// bones.cpp — client-side studio bone/hitbox access.
//
// C_BaseAnimating implements IClientRenderable::SetupBones(), which fills an
// array of world-space bone matrices. The studio header (from
// IVModelInfoClient::GetStudiomodel) gives bone names/parents and hitboxes.
// Everything here is client-side; no server access is involved.

#include "hl2h.h"
#include <cstdint>
#include <cstring>
#include <ctime>
#include <strings.h>

namespace {

constexpr int MAX_BONES = 256;
constexpr int BONE_USED_BY_ANYTHING = 0x0007FF00;
constexpr uint32_t STUDIO_ID = 0x54534449; // ('T'<<24)+('S'<<16)+('D'<<8)+'I'

struct Matrix3x4 {
  float m[3][4];
};

// Partial mirrors of the Source 2013 studio structures (32-bit). Only the
// fields we use are named; layout must still match exactly.
struct StudioHdr {
  int id;
  int version;
  int checksum;
  char name[64];
  int length;
  Vector eyeposition;
  Vector illumposition;
  Vector hull_min;
  Vector hull_max;
  Vector view_bbmin;
  Vector view_bbmax;
  int flags;
  int numbones;
  int boneindex;
  int numbonecontrollers;
  int bonecontrollerindex;
  int numhitboxsets;
  int hitboxsetindex;
};

struct StudioBone {
  int sznameindex;
  int parent;
  int bonecontroller[6];
  Vector pos;
  float quat[4];
  Vector rot;
  Vector posscale;
  Vector rotscale;
  float poseToBone[12];
  float qAlignment[4];
  int flags;
  int proctype;
  int procindex;
  int physicsbone;
  int surfacepropidx;
  int contents;
  int unused[8];
};

struct HitboxSet {
  int sznameindex;
  int numhitboxes;
  int hitboxindex;
};

struct Hitbox {
  int bone;
  int group;
  Vector bbmin;
  Vector bbmax;
  int szhitboxnameindex;
  int unused[8];
};

static_assert(sizeof(Vector) == 12, "Vector layout");
static_assert(sizeof(Matrix3x4) == 48, "matrix3x4 layout");
static_assert(sizeof(StudioHdr) == 0xB4, "studiohdr prefix layout");
static_assert(sizeof(StudioBone) == 0xD8, "mstudiobone_t layout");
static_assert(sizeof(HitboxSet) == 12, "mstudiohitboxset_t layout");
static_assert(sizeof(Hitbox) == 0x44, "mstudiobbox_t layout");

struct BoneEntry {
  int idx;
  void *ent;
  double stamp;
  bool valid;
  bool humanoid;
  const StudioHdr *hdr;
  int count;
  bool core[MAX_BONES];
  Matrix3x4 mats[MAX_BONES];
};

static BoneEntry g_entries[64];
static int g_next = 0;
static int g_logged = 0;
static bool g_renderable_warned = false;

static double bone_now() {
  timespec ts;
  clock_gettime(CLOCK_MONOTONIC, &ts);
  return (double)ts.tv_sec + (double)ts.tv_nsec * 1e-9;
}

static BoneEntry *find_entry(int idx) {
  for (int i = 0; i < 64; i++)
    if (g_entries[i].ent && g_entries[i].idx == idx)
      return &g_entries[i];
  return nullptr;
}

static BoneEntry *alloc_entry(int idx, void *ent) {
  BoneEntry *e = &g_entries[g_next++ % 64];
  memset(e, 0, sizeof(*e));
  e->idx = idx;
  e->ent = ent;
  return e;
}

static const StudioBone *bone_at(const StudioHdr *h, int i) {
  return (const StudioBone *)((const uint8_t *)h + h->boneindex) + i;
}

static const char *bone_name_raw(const StudioHdr *h, int i) {
  if (!h || i < 0 || i >= h->numbones)
    return nullptr;
  const StudioBone *b = bone_at(h, i);
  if (b->sznameindex <= 0 || b->sznameindex > 0x10000)
    return nullptr;
  const char *n = (const char *)b + b->sznameindex;
  return n[0] ? n : nullptr;
}

static const HitboxSet *hitbox_set0(const StudioHdr *h) {
  if (!h || h->numhitboxsets <= 0 || h->hitboxsetindex <= 0)
    return nullptr;
  const HitboxSet *s =
      (const HitboxSet *)((const uint8_t *)h + h->hitboxsetindex);
  if (s->numhitboxes <= 0 || s->numhitboxes > 512 || s->hitboxindex <= 0)
    return nullptr;
  return s;
}

