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use ckb_vm_definitions::instructions as insts;

use super::utils::{funct3, funct7, opcode, rd, rs1, rs2};
use super::{set_instruction_length_4, Instruction, Register, Rtype};

pub fn factory<R: Register>(instruction_bits: u32, _: u32) -> Option<Instruction> {
    let bit_length = R::BITS;
    if bit_length != 32 && bit_length != 64 {
        return None;
    }
    let rv64 = bit_length == 64;
    if funct7(instruction_bits) != 0b_0000001 {
        return None;
    }
    let inst_opt = match opcode(instruction_bits) {
        0b_0110011 => match funct3(instruction_bits) {
            0b_000 => Some(insts::OP_MUL),
            0b_001 => Some(insts::OP_MULH),
            0b_010 => Some(insts::OP_MULHSU),
            0b_011 => Some(insts::OP_MULHU),
            0b_100 => Some(insts::OP_DIV),
            0b_101 => Some(insts::OP_DIVU),
            0b_110 => Some(insts::OP_REM),
            0b_111 => Some(insts::OP_REMU),
            _ => None,
        },
        0b_0111011 if rv64 => match funct3(instruction_bits) {
            0b_000 => Some(insts::OP_MULW),
            0b_100 => Some(insts::OP_DIVW),
            0b_101 => Some(insts::OP_DIVUW),
            0b_110 => Some(insts::OP_REMW),
            0b_111 => Some(insts::OP_REMUW),
            _ => None,
        },
        _ => None,
    };
    inst_opt
        .map(|inst| {
            Rtype::new(
                inst,
                rd(instruction_bits),
                rs1(instruction_bits),
                rs2(instruction_bits),
            )
            .0
        })
        .map(set_instruction_length_4)
}