/*
Copyright (C) 1996-2001 Id Software, Inc.
Copyright (C) 2002-2009 John Fitzgibbons and others
Copyright (C) 2010-2014 QuakeSpasm developers

This program 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.

This program 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 this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

*/
// sv_move.c -- monster movement

#include "quakedef.h"

#define STEPSIZE 18

/*
=============
SV_CheckBottom

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

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

qboolean SV_CheckBottom (edict_t *ent)
{
	vec3_t	mins, maxs, start, stop;
	trace_t trace;
	int		x, y;
	float	mid, bottom;

	VectorAdd (ent->v.origin, ent->v.mins, mins);
	VectorAdd (ent->v.origin, ent->v.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 (SV_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 = SV_Move (start, vec3_origin, vec3_origin, stop, true, ent);

	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 = SV_Move (start, vec3_origin, vec3_origin, stop, true, ent);

			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;
}

/*
=============
SV_movestep

Called by monster program code.
The move will be adjusted for slopes and stairs, but if the move isn't
possible, no move is done, false is returned, and
pr_global_struct->trace_normal is set to the normal of the blocking wall
=============
*/
qboolean SV_movestep (edict_t *ent, vec3_t move, qboolean relink)
{
	float	 dz;
	vec3_t	 oldorg, neworg, end;
	trace_t	 trace;
	int		 i;
	edict_t *enemy;

	assert (!ent->free);

	// try the move
	VectorCopy (ent->v.origin, oldorg);
	VectorAdd (ent->v.origin, move, neworg);

	// flying monsters don't step up
	if ((int)ent->v.flags & (FL_SWIM | FL_FLY))
	{
		// try one move with vertical motion, then one without
		for (i = 0; i < 2; i++)
		{
			VectorAdd (ent->v.origin, move, neworg);
			enemy = PROG_TO_EDICT (ent->v.enemy);
			if (i == 0 && enemy != qcvm->edicts)
			{
				dz = ent->v.origin[2] - PROG_TO_EDICT (ent->v.enemy)->v.origin[2];
				if (dz > 40)
					neworg[2] -= 8;
				if (dz < 30)
					neworg[2] += 8;
			}
			trace = SV_Move (ent->v.origin, ent->v.mins, ent->v.maxs, neworg, false, ent);

			if (trace.fraction == 1)
			{
				if (((int)ent->v.flags & FL_SWIM) && SV_PointContents (trace.endpos) == CONTENTS_EMPTY)
					return false; // swim monster left water

				VectorCopy (trace.endpos, ent->v.origin);
				if (relink)
					SV_LinkEdict (ent, true);
				return true;
			}

			if (enemy == qcvm->edicts)
				break;
		}

		return false;
	}

	// push down from a step height above the wished position
	neworg[2] += STEPSIZE;
	VectorCopy (neworg, end);
	end[2] -= STEPSIZE * 2;

	trace = SV_Move (neworg, ent->v.mins, ent->v.maxs, end, false, ent);

	if (trace.allsolid)
		return false;

	if (trace.startsolid)
	{
		neworg[2] -= STEPSIZE;
		trace = SV_Move (neworg, ent->v.mins, ent->v.maxs, end, false, ent);
		if (trace.allsolid || trace.startsolid)
			return false;
	}
	if (trace.fraction == 1)
	{
		// if monster had the ground pulled out, go ahead and fall
		if ((int)ent->v.flags & FL_PARTIALGROUND)
		{
			VectorAdd (ent->v.origin, move, ent->v.origin);
			if (relink)
				SV_LinkEdict (ent, true);
			ent->v.flags = (int)ent->v.flags & ~FL_ONGROUND;
			//	Con_Printf ("fall down\n");
			return true;
		}

		return false; // walked off an edge
	}

	// check point traces down for dangling corners
	VectorCopy (trace.endpos, ent->v.origin);

	if (!SV_CheckBottom (ent))
	{
		if ((int)ent->v.flags & FL_PARTIALGROUND)
		{ // entity had floor mostly pulled out from underneath it
			// and is trying to correct
			if (relink)
				SV_LinkEdict (ent, true);
			return true;
		}
		VectorCopy (oldorg, ent->v.origin);
		return false;
	}

	if ((int)ent->v.flags & FL_PARTIALGROUND)
	{
		//		Con_Printf ("back on ground\n");
		ent->v.flags = (int)ent->v.flags & ~FL_PARTIALGROUND;
	}
	if (trace.ent)
		ent->v.groundentity = EDICT_TO_PROG (trace.ent);

	// the move is ok
	if (relink)
		SV_LinkEdict (ent, true);
	return true;
}

//============================================================================

/*
======================
SV_StepDirection

Turns to the movement direction, and walks the current distance if
facing it.

