// physics.cpp: no physics books were hurt nor consulted in the construction of this code.
// All physics computations and constants were invented on the fly and simply tweaked until
// they "felt right", and have no basis in reality. Collision detection is simplistic but
// very robust (uses discrete steps at fixed fps).

#include "engine.h"
#include "mpr.h"

const int MAXCLIPPLANES = 1024;
static clipplanes clipcache[MAXCLIPPLANES];
static int clipcacheversion = 0;

static inline clipplanes &getclipplanes(cube &c, const ivec &o, int size)
{
    clipplanes &p = clipcache[int(&c - worldroot)&(MAXCLIPPLANES-1)];
    if(p.owner != &c || p.version != clipcacheversion)
    {
        p.owner = &c;
        p.version = clipcacheversion;
        genclipplanes(c, o.x, o.y, o.z, size, p);
    }
    return p;
}

void resetclipplanes()
{
    if(!clipcacheversion++) memset(clipcache, 0, sizeof(clipcache));
}

/////////////////////////  ray - cube collision ///////////////////////////////////////////////

static inline bool pointinbox(const vec &v, const vec &bo, const vec &br)
{
    return v.x <= bo.x+br.x &&
           v.x >= bo.x-br.x &&
           v.y <= bo.y+br.y &&
           v.y >= bo.y-br.y &&
           v.z <= bo.z+br.z &&
           v.z >= bo.z-br.z;
}

bool pointincube(const clipplanes &p, const vec &v)
{
    if(!pointinbox(v, p.o, p.r)) return false;
    loopi(p.size) if(p.p[i].dist(v)>1e-3f) return false;
    return true;
}

#define INTERSECTPLANES(setentry, exit) \
    float enterdist = -1e16f, exitdist = 1e16f; \
    loopi(p.size) \
    { \
        float pdist = p.p[i].dist(v), facing = ray.dot(p.p[i]); \
        if(facing < 0) \
        { \
            pdist /= -facing; \
            if(pdist > enterdist) \
            { \
                if(pdist > exitdist) exit; \
                enterdist = pdist; \
                setentry; \
            } \
        } \
        else if(facing > 0) \
        { \
            pdist /= -facing; \
            if(pdist < exitdist) \
            { \
                if(pdist < enterdist) exit; \
                exitdist = pdist; \
            } \
        } \
        else if(pdist > 0) exit; \
    }

#define INTERSECTBOX(setentry, exit) \
    loop(i, 3) \
    { \
        if(ray[i]) \
        { \
            float prad = fabs(p.r[i] * invray[i]), pdist = (p.o[i] - v[i]) * invray[i], pmin = pdist - prad, pmax = pdist + prad; \
            if(pmin > enterdist) \
            { \
                if(pmin > exitdist) exit; \
                enterdist = pmin; \
                setentry; \
            } \
            if(pmax < exitdist) \
            { \
                if(pmax < enterdist) exit; \
                exitdist = pmax; \
            } \
         } \
         else if(v[i] < p.o[i]-p.r[i] || v[i] > p.o[i]+p.r[i]) exit; \
    }

vec hitsurface;

static inline bool raycubeintersect(clipplanes &p, const cube &c, const vec &v, const vec &ray, const vec &invray, float &dist)
{
    int entry = -1, bbentry = -1;
    INTERSECTPLANES(entry = i, return false);
    INTERSECTBOX(bbentry = i, return false);
    if(exitdist < 0) return false;
    dist = max(enterdist+0.1f, 0.0f);
    if(bbentry>=0) { hitsurface = vec(0, 0, 0); hitsurface[bbentry] = ray[bbentry]>0 ? -1 : 1; }
    else hitsurface = p.p[entry];
    return true;
}

extern void entselectionbox(const entity &e, vec &eo, vec &es);
extern int entselradius;
float hitentdist;
int hitent, hitorient;

static float disttoent(octaentities *oc, octaentities *last, const vec &o, const vec &ray, float radius, int mode, extentity *t)
{
    vec eo, es;
    int orient;
    float dist = 1e16f, f = 0.0f;
    if(oc == last) return dist;
    const vector<extentity *> &ents = entities::getents();

    #define entintersect(mask, type, func) {\
        if((mode&(mask))==(mask)) \
        { \
            loopv(oc->type) \
                if(!last || last->type.find(oc->type[i])<0) \
                { \
                    extentity &e = *ents[oc->type[i]]; \
                    if(!e.inoctanode || &e==t) continue; \
                    func; \
                    if(f<dist && f>0) \
                    { \
                        hitentdist = dist = f; \
                        hitent = oc->type[i]; \
                        hitorient = orient; \
                    } \
                } \
        } \
    }

    entintersect(RAY_POLY, mapmodels,
        orient = 0; // FIXME, not set
        if(!mmintersect(e, o, ray, radius, mode, f)) continue;
    );

    entintersect(RAY_ENTS, other,
        entselectionbox(e, eo, es);
        if(!rayrectintersect(eo, es, o, ray, f, orient)) continue;
    );

    entintersect(RAY_ENTS, mapmodels,
        entselectionbox(e, eo, es);
        if(!rayrectintersect(eo, es, o, ray, f, orient)) continue;
    );

    return dist;
}

static float disttooutsideent(const vec &o, const vec &ray, float radius, int mode, extentity *t)
{
    vec eo, es;
    int orient;
    float dist = 1e16f, f = 0.0f;
    const vector<extentity *> &ents = entities::getents();
    loopv(outsideents)
    {
        extentity &e = *ents[outsideents[i]];
        if(!e.inoctanode || &e == t) continue;
        entselectionbox(e, eo, es);
        if(!rayrectintersect(eo, es, o, ray, f, orient)) continue;
        if(f<dist && f>0)
        {
            hitentdist = dist = f;
            hitent = outsideents[i];
            hitorient = orient;
        }
    }
    return dist;
}

// optimized shadow version
static float shadowent(octaentities *oc, octaentities *last, const vec &o, const vec &ray, float radius, int mode, extentity *t)
{
    float dist = 1e16f, f = 0.0f;
    if(oc == last) return dist;
    const vector<extentity *> &ents = entities::getents();
    loopv(oc->mapmodels) if(!last || last->mapmodels.find(oc->mapmodels[i])<0)
    {
        extentity &e = *ents[oc->mapmodels[i]];
        if(!e.inoctanode || &e==t) continue;
        if(!mmintersect(e, o, ray, radius, mode, f)) continue;
        if(f>0 && f<dist) dist = f;
    }
    return dist;
}

#define INITRAYCUBE \
    octaentities *oclast = NULL; \
    float dist = 0, dent = mode&RAY_BB ? 1e16f : 1e14f; \
    vec v(o), invray(ray.x ? 1/ray.x : 1e16f, ray.y ? 1/ray.y : 1e16f, ray.z ? 1/ray.z : 1e16f); \
    cube *levels[20]; \
    levels[worldscale] = worldroot; \
    int lshift = worldscale, elvl = worldscale; \
    ivec lsizemask(invray.x>0 ? 1 : 0, invray.y>0 ? 1 : 0, invray.z>0 ? 1 : 0); \

#define CHECKINSIDEWORLD \
    if(!insideworld(o)) \
    { \
        float disttoworld = 0, exitworld = 1e16f; \
        loopi(3) \
        { \
            float c = v[i]; \
            if(c<0 || c>=worldsize) \
            { \
                float d = ((invray[i]>0?0:worldsize)-c)*invray[i]; \
                if(d<0) return (radius>0?radius:-1); \
                disttoworld = max(disttoworld, 0.1f + d); \
            } \
            float e = ((invray[i]>0?worldsize:0)-c)*invray[i]; \
            exitworld = min(exitworld, e); \
        } \
        if(disttoworld > exitworld) return (radius>0?radius:-1); \
        v.add(vec(ray).mul(disttoworld)); \
        dist += disttoworld; \
    }

#define DOWNOCTREE(disttoent, earlyexit) \
        cube *lc = levels[lshift]; \
        for(;;) \
        { \
            lshift--; \
            lc += octastep(x, y, z, lshift); \
            if(lc->ext && lc->ext->ents && lshift < elvl) \
            { \
                float edist = disttoent(lc->ext->ents, oclast, o, ray, radius, mode, t); \
                if(edist < 1e15f) \
                { \
                    if(earlyexit) return min(edist, dist); \
                    elvl = lshift; \
                    dent = min(dent, edist); \
                } \
                oclast = lc->ext->ents; \
            } \
            if(lc->children==NULL) break; \
            lc = lc->children; \
            levels[lshift] = lc; \
        }

#define FINDCLOSEST(xclosest, yclosest, zclosest) \
        float dx = (lo.x+(lsizemask.x<<lshift)-v.x)*invray.x, \
              dy = (lo.y+(lsizemask.y<<lshift)-v.y)*invray.y, \
              dz = (lo.z+(lsizemask.z<<lshift)-v.z)*invray.z; \
        float disttonext = dx; \
        xclosest; \
        if(dy < disttonext) { disttonext = dy; yclosest; } \
        if(dz < disttonext) { disttonext = dz; zclosest; } \
        disttonext += 0.1f; \
        v.add(vec(ray).mul(disttonext)); \
        dist += disttonext;

#define UPOCTREE(exitworld) \
        x = int(v.x); \
        y = int(v.y); \
        z = int(v.z); \
        uint diff = uint(lo.x^x)|uint(lo.y^y)|uint(lo.z^z); \
        if(diff >= uint(worldsize)) exitworld; \
        diff >>= lshift; \
        if(!diff) exitworld; \
        do \
        { \
            lshift++; \
            diff >>= 1; \
        } while(diff);

float raycube(const vec &o, const vec &ray, float radius, int mode, int size, extentity *t)
{
    if(ray.iszero()) return 0;

    INITRAYCUBE;
    CHECKINSIDEWORLD;

    int closest = -1, x = int(v.x), y = int(v.y), z = int(v.z);
    for(;;)
    {
        DOWNOCTREE(disttoent, mode&RAY_SHADOW);

        int lsize = 1<<lshift;

        cube &c = *lc;
        if((dist>0 || !(mode&RAY_SKIPFIRST)) &&
           (((mode&RAY_CLIPMAT) && isclipped(c.material&MATF_VOLUME)) ||
            ((mode&RAY_EDITMAT) && c.material != MAT_AIR) ||
            (!(mode&RAY_PASS) && lsize==size && !isempty(c)) ||
            isentirelysolid(c) ||
            dent < dist))
        {
            if(closest >= 0) { hitsurface = vec(0, 0, 0); hitsurface[closest] = ray[closest]>0 ? -1 : 1; }
            return min(dent, dist);
        }

        ivec lo(x&(~0<<lshift), y&(~0<<lshift), z&(~0<<lshift));

        if(!isempty(c))
        {
            clipplanes &p = getclipplanes(c, lo, lsize);
            float f = 0;
            if(raycubeintersect(p, c, v, ray, invray, f) && (dist+f>0 || !(mode&RAY_SKIPFIRST)))
                return min(dent, dist+f);
        }

