#include "VM.hpp"
#include "src/Program.hpp"

namespace zn
{
  /*explicit*/ VM::VM()
  {
  }

  /*virtual*/ VM::~VM()
  {
  }

  void VM::execute(Program& program)
  {
    m_pc = 0;
    m_frames.push_back(Frame {program});

    while (m_pc < program.size())
      {
        auto instr = program.instr(m_pc);
        execute(instr.opcode, instr.param);
      }
  }

  void VM::execute(Opcode opcode, int param)
  {
    switch (opcode)
      {
      case OPCODE_LOAD_CONST: {
        push(param);
        m_pc++;
      } break;

      case OPCODE_POP: {
        pop();
        m_pc++;
      } break;

      default: {
        std::cerr << "cannot execute opcode '"
                  << OpcodeStr[opcode]
                  << "'" << std::endl;
        abort();
      } break;
      }
  }

  std::string VM::string() const
  {
    std::stringstream ss;

    ss << "======== VM Stack ========\n";

    size_t addr = 0;

    for (int val: m_stack)
      {
        ss << addr << " " << val << "\n";
        addr++;
      }

    return ss.str();
  }

  void VM::push(int value)
  {
    m_stack.push_back(value);
  }

  int VM::pop()
  {
    assert(m_stack.size() > 0);
    int value = m_stack.back();
    m_stack.pop_back();
    return value;
  }
}