Implement Galileo E1B I/NAV navigation decoding

tests/navigation/test_page_sync.py

@@ -0,0 +1,54 @@
+from __future__ import annotations
+
+import numpy as np
+
+from galileo_rx.navigation.e1b_symbol_sync import NavigationSymbol
+from galileo_rx.navigation.inav_page_sync import INAV_SYNC_BITS, InavPageSynchronizer
+
+
+def _symbols(bits: np.ndarray, *, invert: bool = False, prefix: int = 17) -> list[NavigationSymbol]:
+    raw = np.concatenate((np.zeros(prefix, dtype=np.int8), bits))
+    if invert:
+        raw = 1 - raw
+    return [NavigationSymbol(1, i, i * 4, (i + 1) * 4, 1.0 if bit else -1.0, int(bit), 1.0, False, True) for i, bit in enumerate(raw)]
+
+
+def test_page_sync_rejects_wrong_boundary_and_requires_repetition() -> None:
+    rng = np.random.default_rng(4)
+    part = np.concatenate((INAV_SYNC_BITS, rng.integers(0, 2, 240, dtype=np.int8)))
+    stream = _symbols(np.tile(part, 3))
+    sync = InavPageSynchronizer(required_confirmations=2)
+    first = sync.process_many(stream[:267])
+    assert first == []
+    output = sync.process_many(stream[267:])
+    assert len(output) == 3
+    assert all(item.sync_valid for item in output)
+
+
+def test_page_sync_records_global_inversion() -> None:
+    body = np.zeros(240, dtype=np.int8)
+    parts = InavPageSynchronizer().process_many(_symbols(np.tile(np.concatenate((INAV_SYNC_BITS, body)), 3), invert=True))
+    assert len(parts) == 3
+    assert all(item.polarity_inverted for item in parts)
+    assert np.array_equal(parts[0].hard_symbols[:10], INAV_SYNC_BITS)
+
+
+def test_page_sync_loses_and_reacquires_after_corrupted_sync() -> None:
+    body = np.zeros(240, dtype=np.int8)
+    part = np.concatenate((INAV_SYNC_BITS, body))
+    bits = np.tile(part, 6)
+    bits[3 * 250] ^= 1
+    output = InavPageSynchronizer().process_many(_symbols(bits, prefix=0))
+    assert len(output) == 5
+    assert [item.receive_sample_timestamp // (250 * 4) for item in output] == [0, 1, 2, 4, 5]
+
+
+def test_page_sync_does_not_lock_through_symbol_erasure() -> None:
+    body = np.zeros(240, dtype=np.int8)
+    symbols = _symbols(np.tile(np.concatenate((INAV_SYNC_BITS, body)), 3), prefix=0)
+    erased = symbols[250]
+    symbols[250] = NavigationSymbol(
+        erased.prn, erased.symbol_index, erased.start_sample_timestamp,
+        erased.end_sample_timestamp, 0.0, 0, 0.0, False, False,
+    )
+    assert InavPageSynchronizer().process_many(symbols) == []