        FINDCLOSEST(closest = 0, closest = 1, closest = 2);

        if(radius>0 && dist>=radius) return min(dent, dist);

        UPOCTREE(return min(dent, radius>0 ? radius : dist));
    }
}

// optimized version for lightmap shadowing... every cycle here counts!!!
float shadowray(const vec &o, const vec &ray, float radius, int mode, extentity *t)
{
    INITRAYCUBE;
    CHECKINSIDEWORLD;

    int side = O_BOTTOM, x = int(v.x), y = int(v.y), z = int(v.z);
    for(;;)
    {
        DOWNOCTREE(shadowent, true);

        cube &c = *lc;
        ivec lo(x&(~0<<lshift), y&(~0<<lshift), z&(~0<<lshift));

        if(!isempty(c) && !(c.material&MAT_ALPHA))
        {
            if(isentirelysolid(c)) return c.texture[side]==DEFAULT_SKY && mode&RAY_SKIPSKY ? radius : dist;
            clipplanes &p = getclipplanes(c, lo, 1<<lshift);
            INTERSECTPLANES(side = p.side[i], goto nextcube);
            INTERSECTBOX(side = (i<<1) + 1 - lsizemask[i], goto nextcube);
            if(exitdist >= 0) return c.texture[side]==DEFAULT_SKY && mode&RAY_SKIPSKY ? radius : dist+max(enterdist+0.1f, 0.0f);
        }

    nextcube:
        FINDCLOSEST(side = O_RIGHT - lsizemask.x, side = O_FRONT - lsizemask.y, side = O_TOP - lsizemask.z);

        if(dist>=radius) return dist;

        UPOCTREE(return radius);
    }
}

// thread safe version

struct ShadowRayCache
{
    clipplanes clipcache[MAXCLIPPLANES];
    int version;

    ShadowRayCache() : version(0) {}
};

ShadowRayCache *newshadowraycache() { return new ShadowRayCache; }

void freeshadowraycache(ShadowRayCache *&cache) { delete cache; cache = NULL; }

void resetshadowraycache(ShadowRayCache *cache)
{
    if(!cache->version++) memset(cache->clipcache, 0, sizeof(cache->clipcache));
}

float shadowray(ShadowRayCache *cache, const vec &o, const vec &ray, float radius, int mode, extentity *t)
{
    INITRAYCUBE;
    CHECKINSIDEWORLD;

    int side = O_BOTTOM, x = int(v.x), y = int(v.y), z = int(v.z);
    for(;;)
    {
        DOWNOCTREE(shadowent, true);

        cube &c = *lc;
        ivec lo(x&(~0<<lshift), y&(~0<<lshift), z&(~0<<lshift));

        if(!isempty(c) && !(c.material&MAT_ALPHA))
        {
            if(isentirelysolid(c)) return c.texture[side]==DEFAULT_SKY && mode&RAY_SKIPSKY ? radius : dist;
            clipplanes &p = cache->clipcache[int(&c - worldroot)&(MAXCLIPPLANES-1)];
            if(p.owner != &c || p.version != cache->version) { p.owner = &c; p.version = cache->version; genclipplanes(c, lo.x, lo.y, lo.z, 1<<lshift, p); }
            INTERSECTPLANES(side = p.side[i], goto nextcube);
            INTERSECTBOX(side = (i<<1) + 1 - lsizemask[i], goto nextcube);
            if(exitdist >= 0) return c.texture[side]==DEFAULT_SKY && mode&RAY_SKIPSKY ? radius : dist+max(enterdist+0.1f, 0.0f);
        }

    nextcube:
        FINDCLOSEST(side = O_RIGHT - lsizemask.x, side = O_FRONT - lsizemask.y, side = O_TOP - lsizemask.z);

        if(dist>=radius) return dist;

        UPOCTREE(return radius);
    }
}

float rayent(const vec &o, const vec &ray, float radius, int mode, int size, int &orient, int &ent)
{
    hitent = -1;
    hitentdist = radius;
    float dist = raycube(o, ray, radius, mode, size);
    if((mode&RAY_ENTS) == RAY_ENTS)
    {
        float dent = disttooutsideent(o, ray, dist < 0 ? 1e16f : dist, mode, NULL);
        if(dent < 1e15f && (dist < 0 || dent < dist)) dist = dent;
    }
    orient = hitorient;
    ent = hitentdist == dist ? hitent : -1;
    return dist;
}

float raycubepos(const vec &o, const vec &ray, vec &hitpos, float radius, int mode, int size)
{
    hitpos = ray;
    float dist = raycube(o, ray, radius, mode, size);
    if(radius>0 && dist>=radius) dist = radius;
    hitpos.mul(dist).add(o);
    return dist;
}

bool raycubelos(const vec &o, const vec &dest, vec &hitpos)
{
    vec ray(dest);
    ray.sub(o);
    float mag = ray.magnitude();
    ray.mul(1/mag);
    float distance = raycubepos(o, ray, hitpos, mag, RAY_CLIPMAT|RAY_POLY);
    return distance >= mag;
}

float rayfloor(const vec &o, vec &floor, int mode, float radius)
{
    if(o.z<=0) return -1;
    hitsurface = vec(0, 0, 1);
    float dist = raycube(o, vec(0, 0, -1), radius, mode);
    if(dist<0 || (radius>0 && dist>=radius)) return dist;
    floor = hitsurface;
    return dist;
}

/////////////////////////  entity collision  ///////////////////////////////////////////////

// info about collisions
bool inside; // whether an internal collision happened
physent *hitplayer; // whether the collection hit a player
vec wall; // just the normal vectors.
const float STAIRHEIGHT = 4.1f;
const float FLOORZ = 0.867f;
const float SLOPEZ = 0.5f;
const float WALLZ = 0.2f;
FVARR(movespeed, 10, 100, 1000);
FVARR(jumpvel, 10, 200, 5000);
FVARR(gravity, 10, 200, 1000);

bool ellipserectcollide(physent *d, const vec &dir, const vec &o, const vec &center, float yaw, float xr, float yr, float hi, float lo)
{
    float below = (o.z+center.z-lo) - (d->o.z+d->aboveeye),
          above = (d->o.z-d->eyeheight) - (o.z+center.z+hi);
    if(below>=0 || above>=0) return true;

    vec yo(d->o);
    yo.sub(o);
    yo.rotate_around_z(-yaw*RAD);
    yo.sub(center);

    float dx = clamp(yo.x, -xr, xr) - yo.x, dy = clamp(yo.y, -yr, yr) - yo.y,
          dist = sqrtf(dx*dx + dy*dy) - d->radius;
    if(dist < 0)
    {
        int sx = yo.x <= -xr ? -1 : (yo.x >= xr ? 1 : 0),
            sy = yo.y <= -yr ? -1 : (yo.y >= yr ? 1 : 0);
        if(dist > (yo.z < 0 ? below : above) && (sx || sy))
        {
            vec ydir(dir);
            ydir.rotate_around_z(-yaw*RAD);
            if(sx*yo.x - xr > sy*yo.y - yr)
            {
                if(dir.iszero() || sx*ydir.x < -1e-6f)
                {
                    wall = vec(sx, 0, 0);
                    wall.rotate_around_z(yaw*RAD);
                    return false;
                }
            }
            else if(dir.iszero() || sy*ydir.y < -1e-6f)
            {
                wall = vec(0, sy, 0);
                wall.rotate_around_z(yaw*RAD);
                return false;
            }
        }
        if(yo.z < 0)
        {
            if(dir.iszero() || (dir.z > 0 && (d->type>=ENT_INANIMATE || below >= d->zmargin-(d->eyeheight+d->aboveeye)/4.0f)))
            {
                wall = vec(0, 0, -1);
                return false;
            }
        }
        else if(dir.iszero() || (dir.z < 0 && (d->type>=ENT_INANIMATE || above >= d->zmargin-(d->eyeheight+d->aboveeye)/3.0f)))
        {
            wall = vec(0, 0, 1);
            return false;
        }
        inside = true;
    }
    return true;
}

bool ellipsecollide(physent *d, const vec &dir, const vec &o, const vec &center, float yaw, float xr, float yr, float hi, float lo)
{
    float below = (o.z+center.z-lo) - (d->o.z+d->aboveeye),
          above = (d->o.z-d->eyeheight) - (o.z+center.z+hi);
    if(below>=0 || above>=0) return true;
    vec yo(center);
    yo.rotate_around_z(yaw*RAD);
    yo.add(o);
    float x = yo.x - d->o.x, y = yo.y - d->o.y;
    float angle = atan2f(y, x), dangle = angle-(d->yaw+90)*RAD, eangle = angle-(yaw+90)*RAD;
    float dx = d->xradius*cosf(dangle), dy = d->yradius*sinf(dangle);
    float ex = xr*cosf(eangle), ey = yr*sinf(eangle);
    float dist = sqrtf(x*x + y*y) - sqrtf(dx*dx + dy*dy) - sqrtf(ex*ex + ey*ey);
    if(dist < 0)
    {
        if(dist > (d->o.z < yo.z ? below : above) && (dir.iszero() || x*dir.x + y*dir.y > 0))
        {
            wall = vec(-x, -y, 0);
            if(!wall.iszero()) wall.normalize();
            return false;
        }
        if(d->o.z < yo.z)
        {
            if(dir.iszero() || (dir.z > 0 && (d->type>=ENT_INANIMATE || below >= d->zmargin-(d->eyeheight+d->aboveeye)/4.0f)))
            {
                wall = vec(0, 0, -1);
                return false;
            }
        }
        else if(dir.iszero() || (dir.z < 0 && (d->type>=ENT_INANIMATE || above >= d->zmargin-(d->eyeheight+d->aboveeye)/3.0f)))
        {
            wall = vec(0, 0, 1);
            return false;
        }
        inside = true;
    }
    return true;
}

