/*
  Copyright (C) 2010-2011  Charles Pence <charles@charlespence.net>
  Copyright (C) 1996-1997  Id Software, Inc.

  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 3 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, see <http://www.gnu.org/licenses/>.
*/
#include "pch.h"
#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.

=============
*/
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;

// 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 != sv.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 == 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, 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;
    }
    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);
        }
        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");

    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 ( ((rand()&3) & 1) ||  abs(deltay)>abs(deltax))
    {
        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;

    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) != sv.edicts &&  SV_CloseEnough (ent, goal, dist) )
        return;

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

