#include "codes.h"

#include "byteorder.h"
#include "minicc.h"
#include "../operators.h"

#include <exception>
#include <unordered_map>

using namespace std::string_literals;

// REX prefix: 0b0100WRXB
std::vector<uint8_t> REX(const std::string& s) {
 uint8_t result{0b01000000};
 if (s == "W")
  result |= 0b00001000;
 if (s == "R")
  result |= 0b00000100;
 if (s == "X")
  result |= 0b00000010;
 if (s == "B")
  result |= 0b00000001;

 return { result }; 
}

namespace {

 std::unordered_map<std::string, size_t> IndexOfRegister{
  {"al", 0}, {"ah", 4},
  {"bl", 3}, {"bh", 7},
  {"cl", 1}, {"ch", 5},
  {"dl", 2}, {"dh", 6},

  {"ax", 0}, {"sp", 4},
  {"bx", 3}, {"bp", 5},
  {"cx", 1}, {"si", 6},
  {"dx", 2}, {"di", 7},

  {"eax", 0}, {"esp", 4},
  {"ebx", 3}, {"ebp", 5},
  {"ecx", 1}, {"esi", 6},
  {"edx", 2}, {"edi", 7},
  
  {"rax", 0}, {"rsp", 4},
  {"rbx", 3}, {"rbp", 5},
  {"rcx", 1}, {"rsi", 6},
  {"rdx", 2}, {"rdi", 7},
 };

} // namespace

// Manual, page 530
// Reg + Reg/Memory
std::vector<uint8_t> ModRM(const std::string& reg, const std::string& rm, int32_t disp) {
 uint8_t result{}; // MOD is highest 2 bits, then 3 bits Reg, the 3 bits R/M
 std::vector<uint8_t> displacement_bytes;

 size_t val_reg{};
 // reg
 if (reg.size() > 0 && reg[0] == '/') { // "/digit"
  try {
   val_reg = stoull(reg.substr(1));
  } catch (const std::exception& ex) {
   throw std::runtime_error("ModRM: Bad digit in arg1: "s + reg);
  }
 } else { // reg
  val_reg = RegNo(reg);
 }

 result |= (val_reg << 3);

 // rm
 if (rm.size() > 2 && rm.front() == '[' && rm.back() == ']') { // indexed / MemPtr
  uint8_t rm_bits {RegNo(rm.substr(1, rm.size() - 2))};
  if (rm_bits == 4)
   throw std::runtime_error("ICE: SIB byte not yet supported");

  if (disp == 0 && rm_bits != 5) { // no displacement
   // ignore: keep MOD == 00, no displacement bytes
   if (rm_bits == 5)
    throw std::runtime_error("ICE: [rbp] with no displacement is not supported"); // TODO: Support this, and SIB byte
  } else if (disp >= -128 && disp < 128) {
   result |= 0b01000000; // 8 bit displacement
   displacement_bytes.push_back(uint8_t(disp));
  } else {
   result |= 0b10000000; // 32 bit displacement
   displacement_bytes += endian::to_little(uint32_t(disp));
  }
  result |= rm_bits;
 } else { // normal register access
  result |= 0b11000000;
  result |= RegNo(rm);
 }

 return std::vector<uint8_t>{result} + displacement_bytes;
}

uint8_t RegNo(const std::string& reg)
{
 auto index{ IndexOfRegister.find(reg) };
 if (index == IndexOfRegister.end())
  throw std::runtime_error("Reg: Unknown register for arg: "s + reg);

 return index->second;
}

// Switch from operand size 64bit to 32bit
std::vector<uint8_t> OpSizePrefix()
{
 return {0x66};
}

#if 0
 prefixes{
  "lock", 0xf0,

  // branch hint
  0x2e, "branch not taken"
  0x3e, "branch taken"

  0x66, "operand size override" // switch between 16 and 32 bit operands
  0x67, "address size override" // switch between 16 and 32 bit addresses
 };
 };
#endif