/**
  ******************************************************************************
  * @file           : vm.c
  * @author         : simon
  * @brief          : Interpret the bytecode from chunk
  * @attention      : None
  * @date           : 2023/8/17
  ******************************************************************************
  */
#include "common.h"
#include "vm.h"
#include "debug.h"
#include "compiler.h"

VM vm;

/// \brief 重置栈
static void resetStack() {
  vm.stackTop = vm.stack; // 指针指向栈顶
}

void initVM() {
  resetStack();
}
static InterpretResult run() {
//! <macro> reads the byte currently pointed at by ip
//! and then advances the instruction pointer
#define READ_BYTE() (*vm.ip++)
//! reads the next byte from the bytecode
//! treats the resulting number as an index
#define READ_CONSTANT() (vm.chunk->constants.values[READ_BYTE()])
#define BINARY_OP(op) \
   do { \
     double b = pop(); \
     double a = pop(); \
     push(a op b); \
   } while(false)

  for (;;) {
#ifdef DEBUG_TRACE_EXECUTION
    //! <Stack tracing> start
    printf("------------------------\n|");
    for (Value *slot = vm.stack; slot < vm.stackTop; slot++) {
      printf("[ ");
      printValue(*slot);
      printf(" ]");
    }
    printf("\n------------------------");
    printf("\n");
    //! <Stack tracing> end
    disassembleInstruction(vm.chunk, (int) (vm.ip - vm.chunk->code));
#endif
    uint8_t instruction;
    switch (instruction = READ_BYTE()) {
      case OP_CONSTANT: {
        Value constant = READ_CONSTANT();
        push(constant);
        break;
      }
      case OP_ADD: BINARY_OP(+);
        break;
      case OP_SUBTRACT: BINARY_OP(-);
        break;
      case OP_MULTIPLY: BINARY_OP(*);
        break;
      case OP_DIVIDE: BINARY_OP(/);
        break;
      case OP_NEGATE: push(-pop());
        break;
      case OP_RETURN: {
        printValue(pop());
        printf("\n");
        return INTERPRET_OK;
      }
    }
  }

#undef READ_BYTE
#undef READ_CONSTANT
#undef BINARY_OP
}
void freeVM() {

}
InterpretResult interpret(const char *source) {
  compile(source);
  return INTERPRET_OK;
}
void push(Value value) {
  *vm.stackTop = value;
  vm.stackTop++;
}
Value pop() {
  vm.stackTop--;
  //! NOTE： 出栈后，里面的值没有清除
  return *vm.stackTop;
}