// Copyright (C) 2010, Guy Barrand. All rights reserved.
// See the file tools.license for terms.

#ifndef tools_zb_buffer
#define tools_zb_buffer

#include <cfloat> //DBL_MAX

#include "polygon"

namespace tools {
namespace zb {

// ZPos, ZZ defined in point.

class buffer {

  typedef double ZReal;
  static ZReal ZREAL_HUGE() {return DBL_MAX;}

public:
  typedef unsigned int ZPixel;
  //NOTE : with X11, bits_per_pixel can't be > 32.
protected:

  class writer {
  public:
    virtual void write(ZPos,ZPos,ZZ) = 0;
  public:
    writer(ZPixel a_pixel):m_pixel(a_pixel){}
    virtual ~writer(){}
  public:
    writer(const writer& a_from):m_pixel(a_from.m_pixel){}
    writer& operator=(const writer& a_from){
      m_pixel = a_from.m_pixel;
      return *this;
    }
  public:
    ZPixel m_pixel;
  };

  void _write_point(ZPos a_x,ZPos a_y,ZZ a_z,ZPixel a_pixel) {
    if((a_x<m_begX) || (a_x>m_endX)) return;
    if((a_y<m_begY) || (a_y>m_endY)) return;

    ZReal zpoint = (ZReal)a_z;
    unsigned long offset = a_y * m_zbw + a_x;
    ZReal* zbuff = m_zbuffer + offset;

    if(m_depth_test) {if(zpoint<*zbuff) return;}

    ZPixel* zimage = m_zimage  + offset;

    *zbuff = zpoint;
    blend(*zimage,a_pixel);
  }
  void write_point(ZPos a_x,ZPos a_y,ZZ a_z,unsigned int a_size,ZPixel a_pixel) {
    if(a_size>=1) { //see zb_action::npix().
      ZPos x,y;
      for(int i=-int(a_size);i<=int(a_size);i++) {
        x = a_x + i;
        for(int j=-int(a_size);j<=int(a_size);j++) {
          y = a_y + j;
          _write_point(x,y,a_z,a_pixel);
        }
      }
    } else {
      _write_point(a_x,a_y,a_z,a_pixel);
    }
  }

public:
  buffer()
  :m_depth_test(true)
  ,m_blend(false)
  ,m_zbuffer(0)
  ,m_zimage(0)
  ,m_zbw(0),m_zbh(0)
  ,m_begX(0),m_begY(0),m_endX(0),m_endY(0)
  ,m_scan_pixel(0L)
  ,m_planeAC(0),m_planeBC(0),m_planeDC(0)
  {}
  virtual ~buffer(){
    cmem_free(m_zbuffer);
    cmem_free(m_zimage);
    m_zbw = 0;
    m_zbh = 0;
    m_polygon.clear();
  }
protected:
  buffer(const buffer& a_from)
  :m_depth_test(a_from.m_depth_test)
  ,m_blend(a_from.m_blend)
  {}
  buffer& operator=(const buffer& a_from){
    m_depth_test = a_from.m_depth_test;
    m_blend = a_from.m_blend;
    return *this;
  }
public:
  void set_depth_test(bool a_on) {m_depth_test = a_on;}
  
  void set_blend(bool a_value) {m_blend = a_value;}

  bool change_size(unsigned int a_width,unsigned int a_height){
    if(!a_width||!a_height) return false;

    if(m_zbuffer &&  (m_zbw==a_width)  && (m_zbh==a_height)  ) return true;

    if(m_zbuffer){
      cmem_free(m_zbuffer);
      cmem_free(m_zimage);
    }

    m_zbw = a_width;
    m_zbh = a_height;
    m_zbuffer = cmem_alloc<ZReal>(m_zbw*m_zbh);
    if(!m_zbuffer){
      m_zbw = 0;
      m_zbh = 0;
      return false;
    }

    m_zimage = cmem_alloc<ZPixel>(m_zbw*m_zbh);
    if(!m_zimage){
      cmem_free(m_zbuffer);
      m_zbw = 0;
      m_zbh = 0;
      return false;
    }

    set_clip_region(0,0,m_zbw,m_zbh);
    m_polygon.clear();
    return true;
  }

  ZPixel* get_color_buffer(unsigned int& a_width,unsigned int& a_height) const {
    a_width  = m_zbw;
    a_height = m_zbh;
    return m_zimage;
  }

