"""Tests for the subcarrier extractor block."""

import numpy as np
import pytest

try:
    from gnuradio import blocks, gr

    HAS_GNURADIO = True
except ImportError:
    HAS_GNURADIO = False

from apollo.constants import PCM_SUBCARRIER_HZ, SAMPLE_RATE_BASEBAND

pytestmark = pytest.mark.skipif(not HAS_GNURADIO, reason="GNU Radio not installed")


class TestSubcarrierExtract:
    """Test subcarrier extraction and frequency translation."""

    def test_passes_target_frequency(self):
        """A tone at the center frequency should pass through."""
        from apollo.subcarrier_extract import subcarrier_extract

        tb = gr.top_block()
        sample_rate = SAMPLE_RATE_BASEBAND
        n_samples = 50000

        # Generate a pure tone at 1.024 MHz
        t = np.arange(n_samples, dtype=np.float64) / sample_rate
        tone = np.cos(2 * np.pi * PCM_SUBCARRIER_HZ * t).astype(np.float32)

        src = blocks.vector_source_f(tone.tolist())
        extract = subcarrier_extract(
            center_freq=PCM_SUBCARRIER_HZ,
            bandwidth=150_000,
            sample_rate=sample_rate,
        )
        snk = blocks.vector_sink_c()

        tb.connect(src, extract, snk)
        tb.run()

        output = np.array(snk.data())
        # Output should have significant energy (tone passed through)
        assert len(output) > 0
        power = np.mean(np.abs(output[1000:]) ** 2)
        assert power > 0.01, f"Target frequency power too low: {power}"

    def test_rejects_distant_frequency(self):
        """A tone far from the passband should be strongly attenuated."""
        from apollo.subcarrier_extract import subcarrier_extract

        tb = gr.top_block()
        sample_rate = SAMPLE_RATE_BASEBAND
        n_samples = 50000

        # Generate a tone at 500 kHz (far from 1.024 MHz passband)
        t = np.arange(n_samples, dtype=np.float64) / sample_rate
        tone = np.cos(2 * np.pi * 500_000 * t).astype(np.float32)

        src = blocks.vector_source_f(tone.tolist())
        extract = subcarrier_extract(
            center_freq=PCM_SUBCARRIER_HZ,
            bandwidth=150_000,
            sample_rate=sample_rate,
        )
        snk = blocks.vector_sink_c()

        tb.connect(src, extract, snk)
        tb.run()

        output = np.array(snk.data())
        if len(output) > 1000:
            power = np.mean(np.abs(output[1000:]) ** 2)
            assert power < 0.001, f"Out-of-band frequency not rejected: {power}"

    def test_output_sample_rate_property(self):
        """Output sample rate should account for decimation."""
        from apollo.subcarrier_extract import subcarrier_extract

        ext = subcarrier_extract(sample_rate=5_120_000, decimation=4)
        assert ext.output_sample_rate == 1_280_000

    def test_block_instantiation(self):
        from apollo.subcarrier_extract import subcarrier_extract

        ext = subcarrier_extract()
        assert ext is not None