's feeding edge by distance.
        /// This method does not perform any input validation, so make sure edgeAndCommonIndex is distinct and all winged edges belong
        /// to the same face.
        ///<pre>
        /// `appendedVertices` is common index and a list of the new face indexes it was split into.
        ///
        /// _ _ _ _          _ _ _
        /// |              /
        /// |         ->   |
        /// |              |
        /// </pre>
        /// </summary>
        /// <param name="vertices"></param>
        /// <param name="edgeAndCommonIndex"></param>
        /// <param name="distance"></param>
        /// <param name="appendedVertices"></param>
        /// <returns></returns>
        internal static FaceRebuildData ExplodeVertex(
            IList<Vertex> vertices,
            IList<SimpleTuple<WingedEdge, int>> edgeAndCommonIndex,
            float distance,
            out Dictionary<int, List<int>> appendedVertices)
        {
            Face face = edgeAndCommonIndex.FirstOrDefault().item1.face;
            List<Edge> perimeter = WingedEdge.SortEdgesByAdjacency(face);
            appendedVertices = new Dictionary<int, List<int>>();
            Vector3 oldNormal = Math.Normal(vertices, face.indexesInternal);

            // store local and common index of split points
            Dictionary<int, int> toSplit = new Dictionary<int, int>();

            foreach (SimpleTuple<WingedEdge, int> v in edgeAndCommonIndex)
            {
                if (v.item2 == v.item1.edge.common.a)
                    toSplit.Add(v.item1.edge.local.a, v.item2);
                else
                    toSplit.Add(v.item1.edge.local.b, v.item2);
            }

            int pc = perimeter.Count;
            List<Vertex> n_vertices = new List<Vertex>();

            for (int i = 0; i < pc; i++)
            {
                int index = perimeter[i].b;

                // split this index into two
                if (toSplit.ContainsKey(index))
                {
                    // a --- b --- c
                    Vertex a = vertices[perimeter[i].a];
                    Vertex b = vertices[perimeter[i].b];
                    Vertex c = vertices[perimeter[(i + 1) % pc].b];

                    Vertex leading_dir = a - b;
                    Vertex following_dir = c - b;
                    leading_dir.Normalize();
                    following_dir.Normalize();

                    Vertex leading_insert = vertices[index] + leading_dir * distance;
                    Vertex following_insert = vertices[index] + following_dir * distance;

                    appendedVertices.AddOrAppend(toSplit[index], n_vertices.Count);
                    n_vertices.Add(leading_insert);

                    appendedVertices.AddOrAppend(toSplit[index], n_vertices.Count);
                    n_vertices.Add(following_insert);
                }
                else
                {
                    n_vertices.Add(vertices[index]);
                }
            }

            List<int> triangles;

            if (Triangulation.TriangulateVertices(n_vertices, out triangles, false))
            {
                FaceRebuildData data = new FaceRebuildData();
                data.vertices = n_vertices;
                data.face = new Face(face);

                Vector3 newNormal = Math.Normal(n_vertices, triangles);

                if (Vector3.Dot(oldNormal, newNormal) < 0f)
                    triangles.Reverse();

                data.face.indexesInternal = triangles.ToArray();

                return data;
            }

            return null;
        }

        static Edge AlignEdgeWithDirection(EdgeLookup edge, int commonIndex)
        {
            if (edge.common.a == commonIndex)
                return new Edge(edge.local.a, edge.local.b);
            else
                return new Edge(edge.local.b, edge.local.a);
        }
    }
}