//============================================================================
//  Copyright (c) Kitware, Inc.
//  All rights reserved.
//  See LICENSE.txt for details.
//  This software is distributed WITHOUT ANY WARRANTY; without even
//  the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
//  PURPOSE.  See the above copyright notice for more information.
//
//  Copyright 2015 Sandia Corporation.
//  Copyright 2015 UT-Battelle, LLC.
//  Copyright 2015 Los Alamos National Security.
//
//  Under the terms of Contract DE-AC04-94AL85000 with Sandia Corporation,
//  the U.S. Government retains certain rights in this software.
//
//  Under the terms of Contract DE-AC52-06NA25396 with Los Alamos National
//  Laboratory (LANL), the U.S. Government retains certain rights in
//  this software.
//============================================================================
#ifndef vtk_m_rendering_View_h
#define vtk_m_rendering_View_h
#include <vtkm/Math.h>
#include <vtkm/Matrix.h>
#include <vtkm/VectorAnalysis.h>

namespace vtkm {
namespace rendering {

class View
{
    class View3D
    {
    public:
        VTKM_CONT_EXPORT
        View3D() : fieldOfView(0.f)
        {}
        
        VTKM_CONT_EXPORT
        vtkm::Matrix<vtkm::Float32,4,4> CreateViewMatrix()
        {
            return View::ViewMtx(pos, lookAt, up);
        }

        VTKM_CONT_EXPORT
        vtkm::Matrix<vtkm::Float32,4,4> CreateProjectionMatrix(vtkm::Int32 &width,
                                                               vtkm::Int32 &height,
                                                               vtkm::Float32 &nearPlane,
                                                               vtkm::Float32 &farPlane)
        {
            vtkm::Matrix<vtkm::Float32,4,4> mtx;
            vtkm::MatrixIdentity(mtx);
                        
            vtkm::Float32 AspectRatio = vtkm::Float32(width) / vtkm::Float32(height);
            vtkm::Float32 fovRad = (fieldOfView * 3.1415926f)/180.f;
            fovRad = vtkm::Tan( fovRad * 0.5f);
            vtkm::Float32 size = nearPlane * fovRad;
            vtkm::Float32 left = -size * AspectRatio;
            vtkm::Float32 right = size * AspectRatio;
            vtkm::Float32 bottom = -size;
            vtkm::Float32 top = size;
            
            mtx(0,0) = 2.f * nearPlane / (right - left);
            mtx(1,1) = 2.f * nearPlane / (top - bottom);
            mtx(0,2) = (right + left) / (right - left);
            mtx(1,2) = (top + bottom) / (top - bottom);
            mtx(2,2) = -(farPlane + nearPlane)  / (farPlane - nearPlane);
            mtx(3,2) = -1.f;
            mtx(2,3) = -(2.f * farPlane * nearPlane) / (farPlane - nearPlane);
            mtx(3,3) = 0.f;
            return mtx;
        }
        
        
        vtkm::Vec<vtkm::Float32,3> up, lookAt, pos;
        vtkm::Float32 fieldOfView;
    };

    class View2D
    {
    public:
        VTKM_CONT_EXPORT
        View2D() : left(0.f), right(0.f), top(0.f), bottom(0.f), xScale(1.f)
        {}
        
        VTKM_CONT_EXPORT
        vtkm::Matrix<vtkm::Float32,4,4> CreateViewMatrix()
        {
            vtkm::Vec<vtkm::Float32,3> at((left+right)/2.f, (top+bottom)/2.f, 0.f);
            vtkm::Vec<vtkm::Float32,3> pos = at;
            pos[2] = 1.f;
            vtkm::Vec<vtkm::Float32,3> up(0,1,0);
            return View::ViewMtx(pos, at, up);
        }
        
        VTKM_CONT_EXPORT
        vtkm::Matrix<vtkm::Float32,4,4> CreateProjectionMatrix(vtkm::Float32 &size,
                                                               vtkm::Float32 &near,
                                                               vtkm::Float32 &far,
                                                               vtkm::Float32 &aspect)
        {
            vtkm::Matrix<vtkm::Float32,4,4> mtx(0.f);
            vtkm::Float32 L = -size/2.f * aspect;
            vtkm::Float32 R = size/2.f * aspect;
            vtkm::Float32 B = -size/2.f;
            vtkm::Float32 T = size/2.f;

            mtx(0,0) = 2.f/(R-L);
            mtx(1,1) = 2.f/(T-B);
            mtx(2,2) = -2.f/(far-near);
            mtx(0,3) = -(R+L)/(R-L);
            mtx(1,3) = -(T+B)/(T-B);
            mtx(2,3) = -(far+near)/(far-near);
            mtx(3,3) = 1.f;
            return mtx;
        }        
        
        vtkm::Float32 left, right, top, bottom;
        vtkm::Float32 xScale;
    };