  void clear_color_buffer(ZPixel a_pixel) {
    // Erase acoording clip region.
    ZPos row,col;
    for(row=m_begY;row<=m_endY;row++){
      ZPixel* zimage = m_zimage + row * m_zbw + m_begX;
      for(col=m_begX;col<=m_endX;col++,zimage++) *zimage = a_pixel;
    }
  }

  void clear_depth_buffer() {
    // Erase acoording clip region.
    ZPos row,col;

    for(row=m_begY;row<=m_endY;row++) {
      ZReal* zbuff = m_zbuffer + row * m_zbw + m_begX;
      for(col=m_begX;col<=m_endX;col++,zbuff++){
        *zbuff = - ZREAL_HUGE();
      }
    }
  }

  ZPixel* zimage() {return m_zimage;}

  bool get_clipped_pixel(ZPos a_x,ZPos a_y,ZPixel& a_pixel) const {
    if((a_x<m_begX) || (a_x>m_endX))  {a_pixel = 0;return false;}
    if((a_y<m_begY) || (a_y>m_endY))  {a_pixel = 0;return false;}
    a_pixel = *(m_zimage + a_y * m_zbw + a_x);
    return true;
  }

public:
  void set_clip_region(ZPos a_x,ZPos a_y,unsigned int a_width,unsigned int a_height){
    // if a_width or a_height is zero, clip region is empty.

    m_begX      = a_x;
    m_begY      = a_y;
    m_endX      = a_x + a_width  - 1;
    m_endY      = a_y + a_height - 1;

    if(m_begX<0) m_begX = 0;
    if(m_begY<0) m_begY = 0;
    if(m_endX>ZPos(m_zbw-1)) m_endX = m_zbw-1;
    if(m_endY>ZPos(m_zbh-1)) m_endY = m_zbh-1;
  }

  void draw_point(const point& a_p,ZPixel a_pixel,unsigned int a_size){
    write_point(a_p.x,a_p.y,a_p.z,a_size,a_pixel);
  }

  void draw_line(const point& a_beg,const point& a_end,ZPixel a_pixel,unsigned int a_size){
    WriteLine(a_beg,a_end,a_size,a_pixel);
  }

  void draw_lines(int a_number,const point* a_list,ZPixel a_pixel,unsigned int a_size){
    for(int count=1;count<a_number;count++) {
      WriteLine(a_list[count-1],a_list[count],a_size,a_pixel);
    }
  }

  void draw_segments(int a_number,const point* a_list,ZPixel a_pixel,unsigned int a_size){
    int segment_number = a_number/2;
    for(int count=0;count<segment_number;count++) {
      WriteLine(a_list[2*count],a_list[2*count+1],a_size,a_pixel);
    }
  }
  void draw_markers(int a_number,const point* a_list,ZPixel a_pixel,unsigned int a_size){
    for(int count=0;count<a_number;count++){
      const point& p = a_list[count];
      write_point(p.x,p.y,p.z,a_size,a_pixel);
    }
  }

  void draw_polygon(int a_number,const point* a_list,
                    ZZ a_A,ZZ a_B,ZZ a_C,ZZ a_D,
                    //ZZ a_zmin,ZZ a_zmax,
                    ZPixel a_pixel){
    // Assume a_list is closed.
    if(a_number<3) return;
    if(a_C==0) return; //polygone seen from edge

    m_scan_pixel   = a_pixel;
    m_planeAC      = a_A/a_C;
    m_planeBC      = a_B/a_C;
    m_planeDC      = a_D/a_C;

    //if this polygon A is quite perpandicular to screen and close
    //to an other B than |dz| then some pixel of A could overwrite
    //pixel of B. Your have then to give a lower m_zboundPrec

    m_polygon.scan(a_number,a_list,0,WriteScanLine,this,m_zbw,m_zbh);


