#include "vm.h"

u32 pc;       /* program counter */
u32 cp;       /* code pointer */
u32 mp;       /* memory pointer */
u32 fp;       /* frame pointer */
u32 flag;     /* flag */
u8 interrupt; /* device interrupt */
u32 *code;    /* code */
u8 *mem;      /* memory */

bool step_vm() {

  u32 instruction = code[pc];
  u8 opcode = DECODE_OP(instruction);

  switch (opcode) {
  case OP_HALT: {
    /* no need to decode, all are zeros */
    return false;
  }
  case OP_CALL: {
  }
  case OP_RETURN: {
  }
  case OP_SYSCALL: {
    DECODE_A(instruction)
    u32 id = fp + dest;
    u32 args = fp + src1;
    u32 mem_ptr = fp + src2;
    flag = syscall(id, args, mem_ptr);
    return true;
  }
  case OP_LOAD_IMM: {
    DECODE_B(instruction)
    u32 rd = fp + dest;
    mem[rd] = imm;
    return true;
  }
  case OP_LOAD_UPPER_IMM: {
    DECODE_B(instruction)
    u32 rd = fp + dest;
    mem[rd] = (mem[rd] | (((u32)(imm)) << 16));
    return true;
  }
  case OP_LOAD_IND_8: {
  }
  case OP_LOAD_IND_16: {
  }
  case OP_LOAD_IND_32: {
  }
  case OP_LOAD_ABS_8: {
  }
  case OP_LOAD_ABS_16: {
  }
  case OP_LOAD_ABS_32: {
  }
  case OP_LOAD_OFF_8: {
  }
  case OP_LOAD_OFF_16: {
  }
  case OP_LOAD_OFF_32: {
  }
  case OP_STORE_ABS_8: {
  }
  case OP_STORE_ABS_16: {
  }
  case OP_STORE_ABS_32: {
  }
  case OP_STORE_IND_8: {
  }
  case OP_STORE_IND_16: {
  }
  case OP_STORE_IND_32: {
  }
  case OP_STORE_OFF_8: {
  }
  case OP_STORE_OFF_16: {
  }
  case OP_STORE_OFF_32: {
  }
  case OP_MEM_ALLOC: {
  }
  case OP_MEM_CPY: {
  }
  case OP_MEM_SET_8: {
  }
  case OP_MEM_SET_16: {
  }
  case OP_MEM_SET_32: {
  }
  case OP_REG_MOV: {
  }
  case OP_ADD_INT: {
    MATH_OP(i32, +);
  }
  case OP_SUB_INT: {
    MATH_OP(i32, -);
  }
  case OP_MUL_INT: {
    MATH_OP(i32, *);
  }
  case OP_DIV_INT: {
    MATH_OP(i32, /);
  }
  case OP_ADD_NAT: {
    MATH_OP(u32, +);
  }
  case OP_SUB_NAT: {
    MATH_OP(u32, -);
  }
  case OP_MUL_NAT: {
    MATH_OP(u32, *);
  }
  case OP_DIV_NAT: {
    MATH_OP(u32, /);
  }
  case OP_ADD_REAL: {
    MATH_OP(i32, +);
  }
  case OP_SUB_REAL: {
    MATH_OP(i32, -);
  }
  case OP_MUL_REAL: {
    DECODE_A(instruction)
    u32 rd = fp + dest;
    u32 r1 = fp + src1;
    u32 r2 = fp + src2;

    i32 src1_whole = (i32)mem[r1] >> 16;
    i32 src2_whole = (i32)mem[r2] >> 16;

    i32 src1_decimal = (i32)mem[r1] & 16;
    i32 src2_decimal = (i32)mem[r2] & 16;

    i32 result = 0;
    result += (src1_whole * src2_whole) << 16;
    result += (src1_whole * src2_decimal);
    result += (src1_decimal * src2_whole);
    result += ((src1_decimal * src2_decimal) >> 16) & 16;
    mem[rd] = result;
    return true;
  }
  case OP_DIV_REAL: {
    DECODE_A(instruction)
    i32 result;
    u32 rd = fp + dest;
    u32 r1 = fp + src1;
    u32 r2 = fp + src2;

    i32 src1_val = (i32)mem[r1];
    i32 src2_val = (i32)mem[r2];

