"""Qt-independent capture queue, preview and full-record CSV export."""
from dataclasses import dataclass
from queue import Queue
from threading import Thread
import csv
from .tektronix import DPO4034, Waveform
from .plot_decimation import pixel_envelope

@dataclass
class CaptureFrame:
    full: list
    preview: list


def prepare_preview(waveforms, width):
    preview = []
    for wave in waveforms:
        if not wave.seconds:
            preview.append(wave)
            continue
        points = [point for point in pixel_envelope(wave.seconds, wave.values,
                  wave.seconds[0], wave.seconds[-1], width) if point is not None]
        preview.append(Waveform(wave.channel, tuple(x for x, _ in points),
                                tuple(y for _, y in points), wave.unit))
    return preview


class ScopeSession:
    """Serial worker queue: every VISA call, including close, stays off the UI."""

    def __init__(self, factory=DPO4034):
        self.commands = Queue()
        self.results = Queue()
        self.thread = Thread(target=self._run, args=(factory,))
        self.thread.start()

    def _run(self, factory):
        client = factory()
        try:
            while True:
                action, args = self.commands.get()
                if action == "shutdown":
                    break
                try:
                    if action == "capture" and len(args) == 4:
                        value = client.capture(*args[:3])
                        value = CaptureFrame(value, prepare_preview(value, args[3]))
                    elif action == "export":
                        filename, waves = args
                        with open(filename, "w", newline="", encoding="utf-8-sig") as stream:
                            writer = csv.writer(stream)
                            # Native channels share the frozen record's time grid.
                            # Reject mismatched grids rather than misalign exported values.
                            if any(w.seconds != waves[0].seconds for w in waves[1:]):
                                raise ValueError("Для экспорта каналов нужны одинаковые временные сетки")
                            writer.writerow(["time_ms", *(w.channel + " (" + w.unit + ")" for w in waves)])
                            for index, stamp in enumerate(waves[0].seconds):
                                writer.writerow([stamp * 1000, *(w.values[index] for w in waves)])
                        value = filename
                    else:
                        value = getattr(client, action)(*args)
                    self.results.put((action, value, None))
                except Exception as exc:
                    if action != "export":
                        try:
                            client.close()
                        except Exception:
                            pass
                    self.results.put((action, None, str(exc)))
        finally:
            try:
                client.close()
            except Exception:
                pass  # Shutdown must finish even if the device has been unplugged.

    def submit(self, action, *args):
        self.commands.put((action, args))