private:
    static VTKM_CONT_EXPORT
    vtkm::Matrix<vtkm::Float32,4,4> ViewMtx(const vtkm::Vec<vtkm::Float32,3> &pos,
                                            const vtkm::Vec<vtkm::Float32,3> &at,
                                            const vtkm::Vec<vtkm::Float32,3> &up)
    {
        vtkm::Vec<vtkm::Float32,3> viewDir = pos-at;
        vtkm::Vec<vtkm::Float32,3> right = vtkm::Cross(up,viewDir);
        vtkm::Vec<vtkm::Float32,3> ru = vtkm::Cross(viewDir,right);
        
        vtkm::Normalize(viewDir);
        vtkm::Normalize(right);
        vtkm::Normalize(ru);
        
        vtkm::Matrix<vtkm::Float32,4,4> mtx;            
        vtkm::MatrixIdentity(mtx);
        
        mtx(0,0) = right[0];
        mtx(0,1) = right[1];
        mtx(0,2) = right[2];
        mtx(1,0) = ru[0];
        mtx(1,1) = ru[1];
        mtx(1,2) = ru[2];
        mtx(2,0) = viewDir[0];
        mtx(2,1) = viewDir[1];
        mtx(2,2) = viewDir[2];
        
        mtx(0,3) = -vtkm::dot(right,pos);
        mtx(1,3) = -vtkm::dot(ru,pos);
        mtx(2,3) = -vtkm::dot(viewDir,pos);
        
        return mtx;
    }
                                            
public:
    enum ViewType { VIEW_2D, VIEW_3D };
    ViewType viewType;
    View3D view3d;
    View2D view2d;
    
    vtkm::Int32 width, height;
    vtkm::Float32 nearPlane, farPlane;
    vtkm::Float32 vl, vr, vb, vt; //viewport.
    
    VTKM_CONT_EXPORT
    View(ViewType vtype=View::VIEW_3D) : width(-1), height(-1), nearPlane(0.f), farPlane(1.f), viewType(vtype),
                                         vl(-1.f), vr(1.f), vb(-1.f), vt(1.f)
    {}

    VTKM_CONT_EXPORT
    vtkm::Matrix<vtkm::Float32,4,4> CreateViewMatrix()
    {
        if (viewType == View::VIEW_3D)
            return view3d.CreateViewMatrix();
        else
            return view2d.CreateViewMatrix();
    }
    VTKM_CONT_EXPORT
    vtkm::Matrix<vtkm::Float32,4,4> CreateProjectionMatrix()
    {
        if (viewType == View::VIEW_3D)
            return view3d.CreateProjectionMatrix(width, height, nearPlane, farPlane);
        else
        {
            vtkm::Float32 size = vtkm::Abs(view2d.top-view2d.bottom);
            vtkm::Float32 l,r,b,t;
            GetRealViewport(l,r,b,t);
            vtkm::Float32 aspect = (static_cast<vtkm::Float32>(width)*(r-l)) / (static_cast<vtkm::Float32>(height)*(t-b));
            
            return view2d.CreateProjectionMatrix(size, nearPlane, farPlane, aspect);
        }
    }

    VTKM_CONT_EXPORT
    void GetRealViewport(vtkm::Float32 &l, vtkm::Float32 &r,
                         vtkm::Float32 &b, vtkm::Float32 &t)
    {
        if (viewType == View::VIEW_3D)
        {
            l = vl;
            r = vr;
            b = vb;
            t = vt;
        }
        else
        {
            vtkm::Float32 maxvw = (vr-vl) * static_cast<vtkm::Float32>(width);
            vtkm::Float32 maxvh = (vt-vb) * static_cast<vtkm::Float32>(height);
            vtkm::Float32 waspect = maxvw / maxvh;
            vtkm::Float32 daspect = (view2d.right - view2d.left) / (view2d.top - view2d.bottom);
            daspect *= view2d.xScale;
            //cerr << "waspect="<<waspect << "   \tdaspect="<<daspect<<endl;
            const bool center = true; // if false, anchor to bottom-left
            if (waspect > daspect)
            {
                vtkm::Float32 new_w = (vr-vl) * daspect / waspect;
                if (center)
                {
                    l = (vl+vr)/2.f - new_w/2.f;
                    r = (vl+vr)/2.f + new_w/2.f;
                }
                else
                {
                    l = vl;
                    r = vl + new_w;
                }
                b = vb;
                t = vt;
            }
            else
            {
                vtkm::Float32 new_h = (vt-vb) * waspect / daspect;
                if (center)
                {
                    b = (vb+vt)/2.f - new_h/2.f;
                    t = (vb+vt)/2.f + new_h/2.f;
                }
                else
                {
                    b = vb;
                    t = vb + new_h;
                }
                l = vl;
                r = vr;
            }
        }
    }    
};

}} // namespace vtkm::rendering

#endif // vtk_m_rendering_View_h