  }

  typedef unsigned char uchar;
  static void rgba2pix(float a_r,float a_g,float a_b,float a_a,ZPixel& a_pix) {
    uchar* _px = (uchar*)&a_pix;
    *_px = (uchar)(255.0F * a_r);_px++;
    *_px = (uchar)(255.0F * a_g);_px++;
    *_px = (uchar)(255.0F * a_b);_px++;
    *_px = (uchar)(255.0F * a_a);_px++;
  }
  static void pix2rgba(const ZPixel& a_pix,float& a_r,float& a_g,float& a_b,float& a_a) {
    uchar* _px = (uchar*)&a_pix;
    a_r = (*_px)/255.0f;_px++;
    a_g = (*_px)/255.0f;_px++;
    a_b = (*_px)/255.0f;_px++;
    a_a = (*_px)/255.0f;_px++;
  }
protected:
  void scan_write_point_1(ZPos a_x,ZPos a_y,ZZ a_z,ZPos /*a_beg*/,unsigned int a_size,ZPixel a_pixel) {
    write_point(a_x,a_y,a_z,a_size,a_pixel);
  }
  void scan_write_point_2(ZPos a_x,ZPos a_y,ZZ a_z,ZPos /*a_beg*/,unsigned int a_size,ZPixel a_pixel) {
    write_point(a_y,a_x,a_z,a_size,a_pixel);
  }
  void scan_write_point_3(ZPos a_x,ZPos a_y,ZZ a_z,ZPos a_beg,unsigned int a_size,ZPixel a_pixel) {
    write_point(a_x,2*a_beg-a_y,a_z,a_size,a_pixel);
  }
  void scan_write_point_4(ZPos a_x,ZPos a_y,ZZ a_z,ZPos a_beg,unsigned int a_size,ZPixel a_pixel) {
    write_point(2*a_beg-a_y,a_x,a_z,a_size,a_pixel);
  }

  void blend(ZPixel& a_pix,const ZPixel& a_new) {
    if(!m_blend) {
      a_pix = a_new;
      return;
    }
    float _or,_og,_ob,_oa;
    pix2rgba(a_pix,_or,_og,_ob,_oa);
    float nr,ng,nb,na;
    pix2rgba(a_new,nr,ng,nb,na);
    if((0.0f<=na)&&(na<1.0f)) {
      // same as glBlendFunc(GL_SRC_ALPHA,GL_ONE_MINUS_SRC_ALPHA):
      float one_minus_na = 1.0f-na;
      float pr = nr*na+_or*one_minus_na;
      float pg = ng*na+_og*one_minus_na;
      float pb = nb*na+_ob*one_minus_na;
      float pa = 1;
      rgba2pix(pr,pg,pb,pa,a_pix);
    } else {
      a_pix = a_new;
    }
  }

  static void WriteScanLine(void* a_tag,int a_beg,int a_end,int a_y){
    buffer& a_buffer = *((buffer*)a_tag);

    if((a_y<a_buffer.m_begY) || (a_y>a_buffer.m_endY)) return;
    if(a_end<=a_beg) return;

    if(a_beg>a_buffer.m_endX) return;
    if(a_end<a_buffer.m_begX) return;

    // border clip :
    int beg = max_of(a_beg,(int)a_buffer.m_begX);
    int end = min_of(a_end,(int)a_buffer.m_endX);

    unsigned long offset = a_y * a_buffer.m_zbw + beg;
    ZReal* zbuff = a_buffer.m_zbuffer + offset;
    ZPixel* zimage = a_buffer.m_zimage + offset;

    ZReal zpoint;
    for(int x=beg;x<=end;x++){
      zpoint =
        (ZReal)(- a_buffer.m_planeDC
                - a_buffer.m_planeAC * x
                - a_buffer.m_planeBC * a_y);
      if(a_buffer.m_depth_test) {
        if((zpoint>=(*zbuff))
          ){
          *zbuff = zpoint;
          a_buffer.blend(*zimage,a_buffer.m_scan_pixel);
        }
      } else {
        *zbuff = zpoint;
        a_buffer.blend(*zimage,a_buffer.m_scan_pixel);
      }
      zbuff  ++;
      zimage ++;
    }
  }

  typedef void(buffer::*scan_write_point_func)(ZPos,ZPos,ZZ,ZPos,unsigned int,ZPixel);
  void ScanLine(ZPos a_x,ZPos a_y,ZZ a_z,
                ZPos a_dx,ZPos a_dy,ZZ a_dz,
                unsigned int a_size,ZPixel a_pixel,
                scan_write_point_func a_func){
    // Mid point algorithm
    // assume 0<dx    0<=dy<=dx

