#!/usr/bin/env python
# SPDX-License-Identifier: CERN-OHL-S-2.0
"""

Copyright (c) 2021-2025 FPGA Ninja, LLC

Authors:
- Alex Forencich

"""

import itertools
import logging
import os

import cocotb_test.simulator
import pytest

import cocotb
from cocotb.clock import Clock
from cocotb.triggers import RisingEdge
from cocotb.regression import TestFactory

from cocotbext.axi import AxiStreamBus, AxiStreamFrame, AxiStreamSource, AxiStreamSink


def cobs_encode(block):
    block = bytearray(block)
    enc = bytearray()

    seg = bytearray()
    code = 1

    new_data = True

    for b in block:
        if b == 0:
            enc.append(code)
            enc.extend(seg)
            code = 1
            seg = bytearray()
            new_data = True
        else:
            code += 1
            seg.append(b)
            new_data = True
            if code == 255:
                enc.append(code)
                enc.extend(seg)
                code = 1
                seg = bytearray()
                new_data = False

    if new_data:
        enc.append(code)
        enc.extend(seg)

    return bytes(enc)


def cobs_decode(block):
    block = bytearray(block)
    dec = bytearray()

    code = 0

    i = 0

    if 0 in block:
        return None

    while i < len(block):
        code = block[i]
        i += 1
        if i+code-1 > len(block):
            return None
        dec.extend(block[i:i+code-1])
        i += code-1
        if code < 255 and i < len(block):
            dec.append(0)

    return bytes(dec)


def prbs31(state=0x7fffffff):
    while True:
        for i in range(8):
            if bool(state & 0x08000000) ^ bool(state & 0x40000000):
                state = ((state & 0x3fffffff) << 1) | 1
            else:
                state = (state & 0x3fffffff) << 1
        yield state & 0xff


class TB(object):
    def __init__(self, dut):
        self.dut = dut

        self.log = logging.getLogger("cocotb.tb")
        self.log.setLevel(logging.DEBUG)

        cocotb.start_soon(Clock(dut.clk, 10, units="ns").start())

        self.source = AxiStreamSource(AxiStreamBus.from_entity(dut.s_axis), dut.clk, dut.rst)
        self.sink = AxiStreamSink(AxiStreamBus.from_entity(dut.m_axis), dut.clk, dut.rst)

    def set_idle_generator(self, generator=None):
        if generator:
            self.source.set_pause_generator(generator())

    def set_backpressure_generator(self, generator=None):
        if generator:
            self.sink.set_pause_generator(generator())

    async def reset(self):
        self.dut.rst.setimmediatevalue(0)
        await RisingEdge(self.dut.clk)
        await RisingEdge(self.dut.clk)
        self.dut.rst.value = 1
        await RisingEdge(self.dut.clk)
        await RisingEdge(self.dut.clk)
        self.dut.rst.value = 0
        await RisingEdge(self.dut.clk)
        await RisingEdge(self.dut.clk)


async def run_test(dut, payload_lengths=None, payload_data=None, idle_inserter=None, backpressure_inserter=None):

    tb = TB(dut)

    append_zero = int(os.getenv("PARAM_APPEND_ZERO"))

    await tb.reset()

    tb.set_idle_generator(idle_inserter)
    tb.set_backpressure_generator(backpressure_inserter)

    test_frames = [payload_data(x) for x in payload_lengths()]

    for test_data in test_frames:
        test_frame = AxiStreamFrame(test_data)
        await tb.source.send(test_frame)

    for test_data in test_frames:
        rx_frame = await tb.sink.recv()

        if append_zero:
            assert rx_frame.tdata == cobs_encode(test_data)+b'\x00'
            assert cobs_decode(rx_frame.tdata[:-1]) == test_data
        else:
            assert rx_frame.tdata == cobs_encode(test_data)
            assert cobs_decode(rx_frame.tdata) == test_data
        assert not rx_frame.tuser

    assert tb.sink.empty()

    await RisingEdge(dut.clk)
    await RisingEdge(dut.clk)


def cycle_pause():
    return itertools.cycle([1, 1, 1, 0])


def size_list():
    return list(range(1, 33))+list(range(253, 259))+[512]+[1]*64


def zero_payload(length):
    return bytearray(length)


def incrementing_payload(length):
    return bytearray(itertools.islice(itertools.cycle(range(256)), length))


def nonzero_incrementing_payload(length):
    return bytearray(itertools.islice(itertools.cycle(range(1, 256)), length))


def nonzero_incrementing_payload_zero_framed(length):
    return bytearray([0]+list(itertools.islice(itertools.cycle(range(1, 256)), length))+[0])


def prbs_payload(length):
    gen = prbs31()
    return bytearray([next(gen) for x in range(length)])


if getattr(cocotb, 'top', None) is not None:

    factory = TestFactory(run_test)
    factory.add_option("payload_lengths", [size_list])
    factory.add_option("payload_data", [zero_payload, nonzero_incrementing_payload, nonzero_incrementing_payload_zero_framed, prbs_payload])
    factory.add_option("idle_inserter", [None, cycle_pause])
    factory.add_option("backpressure_inserter", [None, cycle_pause])
    factory.generate_tests()


# cocotb-test

tests_dir = os.path.dirname(__file__)
rtl_dir = os.path.abspath(os.path.join(tests_dir, '..', '..', 'rtl'))
lib_dir = os.path.abspath(os.path.join(tests_dir, '..', '..', 'lib'))
taxi_src_dir = os.path.abspath(os.path.join(lib_dir, 'taxi', 'src'))


def process_f_files(files):
    lst = {}
    for f in files:
        if f[-2:].lower() == '.f':
            with open(f, 'r') as fp:
                l = fp.read().split()
            for f in process_f_files([os.path.join(os.path.dirname(f), x) for x in l]):
                lst[os.path.basename(f)] = f
        else:
            lst[os.path.basename(f)] = f
    return list(lst.values())


@pytest.mark.parametrize("append_zero", [0, 1])
def test_taxi_axis_cobs_encode(request, append_zero):
    dut = "taxi_axis_cobs_encode"
    module = os.path.splitext(os.path.basename(__file__))[0]
    toplevel = module

    verilog_sources = [
        os.path.join(tests_dir, f"{toplevel}.sv"),
        os.path.join(rtl_dir, f"{dut}.f"),
    ]

    verilog_sources = process_f_files(verilog_sources)

    parameters = {}

    parameters['APPEND_ZERO'] = append_zero

    extra_env = {f'PARAM_{k}': str(v) for k, v in parameters.items()}

    sim_build = os.path.join(tests_dir, "sim_build",
        request.node.name.replace('[', '-').replace(']', ''))

    cocotb_test.simulator.run(
        simulator="verilator",
        python_search=[tests_dir],
        verilog_sources=verilog_sources,
        toplevel=toplevel,
        module=module,
        parameters=parameters,
        sim_build=sim_build,
        extra_env=extra_env,
    )
