#include "assembler.h"
#include "vector.h"

using namespace vm;

namespace {

enum Register {
  rax = 0,
  rcx = 1,
  rdx = 2,
  rbx = 3,
  rsp = 4,
  rbp = 5,
  rsi = 6,
  rdi = 7,
  r8 = 8,
  r9 = 9,
  r10 = 10,
  r11 = 11,
  r12 = 12,
  r13 = 13,
  r14 = 14,
  r15 = 15,
};

class Task {
 public:
  Task(Task* next): next(next) { }

  virtual ~Task() { }

  virtual void run(uint8_t* code) = 0;

  Task* next;
};

class MyAssembler: public Assembler {
 public:
  MyAssembler(System* s, Allocator* a): s(s), code(s, a, 1024), tasks(0) { }

  virtual unsigned registerCount() {
    return BytesPerWord == 4 ? 8 : 16;
  }

  virtual int base() {
    return rbp;
  }

  virtual int stack() {
    return rsp;
  }

  virtual int thread() {
    return rbx;
  }

  virtual int returnLow() {
    return rax;
  }

  virtual int returnHigh() {
    return (BytesPerWord == 4 ? rdx : NoRegister);
  }

  virtual unsigned argumentRegisterCount() {
    return (BytesPerWord == 4 ? 0 : 6);
  }

  virtual int argumentRegister(unsigned index) {
    assert(s, BytesPerWord == 8);

    switch (index) {
    case 0:
      return rdi;
    case 1:
      return rsi;
    case 2:
      return rdx;
    case 3:
      return rcx;
    case 4:
      return r8;
    case 5:
      return r9;
    default:
      abort(s);
    }
  }

  virtual int stackSyncRegister(unsigned index) {
    switch (index) {
    case 0:
      return rax;
    case 1:
      return rcx;
    case 2:
      return rdx;
    case 3:
      return rsi;
    case 4:
      return rdi;
    default:
      abort(s);
    }
  }

  virtual void getTargets(UnaryOperation /*op*/, unsigned /*size*/,
                          Register* r)
  {
    // todo
    r->low = NoRegister;
    r->high = NoRegister;
  }

  virtual void getTargets(BinaryOperation /*op*/, unsigned /*size*/,
                          Register* a, Register* b)
  {
    // todo
    a->low = NoRegister;
    a->high = NoRegister;
    b->low = NoRegister;
    b->high = NoRegister;
  }

  virtual void apply(Operation /*op*/) {
    // todo
    abort(s);
  }

  virtual void apply(UnaryOperation /*op*/, unsigned /*size*/,
                     OperandType /*type*/, Operand* /*operand*/)
  {
    // todo
    abort(s);
  }

  virtual void apply(BinaryOperation /*op*/, unsigned /*size*/,
                     OperandType /*aType*/, Operand* /*a*/,
                     OperandType /*bType*/, Operand* /*b*/)
  {
    // todo
    abort(s);
  }

  virtual void writeTo(uint8_t* dst) {
    memcpy(dst, code.data, code.length());
    
    for (Task* t = tasks; t; t = t->next) {
      t->run(dst);
    }
  }

  virtual unsigned length() {
    return code.length();
  }

  virtual void updateCall(void* returnAddress, void* newTarget) {
    uint8_t* instruction = static_cast<uint8_t*>(returnAddress) - 5;
    assert(s, *instruction == 0xE8);
    assert(s, reinterpret_cast<uintptr_t>(instruction + 1) % 4 == 0);

    int32_t v = static_cast<uint8_t*>(newTarget)
      - static_cast<uint8_t*>(returnAddress);
    memcpy(instruction + 1, &v, 4);
  }

  System* s;
  Vector code;
  Task* tasks;
};

} // namespace

namespace vm {

Assembler*
makeAssembler(System* system, Allocator* allocator, Zone* zone)
{
  return new (zone->allocate(sizeof(MyAssembler)))
    MyAssembler(system, allocator);  
}

} // namespace vm