// This code is in the public domain -- castanyo@yahoo.es

#pragma once
#ifndef NV_MESH_HALFEDGE_MESH_H
#define NV_MESH_HALFEDGE_MESH_H

#include "nvmesh/nvmesh.h"
#include "nvcore/Array.h"
#include "nvcore/HashMap.h"

/*
If I were to redo this again, there are a number of things that I would do differently.
- Edge map is only useful when importing a mesh to guarantee the result is two-manifold. However, when manipulating the mesh
  it's a pain to maintain the map up to date.
- Edge array only points to the even vertices. There's no good reason for that. The map becomes required to traverse all edges
  or you have to make sure edges are properly paired.
- Linked boundaries. It's cleaner to assume a NULL pair means a boundary edge. Makes easier to seal boundaries. The only reason
  why we link boundaries is to simplify traversal, but that could be done with two helper functions (nextBoundary, prevBoundary).
- Minimize the amount of state that needs to be set in a certain way:
    - boundary vertices point to boundary edge.
- Remove parenthesis! Make some members public.
- Remove member functions with side effects:
    - e->setNext(n) modifies e->next and n->prev, instead use "link(e, n)", or "e->next = n, n->prev = e"
*/


namespace nv
{
    class Vector3;
    class TriMesh;
    class QuadTriMesh;
    //template <typename T> struct Hash<Mesh::Key>;

    namespace HalfEdge
    {
        class Edge;
        class Face;
        class Vertex;

        /// Simple half edge mesh designed for dynamic mesh manipulation.
        class Mesh
        {
        public:

            Mesh();
            Mesh(const Mesh * mesh);
            ~Mesh();

            void clear();

            Vertex * addVertex(const Vector3 & pos);
            //Vertex * addVertex(uint id, const Vector3 & pos);
            //void addVertices(const Mesh * mesh);

            void linkColocals();
            void linkColocalsWithCanonicalMap(const Array<uint> & canonicalMap);
            void resetColocalLinks();

            Face * addFace();
            Face * addFace(uint v0, uint v1, uint v2);
            Face * addFace(uint v0, uint v1, uint v2, uint v3);
            Face * addFace(const Array<uint> & indexArray);
            Face * addFace(const Array<uint> & indexArray, uint first, uint num);
            //void addFaces(const Mesh * mesh);

            // These functions disconnect the given element from the mesh and delete it.
            void disconnect(Edge * edge);
            void disconnectPair(Edge * edge);
            void disconnect(Vertex * vertex);
            void disconnect(Face * face);

            void remove(Edge * edge);
            void remove(Vertex * vertex);
            void remove(Face * face);

            // Remove holes from arrays and reassign indices.
            void compactEdges();
            void compactVertices();
            void compactFaces();

            void triangulate();

            void linkBoundary();
            
            bool splitBoundaryEdges(); // Returns true if any split was made.

            // Sew the boundary that starts at the given edge, returns one edge that still belongs to boundary, or NULL if boundary closed.
            HalfEdge::Edge * sewBoundary(Edge * startEdge);


            // Vertices
            uint vertexCount() const { return m_vertexArray.count(); }
            const Vertex * vertexAt(int i) const { return m_vertexArray[i]; }
            Vertex * vertexAt(int i) { return m_vertexArray[i]; }

            uint colocalVertexCount() const { return m_colocalVertexCount; }

            // Faces
            uint faceCount() const { return m_faceArray.count(); }
            const Face * faceAt(int i) const { return m_faceArray[i]; }
            Face * faceAt(int i) { return m_faceArray[i]; }

            // Edges
            uint edgeCount() const { return m_edgeArray.count();  }
            const Edge * edgeAt(int i) const { return m_edgeArray[i]; }
            Edge * edgeAt(int i) { return m_edgeArray[i]; }

            class ConstVertexIterator;

            class VertexIterator
            {
                friend class ConstVertexIterator;
            public:
                VertexIterator(Mesh * mesh) : m_mesh(mesh), m_current(0) { }

                virtual void advance() { m_current++; }
                virtual bool isDone() const { return m_current == m_mesh->vertexCount(); }
                virtual Vertex * current() const { return m_mesh->vertexAt(m_current); }

            private:
                HalfEdge::Mesh * m_mesh;
                uint m_current;
            };
            VertexIterator vertices() { return VertexIterator(this); }

            class ConstVertexIterator
            {
            public:
                ConstVertexIterator(const Mesh * mesh) : m_mesh(mesh), m_current(0) { }
                ConstVertexIterator(class VertexIterator & it) : m_mesh(it.m_mesh), m_current(it.m_current) { }

