static VECTOR2I pushoutForce( const SHAPE_CIRCLE& aA, const SEG& aB, int aClearance )
{
    VECTOR2I f( 0, 0 );

    const VECTOR2I c = aA.GetCenter();
    const VECTOR2I nearest = aB.NearestPoint( c );

    const int r = aA.GetRadius();

    int dist = ( nearest - c ).EuclideanNorm();
    int min_dist = aClearance + r;

    if( dist < min_dist )
    {
        for( int corr = 0; corr < 5; corr++ )
        {
            f = ( aA.GetCenter() - nearest ).Resize( min_dist - dist + corr );

            if( aB.Distance( c + f ) >= min_dist )
                break;
        }
    }

    return f;
}
static VECTOR2I pushoutForce( const SHAPE_CIRCLE& aA, const SEG& aB, int aClearance )
{
    VECTOR2I nearest = aB.NearestPoint( aA.GetCenter() );
    VECTOR2I f (0, 0);

    int dist = ( nearest - aA.GetCenter() ).EuclideanNorm();
    int min_dist = aClearance + aA.GetRadius();

    if( dist < min_dist )
        f = ( aA.GetCenter() - nearest ).Resize ( min_dist - dist + 10 );

    return f;
}
PNS_WALKAROUND::WalkaroundStatus PNS_WALKAROUND::Route( const PNS_LINE& aInitialPath,
        PNS_LINE& aWalkPath,
        bool aOptimize )
{
    PNS_LINE path_cw( aInitialPath ), path_ccw( aInitialPath );
    WalkaroundStatus s_cw = IN_PROGRESS, s_ccw = IN_PROGRESS;
    SHAPE_LINE_CHAIN best_path;

    start( aInitialPath );

    m_currentObstacle[0] = m_currentObstacle[1] = nearestObstacle( aInitialPath );
    m_recursiveBlockageCount = 0;

    aWalkPath = aInitialPath;

    while( m_iteration < m_iteration_limit )
    {
        if( s_cw != STUCK )
            s_cw = singleStep( path_cw, true );

        if( s_ccw != STUCK )
            s_ccw = singleStep( path_ccw, false );

        if( ( s_cw == DONE && s_ccw == DONE ) || ( s_cw == STUCK && s_ccw == STUCK ) )
        {
            int len_cw  = path_cw.GetCLine().Length();
            int len_ccw = path_ccw.GetCLine().Length();

            if( m_forceLongerPath )
                aWalkPath = (len_cw > len_ccw ? path_cw : path_ccw);
            else
                aWalkPath = (len_cw < len_ccw ? path_cw : path_ccw);

            break;
        }
        else if( s_cw == DONE && !m_forceLongerPath )
        {
            aWalkPath = path_cw;
            break;
        }
        else if( s_ccw == DONE && !m_forceLongerPath )
        {
            aWalkPath = path_ccw;
            break;
        }

        m_iteration++;
    }

    if( m_iteration == m_iteration_limit )
    {
        int len_cw  = path_cw.GetCLine().Length();
        int len_ccw = path_ccw.GetCLine().Length();


        if( m_forceLongerPath )
            aWalkPath = (len_cw > len_ccw ? path_cw : path_ccw);
        else
            aWalkPath = (len_cw < len_ccw ? path_cw : path_ccw);
    }

    if( m_cursorApproachMode )
    {
        // int len_cw = path_cw.GetCLine().Length();
        // int len_ccw = path_ccw.GetCLine().Length();
        bool found = false;

        SHAPE_LINE_CHAIN l = aWalkPath.GetCLine();

        for( int i = 0; i < l.SegmentCount(); i++ )
        {
            const SEG s = l.Segment( i );

            VECTOR2I nearest = s.NearestPoint( m_cursorPos );
            VECTOR2I::extended_type dist_a = ( s.A - m_cursorPos ).SquaredEuclideanNorm();
            VECTOR2I::extended_type dist_b = ( s.B - m_cursorPos ).SquaredEuclideanNorm();
            VECTOR2I::extended_type dist_n = ( nearest - m_cursorPos ).SquaredEuclideanNorm();

            if( dist_n <= dist_a && dist_n < dist_b )
            {
                // PNSDisplayDebugLine( l, 3 );
                l.Remove( i + 1, -1 );
                l.Append( nearest );
                l.Simplify();
                found = true;
                break;
            }
        }

        if( found )
        {
            aWalkPath = aInitialPath;
            aWalkPath.SetShape( l );
        }
    }

    aWalkPath.SetWorld( m_world );
    aWalkPath.GetLine().Simplify();