bool rectcollide(physent *d, const vec &dir, const vec &o, float xr, float yr,  float hi, float lo, uchar visible = 0xFF)
{
    vec s(d->o);
    s.sub(o);
    float dxr = d->collidetype==COLLIDE_AABB ? d->xradius : d->radius, dyr = d->collidetype==COLLIDE_AABB ? d->yradius : d->radius;
    xr += dxr;
    yr += dyr;
    float zr = s.z>0 ? d->eyeheight+hi : d->aboveeye+lo;
    float ax = fabs(s.x)-xr;
    float ay = fabs(s.y)-yr;
    float az = fabs(s.z)-zr;
    if(ax>0 || ay>0 || az>0) return true;
    wall.x = wall.y = wall.z = 0;
#define TRYCOLLIDE(dim, ON, OP, N, P) \
    { \
        if(s.dim<0) { if(visible&(1<<ON) && (dir.iszero() || (dir.dim>0 && (d->type>=ENT_INANIMATE || (N))))) { wall.dim = -1; return false; } } \
        else if(visible&(1<<OP) && (dir.iszero() || (dir.dim<0 && (d->type>=ENT_INANIMATE || (P))))) { wall.dim = 1; return false; } \
    }
    if(ax>ay && ax>az) TRYCOLLIDE(x, O_LEFT, O_RIGHT, ax > -dxr, ax > -dxr);
    if(ay>az) TRYCOLLIDE(y, O_BACK, O_FRONT, ay > -dyr, ay > -dyr);
    TRYCOLLIDE(z, O_BOTTOM, O_TOP,
         az >= d->zmargin-(d->eyeheight+d->aboveeye)/4.0f,
         az >= d->zmargin-(d->eyeheight+d->aboveeye)/3.0f);
    inside = true;
    return true;
}

#define DYNENTCACHESIZE 1024

static uint dynentframe = 0;

static struct dynentcacheentry
{
    int x, y;
    uint frame;
    vector<physent *> dynents;
} dynentcache[DYNENTCACHESIZE];

void cleardynentcache()
{
    dynentframe++;
    if(!dynentframe || dynentframe == 1) loopi(DYNENTCACHESIZE) dynentcache[i].frame = 0;
    if(!dynentframe) dynentframe = 1;
}

VARF(dynentsize, 4, 7, 12, cleardynentcache());

#define DYNENTHASH(x, y) (((((x)^(y))<<5) + (((x)^(y))>>5)) & (DYNENTCACHESIZE - 1))

const vector<physent *> &checkdynentcache(int x, int y)
{
    dynentcacheentry &dec = dynentcache[DYNENTHASH(x, y)];
    if(dec.x == x && dec.y == y && dec.frame == dynentframe) return dec.dynents;
    dec.x = x;
    dec.y = y;
    dec.frame = dynentframe;
    dec.dynents.shrink(0);
    int numdyns = game::numdynents(), dsize = 1<<dynentsize, dx = x<<dynentsize, dy = y<<dynentsize;
    loopi(numdyns)
    {
        dynent *d = game::iterdynents(i);
        if(d->state != CS_ALIVE ||
           d->o.x+d->radius <= dx || d->o.x-d->radius >= dx+dsize ||
           d->o.y+d->radius <= dy || d->o.y-d->radius >= dy+dsize)
            continue;
        dec.dynents.add(d);
    }
    return dec.dynents;
}

#define loopdynentcache(curx, cury, o, radius) \
    for(int curx = max(int(o.x-radius), 0)>>dynentsize, endx = min(int(o.x+radius), worldsize-1)>>dynentsize; curx <= endx; curx++) \
    for(int cury = max(int(o.y-radius), 0)>>dynentsize, endy = min(int(o.y+radius), worldsize-1)>>dynentsize; cury <= endy; cury++)

void updatedynentcache(physent *d)
{
    loopdynentcache(x, y, d->o, d->radius)
    {
        dynentcacheentry &dec = dynentcache[DYNENTHASH(x, y)];
        if(dec.x != x || dec.y != y || dec.frame != dynentframe || dec.dynents.find(d) >= 0) continue;
        dec.dynents.add(d);
    }
}

bool overlapsdynent(const vec &o, float radius)
{
    loopdynentcache(x, y, o, radius)
    {
        const vector<physent *> &dynents = checkdynentcache(x, y);
        loopv(dynents)
        {
            physent *d = dynents[i];
            if(o.dist(d->o)-d->radius < radius) return true;
        }
    }
    return false;
}

template<class E, class O>
static inline bool plcollide(physent *d, const vec &dir, physent *o)
{
    E entvol(d);
    O obvol(o);
    vec cp;
    if(mpr::collide(entvol, obvol, NULL, NULL, &cp))
    {
        vec wn = vec(cp).sub(obvol.center());
        wall = obvol.contactface(wn, dir.iszero() ? vec(wn).neg() : dir);
        if(!wall.iszero()) return false;
        inside = true;
    }
    return true;
}

bool plcollide(physent *d, const vec &dir)    // collide with player or monster
{
    if(d->type==ENT_CAMERA || d->state!=CS_ALIVE) return true;
    loopdynentcache(x, y, d->o, d->radius)
    {
        const vector<physent *> &dynents = checkdynentcache(x, y);
        loopv(dynents)
        {
            physent *o = dynents[i];
            if(o==d || d->o.reject(o->o, d->radius+o->radius)) continue;
            switch(d->collidetype)
            {
                case COLLIDE_ELLIPSE:
                    if(o->collidetype == COLLIDE_ELLIPSE)
                    {
                        if(ellipsecollide(d, dir, o->o, vec(0, 0, 0), o->yaw, o->xradius, o->yradius, o->aboveeye, o->eyeheight)) continue;
                    }
                    else if(ellipserectcollide(d, dir, o->o, vec(0, 0, 0), o->yaw, o->xradius, o->yradius, o->aboveeye, o->eyeheight)) continue;
                    break;
                case COLLIDE_OBB:
                    if(o->collidetype == COLLIDE_ELLIPSE)
                    {
                        if(plcollide<mpr::EntOBB, mpr::EntCylinder>(d, dir, o)) continue;
                    }
                    else if(plcollide<mpr::EntOBB, mpr::EntOBB>(d, dir, o)) continue;
                    break;
                case COLLIDE_AABB:
                default:
                    if(rectcollide(d, dir, o->o, o->collidetype == COLLIDE_AABB ? o->xradius : o->radius, o->collidetype == COLLIDE_AABB ? o->yradius : o->radius, o->aboveeye, o->eyeheight)) continue;
                    break;
            }
            hitplayer = o;
            game::dynentcollide(d, o, wall);
            return false;
        }
    }
    return true;
}

void rotatebb(vec &center, vec &radius, int yaw)
{
    if(yaw < 0) yaw = 360 + yaw%360;
    else if(yaw >= 360) yaw %= 360;
    const vec2 &rot = sincos360[yaw];
    vec2 oldcenter(center), oldradius(radius);
    center.x = oldcenter.x*rot.x - oldcenter.y*rot.y;
    center.y = oldcenter.y*rot.x + oldcenter.x*rot.y;
    radius.x = fabs(oldradius.x*rot.x) + fabs(oldradius.y*rot.y);
    radius.y = fabs(oldradius.y*rot.x) + fabs(oldradius.x*rot.y);
}

template<class E, class M>
static inline bool mmcollide(physent *d, const vec &dir, const extentity &e, const vec &center, const vec &radius, float yaw)
{
    E entvol(d);
    M mdlvol(e.o, center, radius, yaw);
    vec cp;
    if(mpr::collide(entvol, mdlvol, NULL, NULL, &cp))
    {
        vec wn = vec(cp).sub(mdlvol.center());
        wall = mdlvol.contactface(wn, dir.iszero() ? vec(wn).neg() : dir);
        if(!wall.iszero()) return false;
        inside = true;
    }
    return true;
}

bool mmcollide(physent *d, const vec &dir, octaentities &oc)               // collide with a mapmodel
{
    const vector<extentity *> &ents = entities::getents();
    loopv(oc.mapmodels)
    {
        extentity &e = *ents[oc.mapmodels[i]];
        if(e.flags&extentity::F_NOCOLLIDE) continue;
        model *m = loadmodel(NULL, e.attr[1]);
        if(!m || !m->collide) continue;
        vec center, radius;
        m->collisionbox(0, center, radius);
        float yaw = e.attr[0];
        switch(d->collidetype)
        {
            case COLLIDE_ELLIPSE:
                if(m->ellipsecollide)
                {
                    //if(!mmcollide<mpr::EntCylinder, mpr::ModelEllipse>(d, dir, e, center, radius, yaw)) return false;
                    if(!ellipsecollide(d, dir, e.o, center, yaw, radius.x, radius.y, radius.z, radius.z)) return false;
                }
                //else if(!mmcollide<mpr::EntCylinder, mpr::ModelOBB>(d, dir, e, center, radius, yaw)) return false;
                else if(!ellipserectcollide(d, dir, e.o, center, yaw, radius.x, radius.y, radius.z, radius.z)) return false;
                break;
            case COLLIDE_OBB:
                if(m->ellipsecollide)
                {
                    if(!mmcollide<mpr::EntOBB, mpr::ModelEllipse>(d, dir, e, center, radius, yaw)) return false;
                }
                else if(!mmcollide<mpr::EntOBB, mpr::ModelOBB>(d, dir, e, center, radius, yaw)) return false;
                break;
            case COLLIDE_AABB:
            default:
                rotatebb(center, radius, e.attr[0]);
                if(!rectcollide(d, dir, center.add(e.o), radius.x, radius.y, radius.z, radius.z)) return false;
                break;
        }
    }
    return true;
}

template<class E>
static bool fuzzycollidesolid(physent *d, const vec &dir, float cutoff, cube &c, const ivec &co, int size) // collide with solid cube geometry
{
    int crad = size/2;
    if(fabs(d->o.x - co.x - crad) > d->radius + crad || fabs(d->o.y - co.y - crad) > d->radius + crad ||
       d->o.z + d->aboveeye < co.z || d->o.z - d->eyeheight > co.z + size)
        return true;

