"""Tests for the BPSK demodulator 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_HIGH_BIT_RATE, SAMPLE_RATE_BASEBAND

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


class TestBPSKDemod:
    """Test BPSK demodulation with synthetic signals."""

    def test_clean_bpsk_recovery(self):
        """Known BPSK signal should recover original bits."""
        from apollo.bpsk_demod import bpsk_demod

        tb = gr.top_block()
        sample_rate = SAMPLE_RATE_BASEBAND
        symbol_rate = PCM_HIGH_BIT_RATE
        sps = sample_rate / symbol_rate
        n_bits = 200

        # Generate known bit pattern
        np.random.seed(99)
        bits = np.random.randint(0, 2, n_bits)
        nrz = 2.0 * bits - 1.0  # map 0→-1, 1→+1

        # Upsample to sample rate (rectangular pulse shaping)
        samples_per_bit = int(sps)
        baseband = np.repeat(nrz, samples_per_bit).astype(np.complex64)

        src = blocks.vector_source_c(baseband.tolist())
        demod = bpsk_demod(
            symbol_rate=symbol_rate,
            sample_rate=sample_rate,
            loop_bw=0.045,
        )
        snk = blocks.vector_sink_b()

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

        output = np.array(snk.data())
        # Allow for sync-up time; check that most bits match after settling
        if len(output) > 50:
            # Find the best alignment between output and expected bits
            best_match = 0
            for offset in range(min(50, len(output))):
                end = min(len(output) - offset, len(bits))
                matches = np.sum(output[offset : offset + end] == bits[:end])
                best_match = max(best_match, matches / end if end > 0 else 0)
            assert best_match > 0.7, f"Bit recovery rate too low: {best_match:.2%}"

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

        demod = bpsk_demod()
        assert demod is not None