// cinput.cpp — CInput discovery, usercmd CRC, get/fix helpers
#include "hl2h.h"

// ---------------------------------------------------------------------------
// CRC-32 (standard IEEE reflected, matches Valve's implementation)
// ---------------------------------------------------------------------------

static uint32_t g_crc_table[256];
static bool g_crc_inited = false;

static void crc32_init_table() {
  if (g_crc_inited)
    return;
  for (uint32_t i = 0; i < 256; i++) {
    uint32_t c = i;
    for (int k = 0; k < 8; k++)
      c = (c & 1) ? 0xEDB88320u ^ (c >> 1) : c >> 1;
    g_crc_table[i] = c;
  }
  g_crc_inited = true;
}

// field set verified from client.so GetChecksum disassembly
uint32_t usercmd_checksum(const CUserCmd *c) {
  crc32_init_table();
  uint32_t crc = 0xFFFFFFFFu;
  auto upd = [&crc](const void *p, size_t n) {
    const uint8_t *b = (const uint8_t *)p;
    while (n--)
      crc = g_crc_table[(crc ^ *b++) & 0xFF] ^ (crc >> 8);
  };
  upd(&c->command_number, 4);
  upd(&c->tick_count, 4);
  upd(&c->viewangles, 12);
  upd(&c->forwardmove, 4);
  upd(&c->sidemove, 4);
  upd(&c->upmove, 4);
  upd(&c->buttons, 4);
  upd(&c->impulse, 1);
  upd(&c->weaponselect, 4);
  upd(&c->weaponsubtype, 4);
  upd(&c->random_seed, 4);
  upd(&c->mousedx, 2);
  upd(&c->mousedy, 2);
  return ~crc;
}

// CInput: +0xE4 = m_pCommands, +0xE8 = m_pVerifiedCommands
static constexpr size_t CMDOFF_M_PCOMMANDS = 0xE4;
static constexpr size_t CMDOFF_M_PVERIFIED = 0xE8;
static constexpr size_t VERIFIED_STRIDE = 0x58;
static constexpr size_t VERIFIED_CRC_OFF = 0x54;

CUserCmd *get_usercmd(int seq) {
  if (!g_input)
    return nullptr;
  uintptr_t cmds = *(uintptr_t *)(g_input + CMDOFF_M_PCOMMANDS);
  if (!cmds)
    return nullptr;
  auto *cmd = (CUserCmd *)(cmds + (size_t)(seq % 90) * 0x54);
  if (cmd->command_number != seq)
    return nullptr;
  return cmd;
}

void fix_verified_crc(int seq, uint32_t crc) {
  if (!g_input)
    return;
  uintptr_t verified = *(uintptr_t *)(g_input + CMDOFF_M_PVERIFIED);
  if (verified)
    *(uint32_t *)(verified + (size_t)(seq % 90) * VERIFIED_STRIDE +
                  VERIFIED_CRC_OFF) = crc;
}

// ---------------------------------------------------------------------------
// CInput discovery: byte-scan of CHLClient::CreateMove prologue
// ---------------------------------------------------------------------------

bool find_input_global() {
  void **vt = VTABLE(g_iface.client);
  uintptr_t cm = (uintptr_t)vt[21]; // CreateMove slot
  if (!g_client.contains(cm)) {
    logf("CreateMove %p outside client module", (void *)cm);
    return false;
  }
  const uint8_t *b = (const uint8_t *)cm;

  // 1) PIC anchor: call __x86.get_pc_thunk + add $imm,%esi
  uintptr_t anchor = 0;
  for (int i = 0; i <= 0x100 - 11; i++) {
    if (b[i] == 0xE8 && b[i + 5] == 0x81 && b[i + 6] == 0xC6) {
      uint32_t imm;
      memcpy(&imm, b + i + 7, 4);
      anchor = cm + (uintptr_t)(i + 5) + imm;
      break;
    }
  }
  if (!anchor || !g_client.contains(anchor)) {
    logf("PIC anchor not found in CreateMove");
    return false;
  }

  // 2) the input->CreateMove call: "ff 51 0c" preceded by "52", scan back
  //    for "8d 86 imm32" with "8b 10" between
  for (int c = 3; c <= 0x100 - 3; c++) {
    if (!(b[c] == 0xFF && b[c + 1] == 0x51 && b[c + 2] == 0x0C &&
          b[c - 1] == 0x52))
      continue;
    for (int i = c - 8; i > c - 44 && i > 2; i--) {
      if (b[i] != 0x8D || b[i + 1] != 0x86)
        continue;
      bool has_mov = false;
      for (int j = i + 6; j < c - 1; j++)
        if (b[j] == 0x8B && b[j + 1] == 0x10) {
          has_mov = true;
          break;
        }
      if (!has_mov)
        continue;
      uint32_t disp;
      memcpy(&disp, b + i + 2, 4);
      uintptr_t var = anchor + disp;
      if (!g_client.contains(var))
        continue;
      uintptr_t input = *(uintptr_t *)var;
      if (!input || !g_client.contains(input))
        continue;
      uintptr_t vtbl = *(uintptr_t *)input;
      if (!vtbl || !g_client.contains(vtbl))
        continue;
      uintptr_t f3 = *(uintptr_t *)(vtbl + 3 * sizeof(void *));
      if (!g_client.contains(f3))
        continue;
      logf("CInput* = %#lx (ptr var %#lx, vfunc[3] %#lx)", (unsigned long)input,
           (unsigned long)var, (unsigned long)f3);
      g_input = input;
      return true;
    }
  }
  logf("CInput pointer variable not found in CreateMove scan");
  return false;
}