// m_move.c -- monster movement

#include "g_local.h"

#define	STEPSIZE	18

/*
=============
M_CheckBottom

Returns false if any part of the bottom of the entity is off an edge that
is not a staircase.

=============
*/
int c_yes, c_no;

qboolean M_CheckBottom (edict_t *ent)
{
	vec3_t	mins, maxs, start, stop;
	trace_t	trace;
	int		x, y;
	float	mid, bottom;
	
	VectorAdd (ent->s.origin, ent->mins, mins);
	VectorAdd (ent->s.origin, ent->maxs, maxs);

// if all of the points under the corners are solid world, don't bother
// with the tougher checks
// the corners must be within 16 of the midpoint
	start[2] = mins[2] - 1;
	for	(x=0 ; x<=1 ; x++)
		for	(y=0 ; y<=1 ; y++)
		{
			start[0] = x ? maxs[0] : mins[0];
			start[1] = y ? maxs[1] : mins[1];
			if (gi.pointcontents (start) != CONTENTS_SOLID)
				goto realcheck;
		}

	c_yes++;
	return true;		// we got out easy

realcheck:
	c_no++;
//
// check it for real...
//
	start[2] = mins[2];
	
// the midpoint must be within 16 of the bottom
	start[0] = stop[0] = (mins[0] + maxs[0])*0.5;
	start[1] = stop[1] = (mins[1] + maxs[1])*0.5;
	stop[2] = start[2] - 2*STEPSIZE;
	trace = gi.trace (start, vec3_origin, vec3_origin, stop, ent,MASK_PLAYERSOLID /*MASK_MONSTERSOLID*/);

	if (trace.fraction == 1.0)
		return false;
	mid = bottom = trace.endpos[2];
	
// the corners must be within 16 of the midpoint	
	for	(x=0 ; x<=1 ; x++)
		for	(y=0 ; y<=1 ; y++)
		{
			start[0] = stop[0] = x ? maxs[0] : mins[0];
			start[1] = stop[1] = y ? maxs[1] : mins[1];
			
			trace = gi.trace (start, vec3_origin, vec3_origin, stop, ent, MASK_PLAYERSOLID /*MASK_MONSTERSOLID*/);
			
			if (trace.fraction != 1.0 && trace.endpos[2] > bottom)
				bottom = trace.endpos[2];
			if (trace.fraction == 1.0 || mid - trace.endpos[2] > STEPSIZE)
				return false;
		}

	c_yes++;
	return true;
}