/*
 * 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 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.
 */
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, d[3], 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);
}