    WalkaroundStatus st = s_ccw == DONE || s_cw == DONE ? DONE : STUCK;

    if( aOptimize && st == DONE )
        PNS_OPTIMIZER::Optimize( &aWalkPath, PNS_OPTIMIZER::MERGE_OBTUSE, m_world );

    return st;
}
WALKAROUND::WALKAROUND_STATUS WALKAROUND::Route( const LINE& aInitialPath,
        LINE& aWalkPath, bool aOptimize )
{
    LINE path_cw( aInitialPath ), path_ccw( aInitialPath );
    WALKAROUND_STATUS s_cw = IN_PROGRESS, s_ccw = IN_PROGRESS;
    SHAPE_LINE_CHAIN best_path;

    // special case for via-in-the-middle-of-track placement
    if( aInitialPath.PointCount() <= 1 )
    {
        if( aInitialPath.EndsWithVia() && m_world->CheckColliding( &aInitialPath.Via(), m_itemMask ) )
            return STUCK;

        aWalkPath = aInitialPath;
        return DONE;
    }

    start( aInitialPath );

    m_currentObstacle[0] = m_currentObstacle[1] = nearestObstacle( aInitialPath );
    m_recursiveBlockageCount = 0;

    aWalkPath = aInitialPath;

    if( m_forceWinding )
    {
        s_cw = m_forceCw ? IN_PROGRESS : STUCK;
        s_ccw = m_forceCw ? STUCK : IN_PROGRESS;
        m_forceSingleDirection = true;
    } else {
        m_forceSingleDirection = false;
    }

    while( m_iteration < m_iterationLimit )
    {
        if( s_cw != STUCK )
            s_cw = singleStep( path_cw, true );

        if( s_ccw != STUCK )
            s_ccw = singleStep( path_ccw, false );

        if( ( s_cw == DONE && s_ccw == DONE ) || ( s_cw == STUCK && s_ccw == STUCK ) )
        {
            int len_cw  = path_cw.CLine().Length();
            int len_ccw = path_ccw.CLine().Length();

            if( m_forceLongerPath )
                aWalkPath = ( len_cw > len_ccw ? path_cw : path_ccw );
            else
                aWalkPath = ( len_cw < len_ccw ? path_cw : path_ccw );

            break;
        }
        else if( s_cw == DONE && !m_forceLongerPath )
        {
            aWalkPath = path_cw;
            break;
        }
        else if( s_ccw == DONE && !m_forceLongerPath )
        {
            aWalkPath = path_ccw;
            break;
        }

        m_iteration++;
    }

    if( m_iteration == m_iterationLimit )
    {
        int len_cw  = path_cw.CLine().Length();
        int len_ccw = path_ccw.CLine().Length();

        if( m_forceLongerPath )
            aWalkPath = ( len_cw > len_ccw ? path_cw : path_ccw );
        else
            aWalkPath = ( len_cw < len_ccw ? path_cw : path_ccw );
    }

    if( m_cursorApproachMode )
    {
        // int len_cw = path_cw.GetCLine().Length();
        // int len_ccw = path_ccw.GetCLine().Length();
        bool found = false;

        SHAPE_LINE_CHAIN l = aWalkPath.CLine();

        for( int i = 0; i < l.SegmentCount(); i++ )
        {
            const SEG s = l.Segment( i );

            VECTOR2I nearest = s.NearestPoint( m_cursorPos );
            VECTOR2I::extended_type dist_a = ( s.A - m_cursorPos ).SquaredEuclideanNorm();
            VECTOR2I::extended_type dist_b = ( s.B - m_cursorPos ).SquaredEuclideanNorm();
            VECTOR2I::extended_type dist_n = ( nearest - m_cursorPos ).SquaredEuclideanNorm();

            if( dist_n <= dist_a && dist_n < dist_b )
            {
                l.Remove( i + 1, -1 );
                l.Append( nearest );
                l.Simplify();
                found = true;
                break;
            }
        }

        if( found )
        {
            aWalkPath = aInitialPath;
            aWalkPath.SetShape( l );
        }
    }

    aWalkPath.Line().Simplify();

    if( aWalkPath.SegmentCount() < 1 )
        return STUCK;
    if( aWalkPath.CPoint( -1 ) != aInitialPath.CPoint( -1 ) )
        return STUCK;
    if( aWalkPath.CPoint( 0 ) != aInitialPath.CPoint( 0 ) )
        return STUCK;

    WALKAROUND_STATUS st = s_ccw == DONE || s_cw == DONE ? DONE : STUCK;

    if( st == DONE )
    {
        if( aOptimize )
            OPTIMIZER::Optimize( &aWalkPath, OPTIMIZER::MERGE_OBTUSE, m_world );
    }

    return st;
}