    ZPos end = a_x + a_dx;
    ZPos beg = a_y;
    ZZ incz = a_dz/(ZZ)a_dx;
    if(a_dy==0) {
      (this->*a_func)(a_x,a_y,a_z,beg,a_size,a_pixel);
      while(a_x<end){
        a_x++;
        a_z += incz;
        (this->*a_func)(a_x,a_y,a_z,beg,a_size,a_pixel);
      }
    } else if(a_dy==a_dx) {
      (this->*a_func)(a_x,a_y,a_z,beg,a_size,a_pixel);
      while(a_x<end){
        a_x++;
        a_y++;
        a_z += incz;
        (this->*a_func)(a_x,a_y,a_z,beg,a_size,a_pixel);
      }
    } else {
      ZPos d = 2 * a_dy - a_dx;
      ZPos incrE = 2 * a_dy;
      ZPos incrNE = 2 * ( a_dy - a_dx);
      (this->*a_func)(a_x,a_y,a_z,beg,a_size,a_pixel);
      while(a_x<end){
        if(d<=0){
          d += incrE;
          a_x++;
        }else{
          d += incrNE;
          a_x++;
          a_y++;
        }
        a_z += incz;
        (this->*a_func)(a_x,a_y,a_z,beg,a_size,a_pixel);
      }
    }
  }

  void WriteLine(const point& a_beg,
                 const point& a_end,
                 unsigned int a_size,ZPixel a_pixel){
    ZPos dx = a_end.x - a_beg.x;
    ZPos dy = a_end.y - a_beg.y;
    ZZ   dz = a_end.z - a_beg.z;

    //  6  2
    // 5     1
    // 7     3
    //  8  4

    if( (dx==0) && (dy==0) ) {
      write_point(a_beg.x,a_beg.y,a_beg.z,a_size,a_pixel);
      write_point(a_end.x,a_end.y,a_end.z,a_size,a_pixel);

    } else if(dx==0) {
      if(dy>0)
        ScanLine ( a_beg.y, a_beg.x,a_beg.z, dy, dx, dz, a_size,a_pixel,&buffer::scan_write_point_2);
      else
        ScanLine ( a_end.y, a_end.x,a_end.z,-dy, dx,-dz, a_size,a_pixel,&buffer::scan_write_point_2);

    } else if(dx>0) {
           if((0<=dy) && (dy<=dx))  /*1*/
        ScanLine ( a_beg.x, a_beg.y,a_beg.z, dx, dy, dz, a_size,a_pixel,&buffer::scan_write_point_1);
      else if(dx<dy)                /*2*/
        ScanLine ( a_beg.y, a_beg.x,a_beg.z, dy, dx, dz, a_size,a_pixel,&buffer::scan_write_point_2);
      else if((-dx<=dy) && (dy<0) ) /*3*/
        ScanLine ( a_beg.x, a_beg.y,a_beg.z, dx,-dy, dz, a_size,a_pixel,&buffer::scan_write_point_3);
      else if(dy<-dx)               /*4*/
        ScanLine ( a_end.y, a_end.x,a_end.z,-dy, dx,-dz, a_size,a_pixel,&buffer::scan_write_point_4);

    } else { //dx<0
           if((0<=dy) && (dy<=-dx)) /*5*/
        ScanLine ( a_end.x, a_end.y,a_end.z,-dx, dy,-dz, a_size,a_pixel,&buffer::scan_write_point_3);
      else if(-dx<dy)               /*6*/
        ScanLine ( a_beg.y, a_beg.x,a_beg.z, dy,-dx, dz, a_size,a_pixel,&buffer::scan_write_point_4);
      else if((dx<=dy) && (dy<0) )  /*7*/
        ScanLine ( a_end.x, a_end.y,a_end.z,-dx,-dy,-dz, a_size,a_pixel,&buffer::scan_write_point_1);
      else if(dy<dx)                /*8*/
        ScanLine ( a_end.y, a_end.x,a_end.z,-dy,-dx,-dz, a_size,a_pixel,&buffer::scan_write_point_2);
    }

  }


protected:
  bool         m_depth_test;
  bool         m_blend;
  ZReal*       m_zbuffer;

  ZPixel*      m_zimage;

  unsigned int m_zbw,m_zbh;
  ZPos         m_begX,m_begY;
  ZPos         m_endX,m_endY; //could be <0

  ZPixel       m_scan_pixel;
  ZZ           m_planeAC;
  ZZ           m_planeBC;
  ZZ           m_planeDC;
  polygon      m_polygon;
};

}}

#endif
