/*
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 "q_defs.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.

=============
*/
int32_t c_yes, c_no;

bool SV_CheckBottom(edict_t *ent)
{
	vec3_t  mins, maxs, start, stop;
	trace_t trace;
	int32_t         x, y;
	float   mid, bottom;

	VectorAdd(ED_Vector(ent, ED_origin), ED_Vector(ent, ED_mins), mins);
	VectorAdd(ED_Vector(ent, ED_origin), ED_Vector(ent, ED_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 trace_normal is set to the
normal of the blocking wall
=============
*/
bool SV_movestep(edict_t *ent, vec3_t move, bool relink)
{
	float           dz;
	vec3_t          oldorg, neworg, end;
	trace_t         trace;
	int32_t                 i;
	edict_t         *enemy;

// try the move
	VectorCopy(ED_Vector(ent, ED_origin), oldorg);
	VectorAdd(ED_Vector(ent, ED_origin), move, neworg);

// flying monsters don't step up
	if((int32_t)ED_Float(ent, ED_flags) & (FL_SWIM | FL_FLY))
	{
		// try one move with vertical motion, then one without
		for(i = 0 ; i < 2 ; i++)
		{
			VectorAdd(ED_Vector(ent, ED_origin), move, neworg);
			enemy = ProgEdict(ED_PEdict(ent, ED_enemy));
			if(i == 0 && enemy != sv.edicts)
			{
				dz = ED_Vector(ent, ED_origin)[2] - ED_Vector(ProgEdict(ED_PEdict(ent, ED_enemy)), ED_origin)[2];
				if(dz > 40)
					neworg[2] -= 8;
				if(dz < 30)
					neworg[2] += 8;
			}
			trace = SV_Move(ED_Vector(ent, ED_origin), ED_Vector(ent, ED_mins), ED_Vector(ent, ED_maxs), neworg, false, ent);

			if(trace.fraction == 1)
			{
				if(((int32_t)ED_Float(ent, ED_flags) & FL_SWIM) && SV_PointContents(trace.endpos) == CONTENTS_EMPTY)
					return false;   // swim monster left water

				VectorCopy(trace.endpos, ED_Vector(ent, ED_origin));
				if(relink)
					SV_LinkEdict(ent, true);
				return true;
			}

			if(enemy == sv.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, ED_Vector(ent, ED_mins), ED_Vector(ent, ED_maxs), end, false, ent);

	if(trace.allsolid)
		return false;

	if(trace.startsolid)
	{
		neworg[2] -= STEPSIZE;
		trace = SV_Move(neworg, ED_Vector(ent, ED_mins), ED_Vector(ent, ED_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((int32_t)ED_Float(ent, ED_flags) & FL_PARTIALGROUND)
		{
			VectorAdd(ED_Vector(ent, ED_origin), move, ED_Vector(ent, ED_origin));
			if(relink)
				SV_LinkEdict(ent, true);
			ED_Float(ent, ED_flags) = (int32_t)ED_Float(ent, ED_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, ED_Vector(ent, ED_origin));

	if(!SV_CheckBottom(ent))
	{
		if((int32_t)ED_Float(ent, ED_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, ED_Vector(ent, ED_origin));
		return false;
	}

	if((int32_t)ED_Float(ent, ED_flags) & FL_PARTIALGROUND)
	{
//		Con_Printf ("back on ground\n");
		ED_Float(ent, ED_flags) = (int32_t)ED_Float(ent, ED_flags) & ~FL_PARTIALGROUND;
	}
	ED_PEdict(ent, ED_groundentity) = EdictProg(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);
bool SV_StepDirection(edict_t *ent, float yaw, float dist)
{
	vec3_t          move, oldorigin;
	float           delta;

	ED_Float(ent, ED_ideal_yaw) = yaw;
	PF_changeyaw();

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

	VectorCopy(ED_Vector(ent, ED_origin), oldorigin);
	if(SV_movestep(ent, move, false))
	{
		delta = ED_Vector(ent, ED_angles)[YAW] - ED_Float(ent, ED_ideal_yaw);
		if(delta > 45 && delta < 315)
		{
			// not turned far enough, so don't take the step
			VectorCopy(oldorigin, ED_Vector(ent, ED_origin));
		}
		SV_LinkEdict(ent, true);
		return true;
	}
	SV_LinkEdict(ent, true);

	return false;
}

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

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

	ED_Float(ent, ED_flags) = (int32_t)ED_Float(ent, ED_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((int32_t)(ED_Float(actor, ED_ideal_yaw) / 45) * 45);
	turnaround = anglemod(olddir - 180);

	deltax = ED_Vector(enemy, ED_origin)[0] - ED_Vector(actor, ED_origin)[0];
	deltay = ED_Vector(enemy, ED_origin)[1] - ED_Vector(actor, ED_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(((rand() & 3) & 1) ||  abs((int32_t)deltay) > abs((int32_t)deltax)) // ericw -- explicit int32_t 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(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;

	ED_Float(actor, ED_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

======================
*/
bool SV_CloseEnough(edict_t *ent, edict_t *goal, float dist)
{
	int32_t         i;

	for(i = 0 ; i < 3 ; i++)
	{
		if(ED_Vector(goal, ED_absmin)[i] > ED_Vector(ent, ED_absmax)[i] + dist)
			return false;
		if(ED_Vector(goal, ED_absmax)[i] < ED_Vector(ent, ED_absmin)[i] - dist)
			return false;
	}
	return true;
}

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

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

	ent = ProgEdict(G_PEdict(GBL_self));
	goal = ProgEdict(ED_PEdict(ent, ED_goalentity));
	dist = G_Float(GBL_PARM0);

	if(!((int32_t)ED_Float(ent, ED_flags) & (FL_ONGROUND | FL_FLY | FL_SWIM)))
	{
		G_Float(GBL_RETURN) = 0;
		return;
	}

// if the next step hits the enemy, return immediately
	if(ProgEdict(ED_PEdict(ent, ED_enemy)) != sv.edicts &&  SV_CloseEnough(ent, goal, dist))
		return;

// bump around...
	if((rand() & 3) == 1 ||
	                !SV_StepDirection(ent, ED_Float(ent, ED_ideal_yaw), dist))
	{
		SV_NewChaseDir(ent, goal, dist);
	}
}