static const Hitbox *hitboxes(const HitboxSet *s) {
  return (const Hitbox *)((const uint8_t *)s + s->hitboxindex);
}

static const char *hitbox_name(const Hitbox &b) {
  if (b.szhitboxnameindex <= 0 || b.szhitboxnameindex > 0x10000)
    return "";
  return (const char *)&b + b.szhitboxnameindex;
}

static bool contains_ci(const char *hay, const char *needle) {
  if (!hay || !needle || !*needle)
    return false;
  size_t n = strlen(needle);
  for (const char *p = hay; *p; p++)
    if (strncasecmp(p, needle, n) == 0)
      return true;
  return false;
}

static bool hitbox_world(const BoneEntry *e, const Hitbox &b, Vector &out) {
  if (b.bone < 0 || b.bone >= e->count)
    return false;
  Vector local{(b.bbmin.x + b.bbmax.x) * 0.5f,
               (b.bbmin.y + b.bbmax.y) * 0.5f,
               (b.bbmin.z + b.bbmax.z) * 0.5f};
  const Matrix3x4 &m = e->mats[b.bone];
  out.x =
      local.x * m.m[0][0] + local.y * m.m[0][1] + local.z * m.m[0][2] + m.m[0][3];
  out.y =
      local.x * m.m[1][0] + local.y * m.m[1][1] + local.z * m.m[1][2] + m.m[1][3];
  out.z =
      local.x * m.m[2][0] + local.y * m.m[2][1] + local.z * m.m[2][2] + m.m[2][3];
  return true;
}

// HL2 humanoids use the ValveBiped skeleton, but many of its bone names are
// stripped (the zombie's spine/legs/left arm are unnamed). Instead of matching
// names, mark the paths from every hitbox bone up to the root: that yields the
// chest/spine, arms and legs, while fingers/toes have no hitboxes and the
// headcrab's HC_* hitbox is skipped explicitly.
static void build_core_mask(BoneEntry *e) {
  e->humanoid = false;
  for (int i = 0; i < e->count; i++) {
    const char *n = bone_name_raw(e->hdr, i);
    if (n && strncasecmp(n, "ValveBiped.Bip01_", 17) == 0) {
      e->humanoid = true;
      break;
    }
  }
  memset(e->core, 0, sizeof(e->core));
  if (!e->humanoid)
    return;
  const HitboxSet *s = hitbox_set0(e->hdr);
  if (!s)
    return;
  const Hitbox *boxes = hitboxes(s);
  for (int i = 0; i < s->numhitboxes; i++) {
    int b = boxes[i].bone;
    if (b < 0 || b >= e->count)
      continue;
    bool is_head = (boxes[i].group == 1); // HITGROUP_HEAD
    const char *bn = bone_name_raw(e->hdr, b);
    if (bn && (contains_ci(bn, "Finger") || contains_ci(bn, "Toe")))
      continue;
    // A zombie's "head" is the headcrab body (HC_Body_Bone); let the head
    // hitbox through even though its name is HC_*, but keep the headcrab's
    // extra limbs out.
    if (!is_head && bn &&
        (contains_ci(bn, "Headcrab") || contains_ci(bn, "HC_")))
      continue;
    int cur = b;
    for (int guard = 0; cur >= 0 && cur < e->count && guard < 64; guard++) {
      e->core[cur] = true;
      cur = bone_at(e->hdr, cur)->parent;
    }
    // Include a direct "head" child of the head bone (zombie: HC_Head_Bone
    // hanging off HC_Body_Bone).
    if (is_head) {
      for (int c = 0; c < e->count; c++) {
        if (bone_at(e->hdr, c)->parent != b)
          continue;
        const char *cn = bone_name_raw(e->hdr, c);
        if (cn && contains_ci(cn, "Head"))
          e->core[c] = true;
      }
    }
  }
}

static void dump_hitboxes(const BoneEntry *e) {
  const StudioHdr *h = e->hdr;
  logf("hitbox dump: idx=%d sets=%d setidx=%d", e->idx, h->numhitboxsets,
       h->hitboxsetindex);
  const HitboxSet *s = hitbox_set0(h);
  if (!s) {
    logf("hitbox dump: no usable hitbox set");
    return;
  }
  const Hitbox *hb = hitboxes(s);
  logf("hitbox dump: set0 n=%d hitboxindex=%d", s->numhitboxes,
       s->hitboxindex);
  int n = s->numhitboxes < 24 ? s->numhitboxes : 24;
  for (int i = 0; i < n; i++) {
    const char *bn = (hb[i].bone >= 0 && hb[i].bone < e->count)
                         ? bone_name_raw(h, hb[i].bone)
                         : nullptr;
    logf("  hb %d name='%s' bone=%d(%s) bb=(%.1f %.1f %.1f)-(%.1f %.1f %.1f)",
         i, hitbox_name(hb[i]), hb[i].bone, bn ? bn : "?", hb[i].bbmin.x,
         hb[i].bbmin.y, hb[i].bbmin.z, hb[i].bbmax.x, hb[i].bbmax.y,
         hb[i].bbmax.z);
  }
}

