from amaranth import *
from amaranth.sim import Simulator, Settle, Delay

from hdl.utils import cmd

class ShiftReg(Elaboratable):
    def __init__(self, width):
        self.name = "shift_reg"

        self.load_val = Signal(width, reset=0, reset_less=True)
        self.load = Signal()
        self.reg = Signal(width)
        self.en = Signal()
        self.right_left = Signal()

        ports_in = [self.load_val, self.en, self.load, self.right_left]
        ports_out = [self.reg]
        self.ports = {'in': ports_in, 'out': ports_out}

    def elaborate(self, platform):
        m = Module()

        with m.If(self.load):
            m.d.sync += self.reg.eq(self.load_val)
        with m.Else():
            with m.If(self.en):
                with m.If(self.right_left):
                    m.d.sync += self.reg.eq(self.reg << 1)
                with m.Else():
                    m.d.sync += self.reg.eq(self.reg >> 1)

        return m

def test_shift_reg(filename="out.vcd"):
    dut = ShiftReg(8)

    def proc1():
        val = 0xAB

        yield dut.load_val.eq(val)
        yield dut.en.eq(0)
        yield dut.load.eq(1)
        yield
        yield Settle()
        yield dut.load.eq(0)
        yield dut.en.eq(1)   

        for _ in range(9):
            reg_val = yield dut.reg
            assert reg_val == val, f"Incorrect shift ---EXPECTED: {hex(val)}   ---GOT: {hex(reg_val)}"
            val = val >> 1
            yield
            yield Settle()

        val = 0xBD
        yield dut.load_val.eq(val)
        yield dut.load.eq(1)
        yield dut.right_left.eq(1)
        yield
        yield Settle()
        yield dut.load.eq(0)

        for _ in range(9):
            reg_val = yield dut.reg
            assert reg_val == val, f"Incorrect shift ---EXPECTED: {hex(val)}   ---GOT: {hex(reg_val)}"
            val = (val << 1) & 0xff
            yield
            yield Settle()



    sim = Simulator(dut)
    sim.add_clock(1e-6)
    sim.add_sync_process(proc1)
    
    with sim.write_vcd(filename):
        sim.run()


if __name__ == '__main__':
    shift_reg = ShiftReg(8)
    cmd(shift_reg, test_shift_reg)