"""Neutral preprocessing-set helpers — the "run without calibration" path.

A neutral pair is a calibration set carrying unit S21 (1+0j) and a reference set
carrying zero S21. The C++ through-calibrator divides measured/calibration and the
reference is subtracted, so applying both leaves the measured S21 untouched. That
lets an operator start the pipeline before any real calibration exists, which the
required-asset check in `_start_run` would otherwise refuse.

The shortcut is enabled for verified axes: Kamil ADC's processing grid,
synchronized multi-device LibreVNA, and the physical single LibreVNA mock.
"""

from __future__ import annotations

import logging
import time

import numpy as np

from python_app.hardware_full.kamil_adc import (
    KamilAdcProcessingParams,
    KamilAdcSweepProcessor,
)
from python_app.models.dataset_model import ComboKey, SweepCollection, TraceData
from python_app.models.run_config_model import ComboModel, RunConfigModel

logger = logging.getLogger(__name__)


def supports_neutral_preprocess_sets(config: RunConfigModel) -> bool:
    """Enable the shortcut only when the emitted frequency grid is verified."""
    return bool(config.is_kamil_adc or config.is_multi_device or (
        config.radar.model == RunConfigModel.LIBREVNA_MODEL and config.radar.driver_mode == "mock"
    ))


def neutral_frequency_grid_hz(config: RunConfigModel) -> np.ndarray:
    """Derive the neutral axis; the preprocessor verifies it against measured data."""
    if config.is_kamil_adc:
        # Single source of truth for the axis: the same grid the processor emits.
        processor = KamilAdcSweepProcessor(
            KamilAdcProcessingParams.from_kamil_model(config.radar.kamil_adc)
        )
        return processor.grid_hz

    points = int(config.radar.sweep.points)
    if points < 1:
        raise ValueError("Neutral sets require radar.sweep.points >= 1")
    # Mirrors both acquisition paths: the native collector seeds this same linspace
    # and the mock backend generates it outright.
    return np.linspace(
        float(config.radar.sweep.start_hz),
        float(config.radar.sweep.stop_hz),
        points,
        dtype=np.float32,
    )


def build_neutral_s21_sets(
    config: RunConfigModel,
) -> tuple[SweepCollection, SweepCollection]:
    """Build neutral S21 calibration/reference collections for the active radar.

    Covers every combo in the effective matrix, so a matrix radar widened by real
    switches gets a neutral pair for all of its positions and the preprocessor's
    ``validate_combos()`` is satisfied. Returns ``(calibration, reference)``.
    """
    combos = list(config.combos)
    if not combos:
        combos = config.build_runtime_combos()
    if not combos:
        raise ValueError("Neutral sets require at least one switch combo")

    frequency_hz = neutral_frequency_grid_hz(config)

    now_ns = time.monotonic_ns()
    calibration = _neutral_collection(
        combos=combos,
        frequency_hz=frequency_hz,
        s21_value=np.complex64(1.0 + 0.0j),
        monotonic_ns=now_ns,
    )
    reference = _neutral_collection(
        combos=combos,
        frequency_hz=frequency_hz,
        s21_value=np.complex64(0.0 + 0.0j),
        monotonic_ns=now_ns,
    )
    logger.info(
        "Built neutral S21 sets: model=%s combos=%d points=%d",
        config.radar.model,
        len(combos),
        int(frequency_hz.size),
    )
    return calibration, reference


def _neutral_collection(
    *,
    combos: list[ComboModel],
    frequency_hz: np.ndarray,
    s21_value: np.complex64,
    monotonic_ns: int,
) -> SweepCollection:
    point_count = int(frequency_hz.size)
    traces = [
        TraceData(
            combo=ComboKey(input=int(combo.input), output=int(combo.output)),
            frequency_hz=frequency_hz.copy(),
            s11=np.zeros(point_count, dtype=np.complex64),
            s21=np.full(point_count, s21_value, dtype=np.complex64),
        )
        for combo in combos
    ]
    return SweepCollection(
        collection_id=1,
        monotonic_ns=monotonic_ns,
        traces=traces,
        capture_start_ns=monotonic_ns,
        capture_end_ns=monotonic_ns,
    )