from __future__ import annotations

from dataclasses import dataclass
from typing import Iterable


P9_ACK_BIT = 0x80
P9_STROBE_BIT = 0x02


@dataclass(frozen=True)
class P9StrobeEvent:
    edge: str
    ddr: int
    dr: int
    data_bit: int
    bit7_output: bool


@dataclass(frozen=True)
class P9TraceEvent:
    kind: str
    ddr: int
    dr: int
    value: int | None = None
    bit: int | None = None
    source: str | None = None
    success: bool | None = None
    queue_depth: int | None = None

    def line(self) -> str:
        parts = [self.kind, f"ddr={self.ddr:02X}", f"dr={self.dr:02X}"]
        if self.value is not None:
            parts.append(f"value={self.value:02X}")
        if self.bit is not None:
            parts.append(f"bit={self.bit}")
        if self.success is not None:
            parts.append(f"success={int(self.success)}")
        if self.source is not None:
            parts.append(f"source={self.source}")
        if self.queue_depth is not None:
            parts.append(f"queued={self.queue_depth}")
        return " ".join(parts)


class P9Bus:
    """Small model for the ROM's P9 bit-banged serial handshake."""

    def __init__(
        self,
        ddr: int = 0x00,
        dr: int = 0x00,
        input_bits: Iterable[int] = (),
        wrapper_results: Iterable[bool] = (),
    ) -> None:
        self.ddr = ddr & 0xFF
        self.dr_latch = dr & 0xFF
        self.input_bits: list[int] = [1 if bit else 0 for bit in input_bits]
        self.default_input_bit = 0
        self.wrapper_results: list[bool] = [bool(result) for result in wrapper_results]
        self.wrapper_sources: list[str] = ["initial"] * len(self.wrapper_results)
        self.default_wrapper_success = False
        self.strobe_edges: list[P9StrobeEvent] = []
        self.trace_events: list[P9TraceEvent] = []
        self.transmitted_bits: list[int] = []
        self.byte_candidates: list[int] = []

    def write_ddr(self, value: int) -> int:
        self.ddr = value & 0xFF
        self.trace_events.append(P9TraceEvent("write_ddr", self.ddr, self.dr_latch, value=self.ddr))
        return self.ddr

    def write_dr(self, value: int) -> int:
        previous = self.dr_latch
        self.dr_latch = value & 0xFF
        self.trace_events.append(P9TraceEvent("write_dr", self.ddr, self.dr_latch, value=self.dr_latch))

        previous_strobe = bool(previous & P9_STROBE_BIT)
        current_strobe = bool(self.dr_latch & P9_STROBE_BIT)
        if previous_strobe != current_strobe:
            edge = "rising" if current_strobe else "falling"
            data_bit = 1 if self.dr_latch & P9_ACK_BIT else 0
            bit7_output = bool(self.ddr & P9_ACK_BIT)
            self.strobe_edges.append(P9StrobeEvent(edge, self.ddr, self.dr_latch, data_bit, bit7_output))
            self.trace_events.append(P9TraceEvent(f"strobe_{edge}", self.ddr, self.dr_latch, bit=data_bit))
            if edge == "rising" and bit7_output:
                self._record_transmitted_bit(data_bit)

        return self.dr_latch

    def read_ddr(self) -> int:
        return self.ddr

    def read_dr(self) -> int:
        value = self.dr_latch
        input_bit = None
        source = None
        if not (self.ddr & P9_ACK_BIT):
            if self.input_bits:
                input_bit = self.input_bits.pop(0)
                source = "queued_bit"
            else:
                input_bit = self.default_input_bit
                source = "default_bit"
            if input_bit:
                value |= P9_ACK_BIT
            else:
                value &= ~P9_ACK_BIT
        self.trace_events.append(P9TraceEvent("read_dr", self.ddr, value & 0xFF, value=value, bit=input_bit, source=source))
        return value & 0xFF

    def queue_input_bits(self, bits: Iterable[int]) -> None:
        self.input_bits.extend(1 if bit else 0 for bit in bits)

    def set_default_input_bit(self, bit: int) -> None:
        self.default_input_bit = 1 if bit else 0

    def queue_wrapper_results(self, results: Iterable[bool], source: str = "queued_wrapper") -> None:
        for result in results:
            self.wrapper_results.append(bool(result))
            self.wrapper_sources.append(source)

    def consume_wrapper_result(self) -> tuple[bool, str, int]:
        if self.wrapper_results:
            success = self.wrapper_results.pop(0)
            source = self.wrapper_sources.pop(0) if self.wrapper_sources else "queued_wrapper"
        else:
            success = self.default_wrapper_success
            source = "default_success" if success else "default_timeout"
        queue_depth = len(self.wrapper_results)
        self.trace_events.append(
            P9TraceEvent(
                "wrapper_result",
                self.ddr,
                self.dr_latch,
                value=1 if success else 0,
                success=success,
                source=source,
                queue_depth=queue_depth,
            )
        )
        return success, source, queue_depth

    def trace_lines(self, limit: int | None = None) -> list[str]:
        events = self.trace_events if limit is None else self.trace_events[-limit:]
        return [event.line() for event in events]

    def _record_transmitted_bit(self, bit: int) -> None:
        self.transmitted_bits.append(bit)
        self.trace_events.append(P9TraceEvent("tx_bit", self.ddr, self.dr_latch, bit=bit))
        if len(self.transmitted_bits) % 8 == 0:
            byte = 0
            for data_bit in self.transmitted_bits[-8:]:
                byte = (byte << 1) | data_bit
            self.byte_candidates.append(byte)
            self.trace_events.append(P9TraceEvent("tx_byte", self.ddr, self.dr_latch, value=byte))