                virtual void advance() { m_current++; }
                virtual bool isDone() const { return m_current == m_mesh->vertexCount(); }
                virtual const Vertex * current() const { return m_mesh->vertexAt(m_current); }

            private:
                const HalfEdge::Mesh * m_mesh;
                uint m_current;
            };
            ConstVertexIterator vertices() const { return ConstVertexIterator(this); }

            class ConstFaceIterator;

            class FaceIterator
            {
                friend class ConstFaceIterator;
            public:
                FaceIterator(Mesh * mesh) : m_mesh(mesh), m_current(0) { }

                virtual void advance() { m_current++; }
                virtual bool isDone() const { return m_current == m_mesh->faceCount(); }
                virtual Face * current() const { return m_mesh->faceAt(m_current); }

            private:
                HalfEdge::Mesh * m_mesh;
                uint m_current;
            };
            FaceIterator faces() { return FaceIterator(this); }

            class ConstFaceIterator
            {
            public:
                ConstFaceIterator(const Mesh * mesh) : m_mesh(mesh), m_current(0) { }
                ConstFaceIterator(const FaceIterator & it) : m_mesh(it.m_mesh), m_current(it.m_current) { }

                virtual void advance() { m_current++; }
                virtual bool isDone() const { return m_current == m_mesh->faceCount(); }
                virtual const Face * current() const { return m_mesh->faceAt(m_current); }

            private:
                const HalfEdge::Mesh * m_mesh;
                uint m_current;
            };
            ConstFaceIterator faces() const { return ConstFaceIterator(this); }

            class ConstEdgeIterator;

            class EdgeIterator
            {
                friend class ConstEdgeIterator;
            public:
                EdgeIterator(Mesh * mesh) : m_mesh(mesh), m_current(0) { }

                virtual void advance() { m_current++; }
                virtual bool isDone() const { return m_current == m_mesh->edgeCount(); }
                virtual Edge * current() const { return m_mesh->edgeAt(m_current); }

            private:
                HalfEdge::Mesh * m_mesh;
                uint m_current;
            };
            EdgeIterator edges() { return EdgeIterator(this); }

            class ConstEdgeIterator
            {
            public:
                ConstEdgeIterator(const Mesh * mesh) : m_mesh(mesh), m_current(0) { }
                ConstEdgeIterator(const EdgeIterator & it) : m_mesh(it.m_mesh), m_current(it.m_current) { }

                virtual void advance() { m_current++; }
                virtual bool isDone() const { return m_current == m_mesh->edgeCount(); }
                virtual const Edge * current() const { return m_mesh->edgeAt(m_current); }

            private:
                const HalfEdge::Mesh * m_mesh;
                uint m_current;
            };
            ConstEdgeIterator edges() const { return ConstEdgeIterator(this); }

            // @@ Add half-edge iterator.



            // Convert to tri mesh.
            TriMesh * toTriMesh() const;
            QuadTriMesh * toQuadTriMesh() const;

            bool isValid() const;

        public:

            // Error status:
            mutable uint errorCount;
            mutable uint errorIndex0;
            mutable uint errorIndex1;

        private:

            bool canAddFace(const Array<uint> & indexArray, uint first, uint num) const;
            bool canAddEdge(uint i, uint j) const;
            Edge * addEdge(uint i, uint j);

            Edge * findEdge(uint i, uint j) const;

            void linkBoundaryEdge(Edge * edge);
            Vertex * splitBoundaryEdge(Edge * edge, float t, const Vector3 & pos);
            void splitBoundaryEdge(Edge * edge, Vertex * vertex);

        private:

            Array<Vertex *> m_vertexArray;
            Array<Edge *> m_edgeArray;
            Array<Face *> m_faceArray;

            struct Key {
                Key() {}
                Key(const Key & k) : p0(k.p0), p1(k.p1) {}
                Key(uint v0, uint v1) : p0(v0), p1(v1) {}
                void operator=(const Key & k) { p0 = k.p0; p1 = k.p1; }
                bool operator==(const Key & k) const { return p0 == k.p0 && p1 == k.p1; }

                uint p0;
                uint p1;
            };
            friend struct Hash<Mesh::Key>;

            HashMap<Key, Edge *> m_edgeMap;

            uint m_colocalVertexCount;

        };
        /*
        // This is a much better hash than the default and greatly improves performance!
        template <> struct hash<Mesh::Key>
        {
        uint operator()(const Mesh::Key & k) const { return k.p0 + k.p1; }
        };
        */

    } // HalfEdge namespace

} // nv namespace

#endif // NV_MESH_HALFEDGE_MESH_H