from __future__ import annotations

import queue
import threading
import time
from dataclasses import dataclass
from typing import Optional, Tuple

import serial
from PySide6.QtCore import QObject, QThread, Signal, Slot

from ameba_control_panel import config
from ameba_control_panel.services.line_parser import decode_line


@dataclass
class SerialState:
    port: str
    baudrate: int
    connected: bool
    error: Optional[str] = None


class _SerialWorker(QThread):
    line_received = Signal(str, str)  # text, direction
    status_changed = Signal(object)  # SerialState

    def __init__(self, port: str, baudrate: int, parent: Optional[QObject] = None) -> None:
        super().__init__(parent)
        self._port = port
        self._baudrate = baudrate
        self._write_queue: "queue.SimpleQueue[Tuple[bytes, bool]]" = queue.SimpleQueue()
        self._running = threading.Event()
        self._serial: Optional[serial.Serial] = None

    def run(self) -> None:
        try:
            self._serial = serial.Serial(self._port, self._baudrate, timeout=0.05)
            self.status_changed.emit(SerialState(self._port, self._baudrate, True))
        except Exception as exc:  # noqa: BLE001
            self.status_changed.emit(SerialState(self._port, self._baudrate, False, str(exc)))
            return

        self._running.set()
        try:
            while self._running.is_set():
                # writes
                try:
                    while True:
                        payload, log_tx = self._write_queue.get_nowait()
                        self._serial.write(payload)
                        if log_tx:
                            try:
                                text = payload.decode(errors="ignore").rstrip("\r\n")
                            except Exception:
                                text = repr(payload)
                            self.line_received.emit(text, "tx")
                    # fallthrough only when queue empty
                except queue.Empty:
                    pass

                # reads
                line = self._serial.readline()
                if line:
                    try:
                        text = decode_line(line).strip("\r\n")
                    except Exception:
                        text = repr(line)
                    self.line_received.emit(text, "rx")
        finally:
            if self._serial:
                try:
                    self._serial.close()
                except Exception:
                    pass
            self.status_changed.emit(SerialState(self._port, self._baudrate, False))

    @Slot(str)
    def write_text(self, text: str) -> None:
        if not text.endswith("\r\n"):
            text = text + "\r\n"
        self._write_queue.put((text.encode("utf-8", errors="ignore"), True))

    @Slot(bytes)
    def write_bytes(self, payload: bytes) -> None:
        self._write_queue.put((payload, False))

    @Slot()
    def stop(self) -> None:
        self._running.clear()


class _SyntheticWorker(QThread):
    line_received = Signal(str, str)
    status_changed = Signal(object)

    def __init__(self, rate_hz: float = 50.0, parent: Optional[QObject] = None) -> None:
        super().__init__(parent)
        self._rate_hz = rate_hz
        self._running = threading.Event()
        self._counter = 0

    def run(self) -> None:
        self._running.set()
        self.status_changed.emit(SerialState("synthetic", config.DEFAULT_BAUD, True))
        try:
            while self._running.is_set():
                self._counter += 1
                self.line_received.emit(f"SYN {self._counter:06d}", "rx")
                time.sleep(1.0 / self._rate_hz)
        finally:
            self.status_changed.emit(SerialState("synthetic", config.DEFAULT_BAUD, False))

    @Slot(str)
    def write_text(self, text: str) -> None:
        # Echo back as RX to simulate loopback.
        clean = text.rstrip("\r\n")
        self.line_received.emit(clean, "tx")
        self.line_received.emit(f"ECHO: {clean}", "rx")

    @Slot(bytes)
    def write_bytes(self, payload: bytes) -> None:
        try:
            clean = payload.decode(errors="ignore")
        except Exception:
            clean = repr(payload)
        self.line_received.emit(clean, "tx")
        self.line_received.emit(f"ECHO: {clean}", "rx")

    @Slot()
    def stop(self) -> None:
        self._running.clear()


class SerialService(QObject):
    line_received = Signal(str, str)
    status_changed = Signal(object)

    def __init__(self, parent: Optional[QObject] = None) -> None:
        super().__init__(parent)
        self._worker: Optional[QThread] = None

    def open(self, port: str, baudrate: int) -> None:
        self.close()
        if port.lower() == "synthetic":
            worker: QThread = _SyntheticWorker()
        else:
            worker = _SerialWorker(port, baudrate)
        worker.line_received.connect(self.line_received)
        worker.status_changed.connect(self.status_changed)
        self._worker = worker
        worker.start()

    def close(self) -> None:
        if self._worker:
            try:
                self._worker.stop()  # type: ignore[attr-defined]
                self._worker.wait(1000)
            except Exception:
                pass
            self._worker = None

    def write(self, text: str) -> None:
        if self._worker:
            self._worker.write_text(text)  # type: ignore[attr-defined]

    def write_raw(self, data: bytes | str) -> None:
        if isinstance(data, str):
            data = data.encode("utf-8", errors="ignore")
        if self._worker:
            self._worker.write_bytes(data)  # type: ignore[attr-defined]

    def is_connected(self) -> bool:
        return bool(self._worker and self._worker.isRunning())