    E entvol(d);
    wall = vec(0, 0, 0);
    float bestdist = -1e10f;
    int visible = isentirelysolid(c) ? c.collide : 0xFF;
    loopi(6) if(visible&(1<<i))
     {
        int dim = dimension(i), dc = dimcoord(i), dimdir = 2*dc - 1;
        plane w(0, 0, 0, -(dimdir*co[dim] + dc*size));
        w[dim] = dimdir;
        vec pw = entvol.supportpoint(vec(w).neg());
        float dist = w.dist(pw);
        if(dist > 0) return true;
        if(dist <= bestdist) continue;
        if(!dir.iszero())
        {
            if(w.dot(dir) >= -cutoff*dir.magnitude()) continue;
            if(d->type<ENT_CAMERA &&
                dist < (dir.z*w.z < 0 ?
                    d->zmargin-(d->eyeheight+d->aboveeye)/(dir.z < 0 ? 3.0f : 4.0f) :
                    ((dir.x*w.x < 0 || dir.y*w.y < 0) ? -d->radius : 0)))
                continue;
        }
        wall = w;
        bestdist = dist;
    }
    if(wall.iszero())
    {
        inside = true;
        return true;
    }
    return false;
}

template<class E>
static inline bool clampcollide(const clipplanes &p, const E &entvol, const plane &w, const vec &pw)
{
    if(w.x && (w.y || w.z) && fabs(pw.x - p.o.x) > p.r.x)
    {
        vec c = entvol.center();
        float fv = pw.x < p.o.x ? p.o.x-p.r.x : p.o.x+p.r.x, fdist = (w.x*fv + w.y*c.y + w.z*c.z + w.offset) / (w.y*w.y + w.z*w.z);
        vec fdir(fv - c.x, -w.y*fdist, -w.z*fdist);
        if((pw.y-c.y-fdir.y)*w.y + (pw.z-c.z-fdir.z)*w.z >= 0 && entvol.supportpoint(fdir).squaredist(c) < fdir.squaredlen()) return true;
    }
    if(w.y && (w.x || w.z) && fabs(pw.y - p.o.y) > p.r.y)
    {
        vec c = entvol.center();
        float fv = pw.y < p.o.y ? p.o.y-p.r.y : p.o.y+p.r.y, fdist = (w.x*c.x + w.y*fv + w.z*c.z + w.offset) / (w.x*w.x + w.z*w.z);
        vec fdir(-w.x*fdist, fv - c.y, -w.z*fdist);
        if((pw.x-c.x-fdir.x)*w.x + (pw.z-c.z-fdir.z)*w.z >= 0 && entvol.supportpoint(fdir).squaredist(c) < fdir.squaredlen()) return true;
    }
    if(w.z && (w.x || w.y) && fabs(pw.z - p.o.z) > p.r.z)
    {
        vec c = entvol.center();
        float fv = pw.z < p.o.z ? p.o.z-p.r.z : p.o.z+p.r.z, fdist = (w.x*c.x + w.y*c.y + w.z*fv + w.offset) / (w.x*w.x + w.y*w.y);
        vec fdir(-w.x*fdist, -w.y*fdist, fv - c.z);
        if((pw.x-c.x-fdir.x)*w.x + (pw.y-c.y-fdir.y)*w.y >= 0 && entvol.supportpoint(fdir).squaredist(c) < fdir.squaredlen()) return true;
    }
    return false;
}

template<class E>
static bool fuzzycollideplanes(physent *d, const vec &dir, float cutoff, cube &c, const ivec &co, int size) // collide with deformed cube geometry
{
    clipplanes &p = getclipplanes(c, co, size);

    if(fabs(d->o.x - p.o.x) > p.r.x + d->radius || fabs(d->o.y - p.o.y) > p.r.y + d->radius ||
       d->o.z + d->aboveeye < p.o.z - p.r.z || d->o.z - d->eyeheight > p.o.z + p.r.z)
        return true;

    E entvol(d);
    wall = vec(0, 0, 0);
    float bestdist = -1e10f;
    loopi(6) if(p.visible&(1<<i))
    {
        int dim = dimension(i), dimdir = 2*dimcoord(i) - 1;
        plane w(0, 0, 0, -(dimdir*p.o[dim] + p.r[dim]));
        w[dim] = dimdir;
        vec pw = entvol.supportpoint(vec(w).neg());
        float dist = w.dist(pw);
        if(dist >= 0) return true;
        if(dist <= bestdist) continue;
        if(!dir.iszero())
        {
            if(w.dot(dir) >= -cutoff*dir.magnitude()) continue;
            if(d->type<ENT_CAMERA &&
                dist < (dir.z*w.z < 0 ?
                    d->zmargin-(d->eyeheight+d->aboveeye)/(dir.z < 0 ? 3.0f : 4.0f) :
                    ((dir.x*w.x < 0 || dir.y*w.y < 0) ? -d->radius : 0)))
                continue;
        }
        wall = w;
        bestdist = dist;
    }
    int bestplane = -1;
    loopi(p.size)
    {
        plane &w = p.p[i];
        vec pw = entvol.supportpoint(vec(w).neg());
        float dist = w.dist(pw);
        if(dist >= 0) return true;
        if(dist <= bestdist) continue;
        bestplane = -1;
        bestdist = dist;
        if(!dir.iszero())
        {
            if(w.dot(dir) >= -cutoff*dir.magnitude()) continue;
            if(d->type<ENT_CAMERA &&
                dist < (dir.z*w.z < 0 ?
                    d->zmargin-(d->eyeheight+d->aboveeye)/(dir.z < 0 ? 3.0f : 4.0f) :
                    ((dir.x*w.x < 0 || dir.y*w.y < 0) ? -d->radius : 0)))
                continue;
        }
        if(clampcollide(p, entvol, w, pw)) continue;
        bestplane = i;
    }
    if(bestplane >= 0) wall = p.p[bestplane];
    else if(wall.iszero())
    {
        inside = true;
        return true;
    }
    return false;
}

template<class E>
static bool cubecollidesolid(physent *d, const vec &dir, float cutoff, cube &c, const ivec &co, int size) // collide with solid cube geometry
{
    int crad = size/2;
    if(fabs(d->o.x - co.x - crad) > d->radius + crad || fabs(d->o.y - co.y - crad) > d->radius + crad ||
       d->o.z + d->aboveeye < co.z || d->o.z - d->eyeheight > co.z + size)
        return true;

    E entvol(d);
    bool collided = mpr::collide(mpr::SolidCube(co, size), entvol);
    if(!collided) return true;

    wall = vec(0, 0, 0);
    float bestdist = -1e10f;
    int visible = isentirelysolid(c) ? c.collide : 0xFF;
    loopi(6) if(visible&(1<<i))
     {
        int dim = dimension(i), dc = dimcoord(i), dimdir = 2*dc - 1;
        plane w(0, 0, 0, -(dimdir*co[dim] + dc*size));
        w[dim] = dimdir;
        vec pw = entvol.supportpoint(vec(w).neg());
        float dist = w.dist(pw);
        if(dist <= bestdist) continue;
        if(!dir.iszero())
        {
            if(w.dot(dir) >= -cutoff*dir.magnitude()) continue;
            if(d->type<ENT_CAMERA &&
                dist < (dir.z*w.z < 0 ?
                    d->zmargin-(d->eyeheight+d->aboveeye)/(dir.z < 0 ? 3.0f : 4.0f) :
                    ((dir.x*w.x < 0 || dir.y*w.y < 0) ? -d->radius : 0)))
                continue;
        }
        wall = w;
        bestdist = dist;
    }
    if(wall.iszero())
    {
        inside = true;
        return true;
    }
    return false;
}

template<class E>
static bool cubecollideplanes(physent *d, const vec &dir, float cutoff, cube &c, const ivec &co, int size) // collide with deformed cube geometry
{
    clipplanes &p = getclipplanes(c, co, size);

    if(fabs(d->o.x - p.o.x) > p.r.x + d->radius || fabs(d->o.y - p.o.y) > p.r.y + d->radius ||
       d->o.z + d->aboveeye < p.o.z - p.r.z || d->o.z - d->eyeheight > p.o.z + p.r.z)
        return true;

    E entvol(d);
    bool collided = mpr::collide(mpr::CubePlanes(p), entvol);
    if(!collided) return true;

    wall = vec(0, 0, 0);
    float bestdist = -1e10f;
    loopi(6) if(p.visible&(1<<i))
    {
        int dim = dimension(i), dimdir = 2*dimcoord(i) - 1;
        plane w(0, 0, 0, -(dimdir*p.o[dim] + p.r[dim]));
        w[dim] = dimdir;
        vec pw = entvol.supportpoint(vec(w).neg());
        float dist = w.dist(pw);
        if(dist <= bestdist) continue;
        if(!dir.iszero())
        {
            if(w.dot(dir) >= -cutoff*dir.magnitude()) continue;
            if(d->type<ENT_CAMERA &&
                dist < (dir.z*w.z < 0 ?
                    d->zmargin-(d->eyeheight+d->aboveeye)/(dir.z < 0 ? 3.0f : 4.0f) :
                    ((dir.x*w.x < 0 || dir.y*w.y < 0) ? -d->radius : 0)))
                continue;
        }
        wall = w;
        bestdist = dist;
    }
    int bestplane = -1;
    loopi(p.size)
    {
        plane &w = p.p[i];
        vec pw = entvol.supportpoint(vec(w).neg());
        float dist = w.dist(pw);
        if(dist <= bestdist) continue;
        bestplane = -1;
        bestdist = dist;
        if(!dir.iszero())
        {
            if(w.dot(dir) >= -cutoff*dir.magnitude()) continue;
            if(d->type<ENT_CAMERA &&
                dist < (dir.z*w.z < 0 ?
                    d->zmargin-(d->eyeheight+d->aboveeye)/(dir.z < 0 ? 3.0f : 4.0f) :
                    ((dir.x*w.x < 0 || dir.y*w.y < 0) ? -d->radius : 0)))
                continue;
        }
        if(clampcollide(p, entvol, w, pw)) continue;
        bestplane = i;
    }
    if(bestplane >= 0) wall = p.p[bestplane];
    else if(wall.iszero())
    {
        inside = true;
        return true;
    }
    return false;
}

