#include "ExecutorCases.h"

#include "Instruction.h"
#include "Bus.h"

#include <bitset>
#include <iostream>

CPUContext::CPUContext(Instruction& i, uint64_t& ip, uint64_t& flags, uint64_t* reg, std::shared_ptr<Bus>& bus) : m_Instruction(i), m_InstructionPointer(ip), m_Flags(flags), m_Registers(reg), m_Bus(bus) { }

CPUContext::~CPUContext() = default;

// NO SIB SUPPORT YET
ModRM process_modrm(uint8_t modrm){
  uint8_t mod_mask = 0b11000000;
  uint8_t reg_mask = 0b00111000;
  uint8_t rm_mask = 0b00000111;
  
  uint8_t mod = modrm & mod_mask;
  uint8_t reg = (modrm & reg_mask) >> 3;
  uint8_t rm = modrm & rm_mask;

  ModRMState state = ModRMState::INVALID;
  
  switch(mod) {
  case 0b00000000:
    state = ModRMState::LR;
    break;
  case 0b01000000:
    state = ModRMState::LR_DISP8;
    break;
  case 0b10000000:
    state = ModRMState::LR_DISP32;
    break;
  case 0b11000000:
    state = ModRMState::R;
    break;
  default:
    throw std::runtime_error("Mod R/M does not support non-register operands right now!");
  }
  return {.m_State = state, .m_Reg = reg, .m_Rm = rm};  
}

namespace executor_cases {
  void Nop(CPUContext& cc){
    std::cout << "No op" << std::endl;
  }

  void Hlt(CPUContext& cc){
    std::cout << "Program halted!" << std::endl;
    exit(0);
  }

  void Mov_r32_imm32(CPUContext& cc){
    cc.m_Registers[cc.m_Instruction.m_Operand1] = cc.m_Instruction.m_Operand2;
    std::cout << "Contents of " << x86::Register2Str((x86::Register)cc.m_Instruction.m_Operand1) << " changed to " << cc.m_Registers[cc.m_Instruction.m_Operand1] << std::endl;
  }
  
  //NO SIB SUPPORT YET
  void Add_rm32_r32(CPUContext& cc){
    ModRM modrm = process_modrm(cc.m_Instruction.m_Operand1);

    switch(modrm.m_State) {
    case ModRMState::R:
    {
      cc.m_Registers[modrm.m_Rm] += cc.m_Registers[modrm.m_Reg];
      std::cout << "Adding " << x86::Register2Str((x86::Register)modrm.m_Reg) << " to " << x86::Register2Str((x86::Register)modrm.m_Rm) << std::endl;
      break;
    }
    case ModRMState::LR:
    {
      uint32_t dstPrevValue = cc.m_Bus->AccessX<uint32_t>(cc.m_Registers[modrm.m_Rm]);
      uint32_t currRegValue = cc.m_Registers[modrm.m_Reg];
      uint32_t result = dstPrevValue + currRegValue;
      cc.m_Bus->WriteX<uint32_t>(cc.m_Registers[modrm.m_Rm], result);
      std::cout << "Memory address " << std::hex << cc.m_Registers[modrm.m_Rm] << " modified to: " << result << std::endl;
      break;
    }
    case ModRMState::LR_DISP8:
    {
      
    }
    default:
    {
      throw std::runtime_error("Invalid ModRM State encountered during Add_rm32_r32");
    }
    }
  }
}
 
constexpr std::array<ExecutorCase, 255> GenerateExecutorTable(){
  std::array<ExecutorCase, 255> table{};
  table[Opcode::NOP] = executor_cases::Nop;
  table[Opcode::HLT] = executor_cases::Hlt;
  table[Opcode::MOV_R_IMM32] = executor_cases::Mov_r32_imm32;
  table[Opcode::ADD_RM32_R32] = executor_cases::Add_rm32_r32;
  return table;
}

static constexpr std::array<ExecutorCase, 255> s_ExecutorTable = GenerateExecutorTable();

const std::array<ExecutorCase, 255>& GetExecutorTable() {
  return s_ExecutorTable;
}