// server.cpp — authoritative listen-server entity access.
//
// HL2 single-player runs the server (server.so) in the same process as the
// client. The client only receives fields the server actually networks (NPC
// health is *not* networked), but the server's CBaseEntity still holds the real
// m_iHealth. We reach it through IVEngineServer021:
//   PEntityOfEntIndex(engine, idx) -> edict_t*
//   edict->m_pUnk (offset 0xC) -> IServerUnknown*
//   IServerUnknown::GetBaseEntity (vtable slot 6) -> CBaseEntity*
// then read the field offsets from the server datamap, which we resolve by
// scanning server.so for the typedescription_t entries referencing the field
// names (same idea as the client RecvTable walk).

#include "hl2h.h"
#include <cstdlib>

// IVEngineServer (VEngineServer021, no virtual destructor):
//   slot 17 = GetEntityCount, slot 19 = PEntityOfEntIndex(int)
enum { SRV_GetEntityCount = 17, SRV_PEntityOfEntIndex = 19 };
// IServerUnknown derives IHandleEntity (virtual dtor = 2 slots, 2 methods),
// then adds GetCollideable(4), GetNetworkable(5), GetBaseEntity(6).
enum { SRV_GetBaseEntity = 6 };
// CBaseEdict layout: m_fStateFlags@0, serial/index@4, m_pNetworkable@8, m_pUnk@0xC
enum { EDICT_UNKNOWN_OFF = 0x0C };

// typedescription_t (32-bit): fieldType@0, fieldName@4, fieldOffset[0]@8,
// fieldOffset[1]@0xC, fieldSize@0x10, flags@0x12, externalName@0x14
enum { FIELD_INTEGER = 5, FIELD_CHARACTER = 8 };

int g_srv_health = -1;
int g_srv_maxhealth = -1;
int g_srv_lifestate = -1;
int g_srv_modelindex = -1;
static bool g_srv_ready = false;
static bool g_srv_checked = false;

static uintptr_t find_string(const char *s) {
  size_t n = strlen(s) + 1;
  for (auto &r : g_server.ranges) {
    const uint8_t *base = (const uint8_t *)r.lo;
    size_t span = r.hi - r.lo;
    for (size_t i = 0; i + n <= span; i++)
      if (memcmp(base + i, s, n) == 0)
        return r.lo + i;
  }
  return 0;
}

// Find the typedescription_t whose fieldName points at `name` and read its
// fieldOffset. type filters false positives (m_iHealth is FIELD_INTEGER).
static int datamap_offset(const char *name, int want_type) {
  uintptr_t str = find_string(name);
  if (!str)
    return -1;
  for (auto &r : g_server.ranges) {
    const uint8_t *base = (const uint8_t *)r.lo;
    size_t span = r.hi - r.lo;
    for (size_t off = 4; off + 0x18 <= span; off += 4) {
      if (*(const uint32_t *)(base + off) != (uint32_t)str)
        continue;
      const uint8_t *e = base + off - 4; // entry->fieldName
      int ftype = *(const int32_t *)(e + 0x00);
      int foff = *(const int32_t *)(e + 0x08);
      int fsize = *(const uint16_t *)(e + 0x10);
      uintptr_t ext = *(const uintptr_t *)(e + 0x14);
      if (ftype != want_type)
        continue;
      if (foff < 0x40 || foff > 0x2000)
        continue;
      if (fsize < 1 || fsize > 64)
        continue;
      // DEFINE_KEYFIELD entries have an external name ("health"); plain
      // DEFINE_FIELD entries have none. Either way it must be in server.so.
      if (ext && !g_server.contains(ext))
        continue;
      return foff;
    }
  }
  return -1;
}

bool resolve_server_netvars() {
  if (g_srv_ready)
    return true;
  static const bool disabled = getenv("HL2H_NO_SERVER") != nullptr;
  if (disabled) // escape hatch if server-side access misbehaves
    return false;
  // esp_collect runs at ~100 Hz; retry the (cheap-ish) module refresh and
  // datamap scan about once a second until server.so is up and scan succeeds.
  static unsigned retry = 0;
  static bool fail_logged = false;
  if ((retry++ % 100) != 0)
    return false;
  // server.so is only mapped once a map is running; refresh the module list.
  if (!g_server.valid())
    find_modules();
  if (!g_server.valid()) {
    if (!fail_logged) {
      fail_logged = true;
      logf("server datamap: server.so not mapped yet");
    }
    return false;
  }
  g_srv_health = datamap_offset("m_iHealth", FIELD_INTEGER);
  g_srv_maxhealth = datamap_offset("m_iMaxHealth", FIELD_INTEGER);
  g_srv_lifestate = datamap_offset("m_lifeState", FIELD_CHARACTER);
  g_srv_modelindex = datamap_offset("m_nModelIndex", 7); // FIELD_SHORT
  g_srv_ready = g_srv_health > 0;
  if (g_srv_ready) {
    logf("server datamap (%s): health=%d maxhealth=%d lifeste=%d "
         "modelindex=%d",
         g_server.path.c_str(), g_srv_health, g_srv_maxhealth, g_srv_lifestate,
         g_srv_modelindex);
    fail_logged = false;
  } else if (!fail_logged) {
    fail_logged = true;
    logf("server datamap: scan failed (server.so at %s)",
         g_server.path.c_str());
  }
  return g_srv_ready;
}

// Returns the authoritative health of the server entity at this index, or -1.
int server_entity_health(int idx, int *maxhealth, int *lifestate,
                         void **base_out) {
  if (base_out)
    *base_out = nullptr;
  if (!g_srv_ready || !g_iface.engineserver || g_srv_health < 0)
    return -1;

  using PEntityFn = void *(*)(void *, int);
  void *edict = vfunc<PEntityFn>(g_iface.engineserver, SRV_PEntityOfEntIndex)(
      g_iface.engineserver, idx);
  if (!edict)
    return -1;
  void *unk = *(void **)((uintptr_t)edict + EDICT_UNKNOWN_OFF);
  if (!unk)
    return -1;

  using GetBaseFn = void *(*)(void *);
  void *base = vfunc<GetBaseFn>(unk, SRV_GetBaseEntity)(unk);
  if (!base)
    return -1;

  uintptr_t b = (uintptr_t)base;
  int hp = g_srv_health > 0 ? *(int *)(b + g_srv_health) : -1;
  int mx = g_srv_maxhealth > 0 ? *(int *)(b + g_srv_maxhealth) : -1;
  int ls = g_srv_lifestate > 0
               ? (int)*(unsigned char *)(b + g_srv_lifestate)
               : -1;
  if (base_out)
    *base_out = base;
  if (maxhealth)
    *maxhealth = mx;
  if (lifestate)
    *lifestate = ls;

  if (!g_srv_checked) {
    g_srv_checked = true;
    using CountFn = int (*)(void *);
    int count = vfunc<CountFn>(g_iface.engineserver, SRV_GetEntityCount)(
        g_iface.engineserver);
    logf("server access: entity_count=%d first_idx=%d base=%p hp=%d maxhp=%d "
         "life=%d srv_model=%d",
         count, idx, base, hp, mx, ls,
         g_srv_modelindex > 0
             ? (int)*(short *)(b + g_srv_modelindex)
             : -1);
  }
  return hp;
}

int server_model_index(void *base) {
  if (!base || g_srv_modelindex <= 0)
    return -1;
  return (int)*(short *)((uintptr_t)base + g_srv_modelindex);
}