static inline bool cubecollide(physent *d, const vec &dir, float cutoff, cube &c, const ivec &co, int size, bool solid)
{
    switch(d->collidetype)
    {
    case COLLIDE_AABB:
        if(isentirelysolid(c) || solid)
        {
            if(cutoff <= 0)
            {
                int crad = size/2;
                return rectcollide(d, dir, vec(co.x + crad, co.y + crad, co.z), crad, crad, size, 0, isentirelysolid(c) ? c.collide : 0xFF);
            }
#if 0
            else return cubecollidesolid<mpr::EntAABB>(d, dir, cutoff, c, co, size);
#else
            else return fuzzycollidesolid<mpr::EntAABB>(d, dir, cutoff, c, co, size);
#endif
        }
        else
        {
#if 0
            if(cutoff <= 0)
            {
                clipplanes &p = getclipplanes(c, co, size);
                if(!p.size) return rectcollide(d, dir, p.o, p.r.x, p.r.y, p.r.z, p.r.z, p.visible);
            }
            return cubecollideplanes<mpr::EntAABB>(d, dir, cutoff, c, co, size);
#else
            return fuzzycollideplanes<mpr::EntAABB>(d, dir, cutoff, c, co, size);
#endif
        }
    case COLLIDE_OBB:
        if(isentirelysolid(c) || solid) return cubecollidesolid<mpr::EntOBB>(d, dir, cutoff, c, co, size);
        else return cubecollideplanes<mpr::EntOBB>(d, dir, cutoff, c, co, size);
    case COLLIDE_ELLIPSE:
    default:
        if(d->type < ENT_CAMERA)
        {
            if(isentirelysolid(c) || solid) return fuzzycollidesolid<mpr::EntCapsule>(d, dir, cutoff, c, co, size);
            else return fuzzycollideplanes<mpr::EntCapsule>(d, dir, cutoff, c, co, size);
        }
        else if(isentirelysolid(c) || solid) return cubecollidesolid<mpr::EntCapsule>(d, dir, cutoff, c, co, size);
        else return cubecollideplanes<mpr::EntCapsule>(d, dir, cutoff, c, co, size);
    }
}

static inline bool octacollide(physent *d, const vec &dir, float cutoff, const ivec &bo, const ivec &bs, cube *c, const ivec &cor, int size) // collide with octants
{
    loopoctabox(cor, size, bo, bs)
    {
        if(c[i].ext && c[i].ext->ents) if(!mmcollide(d, dir, *c[i].ext->ents)) return false;
        ivec o(i, cor.x, cor.y, cor.z, size);
        if(c[i].children)
        {
            if(!octacollide(d, dir, cutoff, bo, bs, c[i].children, o, size>>1)) return false;
        }
        else
        {
            bool solid = false;
            switch(c[i].material&MATF_CLIP)
            {
                case MAT_NOCLIP: continue;
                case MAT_GAMECLIP: if(d->type==ENT_AI) solid = true; break;
                case MAT_CLIP: if(isclipped(c[i].material&MATF_VOLUME) || d->type<ENT_CAMERA) solid = true; break;
            }
            if(!solid && isempty(c[i])) continue;
            if(!cubecollide(d, dir, cutoff, c[i], o, size, solid)) return false;
        }
    }
    return true;
}

static inline bool octacollide(physent *d, const vec &dir, float cutoff, const ivec &bo, const ivec &bs)
{
    int diff = (bo.x^(bo.x+bs.x)) | (bo.y^(bo.y+bs.y)) | (bo.z^(bo.z+bs.z)),
        scale = worldscale-1;
    if(diff&~((1<<scale)-1) || uint(bo.x|bo.y|bo.z|(bo.x+bs.x)|(bo.y+bs.y)|(bo.z+bs.z)) >= uint(worldsize))
       return octacollide(d, dir, cutoff, bo, bs, worldroot, ivec(0, 0, 0), worldsize>>1);
    cube *c = &worldroot[octastep(bo.x, bo.y, bo.z, scale)];
    if(c->ext && c->ext->ents && !mmcollide(d, dir, *c->ext->ents)) return false;
    scale--;
    while(c->children && !(diff&(1<<scale)))
    {
        c = &c->children[octastep(bo.x, bo.y, bo.z, scale)];
        if(c->ext && c->ext->ents && !mmcollide(d, dir, *c->ext->ents)) return false;
        scale--;
    }
    if(c->children) return octacollide(d, dir, cutoff, bo, bs, c->children, ivec(bo).mask(~((2<<scale)-1)), 1<<scale);
    bool solid = false;
    switch(c->material&MATF_CLIP)
    {
        case MAT_NOCLIP: return true;
        case MAT_GAMECLIP: if(d->type==ENT_AI) solid = true; break;
        case MAT_CLIP: if(isclipped(c->material&MATF_VOLUME) || d->type<ENT_CAMERA) solid = true; break;
    }
    if(!solid && isempty(*c)) return true;
    int csize = 2<<scale, cmask = ~(csize-1);
    return cubecollide(d, dir, cutoff, *c, ivec(bo).mask(cmask), csize, solid);
}

// all collision happens here
bool collide(physent *d, const vec &dir, float cutoff, bool playercol)
{
    inside = false;
    hitplayer = NULL;
    wall.x = wall.y = wall.z = 0;
    ivec bo(int(d->o.x-d->radius), int(d->o.y-d->radius), int(d->o.z-d->eyeheight)),
         bs(int(d->radius*2), int(d->radius*2), int(d->eyeheight+d->aboveeye));
    bs.add(2);  // guard space for rounding errors
    if(!octacollide(d, dir, cutoff, bo, bs)) return false;//, worldroot, ivec(0, 0, 0), worldsize>>1)) return false; // collide with world
    return !playercol || plcollide(d, dir);
}

void recalcdir(physent *d, const vec &oldvel, vec &dir)
{
    float speed = oldvel.magnitude();
    if(speed > 1e-6f)
    {
        float step = dir.magnitude();
        dir = d->vel;
        dir.add(d->falling);
        dir.mul(step/speed);
    }
}

void slideagainst(physent *d, vec &dir, const vec &obstacle, bool foundfloor, bool slidecollide)
{
    vec wall(obstacle);
    if(foundfloor ? wall.z > 0 : slidecollide)
    {
        wall.z = 0;
        if(!wall.iszero()) wall.normalize();
    }
    vec oldvel(d->vel);
    oldvel.add(d->falling);
    d->vel.project(wall);
    d->falling.project(wall);
    recalcdir(d, oldvel, dir);
}

void switchfloor(physent *d, vec &dir, const vec &floor)
{
    if(floor.z >= FLOORZ) d->falling = vec(0, 0, 0);

    vec oldvel(d->vel);
    oldvel.add(d->falling);
    if(dir.dot(floor) >= 0)
    {
        if(d->physstate < PHYS_SLIDE || fabs(dir.dot(d->floor)) > 0.01f*dir.magnitude()) return;
        d->vel.projectxy(floor, 0.0f);
    }
    else d->vel.projectxy(floor);
    d->falling.project(floor);
    recalcdir(d, oldvel, dir);
}

bool trystepup(physent *d, vec &dir, const vec &obstacle, float maxstep, const vec &floor)
{
    vec old(d->o), stairdir = (obstacle.z >= 0 && obstacle.z < SLOPEZ ? vec(-obstacle.x, -obstacle.y, 0) : vec(dir.x, dir.y, 0)).rescale(1);
    bool cansmooth = true;
    /* check if there is space atop the stair to move to */
    if(d->physstate != PHYS_STEP_UP)
    {
        vec checkdir = stairdir;
        checkdir.mul(0.1f);
        checkdir.z += maxstep + 0.1f;
        d->o.add(checkdir);
        if(!collide(d))
        {
            d->o = old;
            if(collide(d, vec(0, 0, -1), SLOPEZ)) return false;
            cansmooth = false;
        }
    }

    if(cansmooth)
    {
        vec checkdir = stairdir;
        checkdir.z += 1;
        checkdir.mul(maxstep);
        d->o = old;
        d->o.add(checkdir);
        int scale = 2;
        if(!collide(d, checkdir))
        {
            if(collide(d, vec(0, 0, -1), SLOPEZ))
            {
                d->o = old;
                return false;
            }
            d->o.add(checkdir);
            if(!collide(d, vec(0, 0, -1), SLOPEZ)) scale = 1;
        }
        if(scale != 1)
        {
            d->o = old;
            d->o.sub(checkdir.mul(vec(2, 2, 1)));
            if(collide(d, vec(0, 0, -1), SLOPEZ)) scale = 1;
        }

        d->o = old;
        vec smoothdir(dir.x, dir.y, 0);
        float magxy = smoothdir.magnitude();
        if(magxy > 1e-9f)
        {
            if(magxy > scale*dir.z)
            {
                smoothdir.mul(1/magxy);
                smoothdir.z = 1.0f/scale;
                smoothdir.mul(dir.magnitude()/smoothdir.magnitude());
            }
            else smoothdir.z = dir.z;
            d->o.add(smoothdir);
            d->o.z += maxstep + 0.1f;
            if(collide(d, smoothdir))
            {
                d->o.z -= maxstep + 0.1f;
                if(d->physstate == PHYS_FALL || d->floor != floor)
                {
                    d->timeinair = 0;
                    d->floor = floor;
                    switchfloor(d, dir, d->floor);
                }
                d->physstate = PHYS_STEP_UP;
                return true;
            }
        }
    }