======================
*/
void	 PF_changeyaw (void);
qboolean SV_StepDirection (edict_t *ent, float yaw, float dist)
{
	vec3_t move, oldorigin;
	float  delta;

	ent->v.ideal_yaw = yaw;
	PF_changeyaw ();

	yaw = yaw * M_PI * 2 / 360;
	move[0] = cos (yaw) * dist;
	move[1] = sin (yaw) * dist;
	move[2] = 0;

	VectorCopy (ent->v.origin, oldorigin);
	if (SV_movestep (ent, move, false))
	{
		delta = ent->v.angles[YAW] - ent->v.ideal_yaw;
		if (delta > 45 && delta < 315)
		{ // not turned far enough, so don't take the step
			VectorCopy (oldorigin, ent->v.origin);
		}
		assert (!ent->free);
		SV_LinkEdict (ent, true);
		return true;
	}
	assert (!ent->free);
	SV_LinkEdict (ent, true);
	return false;
}

/*
======================
SV_FixCheckBottom

======================
*/
void SV_FixCheckBottom (edict_t *ent)
{
	//	Con_Printf ("SV_FixCheckBottom\n");

	ent->v.flags = (int)ent->v.flags | FL_PARTIALGROUND;
}

/*
================
SV_NewChaseDir

================
*/
#define DI_NODIR -1
void SV_NewChaseDir (edict_t *actor, edict_t *enemy, float dist)
{
	float deltax, deltay;
	float d[3];
	float tdir, olddir, turnaround;

	olddir = anglemod ((int)(actor->v.ideal_yaw / 45) * 45);
	turnaround = anglemod (olddir - 180);

	deltax = enemy->v.origin[0] - actor->v.origin[0];
	deltay = enemy->v.origin[1] - actor->v.origin[1];
	if (deltax > 10)
		d[1] = 0;
	else if (deltax < -10)
		d[1] = 180;
	else
		d[1] = DI_NODIR;
	if (deltay < -10)
		d[2] = 270;
	else if (deltay > 10)
		d[2] = 90;
	else
		d[2] = DI_NODIR;

	// try direct route
	if (d[1] != DI_NODIR && d[2] != DI_NODIR)
	{
		if (d[1] == 0)
			tdir = d[2] == 90 ? 45 : 315;
		else
			tdir = d[2] == 90 ? 135 : 215;

		if (tdir != turnaround && SV_StepDirection (actor, tdir, dist))
			return;
	}

	// try other directions
	if (((COM_Rand () & 3) & 1) || abs ((int)deltay) > abs ((int)deltax)) // ericw -- explicit int cast to suppress clang suggestion to use fabsf
	{
		tdir = d[1];
		d[1] = d[2];
		d[2] = tdir;
	}

	if (d[1] != DI_NODIR && d[1] != turnaround && SV_StepDirection (actor, d[1], dist))
		return;

	if (d[2] != DI_NODIR && d[2] != turnaround && SV_StepDirection (actor, d[2], dist))
		return;

	/* there is no direct path to the player, so pick another direction */

	if (olddir != DI_NODIR && SV_StepDirection (actor, olddir, dist))
		return;

	if (COM_Rand () & 1) /*randomly determine direction of search*/
	{
		for (tdir = 0; tdir <= 315; tdir += 45)
			if (tdir != turnaround && SV_StepDirection (actor, tdir, dist))
				return;
	}
	else
	{
		for (tdir = 315; tdir >= 0; tdir -= 45)
			if (tdir != turnaround && SV_StepDirection (actor, tdir, dist))
				return;
	}

	if (turnaround != DI_NODIR && SV_StepDirection (actor, turnaround, dist))
		return;

	actor->v.ideal_yaw = olddir; // can't move

	// if a bridge was pulled out from underneath a monster, it may not have
	// a valid standing position at all

	if (!SV_CheckBottom (actor))
		SV_FixCheckBottom (actor);
}

/*
======================
SV_CloseEnough

======================
*/
qboolean SV_CloseEnough (edict_t *ent, edict_t *goal, float dist)
{
	int i;

	for (i = 0; i < 3; i++)
	{
		if (goal->v.absmin[i] > ent->v.absmax[i] + dist)
			return false;
		if (goal->v.absmax[i] < ent->v.absmin[i] - dist)
			return false;
	}
	return true;
}

/*
======================
SV_MoveToGoal

======================
*/
void SV_MoveToGoal (void)
{
	edict_t *ent, *goal;
	float	 dist;

	ent = PROG_TO_EDICT (pr_global_struct->self);
	goal = PROG_TO_EDICT (ent->v.goalentity);
	dist = G_FLOAT (OFS_PARM0);

	if (!((int)ent->v.flags & (FL_ONGROUND | FL_FLY | FL_SWIM)))
	{
		G_FLOAT (OFS_RETURN) = 0;
		return;
	}

	// if the next step hits the enemy, return immediately
	if (PROG_TO_EDICT (ent->v.enemy) != qcvm->edicts && SV_CloseEnough (ent, goal, dist))
		return;

	// bump around...
	if ((COM_Rand () & 3) == 1 || !SV_StepDirection (ent, ent->v.ideal_yaw, dist))
	{
		SV_NewChaseDir (ent, goal, dist);
	}
}