} // namespace

bool bones_update(int idx, void *ent) {
  if (!ent || !g_iface.modelinfo || !g_iface.engine || g_net.modelindex < 0)
    return false;

  BoneEntry *e = find_entry(idx);
  double now = bone_now();
  // Refresh every frame; the renderer's bone cache makes this a cheap memcpy
  // for visible entities. A 30 Hz cache made the head marker visibly lag.
  if (e && e->ent == ent && e->valid && now - e->stamp < 0.001)
    return true;
  if (!e)
    e = alloc_entry(idx, ent);
  if (e->ent != ent) {
    e->ent = ent;
    e->valid = false;
  }

  int modelindex = *(int *)((uintptr_t)ent + g_net.modelindex);
  if (modelindex <= 0) {
    e->valid = false;
    return false;
  }

  using GetModelFn = const void *(*)(void *);
  using GetModelIdxFn = const void *(*)(void *, int);
  using GetStudioFn = const StudioHdr *(*)(void *, const void *);
  using SetupFn = bool (*)(void *, Matrix3x4 *, int, int, float);
  using GetRenderableFn = void *(*)(void *);
  using TimeFn = float (*)(void *);

  const void *expected =
      vfunc<GetModelIdxFn>(g_iface.modelinfo, 2)(g_iface.modelinfo, modelindex);
  if (!expected)
    return false;

  // IClientUnknown::GetClientRenderable = primary vtable slot 6.
  void *r = vfunc<GetRenderableFn>(ent, 6)(ent);
  if (!r)
    return false;
  // Validate the interface before using SetupBones on it.
  const void *rmodel = vfunc<GetModelFn>(r, 9)(r);
  if (rmodel != expected) {
    if (!g_renderable_warned) {
      g_renderable_warned = true;
      logf("bones: renderable/model mismatch (renderable=%p model=%p "
           "expected=%p)",
           r, rmodel, expected);
    }
    e->valid = false;
    return false;
  }

  const StudioHdr *hdr =
      vfunc<GetStudioFn>(g_iface.modelinfo, 29)(g_iface.modelinfo, expected);
  if (!hdr || hdr->id != STUDIO_ID || hdr->numbones <= 0 ||
      hdr->numbones > MAX_BONES || hdr->boneindex <= 0) {
    e->valid = false;
    return false;
  }

  float curtime = vfunc<TimeFn>(g_iface.engine, 14)(g_iface.engine);
  // IClientRenderable::SetupBones = slot 16.
  if (!vfunc<SetupFn>(r, 16)(r, e->mats, MAX_BONES, BONE_USED_BY_ANYTHING,
                            curtime)) {
    e->valid = false;
    return false;
  }

  e->hdr = hdr;
  e->count = hdr->numbones;
  build_core_mask(e);
  e->valid = true;
  e->stamp = now;
  if (g_logged < 4) {
    g_logged++;
    logf("bones: idx=%d count=%d bone0=%s", idx, e->count,
         bone_name_raw(hdr, 0) ? bone_name_raw(hdr, 0) : "?");
  }
  return true;
}

int bones_count(int idx) {
  BoneEntry *e = find_entry(idx);
  return (e && e->valid) ? e->count : 0;
}

int bone_find(int idx, const char *name) {
  BoneEntry *e = find_entry(idx);
  if (!e || !e->valid || !name)
    return -1;
  for (int i = 0; i < e->count; i++) {
    const char *n = bone_name_raw(e->hdr, i);
    if (n && strcasecmp(n, name) == 0)
      return i;
  }
  return -1;
}

int bone_parent(int idx, int bone) {
  BoneEntry *e = find_entry(idx);
  if (!e || !e->valid || bone < 0 || bone >= e->count)
    return -1;
  return bone_at(e->hdr, bone)->parent;
}