    /* try stepping up */
    d->o = old;
    d->o.z += dir.magnitude();
    if(collide(d, vec(0, 0, 1)))
    {
        if(d->physstate == PHYS_FALL || d->floor != floor)
        {
            d->timeinair = 0;
            d->floor = floor;
            switchfloor(d, dir, d->floor);
        }
        if(cansmooth) d->physstate = PHYS_STEP_UP;
        return true;
    }
    d->o = old;
    return false;
}

bool trystepdown(physent *d, vec &dir, float step, float xy, float z, bool init = false)
{
    vec stepdir(dir.x, dir.y, 0);
    stepdir.z = -stepdir.magnitude2()*z/xy;
    if(!stepdir.z) return false;
    stepdir.normalize();

    vec old(d->o);
    d->o.add(vec(stepdir).mul(STAIRHEIGHT/fabs(stepdir.z))).z -= STAIRHEIGHT;
    d->zmargin = -STAIRHEIGHT;
    if(!collide(d, vec(0, 0, -1), SLOPEZ))
    {
        d->o = old;
        d->o.add(vec(stepdir).mul(step));
        d->zmargin = 0;
        if(collide(d, vec(0, 0, -1)))
        {
            vec stepfloor(stepdir);
            stepfloor.mul(-stepfloor.z).z += 1;
            stepfloor.normalize();
            if(d->physstate >= PHYS_SLOPE && d->floor != stepfloor)
            {
                // prevent alternating step-down/step-up states if player would keep bumping into the same floor
                vec stepped(d->o);
                d->o.z -= 0.5f;
                d->zmargin = -0.5f;
                if(!collide(d, stepdir) && wall == d->floor)
                {
                    d->o = old;
                    if(!init) { d->o.x += dir.x; d->o.y += dir.y; if(dir.z <= 0 || !collide(d, dir)) d->o.z += dir.z; }
                    d->zmargin = 0;
                    d->physstate = PHYS_STEP_DOWN;
                    d->timeinair = 0;
                    return true;
                }
                d->o = init ? old : stepped;
                d->zmargin = 0;
            }
            else if(init) d->o = old;
            switchfloor(d, dir, stepfloor);
            d->floor = stepfloor;
            d->physstate = PHYS_STEP_DOWN;
            d->timeinair = 0;
            return true;
        }
    }
    d->o = old;
    d->zmargin = 0;
    return false;
}

bool trystepdown(physent *d, vec &dir, bool init = false)
{
    if(!game::allowmove(d) || (!d->move && !d->strafe)) return false;
    vec old(d->o);
    d->o.z -= STAIRHEIGHT;
    d->zmargin = -STAIRHEIGHT;
    if(collide(d, vec(0, 0, -1), SLOPEZ))
    {
        d->o = old;
        d->zmargin = 0;
        return false;
    }
    d->o = old;
    d->zmargin = 0;
    float step = dir.magnitude();
#if 1
    // weaker check, just enough to avoid hopping up slopes
    if(trystepdown(d, dir, step, 4, 1, init)) return true;
#else
    if(trystepdown(d, dir, step, 2, 1, init)) return true;
    if(trystepdown(d, dir, step, 1, 1, init)) return true;
    if(trystepdown(d, dir, step, 1, 2, init)) return true;
#endif
    return false;
}

void falling(physent *d, vec &dir, const vec &floor)
{
    if(floor.z > 0.0f && floor.z < SLOPEZ)
    {
        if(floor.z >= WALLZ) switchfloor(d, dir, floor);
        d->timeinair = 0;
        d->physstate = PHYS_SLIDE;
        d->floor = floor;
    }
    else if(d->physstate < PHYS_SLOPE || dir.dot(d->floor) > 0.01f*dir.magnitude() || (floor.z != 0.0f && floor.z != 1.0f) || !trystepdown(d, dir, true))
        d->physstate = PHYS_FALL;
}

void landing(physent *d, vec &dir, const vec &floor, bool collided)
{
#if 0
    if(d->physstate == PHYS_FALL)
    {
        d->timeinair = 0;
        if(dir.z < 0.0f) dir.z = d->vel.z = 0.0f;
    }
#endif
    switchfloor(d, dir, floor);
    d->timeinair = 0;
    if((d->physstate!=PHYS_STEP_UP && d->physstate!=PHYS_STEP_DOWN) || !collided)
        d->physstate = floor.z >= FLOORZ ? PHYS_FLOOR : PHYS_SLOPE;
    d->floor = floor;
}

bool findfloor(physent *d, bool collided, const vec &obstacle, bool &slide, vec &floor)
{
    bool found = false;
    vec moved(d->o);
    d->o.z -= 0.1f;
    if(!collide(d, vec(0, 0, -1), d->physstate == PHYS_SLOPE || d->physstate == PHYS_STEP_DOWN ? SLOPEZ : FLOORZ))
    {
        floor = wall;
        found = true;
    }
    else if(collided && obstacle.z >= SLOPEZ)
    {
        floor = obstacle;
        found = true;
        slide = false;
    }
    else if(d->physstate == PHYS_STEP_UP || d->physstate == PHYS_SLIDE)
    {
        if(!collide(d, vec(0, 0, -1)) && wall.z > 0.0f)
        {
            floor = wall;
            if(floor.z >= SLOPEZ) found = true;
        }
    }
    else if(d->physstate >= PHYS_SLOPE && d->floor.z < 1.0f)
    {
        if(!collide(d, vec(d->floor).neg(), 0.95f) || !collide(d, vec(0, 0, -1)))
        {
            floor = wall;
            if(floor.z >= SLOPEZ && floor.z < 1.0f) found = true;
        }
    }
    if(collided && (!found || obstacle.z > floor.z))
    {
        floor = obstacle;
        slide = !found && (floor.z < WALLZ || floor.z >= SLOPEZ);
    }
    d->o = moved;
    return found;
}

bool move(physent *d, vec &dir)
{
    vec old(d->o);
    bool collided = false, slidecollide = false;
    vec obstacle;
    d->o.add(dir);
    if(!collide(d, dir) || ((d->type==ENT_AI || d->type==ENT_INANIMATE) && !collide(d, vec(0, 0, 0), 0, false)))
    {
        obstacle = wall;
        /* check to see if there is an obstacle that would prevent this one from being used as a floor (or ceiling bump) */
        if(d->type==ENT_PLAYER && ((wall.z>=SLOPEZ && dir.z<0) || (wall.z<=-SLOPEZ && dir.z>0)) && (dir.x || dir.y) && !collide(d, vec(dir.x, dir.y, 0)))
        {
            if(wall.dot(dir) >= 0) slidecollide = true;
            obstacle = wall;
        }
        d->o = old;
        d->o.z -= STAIRHEIGHT;
        d->zmargin = -STAIRHEIGHT;
        if(d->physstate == PHYS_SLOPE || d->physstate == PHYS_FLOOR || (!collide(d, vec(0, 0, -1), SLOPEZ) && (d->physstate==PHYS_STEP_UP || d->physstate==PHYS_STEP_DOWN || wall.z>=FLOORZ)))
        {
            d->o = old;
            d->zmargin = 0;
            if(trystepup(d, dir, obstacle, STAIRHEIGHT, d->physstate == PHYS_SLOPE || d->physstate == PHYS_FLOOR ? d->floor : vec(wall))) return true;
        }
        else
        {
            d->o = old;
            d->zmargin = 0;
        }
        /* can't step over the obstacle, so just slide against it */
        collided = true;
    }
    else if(d->physstate == PHYS_STEP_UP)
    {
        if(!collide(d, vec(0, 0, -1), SLOPEZ))
        {
            d->o = old;
            if(trystepup(d, dir, vec(0, 0, 1), STAIRHEIGHT, vec(wall))) return true;
            d->o.add(dir);
        }
    }
    else if(d->physstate == PHYS_STEP_DOWN && dir.dot(d->floor) <= 1e-6f)
    {
        vec moved(d->o);
        d->o = old;
        if(trystepdown(d, dir)) return true;
        d->o = moved;
    }
    vec floor(0, 0, 0);
    bool slide = collided,
         found = findfloor(d, collided, obstacle, slide, floor);
    if(slide || (!collided && floor.z > 0 && floor.z < WALLZ))
    {
        slideagainst(d, dir, slide ? obstacle : floor, found, slidecollide);
        //if(d->type == ENT_AI || d->type == ENT_INANIMATE)
        d->blocked = true;
    }
    if(found) landing(d, dir, floor, collided);
    else falling(d, dir, floor);
    return !collided;
}

bool bounce(physent *d, float secs, float elasticity, float waterfric)
{
    // make sure bouncers don't start inside geometry
    if(d->physstate!=PHYS_BOUNCE && !collide(d, vec(0, 0, 0), 0, false)) return true;
    int mat = lookupmaterial(vec(d->o.x, d->o.y, d->o.z + (d->aboveeye - d->eyeheight)/2));
    bool water = isliquid(mat);
    if(water)
    {
        d->vel.z -= gravity/16*secs;
        d->vel.mul(max(1.0f - secs/waterfric, 0.0f));
    }
    else d->vel.z -= gravity*secs;
    vec old(d->o);
    loopi(2)
    {
        vec dir(d->vel);
        dir.mul(secs);
        d->o.add(dir);
        if(collide(d, dir))
        {
            if(inside)
            {
                d->o = old;
                d->vel.mul(-elasticity);
            }
            break;
        }
        else if(hitplayer) break;
        d->o = old;
        game::bounced(d, wall);
        float c = wall.dot(d->vel),
              k = 1.0f + (1.0f-elasticity)*c/d->vel.magnitude();
        d->vel.mul(k);
        d->vel.sub(vec(wall).mul(elasticity*2.0f*c));
    }
    if(d->physstate!=PHYS_BOUNCE)
    {
        // make sure bouncers don't start inside geometry
        if(d->o == old) return !hitplayer;
        d->physstate = PHYS_BOUNCE;
    }
    return hitplayer!=0;
}

void avoidcollision(physent *d, const vec &dir, physent *obstacle, float space)
{
    float rad = obstacle->radius+d->radius;
    vec bbmin(obstacle->o);
    bbmin.x -= rad;
    bbmin.y -= rad;
    bbmin.z -= obstacle->eyeheight+d->aboveeye;
    bbmin.sub(space);
    vec bbmax(obstacle->o);
    bbmax.x += rad;
    bbmax.y += rad;
    bbmax.z += obstacle->aboveeye+d->eyeheight;
    bbmax.add(space);

    loopi(3) if(d->o[i] <= bbmin[i] || d->o[i] >= bbmax[i]) return;

    float mindist = 1e16f;
    loopi(3) if(dir[i] != 0)
    {
        float dist = ((dir[i] > 0 ? bbmax[i] : bbmin[i]) - d->o[i]) / dir[i];
        mindist = min(mindist, dist);
    }
    if(mindist >= 0.0f && mindist < 1e15f) d->o.add(vec(dir).mul(mindist));
}

bool movecamera(physent *pl, const vec &dir, float dist, float stepdist)
{
    int steps = (int)ceil(dist/stepdist);
    if(steps <= 0) return true;

    vec d(dir);
    d.mul(dist/steps);
    loopi(steps)
    {
        vec oldpos(pl->o);
        pl->o.add(d);
        if(!collide(pl, vec(0, 0, 0), 0, false))
        {
            pl->o = oldpos;
            return false;
        }
    }
    return true;
}

