#include <md/md.hpp>

namespace MegaDrive {

CPU cpu;

auto CPU::Enter() -> void {
  cpu.boot();
  while(true) scheduler.synchronize(), cpu.main();
}

auto CPU::boot() -> void {
  r.a[7] = read(1, 0) << 16 | read(1, 2) << 0;
  r.pc   = read(1, 4) << 16 | read(1, 6) << 0;
}

auto CPU::main() -> void {
  instruction();
}

auto CPU::step(uint clocks) -> void {
  Thread::step(clocks);
  cycles += clocks;
  if(cycles >= frequency() / 60) {
    cycles = 0;
    scheduler.exit(Scheduler::Event::Frame);
  }
}

auto CPU::power() -> void {
  M68K::power();

  for(auto& byte : ram) byte = 0x00;
}

auto CPU::reset() -> void {
  M68K::reset();
  create(CPU::Enter, system.colorburst() * 15.0 / 7.0);
  cycles = 0;
}

auto CPU::read(bool word, uint24 addr) -> uint16 {
  if(addr < 0x400000) return cartridge.read(word, addr);
  if(addr < 0xe00000) return 0x0000;

  uint16 data = ram[addr & 65535];
  if(word) data = data << 8 | ram[addr + 1 & 65535];
  return data;
}

auto CPU::write(bool word, uint24 addr, uint16 data) -> void {
  if(addr < 0x400000) return cartridge.write(word, addr, data);
  if(addr < 0xe00000) return;

  if(!word) {
    ram[addr & 65535] = data;
  } else {
    ram[addr + 0 & 65535] = data >> 8;
    ram[addr + 1 & 65535] = data >> 0;
  }
}

}