"""
Tests for minimateplus.waveform_codec — Blastware waveform-file body block walker.

These tests lock in the STRUCTURAL framing of the body codec.  The byte-to-sample
mapping is open (see waveform_codec module docstring) — until that's nailed down,
:func:`decode_waveform_v2` returns ``None`` and there is no per-sample assertion
to make.
"""
from __future__ import annotations

import os

import pytest

from minimateplus.waveform_codec import (
    WaveformBlock,
    decode_tran_initial,
    decode_waveform_v2,
    find_data_start,
    parse_segment_header,
    split_segments,
    walk_body,
)


FIXTURES = os.path.join(
    os.path.dirname(__file__), "fixtures", "decode-re-5-8-26"
)


def _bw_body(path):
    """Strip the 22-byte header and 21-byte STRT and 26-byte footer to get the body."""
    with open(path, "rb") as f:
        binary = f.read()
    return binary[43:-26]


# Fixture metadata — bundled BW binaries from a real BE11529 unit, May 8 2026.
# Each is paired with a Blastware TXT export (the ASCII ground truth).
FIXTURES_INFO = {
    "event-a": {
        "filename": "M529LKVQ.6S0",
        "n_samples": 3328,    # 3.0 s rectime + 0.25 s pretrig at 1024 sps
        "rectime": 3.0,
    },
    "event-b": {
        "filename": "M529LK5Q.RG0",
        "n_samples": 2304,    # 2.0 s
        "rectime": 2.0,
    },
    "event-c": {
        "filename": "M529LK44.AB0",
        "n_samples": 1280,    # 1.0 s
        "rectime": 1.0,
    },
    "event-d": {
        "filename": "M529LK2V.470",
        "n_samples": 1280,
        "rectime": 1.0,
    },
}


def _fixture_path(event_name):
    info = FIXTURES_INFO[event_name]
    return os.path.join(FIXTURES, event_name, info["filename"])


# ── Find data start ──────────────────────────────────────────────────────────


@pytest.mark.parametrize("event_name", list(FIXTURES_INFO.keys()))
def test_find_data_start_locates_first_block(event_name):
    """The walker auto-detects the first ``10 NN`` tag within the first 20 bytes."""
    path = _fixture_path(event_name)
    if not os.path.exists(path):
        pytest.skip(f"fixture missing: {path}")
    body = _bw_body(path)
    start = find_data_start(body)
    assert 0 <= start < 20, f"expected start in [0, 20), got {start}"
    assert body[start] in (0x00, 0x10, 0x20, 0x30, 0x40), (
        f"first tag byte 0x{body[start]:02x} not a recognized block type"
    )
    assert body[start + 1] % 4 == 0 or (body[start] == 0x40 and body[start + 1] == 0x02)


def test_find_data_start_canonical_offset_7():
    """All events have a 7-byte preamble (3-byte magic + 4-byte Tran anchors)."""
    for name in FIXTURES_INFO:
        path = _fixture_path(name)
        if not os.path.exists(path):
            pytest.skip(f"fixture missing: {path}")
        body = _bw_body(path)
        # Sanity: magic
        assert body[0:3] == b"\x00\x02\x00", f"{name}: bad magic"
        # First tag at offset 7
        assert find_data_start(body) == 7, f"{name}: expected start=7"


# ── Block walker ─────────────────────────────────────────────────────────────


def test_walk_body_empty_returns_empty():
    assert walk_body(b"") == []


def test_walk_body_invalid_start_returns_empty():
    # Body that does not begin with a recognized tag.
    assert walk_body(b"\xff\xff\xff\xff", start=0) == []


@pytest.mark.parametrize("event_name", list(FIXTURES_INFO.keys()))
def test_walk_body_produces_blocks(event_name):
    """The walker should produce a non-empty stream of blocks for every fixture."""
    path = _fixture_path(event_name)
    if not os.path.exists(path):
        pytest.skip(f"fixture missing: {path}")
    body = _bw_body(path)
    blocks = walk_body(body)
    assert len(blocks) > 0
    # All blocks have one of the 5 known tag types.
    for b in blocks:
        assert b.tag_hi in (0x10, 0x20, 0x00, 0x30, 0x40), (
            f"unknown tag {b.tag_hi:#04x} at offset {b.offset}"
        )


@pytest.mark.parametrize("event_name", list(FIXTURES_INFO.keys()))
def test_walk_body_block_lengths_consistent(event_name):
    """Each block's recorded length matches its on-wire footprint."""
    path = _fixture_path(event_name)
    if not os.path.exists(path):
        pytest.skip(f"fixture missing: {path}")
    body = _bw_body(path)
    blocks = walk_body(body)
    for b in blocks:
        # Tag (2 bytes) + payload should equal length.
        assert 2 + len(b.data) == b.length, (
            f"block at {b.offset} length mismatch: tag(2) + data({len(b.data)}) != length({b.length})"
        )


@pytest.mark.parametrize("event_name", list(FIXTURES_INFO.keys()))
def test_walk_body_blocks_contiguous(event_name):
    """Block n+1 starts exactly where block n ends (no gaps, no overlaps)."""
    path = _fixture_path(event_name)
    if not os.path.exists(path):
        pytest.skip(f"fixture missing: {path}")
    body = _bw_body(path)
    blocks = walk_body(body)
    for i in range(1, len(blocks)):
        prev = blocks[i - 1]
        cur = blocks[i]
        assert cur.offset == prev.offset + prev.length, (
            f"gap/overlap between block {i-1} (off={prev.offset} len={prev.length}) "
            f"and block {i} (off={cur.offset})"
        )


# ── Segment splitting ────────────────────────────────────────────────────────


@pytest.mark.parametrize("event_name", list(FIXTURES_INFO.keys()))
def test_split_segments_yields_at_least_one(event_name):
    path = _fixture_path(event_name)
    if not os.path.exists(path):
        pytest.skip(f"fixture missing: {path}")
    body = _bw_body(path)
    blocks = walk_body(body)
    segments = split_segments(blocks)
    assert len(segments) > 0


def test_split_segments_segment_count_at_least_one_per_event():
    """The walker should produce at least one ``40 02`` segment header per event.

