#include "insn.h"

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

#include "cpu.h"
#include "log.h"

#define TABLE_SIZE 0x34

#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)

static cpu_insn_handler primary_insn_handler[TABLE_SIZE];
static cpu_insn_handler secondary_insn_handler[TABLE_SIZE];

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);
        return;
    }

    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 rt = RT(insn);
    const uint8_t rs = RS(insn);
    const uint16_t imm = IMM(insn);

    debug("LW %s, [%s + %x]", REG_NAMES[rt], REG_NAMES[rs], imm);
    cpu->regs[rt] = cpu_read32(cpu, cpu->regs[rs] + imm);
}

void insn_srl(cpu_t *cpu, uint32_t insn) {
    const uint8_t rd = RD(insn);
    const uint8_t rt = RT(insn);
    const uint8_t imm5 = IMM5(insn);

    debug("SRL %s, %s, %u", REG_NAMES[rd], REG_NAMES[rt], imm5);
    cpu->regs[rd] = cpu->regs[rt] >> imm5;
}

void insn_addu(cpu_t *cpu, uint32_t insn) {
    const uint8_t rd = RD(insn);
    const uint8_t rs = RS(insn);
    const uint8_t rt = RT(insn);

    debug("ADDU %s, %s, %s", REG_NAMES[rd], REG_NAMES[rs], REG_NAMES[rt]);
    cpu->regs[rd] = cpu->regs[rs] + cpu->regs[rt];
}

void insn_addiu(cpu_t *cpu, uint32_t insn) {
    const uint8_t rt = RT(insn);
    const uint8_t rs = RS(insn);
    const int16_t imm = (int16_t)IMM(insn);

    debug("ADDIU %s, %s, %x", REG_NAMES[rt], REG_NAMES[rs], imm);
    cpu->regs[rt] = cpu->regs[rs] + imm;
}

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

    debug("SW %s, [%s + %x]", REG_NAMES[rt], REG_NAMES[rt], imm);
    cpu_write32(cpu, cpu->regs[rt], imm + cpu->regs[rs]);
}

void insn_sll(cpu_t *cpu, uint32_t insn) {
    const uint8_t rd = RD(insn);
    const uint8_t rt = RT(insn);
    const uint8_t imm5 = IMM5(insn);

    debug("SLL %s, %s, %u", REG_NAMES[rd], REG_NAMES[rt], imm5);
    cpu->regs[rd] = cpu->regs[rt] << imm5;
}

static cpu_insn_handler primary_insn_handler[TABLE_SIZE] = {
    [LW] = insn_lw,
    [ADDIU] = insn_addiu,
    [SW] = insn_sw,
};

static cpu_insn_handler secondary_insn_handler[TABLE_SIZE] = {
    [SLL] = insn_sll,
    [ADDU] = insn_addu,
    [SRL] = insn_srl,
};