#include "insn.h"
#include "cpu.h"
#include "util.h"

#include <stddef.h>
#include <stdio.h>

#define TABLE_SIZE 0x34

void insn_lw(cpu_t *cpu, uint32_t insn);

static cpu_insn_handler primary_insn_handler[TABLE_SIZE] = {
    [LW] = insn_lw,
};

static cpu_insn_handler secondary_insn_handler[TABLE_SIZE] = {NULL};

#define BITS(x, start, len) (((x) >> (start)) & ((1 << (len)) - 1))

#define OP(insn) BITS(insn, 26, 6)
#define RS(insn) BITS(insn, 21, 5)
#define RT(insn) BITS(insn, 16, 5)
#define RD(insn) BITS(insn, 11, 5)
#define COMMENT(insn) BITS(insn, 6, 20)
#define IMM5(insn) BITS(insn, 6, 5)
#define OP2(insn) BITS(insn, 0, 6)
#define IMM(insn) BITS(insn, 0, 16)

void insn_execute(cpu_t *cpu, uint32_t insn)
{
  const op_primary_t op = OP(insn);

  if (op == SPECIAL)
  {
    const op_secondary_t op2 = OP2(insn);

    if (op2 > TABLE_SIZE || secondary_insn_handler[op2] == NULL)
    {
      fatal("unsupported instruction: insn=%08x, op=%02x, op2=%02x", insn,
            op, op2);
    }

    secondary_insn_handler[op2](cpu, insn);
  }

  if (op > TABLE_SIZE || primary_insn_handler[op] == NULL)
  {
    fatal("unsupported instruction: insn=%08x, op=%02x", insn, op);
  }

  primary_insn_handler[op](cpu, insn);
}

void insn_lw(cpu_t *cpu, uint32_t insn)
{
  const uint8_t rs = RS(insn);
  const uint8_t rt = RT(insn);
  const uint16_t imm = IMM(insn);

  printf("LW R%u, [R%u + %x]\n", rt, rs, imm);
  cpu->regs[rt] = cpu_read32(cpu, cpu->regs[rs] + imm);
}