"""Render captured traces (amplitude + phase) to standalone PNG files.

The preprocess preview pane only shows the *last* radar variant of each combo,
so during a multi-config reference capture the operator never sees the other
variants. This helper renders the same amplitude/phase plot pair used in the
preview into off-screen PNG files, letting us persist a graph for every config.
"""

from __future__ import annotations

import logging
from pathlib import Path

import numpy as np
import pyqtgraph as pg
from PyQt6.QtCore import QRectF
from pyqtgraph.exporters import ImageExporter

from python_app.models.dataset_model import TraceData

logger = logging.getLogger(__name__)

# Matches the preview pane styling in preprocess_dialog so saved PNGs and the
# on-screen preview look the same.
_BACKGROUND = "#101418"
_MAGNITUDE_PEN = pg.mkPen("#4cc9f0", width=1.8)
_PHASE_PEN = pg.mkPen("#f48c06", width=1.8)
_EXPORT_SIZE = (1400, 520)


def export_trace_png(
    trace: TraceData,
    output_path: Path,
    *,
    channel: str,
    title: str,
) -> None:
    """Render one trace's amplitude (dB) and wrapped phase (deg) panes to a PNG.

    Builds an off-screen ``GraphicsLayoutWidget`` (never shown), plots the same
    curves as the live preview, and exports the scene as a PNG. Requires a
    running ``QApplication`` (always true inside the GUI).
    """
    samples = trace.s11 if channel == "s11" else trace.s21
    magnitude_db = 20.0 * np.log10(np.maximum(np.abs(samples), 1e-12))
    phase_deg = np.degrees(np.angle(samples))

    layout = pg.GraphicsLayoutWidget(show=False, size=_EXPORT_SIZE)
    layout.setBackground(_BACKGROUND)
    try:
        layout.addLabel(title, row=0, col=0, colspan=2)

        magnitude_plot = layout.addPlot(row=1, col=0)
        magnitude_plot.showGrid(x=True, y=True, alpha=0.2)
        magnitude_plot.setLabel("bottom", "Frequency", units="Hz")
        magnitude_plot.setLabel("left", "Magnitude", units="dB")
        magnitude_plot.plot(trace.frequency_hz, magnitude_db, pen=_MAGNITUDE_PEN)

        phase_plot = layout.addPlot(row=1, col=1)
        phase_plot.showGrid(x=True, y=True, alpha=0.2)
        phase_plot.setLabel("bottom", "Frequency", units="Hz")
        phase_plot.setLabel("left", "Phase", units="deg")
        phase_plot.plot(trace.frequency_hz, phase_deg, pen=_PHASE_PEN)

        # An off-screen widget never receives a resizeEvent, so its central
        # GraphicsLayout keeps its small preferred size and both plots would be
        # squeezed into the left edge of the image. Force the layout geometry to
        # the target size, doing manually what a resizeEvent normally triggers.
        layout.ci.setGeometry(QRectF(0, 0, _EXPORT_SIZE[0], _EXPORT_SIZE[1]))

        output_path.parent.mkdir(parents=True, exist_ok=True)
        exporter = ImageExporter(layout.scene())
        exporter.parameters()["width"] = _EXPORT_SIZE[0]
        exporter.export(str(output_path))
    finally:
        layout.close()
        layout.deleteLater()