/*
	Collision grid, 16x16 tiles
	
	- create
	+ set( x16, y16 )
	+ unset( x16, y16 )
	+ test( x, y )
	+ raycast( x1, y1, x2, y2, notestfirst ) => null / dt, isp_x, isp_y
	+ aabbtest( x1, y1, x2, y2 ) => null / true, xnrm, ynrm, push
*/

global ColGrid = {};

function ColGrid.create()
{
	data =
	{
		tiles = map(),
	};
	return class( data, ColGrid );
}

function ColGrid._getkey( x16, y16 )
{
	return ((x16&0xffff)<<16) | (y16&0xffff);
}

function ColGrid.set( x16, y16 )
{
	this.tiles[ this._getkey( x16, y16 ) ] = true;
}

function ColGrid.unset( x16, y16 )
{
	unset( this.tiles, this._getkey( x16, y16 ) );
}

function ColGrid.test( x, y )
{
	x16 = toint( floor( x / 16 ) );
	y16 = toint( floor( y / 16 ) );
	return isset( this.tiles, this._getkey( x16, y16 ) );
}

function ColGrid.raycast( x1, y1, x2, y2, notestfirst )
{
	x1_16 = toint( floor( x1 / 16 ) );
	y1_16 = toint( floor( y1 / 16 ) );
	x2_16 = toint( floor( x2 / 16 ) );
	y2_16 = toint( floor( y2 / 16 ) );
	
	if( !notestfirst && isset( this.tiles, this._getkey( x1_16, y1_16 ) ) )
		return 0, x1, y1;
	if( x1_16 == x2_16 && y1_16 == y2_16 )
		return null;
	
	x16 = x1_16;
	y16 = y1_16;
	xdist = x2 - x1;
	ydist = y2 - y1;
	stepX = if( xdist >= 0, 1, -1 );
	stepY = if( ydist >= 0, 1, -1 );
	len = sqrt( xdist * xdist + ydist * ydist );
	if( xdist == 0 )
	{
		tMaxX = 3.8e+10;
		tDeltaX = 0;
	}
	else
	{
		tMaxX = ( floor( x1_16 + ( xdist > 0 ) ) * 16 - x1 ) * len / xdist; // should be +
		tDeltaX = 16 * len / abs( xdist );
	}
	if( ydist == 0 )
	{
		tMaxY = 3.8e+10;
		tDeltaY = 0;
	}
	else
	{
		tMaxY = ( floor( y1_16 + ( ydist > 0 ) ) * 16 - y1 ) * len / ydist; // should be +
		tDeltaY = 16 * len / abs( ydist );
	}
	t = if( tMaxX < tMaxY, tMaxX, tMaxY );
	
	while( x16 != x2_16 || y16 != y2_16 )
	{
		if( tMaxX < tMaxY )
		{
			t += tMaxX;
			tMaxX += tDeltaX;
			x16 += stepX;
		}
		else
		{
			t = tMaxY;
			tMaxY += tDeltaY;
			y16 += stepY;
		}
		
		if( isset( this.tiles, this._getkey( x16, y16 ) ) )
		{
			q = t / len;
			q1 = 1 - q;
			return q, x1 * q1 + x2 * q, y1 * q1 + y2 * q;
		}
	}
	
	return null;
}

function _aabb_aabb_resolve( ax1, ay1, ax2, ay2, bx1, by1, bx2, by2 )
{
	// in an intersection all of these are non-negative
	dx1 = ax2 - bx1;
	dx2 = bx2 - ax1;
	dy1 = ay2 - by1;
	dy2 = by2 - ay1;
	
	// find smallest of those and resolve assuming BB1 is to be moved
	if( dx1 < dx2 )
	{
		if( dx1 < dy1 )
		{
			if( dx1 < dy2 )
				return -dx1, 0;
			else // dy2
				return 0, dy2;
		}
		else // dy1
		{
			if( dy1 < dy2 )
				return 0, -dy1;
			else // dy2
				return 0, dy2;
		}
	}
	else // dx2
	{
		if( dx2 < dy1 )
		{
			if( dx2 < dy2 )
				return dx2, 0;
			else
				return 0, dy2;
		}
		else // dy1
		{
			if( dy1 < dy2 )
				return 0, -dy1;
			else // dy2
				return 0, dy2;
		}
	}
}

function ColGrid.aabbtest( x1, y1, x2, y2 )
{
	x1_16 = toint( floor( x1 / 16 ) );
	y1_16 = toint( floor( y1 / 16 ) );
	x2_16 = toint( floor( x2 / 16 ) );
	y2_16 = toint( floor( y2 / 16 ) );
	
	nx = 0;
	ny = 0;
	isc = 0;
	
	for( y16 = y1_16; y16 <= y2_16; ++y16 )
	{
		for( x16 = x1_16; x16 <= x2_16; ++x16 )
		{
			if( isset( this.tiles, this._getkey( x16, y16 ) ) )
			{
				(cx,cy) = _aabb_aabb_resolve( x1, y1, x2, y2, x16 * 16, y16 * 16, x16 * 16 + 16, y16 * 16 + 16 );
				nx += cx;
				ny += cy;
				isc++;
			}
		}
	}
	
	if( isc )
	{
		nx /= isc;
		ny /= isc;
	}
	
	if( nx != 0 || ny != 0 )
	{
		nd = sqrt( nx * nx + ny * ny );
		nx /= nd;
		ny /= nd;
		return true, nx, ny, nd;
	}
}