bool bone_is_skeleton_core(int idx, int bone) {
  BoneEntry *e = find_entry(idx);
  if (!e || !e->valid || bone < 0 || bone >= e->count)
    return false;
  if (!e->humanoid)
    return true; // non-humanoid: draw its full bone tree
  return e->core[bone];
}

int bone_nearest_core_parent(int idx, int bone) {
  BoneEntry *e = find_entry(idx);
  if (!e || !e->valid || bone < 0 || bone >= e->count)
    return -1;
  int p = bone_at(e->hdr, bone)->parent;
  if (!e->humanoid)
    return (p >= 0 && p < e->count) ? p : -1;
  for (int guard = 0; p >= 0 && p < e->count && guard < 64; guard++) {
    if (e->core[p])
      return p;
    p = bone_at(e->hdr, p)->parent;
  }
  return -1;
}

bool bones_is_humanoid(int idx) {
  BoneEntry *e = find_entry(idx);
  return e && e->valid && e->humanoid;
}

bool bone_pos(int idx, int bone, Vector &out) {
  BoneEntry *e = find_entry(idx);
  if (!e || !e->valid || bone < 0 || bone >= e->count)
    return false;
  const Matrix3x4 &m = e->mats[bone];
  out = {m.m[0][3], m.m[1][3], m.m[2][3]};
  return true;
}

bool hitbox_center(int idx, const char *name, Vector &out) {
  BoneEntry *e = find_entry(idx);
  if (!e || !e->valid || !name || !e->hdr)
    return false;
  const HitboxSet *s = hitbox_set0(e->hdr);
  if (!s)
    return false;
  const Hitbox *boxes = hitboxes(s);
  for (int i = 0; i < s->numhitboxes; i++) {
    if (strcasecmp(hitbox_name(boxes[i]), name) == 0)
      return hitbox_world(e, boxes[i], out);
  }
  return false;
}

// Head position with fallbacks, because several HL2 models have no hitbox
// names: exact "head" hitbox -> hitbox whose bone name contains "head" ->
// head bone origin. Dumps the hitbox set once for diagnosis.
bool head_position(int idx, Vector &out) {
  BoneEntry *e = find_entry(idx);
  if (!e || !e->valid || !e->hdr)
    return false;
  static bool dumped = false;
  if (!dumped) {
    dumped = true;
    dump_hitboxes(e);
  }
  if (hitbox_center(idx, "head", out))
    return true;
  const HitboxSet *s = hitbox_set0(e->hdr);
  if (s) {
    const Hitbox *boxes = hitboxes(s);
    // HITGROUP_HEAD == 1. HL2 models often have no hitbox names, so use the
    // damage-group head hitbox first (zombie: headcrab body, humanoids: head).
    for (int i = 0; i < s->numhitboxes; i++) {
      if (boxes[i].group == 1 && hitbox_world(e, boxes[i], out))
        return true;
    }
    for (int i = 0; i < s->numhitboxes; i++) {
      if (boxes[i].bone < 0 || boxes[i].bone >= e->count)
        continue;
      const char *bn = bone_name_raw(e->hdr, boxes[i].bone);
      if (bn && contains_ci(bn, "head"))
        return hitbox_world(e, boxes[i], out);
    }
  }
  for (int i = 0; i < e->count; i++) {
    const char *bn = bone_name_raw(e->hdr, i);
    if (bn && contains_ci(bn, "head"))
      return bone_pos(idx, i, out);
  }
  return false;
}

// Collect world-space aim points for the selected hit groups (HITGROUP_*).
// Group 1 (head) uses head_position for its bone fallback; other groups are
// the hitbox centers. The caller picks the point nearest to the crosshair.
int aim_points(int idx, unsigned group_mask, Vector *out, int max) {
  if (!out || max <= 0)
    return 0;
  BoneEntry *e = find_entry(idx);
  if (!e || !e->valid || !e->hdr)
    return 0;
  int n = 0;
  if ((group_mask & (1u << 1)) && n < max) {
    Vector head;
    if (head_position(idx, head))
      out[n++] = head;
  }
  const HitboxSet *s = hitbox_set0(e->hdr);
  if (!s)
    return n;
  const Hitbox *boxes = hitboxes(s);
  for (int i = 0; i < s->numhitboxes && n < max; i++) {
    int g = boxes[i].group;
    if (g <= 1 || g > 7)
      continue;
    if (!(group_mask & (1u << g)))
      continue;
    Vector p;
    if (hitbox_world(e, boxes[i], p))
      out[n++] = p;
  }
  return n;
}