bool droptofloor(vec &o, float radius, float height)
{
    static struct dropent : physent
    {
        dropent()
        {
            type = ENT_CAMERA;
            collidetype = COLLIDE_AABB;
            vel = vec(0, 0, -1);
        }
    } d;
    d.o = o;
    if(!insideworld(d.o))
    {
        if(d.o.z < worldsize) return false;
        d.o.z = worldsize - 1e-3f;
        if(!insideworld(d.o)) return false;
    }
    vec v(0.0001f, 0.0001f, -1);
    v.normalize();
    if(raycube(d.o, v, worldsize) >= worldsize) return false;
    d.radius = d.xradius = d.yradius = radius;
    d.eyeheight = height;
    d.aboveeye = radius;
    if(!movecamera(&d, d.vel, worldsize, 1))
    {
        o = d.o;
        return true;
    }
    return false;
}

float dropheight(entity &e)
{
    switch(e.type)
    {
        case ET_PARTICLES:
        case ET_MAPMODEL: return 0.0f;
        default:
            if(e.type >= ET_GAMESPECIFIC) return entities::dropheight(e);
            return 4.0f;
    }
}

void dropenttofloor(entity *e)
{
    droptofloor(e->o, 1.0f, dropheight(*e));
}

void phystest()
{
    static const char *states[] = {"float", "fall", "slide", "slope", "floor", "step up", "step down", "bounce"};
    printf ("PHYS(pl): %s, air %d, floor: (%f, %f, %f), vel: (%f, %f, %f), g: (%f, %f, %f)\n", states[player->physstate], player->timeinair, player->floor.x, player->floor.y, player->floor.z, player->vel.x, player->vel.y, player->vel.z, player->falling.x, player->falling.y, player->falling.z);
    printf ("PHYS(cam): %s, air %d, floor: (%f, %f, %f), vel: (%f, %f, %f), g: (%f, %f, %f)\n", states[camera1->physstate], camera1->timeinair, camera1->floor.x, camera1->floor.y, camera1->floor.z, camera1->vel.x, camera1->vel.y, camera1->vel.z, camera1->falling.x, camera1->falling.y, camera1->falling.z);
}

COMMAND(phystest, "");

void vecfromyawpitch(float yaw, float pitch, int move, int strafe, vec &m)
{
    if(move)
    {
        m.x = move*-sinf(RAD*yaw);
        m.y = move*cosf(RAD*yaw);
    }
    else m.x = m.y = 0;

    if(pitch)
    {
        m.x *= cosf(RAD*pitch);
        m.y *= cosf(RAD*pitch);
        m.z = move*sinf(RAD*pitch);
    }
    else m.z = 0;

    if(strafe)
    {
        m.x += strafe*cosf(RAD*yaw);
        m.y += strafe*sinf(RAD*yaw);
    }
}

void vectoyawpitch(const vec &v, float &yaw, float &pitch)
{
    yaw = -atan2(v.x, v.y)/RAD;
    pitch = asin(v.z/v.magnitude())/RAD;
}

#define PHYSFRAMETIME 5

VARP(maxroll, 0, 0, 20);
FVAR(straferoll, 0, 0.033f, 90);
FVAR(faderoll, 0, 0.95f, 1);
VAR(floatspeed, 1, 100, 10000);

void modifyvelocity(physent *pl, bool local, bool water, bool floating, int curtime)
{
    if(floating)
    {
        if(pl->jumping)
        {
            pl->jumping = false;
            pl->vel.z = max(pl->vel.z, pl->jumpvel * (jumpvel / 200.0f));
            pl->lastjump = lastmillis;
        }
    }
    else if(pl->physstate >= PHYS_SLOPE || water || game::allowdoublejump())
    {
        if(water && !pl->inwater) pl->vel.div(8);
        if(pl->jumping)
        {
            pl->jumping = false;

            if(pl->physstate < PHYS_SLOPE && !water)
            {
                particle_splash(PART_STEAM, 80, 200, vec(pl->o.x, pl->o.y, pl->o.z-pl->eyeheight), 0xBFBFBF, 2, 150, -10); //double jump
                pl->falling.div(8);
            }

            pl->vel.z = max(pl->vel.z, pl->jumpvel * (jumpvel / 200.0f)); // physics impulse upwards
            pl->lastjump = lastmillis;
            if(water) { pl->vel.x /= 8.0f; pl->vel.y /= 8.0f; } // dampen velocity change even harder, gives correct water feel

            game::physicstrigger(pl, local, 1, 0);
        }
    }
    if(!floating && pl->physstate == PHYS_FALL) pl->timeinair += curtime;

    vec m(0.0f, 0.0f, 0.0f);
    if(game::allowmove(pl) && (pl->move || pl->strafe))
    {
        vecfromyawpitch(pl->yaw, floating || water || pl->type==ENT_CAMERA ? pl->pitch : 0, pl->move, pl->strafe, m);

        if(!floating && pl->physstate >= PHYS_SLOPE)
        {
            /* move up or down slopes in air
             * but only move up slopes in water
             */
            float dz = -(m.x*pl->floor.x + m.y*pl->floor.y)/pl->floor.z;
            m.z = water ? max(m.z, dz) : dz;
        }

        m.normalize();
    }
    if(editmode && pl->altitude) {m.z = pl->altitude;}

    vec d(m);
    d.mul(pl->maxspeed);

    if(pl->type==ENT_PLAYER)
    {
        if(!floating)
        {
            d.mul(movespeed/100.0f);
        }
        if(floating)
        {
            if(pl==player)
                d.mul(floatspeed/pl->maxspeed);
        }
        else if(!water && game::allowmove(pl)) d.mul((pl->move && !pl->strafe ? 1.3f : 1.0f) * (pl->physstate < PHYS_SLOPE ? 1.3f : 1.0f));
    }
    float fric = water && !floating ? 20.0f : (pl->physstate >= PHYS_SLOPE || floating ? 6.0f : 30.0f);
    pl->vel.lerp(d, pl->vel, pow(1 - 1/fric, curtime/20.0f));
// old fps friction
//    float friction = water && !floating ? 20.0f : (pl->physstate >= PHYS_SLOPE || floating ? 6.0f : 30.0f);
//    float fpsfric = min(curtime/(20.0f*friction), 1.0f);
//    pl->vel.lerp(pl->vel, d, fpsfric);
}

void modifygravity(physent *pl, bool water, int curtime)
{
    float secs = curtime/1000.0f;
    vec g(0, 0, 0);
    if(pl->physstate == PHYS_FALL) g.z -= gravity*secs;
    else if(pl->floor.z > 0 && pl->floor.z < FLOORZ)
    {
        g.z = -1;
        g.project(pl->floor);
        g.normalize();
        g.mul(gravity*secs);
    }
    if(!water || !game::allowmove(pl) || (!pl->move && !pl->strafe)) pl->falling.add(g);

    if(water || pl->physstate >= PHYS_SLOPE)
    {
        float fric = water ? 2.0f : 6.0f,
              c = water ? 1.0f : clamp((pl->floor.z - SLOPEZ)/(FLOORZ-SLOPEZ), 0.0f, 1.0f);
        pl->falling.mul(pow(1 - c/fric, curtime/20.0f));
// old fps friction
//        float friction = water ? 2.0f : 6.0f,
//              fpsfric = friction/curtime*20.0f,
//              c = water ? 1.0f : clamp((pl->floor.z - SLOPEZ)/(FLOORZ-SLOPEZ), 0.0f, 1.0f);
//        pl->falling.mul(1 - c/fpsfric);
    }
}

// main physics routine, moves a player/monster for a curtime step
// moveres indicated the physics precision (which is lower for monsters and multiplayer prediction)
// local is false for multiplayer prediction

VARR(nastylava, 0, 1, 1);

bool moveplayer(physent *pl, int moveres, bool local, int curtime)
{
    int material = lookupmaterial(vec(pl->o.x, pl->o.y, pl->o.z + (3*pl->aboveeye - pl->eyeheight)/4));
    bool water = isliquid(material&MATF_VOLUME);
    bool floating = pl->type==ENT_PLAYER && (pl->state==CS_EDITING || pl->state==CS_SPECTATOR);
    float secs = curtime/1000.f;

    // apply gravity
    if(!floating) modifygravity(pl, water, curtime);
    // apply any player generated changes in velocity
    modifyvelocity(pl, local, water, floating, curtime);

    vec d(pl->vel), oldpos(pl->o);
    if(!floating && water) d.mul(0.5f);
    d.add(pl->falling);
    d.mul(secs);

    pl->blocked = false;

    if(floating)                // just apply velocity
    {
        if(pl->physstate != PHYS_FLOAT)
        {
            pl->physstate = PHYS_FLOAT;
            pl->timeinair = 0;
            pl->falling = vec(0, 0, 0);
        }
        pl->o.add(d);
    }
    else                        // apply velocity with collision
    {
        const float f = 1.0f/moveres;
        const int timeinair = pl->timeinair;
        int collisions = 0;

        d.mul(f);
        loopi(moveres) if(!move(pl, d) && ++collisions<5) i--; // discrete steps collision detection & sliding
        if(timeinair > 800 && !pl->timeinair && !water) // if we land after long time must have been a high jump, make thud sound
        {
            game::physicstrigger(pl, local, -1, 0);
        }
    }

    if(pl->state==CS_ALIVE) updatedynentcache(pl);

    // automatically apply smooth roll when strafing

    if(pl->strafe && maxroll) pl->roll = clamp(pl->roll - pow(clamp(1.0f + pl->strafe*pl->roll/maxroll, 0.0f, 1.0f), 0.33f)*pl->strafe*curtime*straferoll, -maxroll, maxroll);
    else pl->roll *= curtime == PHYSFRAMETIME ? faderoll : pow(faderoll, curtime/float(PHYSFRAMETIME));

    // play sounds on water transitions

    if(pl->inwater && !water)
    {
        material = lookupmaterial(vec(pl->o.x, pl->o.y, pl->o.z + (pl->aboveeye - pl->eyeheight)/2));
        water = isliquid(material&MATF_VOLUME);
    }
    if(!pl->inwater && water) game::physicstrigger(pl, local, 0, -1, material&MATF_VOLUME);
    else if(pl->inwater && !water) game::physicstrigger(pl, local, 0, 1, pl->inwater);
    pl->inwater = water ? material&MATF_VOLUME : MAT_AIR;

    if(pl->state==CS_ALIVE && (pl->o.z < 0 || (material&MAT_DEATH && nastylava))) game::suicide(pl);

    return true;
}

int physsteps = 0, physframetime = PHYSFRAMETIME, lastphysframe = 0;

void physicsframe()          // optimally schedule physics frames inside the graphics frames
{
    int diff = lastmillis - lastphysframe;
    if(diff <= 0) physsteps = 0;
    else
    {
        extern int gamespeed;
        physframetime = clamp((PHYSFRAMETIME*gamespeed)/100, 1, PHYSFRAMETIME);
        physsteps = (diff + physframetime - 1)/physframetime;
        lastphysframe += physsteps * physframetime;
    }
    cleardynentcache();
}

