//----------------------------------------------------------------------------
// Anti-Grain Geometry (AGG) - Version 2.5
// A high quality rendering engine for C++
// Copyright (C) 2002-2006 Maxim Shemanarev
// Contact: mcseem@antigrain.com
//          mcseemagg@yahoo.com
//          http://antigrain.com
// 
// AGG is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
// 
// AGG is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
// 
// You should have received a copy of the GNU General Public License
// along with AGG; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, 
// MA 02110-1301, USA.
//----------------------------------------------------------------------------

#include <math.h>
#include "agg_arc.h"


namespace agg
{
    //------------------------------------------------------------------------
    arc::arc(double x,  double y, 
             double rx, double ry, 
             double a1, double a2, 
             bool ccw) :
        m_x(x), m_y(y), m_rx(rx), m_ry(ry), m_scale(1.0)
    {
        normalize(a1, a2, ccw);
    }

    //------------------------------------------------------------------------
    void arc::init(double x,  double y, 
                   double rx, double ry, 
                   double a1, double a2, 
                   bool ccw)
    {
        m_x   = x;  m_y  = y;
        m_rx  = rx; m_ry = ry; 
        normalize(a1, a2, ccw);
    }
    
    //------------------------------------------------------------------------
    void arc::approximation_scale(double s)
    {
        m_scale = s;
        if(m_initialized)
        {
            normalize(m_start, m_end, m_ccw);
        }
    }

    //------------------------------------------------------------------------
    void arc::rewind(unsigned)
    {
        m_path_cmd = path_cmd_move_to; 
        m_angle = m_start;
    }

    //------------------------------------------------------------------------
    unsigned arc::vertex(double* x, double* y)
    {
        if(is_stop(m_path_cmd)) return path_cmd_stop;
        if((m_angle < m_end - m_da/4) != m_ccw)
        {
            *x = m_x + cos(m_end) * m_rx;
            *y = m_y + sin(m_end) * m_ry;
            m_path_cmd = path_cmd_stop;
            return path_cmd_line_to;
        }

        *x = m_x + cos(m_angle) * m_rx;
        *y = m_y + sin(m_angle) * m_ry;

        m_angle += m_da;

        unsigned pf = m_path_cmd;
        m_path_cmd = path_cmd_line_to;
        return pf;
    }

    //------------------------------------------------------------------------
    void arc::normalize(double a1, double a2, bool ccw)
    {
        double ra = (fabs(m_rx) + fabs(m_ry)) / 2;
        m_da = acos(ra / (ra + 0.125 / m_scale)) * 2;
        if(ccw)
        {
            while(a2 < a1) a2 += pi * 2.0;
        }
        else
        {
            while(a1 < a2) a1 += pi * 2.0;
            m_da = -m_da;
        }
        m_ccw   = ccw;
        m_start = a1;
        m_end   = a2;
        m_initialized = true;
    }

}