import enum
import sys
import os
from amaranth import *
from amaranth.back import verilog
from amaranth.sim import Simulator

#####
# Hardware Description.
#####

class ClockState(enum.Enum):
    LOW     = 0
    FALLING = 1
    HIGH    = 2
    RISING  = 3

class ShiftRegister(Elaboratable):
    def __init__(self, width):
        self.width = width

        # Ports
        self.nen = Signal()
        self.rst = Signal()

        self.inb = Signal()
        self.exiClk = Signal()
        self.data = Signal(self.width, reset=0)

        # State
        self.prevExiClkValid = Signal()
        self.prevExiClk = Signal()
        self.prevExiClkState = Signal(2)
        self.exiClkState = Signal(2)

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

        with m.If(self.rst):
            m.d.sync += self.data.eq(self.data.reset)

        with m.If(~self.nen):
            with m.If(self.prevExiClkValid):
                m.d.sync += self.prevExiClkState.eq(self.exiClkState)
                with m.If(self.prevExiClk ^ self.exiClk):
                    m.d.sync += self.exiClkState.eq(Cat(self.exiClk, 1))
                with m.Else():
                    m.d.sync += self.exiClkState.eq(Cat(self.exiClk, 0))

                with m.If((self.exiClkState == ClockState.FALLING).bool() & (self.exiClkState != self.prevExiClkState).bool()):
                    m.d.sync += self.data.eq(self.data.shift_left(1) | self.inb )

            m.d.sync += self.prevExiClkValid.eq(1)
            m.d.sync += self.prevExiClk.eq(self.exiClk)
        with m.Else():
            m.d.sync += self.prevExiClkValid.eq(0)
        
        return m

#####
# TestBench
#####
class TestBench:
    def __init__(self):
        pass

    def simExiClock(self, dut):
        yield dut.exiClk.eq(~dut.exiClk)

    def enabled_test(self):
        dut = self.dut

        # Disabled ShiftRegister should not Change.
        yield dut.nen.eq(1)
        for _ in range(10):
            yield dut.inb.eq(~dut.inb)
            yield from self.simExiClock(dut)
            yield from self.simExiClock(dut)
            assert not (yield dut.data)
            yield
            yield
            yield
            yield from self.simExiClock(dut)
            yield from self.simExiClock(dut)
            assert not (yield dut.data)
            yield
            yield
            yield

    def normal_operation(self):
        dut = self.dut

        def oracle(i):
            if i == 0: return 0x01
            if i == 1: return 0x02
            if i == 2: return 0x05
            if i == 3: return 0x0A
            if i == 4: return 0x15
            if i == 5: return 0x2A
            if i == 6: return 0x55
            if i == 7: return 0xAA
            if i == 8: return 0x55
            if i == 9: return 0xAA

        yield dut.nen.eq(0)
        for i in range(10):
            yield dut.inb.eq(~dut.inb)
            yield from self.simExiClock(dut)
            yield
            yield
            yield from self.simExiClock(dut)
            yield
            yield
            assert (yield dut.data) == oracle(i)

    def simulate(self):
        self.dut = ShiftRegister(8)

        sim = Simulator(self.dut)
        sim.add_clock(1e-6) # 1 MHz
        sim.add_sync_process(self.enabled_test)

        with sim.write_vcd(os.path.dirname(os.path.abspath(__file__)) + "/ShiftRegister_enable.vcd"):
            sim.run()

        self.dut = ShiftRegister(8)

        sim = Simulator(self.dut)
        sim.add_clock(1e-6) # 1 MHz
        sim.add_sync_process(self.normal_operation)

        with sim.write_vcd(os.path.dirname(os.path.abspath(__file__)) + "/ShiftRegister_shift.vcd"):
            sim.run()

def main():
    if(len(sys.argv) == 2):

        if sys.argv[1] == "s":
            bench = TestBench()
            bench.simulate()
        
        if sys.argv[1] == "v":
            mod = ShiftRegister(8)
            with open(os.path.dirname(os.path.abspath(__file__)) + "/shift_register.v", "w") as f:
                f.write(verilog.convert(mod, ports=[mod.exiClk, mod.inb, mod.data]))
    
    else:
        bench = TestBench()
        bench.simulate()


#####
# Main portion
#####

if __name__ == "__main__":
    main()