    u32 src2_reciprocal = 1;
    src2_reciprocal <<= 31;
    src2_reciprocal = (u32)(src2_reciprocal / src2_val);

    result = src1_val * src2_reciprocal;
    result <<= 1;
    mem[rd] = result;
    return true;
  }
  case OP_INT_TO_REAL: {
    DECODE_A(instruction)
    u32 rd = fp + dest;
    u32 r1 = fp + src1;
    USED(src2);
    mem[rd] = (i32)mem[r1] << 16;
    return true;                  
  }
  case OP_INT_TO_NAT: {
    DECODE_A(instruction)
    u32 rd = fp + dest;
    u32 r1 = fp + src1;
    USED(src2);
    mem[rd] = (u32)mem[r1];
    return true;
  }
  case OP_NAT_TO_REAL: {
    DECODE_A(instruction)
    u32 rd = fp + dest;
    u32 r1 = fp + src1;
    USED(src2);
    mem[rd] = (i32)mem[r1] << 16;
    return true;                  
  }
  case OP_NAT_TO_INT: {
    DECODE_A(instruction)
    u32 rd = fp + dest;
    u32 r1 = fp + src1;
    USED(src2);
    mem[rd] = (i32)mem[r1];
    return true;
  }
  case OP_REAL_TO_INT: {
    DECODE_A(instruction)
    u32 rd = fp + dest;
    u32 r1 = fp + src1;
    USED(src2);
    mem[rd] = (i32)mem[r1] >> 16;
    return true;
  }
  case OP_REAL_TO_NAT: {
    DECODE_A(instruction)
    u32 rd = fp + dest;
    u32 r1 = fp + src1;
    USED(src2);
    mem[rd] = (u32)mem[r1] >> 16;
    return true;
  }
  case OP_BIT_SHIFT_LEFT: {
  }
  case OP_BIT_SHIFT_RIGHT: {
  }
  case OP_BIT_SHIFT_R_EXT: {
  }
  case OP_BIT_AND: {
  }
  case OP_BIT_OR: {
  }
  case OP_BIT_XOR: {
  }
  case OP_JMP_IMM: {
    DECODE_C(instruction)
    pc = imm;
    return true;
  }
  case OP_JMP_ABS: {
  }
  case OP_JMP_OFF: {
  }
  case OP_JMP_FLAG: {
  }
  case OP_JEQ_INT: {
    COMPARE_AND_JUMP(i32, ==);
  }
  case OP_JNE_INT: {
    COMPARE_AND_JUMP(i32, !=);
  }
  case OP_JGT_INT: {
    COMPARE_AND_JUMP(i32, >);
  }
  case OP_JLT_INT: {
    COMPARE_AND_JUMP(i32, <);
  }
  case OP_JLE_INT: {
    COMPARE_AND_JUMP(i32, <=);
  }
  case OP_JGE_INT: {
    COMPARE_AND_JUMP(i32, >=);
  }
  case OP_JEQ_NAT: {
    COMPARE_AND_JUMP(u32, ==);
  }
  case OP_JNE_NAT: {
    COMPARE_AND_JUMP(u32, !=);
  }
  case OP_JGT_NAT: {
    COMPARE_AND_JUMP(u32, >);
  }
  case OP_JLT_NAT: {
    COMPARE_AND_JUMP(u32, <);
  }
  case OP_JLE_NAT: {
    COMPARE_AND_JUMP(u32, <=);
  }
  case OP_JGE_NAT: {
    COMPARE_AND_JUMP(u32, >=);
  }
  case OP_JEQ_REAL: {
    COMPARE_AND_JUMP(i32, ==);
  }
  case OP_JNE_REAL: {
    COMPARE_AND_JUMP(i32, !=);
  }
  case OP_JGE_REAL: {
    COMPARE_AND_JUMP(i32, >=);
  }
  case OP_JGT_REAL: {
    COMPARE_AND_JUMP(i32, >);
  }
  case OP_JLT_REAL: {
    COMPARE_AND_JUMP(i32, <);
  }
  case OP_JLE_REAL: {
    COMPARE_AND_JUMP(i32, <=);
  }
  }

  /* something went very wrong */
  flag = 255;
  return false;
}