// Copyright (C) 2012-2013 ChaosForge / Kornel Kisielewicz
// http://chaosforge.org/
//
// This file is part of NV Libraries.
// For conditions of distribution and use, see copyright notice in nv.hh

#include "nv/gl/texture_atlas.hh"

using namespace nv;

texture_atlas::texture_atlas( glm::ivec2 size, size_t depth )
	: m_size( size ), m_depth( depth ), m_used( 0 ), m_data( nullptr )
{
	m_nodes.push_back( glm::ivec3( 1, 1, m_size.x - 2 ) );
	m_data = new uint8[ m_size.x * m_size.y * m_depth ];
	fill( 0 );
}

glm::ivec4 texture_atlas::get_region( glm::ivec2 size )
{
	glm::ivec4 region (0,0,size.x,size.y);
    size_t i;

    int best_height = INT_MAX;
    int best_index  = -1;
    int best_width  = INT_MAX;
	for( size_t i=0; i < m_nodes.size(); ++i )
	{
        int y = fit( i, size );
		if( y >= 0 )
		{
            glm::ivec3 node = m_nodes[ i ];
			if ( ( (y + size.y) < best_height ) ||
                ( ((y + size.y) == best_height) && (node.z < best_width)) )
			{
				best_height = y + size.y;
				best_index = i;
				best_width = node.z;
				region.x = node.x;
				region.y = y;
			}
        }
    }
   
	if( best_index == -1 )
    {
        return glm::ivec4( -1, -1, 0, 0 );
    }

    m_nodes.insert( m_nodes.begin() + best_index, glm::ivec3( region.x, region.y + size.y, size.x ) );

    for( size_t i = best_index+1; i < m_nodes.size(); ++i )
    {
        glm::ivec3 node = m_nodes[ i ];
        glm::ivec3 prev = m_nodes[ i-1 ];

        if (node.x < (prev.x + prev.z) )
        {
            int shrink = prev.x + prev.z - node.x;
			m_nodes[ i ].x += shrink;
			m_nodes[ i ].z -= shrink;

            if (m_nodes[ i ].z <= 0)
            {
				m_nodes.erase( m_nodes.begin() + i );
                --i;
            }
            else
            {
                break;
            }
        }
        else
        {
            break;
        }
    }
    merge();
    m_used += size.x * size.y;
    return region;
}

void texture_atlas::set_region( glm::ivec4 region, const uint8 * data, size_t stride )
{
    for( size_t i = 0; i < region[3]; ++i )
    {
        memcpy( m_data+((region.y+i)*m_size.x + region.x ) * m_depth, 
                data + (i*stride), m_size.x * m_depth );
    }
}

int texture_atlas::fit( size_t index, glm::ivec2 size )
{
	glm::ivec3 node = m_nodes[ index ];

	if ( (  node.x + size.x ) > ( m_size.x - 1 ) ) 
	{
		return -1;
	}

	int y     = node.y;
	int wleft = size.x;
	size_t i  = index;

	while( wleft > 0 )
	{
        node = m_nodes[ i ];
        if( node.y > y )
        {
            y = node.y;
        }
		if( (y + size.y) > (m_size.y-1) )
        {
			return -1;
        }
		wleft -= node.z;
		++i;
	}
	return y;
}

void texture_atlas::merge()
{
	for( size_t i=0; i < m_nodes.size()-1; ++i )
    {
		if( m_nodes[ i ].y == m_nodes[ i+1 ].y )
		{
			m_nodes[ i ].z += m_nodes[ i+1 ].z;
            m_nodes.erase( m_nodes.begin()+i+1 );
			--i;
		}
    }
}

void texture_atlas::clear()
{
	m_nodes.clear();
	m_used = 0;
	m_nodes.push_back( glm::ivec3( 1, 1, m_size.x - 2 ) );
	fill( 0 );
}

void texture_atlas::fill( uint8 value )
{
	memset( m_data, value, m_size.x * m_size.y * m_depth );
}

texture_atlas::~texture_atlas()
{
	delete[] m_data;
}