from typing import TYPE_CHECKING
from collections import namedtuple

from systemrdl.component import Reg
from systemrdl.node import RegNode

from ..forloop_generator import RDLForLoopGenerator

if TYPE_CHECKING:
    from . import WriteBuffering

class WBufLogicGenerator(RDLForLoopGenerator):
    i_type = "genvar"
    def __init__(self, wbuf: 'WriteBuffering') -> None:
        super().__init__()
        self.wbuf = wbuf
        self.exp = wbuf.exp
        self.template = self.exp.jj_env.get_template(
            "write_buffering/template.sv"
        )

    def enter_Reg(self, node: 'RegNode') -> None:
        super().enter_Reg(node)
        assert isinstance(node.inst, Reg)

        if not node.get_property('buffer_writes'):
            return

        regwidth = node.get_property('regwidth')
        accesswidth = node.get_property('accesswidth')
        strb_prefix = self.exp.dereferencer.get_access_strobe(node, reduce_substrobes=False)
        Segment = namedtuple("Segment", ["strobe", "bslice"])
        segments = []
        if accesswidth < regwidth:
            n_subwords = regwidth // accesswidth
            for i in range(n_subwords):
                strobe = strb_prefix + f"[{i}]"
                if node.inst.is_msb0_order:
                    bslice = f"[{regwidth - (accesswidth * i) - 1}: {regwidth - (accesswidth * (i+1))}]"
                else:
                    bslice = f"[{(accesswidth * (i + 1)) - 1}:{accesswidth * i}]"
                segments.append(Segment(strobe, bslice))
        else:
            segments.append(Segment(strb_prefix, ""))

        trigger = node.get_property('wbuffer_trigger')
        is_own_trigger = (isinstance(trigger, RegNode) and trigger == node)

        context = {
            'wbuf': self.wbuf,
            'wbuf_prefix': self.wbuf.get_wbuf_prefix(node),
            'segments': segments,
            'node': node,
            'cpuif': self.exp.cpuif,
            'get_resetsignal': self.exp.dereferencer.get_resetsignal,
            'get_always_ff_event': self.exp.dereferencer.get_always_ff_event,
            'is_own_trigger': is_own_trigger,
        }
        self.add_content(self.template.render(context))