VAR(physinterp, 0, 1, 1);

void interppos(physent *pl)
{
    pl->o = pl->newpos;

    int diff = lastphysframe - lastmillis;
    if(diff <= 0 || !physinterp) return;

    vec deltapos(pl->deltapos);
    deltapos.mul(min(diff, physframetime)/float(physframetime));
    pl->o.add(deltapos);
}

void moveplayer(physent *pl, int moveres, bool local)
{
    if(physsteps <= 0)
    {
        if(local) interppos(pl);
        return;
    }

    if(local) pl->o = pl->newpos;
    loopi(physsteps-1) moveplayer(pl, moveres, local, physframetime);
    if(local) pl->deltapos = pl->o;
    moveplayer(pl, moveres, local, physframetime);
    if(local)
    {
        pl->newpos = pl->o;
        pl->deltapos.sub(pl->newpos);
        interppos(pl);
    }
}

bool bounce(physent *d, float elasticity, float waterfric)
{
    if(physsteps <= 0)
    {
        interppos(d);
        return false;
    }

    d->o = d->newpos;
    bool hitplayer = false;
    loopi(physsteps-1)
    {
        if(bounce(d, physframetime/1000.0f, elasticity, waterfric)) hitplayer = true;
    }
    d->deltapos = d->o;
    if(bounce(d, physframetime/1000.0f, elasticity, waterfric)) hitplayer = true;
    d->newpos = d->o;
    d->deltapos.sub(d->newpos);
    interppos(d);
    return hitplayer;
}

void updatephysstate(physent *d)
{
    if(d->physstate == PHYS_FALL) return;
    d->timeinair = 0;
    vec old(d->o);
    /* Attempt to reconstruct the floor state.
     * May be inaccurate since movement collisions are not considered.
     * If good floor is not found, just keep the old floor and hope it's correct enough.
     */
    switch(d->physstate)
    {
        case PHYS_SLOPE:
        case PHYS_FLOOR:
        case PHYS_STEP_DOWN:
            d->o.z -= 0.15f;
            if(!collide(d, vec(0, 0, -1), d->physstate == PHYS_SLOPE || d->physstate == PHYS_STEP_DOWN ? SLOPEZ : FLOORZ))
                d->floor = wall;
            break;

        case PHYS_STEP_UP:
            d->o.z -= STAIRHEIGHT+0.15f;
            if(!collide(d, vec(0, 0, -1), SLOPEZ))
                d->floor = wall;
            break;

        case PHYS_SLIDE:
            d->o.z -= .15f;
            if(!collide(d, vec(0, 0, -1)) && wall.z < SLOPEZ)
                d->floor = wall;
            break;
    }
    if(d->physstate > PHYS_FALL && d->floor.z <= 0) d->floor = vec(0, 0, 1);
    d->o = old;
}

const float PLATFORMMARGIN = 0.2f;
const float PLATFORMBORDER = 10.0f;

struct platforment
{
    physent *d;
    int stacks, chains;

    platforment() {}
    platforment(physent *d) : d(d), stacks(-1), chains(-1) {}

    bool operator==(const physent *o) const { return d == o; }
};

struct platformcollision
{
    platforment *ent;
    int next;

    platformcollision() {}
    platformcollision(platforment *ent, int next) : ent(ent), next(next) {}
};

template<class E, class O>
static inline bool platformcollide(physent *d, const vec &dir, physent *o, float margin)
{
    E entvol(d);
    O obvol(o, margin);
    vec cp;
    if(mpr::collide(entvol, obvol, NULL, NULL, &cp))
    {
        vec wn = vec(cp).sub(obvol.center());
        return obvol.contactface(wn, dir.iszero() ? vec(wn).neg() : dir).iszero();
    }
    return true;
}

bool platformcollide(physent *d, physent *o, const vec &dir, float margin = 0)
{
    if(d->collidetype == COLLIDE_ELLIPSE)
    {
        if(o->collidetype == COLLIDE_ELLIPSE) return ellipsecollide(d, dir, o->o, vec(0, 0, 0), o->yaw, o->xradius, o->yradius, o->aboveeye, o->eyeheight + margin);
        else return ellipserectcollide(d, dir, o->o, vec(0, 0, 0), o->yaw, o->xradius, o->yradius, o->aboveeye, o->eyeheight + margin);
    }
    else if(o->collidetype == COLLIDE_ELLIPSE) return platformcollide<mpr::EntOBB, mpr::EntCylinder>(d, dir, o, margin);
    else return platformcollide<mpr::EntOBB, mpr::EntOBB>(d, dir, o, margin);
}

bool moveplatform(physent *p, const vec &dir)
{
    if(!insideworld(p->newpos)) return false;

    vec oldpos(p->o);
    (p->o = p->newpos).add(dir);
    if(!collide(p, dir, 0, dir.z<=0))
    {
        p->o = oldpos;
        return false;
    }
    p->o = oldpos;

    static vector<platforment> ents;
    ents.setsize(0);
    for(int x = int(max(p->o.x-p->radius-PLATFORMBORDER, 0.0f))>>dynentsize, ex = int(min(p->o.x+p->radius+PLATFORMBORDER, worldsize-1.0f))>>dynentsize; x <= ex; x++)
    for(int y = int(max(p->o.y-p->radius-PLATFORMBORDER, 0.0f))>>dynentsize, ey = int(min(p->o.y+p->radius+PLATFORMBORDER, worldsize-1.0f))>>dynentsize; y <= ey; y++)
    {
        const vector<physent *> &dynents = checkdynentcache(x, y);
        loopv(dynents)
        {
            physent *d = dynents[i];
            if(p==d || d->o.z-d->eyeheight < p->o.z+p->aboveeye || p->o.reject(d->o, p->radius+PLATFORMBORDER+d->radius) || ents.find(d) >= 0) continue;
            ents.add(d);
        }
    }
    static vector<platforment *> passengers, colliders;
    passengers.setsize(0);
    colliders.setsize(0);
    static vector<platformcollision> collisions;
    collisions.setsize(0);
    // build up collision DAG of colliders to be pushed off, and DAG of stacked passengers
    loopv(ents)
    {
        platforment &ent = ents[i];
        physent *d = ent.d;
        // check if the dynent is on top of the platform
        if(!platformcollide(p, d, vec(0, 0, 1), PLATFORMMARGIN)) passengers.add(&ent);
        vec doldpos(d->o);
        (d->o = d->newpos).add(dir);
        if(!collide(d, dir, 0, false)) colliders.add(&ent);
        d->o = doldpos;
        loopvj(ents)
        {
            platforment &o = ents[j];
            if(!platformcollide(d, o.d, dir))
            {
                collisions.add(platformcollision(&ent, o.chains));
                o.chains = collisions.length() - 1;
            }
            if(d->o.z < o.d->o.z && !platformcollide(d, o.d, vec(0, 0, 1), PLATFORMMARGIN))
            {
                collisions.add(platformcollision(&o, ent.stacks));
                ent.stacks = collisions.length() - 1;
            }
        }
    }
    loopv(colliders) // propagate collisions
    {
        platforment *ent = colliders[i];
        for(int n = ent->chains; n>=0; n = collisions[n].next)
        {
            platforment *o = collisions[n].ent;
            if(colliders.find(o)<0) colliders.add(o);
        }
    }
    if(dir.z>0)
    {
        loopv(passengers) // if any stacked passengers collide, stop the platform
        {
            platforment *ent = passengers[i];
            if(colliders.find(ent)>=0) return false;
            for(int n = ent->stacks; n>=0; n = collisions[n].next)
            {
                platforment *o = collisions[n].ent;
                if(passengers.find(o)<0) passengers.add(o);
            }
        }
        loopv(passengers)
        {
            physent *d = passengers[i]->d;
            d->o.add(dir);
            d->newpos.add(dir);
            if(dir.x || dir.y) updatedynentcache(d);
        }
    }
    else loopv(passengers) // move any stacked passengers who aren't colliding with non-passengers
    {
        platforment *ent = passengers[i];
        if(colliders.find(ent)>=0) continue;

        physent *d = ent->d;
        d->o.add(dir);
        d->newpos.add(dir);
        if(dir.x || dir.y) updatedynentcache(d);

        for(int n = ent->stacks; n>=0; n = collisions[n].next)
        {
            platforment *o = collisions[n].ent;
            if(passengers.find(o)<0) passengers.add(o);
        }
    }

    p->o.add(dir);
    p->newpos.add(dir);
    if(dir.x || dir.y) updatedynentcache(p);

    return true;
}

#define dir(name,v,d,s,os) ICOMMAND(name, "D", (int *down), { player->s = *down!=0; player->v = player->s ? d : (player->os ? -(d) : 0); });

dir(backward, move,   -1, k_down,  k_up);
dir(forward,  move,    1, k_up,    k_down);
dir(left,     strafe,  1, k_left,  k_right);
dir(right,    strafe, -1, k_right, k_left);

dir(rise, altitude, 1, k_rise, k_des);
dir(descent, altitude, -1, k_des, k_rise);

ICOMMAND(jump,   "D", (int *down), { if(!*down || game::canjump()) player->jumping = *down!=0; });

bool entinmap(dynent *d, bool avoidplayers)        // brute force but effective way to find a free spawn spot in the map
{
    d->o.z += d->eyeheight; // pos specified is at feet
    vec orig = d->o;
    loopi(100)              // try max 100 times
    {
        if(i)
        {
            d->o = orig;
            d->o.x += (rnd(21)-10)*i/5;  // increasing distance
            d->o.y += (rnd(21)-10)*i/5;
            d->o.z += (rnd(21)-10)*i/5;
        }

        if(collide(d) && !inside)
        {
            if(hitplayer)
            {
                if(!avoidplayers) continue;
                d->o = orig;
                d->resetinterp();
                return false;
            }

            d->resetinterp();
            return true;
        }
    }
    // leave ent at original pos, possibly stuck
    d->o = orig;
    d->resetinterp();
    conoutf(CON_WARN, "can't find entity spawn spot! (%.1f, %.1f, %.1f)", d->o.x, d->o.y, d->o.z);
    return false;
}