    Note: the walker currently bails out partway through event-b (still an
    open issue — the body codec uses block lengths the walker doesn't
    handle correctly past offset ~427).  The other 3 events walk farther
    and have many segment headers.
    """
    for name in FIXTURES_INFO:
        path = _fixture_path(name)
        if not os.path.exists(path):
            continue
        body = _bw_body(path)
        blocks = walk_body(body)
        n_40 = sum(1 for b in blocks if b.tag_hi == 0x40)
        assert n_40 >= 1, f"{name}: no 40 02 segment header found"


# ── Segment header parsing ───────────────────────────────────────────────────


def test_parse_segment_header_returns_none_for_non_40():
    block = WaveformBlock(offset=0, tag_hi=0x10, tag_lo=0x04, data=b"\x00\x00", length=4)
    assert parse_segment_header(block) is None


def test_parse_segment_header_decodes_fields():
    """Decode a known 40 02 block to verify field offsets."""
    # First segment header from event-c at body offset 235:
    # 40 02 00 00 00 00 0a 4b 01 1e 47 00 00 00 02 00 00 01 00 01
    payload = bytes.fromhex("00000000 0a4b011e 47000000 02000001 0001".replace(" ", ""))
    block = WaveformBlock(
        offset=235, tag_hi=0x40, tag_lo=0x02, data=payload, length=20
    )
    decoded = parse_segment_header(block)
    assert decoded is not None
    assert decoded["counter"] == 0x47       # uint32 LE
    assert decoded["fixed_pattern"] == b"\x02\x00\x00\x01"
    assert decoded["anchor_bytes"] == b"\x00\x00\x00\x00"


def test_segment_counter_increments():
    """The 4-byte counter at bytes [8:12] of each 40 02 payload increments by 1."""
    path = _fixture_path("event-c")
    if not os.path.exists(path):
        pytest.skip("fixture missing")
    body = _bw_body(path)
    blocks = walk_body(body)
    headers = [b for b in blocks if b.tag_hi == 0x40 and b.tag_lo == 0x02]
    counters = [parse_segment_header(b)["counter"] for b in headers]
    assert len(counters) >= 5, "expect at least 5 segments to verify increments"
    # First few counters should be strictly monotonic (the BW counter is global,
    # incrementing across the whole flash buffer; some events may share counter
    # values with the previous event's tail block, so allow non-strict).
    for i in range(1, min(8, len(counters))):
        assert counters[i] >= counters[i - 1], (
            f"counter went backwards: {counters[i-1]} → {counters[i]}"
        )


# ── decode_waveform_v2: currently a stub ─────────────────────────────────────


@pytest.mark.parametrize("event_name", list(FIXTURES_INFO.keys()))
def test_decode_waveform_v2_returns_none_until_verified(event_name):
    """
    The full per-channel decoder is not yet wired up.

    This test ensures decode_waveform_v2 returns ``None`` so callers know
    to keep using the legacy decoder.  When a verified decoder lands,
    flip this assertion and add ground-truth tests against the bundled
    TXT exports.
    """
    path = _fixture_path(event_name)
    if not os.path.exists(path):
        pytest.skip(f"fixture missing: {path}")
    body = _bw_body(path)
    assert decode_waveform_v2(body) is None


# ── decode_tran_initial: confirmed correct against ground truth ──────────────

# Bundled fixtures for the high-amplitude 5-11-26 events (PPV ~6-7 in/s).
# These cracked the Tran codec — see waveform_codec module docstring.
TRAN_INITIAL_FIXTURES = [
    # (path, expected first N Tran samples in 16-count units, # of samples to verify)
    (
        os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1A.SP0"),
        [4, 4, 3, 3, 3, 2, 2, 3, 2, 2, 2, 2, 1, 1, 1, 2, 1, 1, 1, 0, 1, 0],
        22,
    ),
    (
        os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1A.SS0"),
        [-89, -89, -91, -91, -92, -93, -94, -94, -94, -94],
        42,
    ),
    (
        os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1A.SV0"),
        [-745, -762, -771, -774, -779, -794, -808, -811, -811, -819],
        46,
    ),
    # Vert-heavy event (T near zero) — segment 0 = 510 samples, all decode correctly.
    (
        os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1L.JQ0"),
        [0] * 4 + [-1, 0, 0, -1, -1, 0],
        38,
    ),
    # Mic-heavy event (geos all near zero) — segment 0 = 482 samples.
    (
        os.path.join(os.path.dirname(__file__), "fixtures", "5-11-26", "M529LL1L.V70"),
        [0] * 10,
        6,
    ),
]


def _full_truth(path):
    """Load the BW ASCII truth for an event."""
    import re
    with open(path + ".TXT", "r", encoding="utf-8", errors="replace") as f:
        lines = f.read().splitlines()
    # Find columns header.
    header_idx = None
    for i, line in enumerate(lines):
        if "Tran" in line and "Vert" in line and "Long" in line and "MicL" in line:
            header_idx = i
            break
    if header_idx is None:
        return None
    out = []
    for line in lines[header_idx + 1:]:
        parts = re.split(r"\s+", line.strip())
        if len(parts) < 4:
            continue
        try:
            out.append(round(float(parts[0]) * 200))
        except ValueError:
            continue
    return out


@pytest.mark.parametrize("path,expected,n_required", TRAN_INITIAL_FIXTURES)
def test_decode_tran_initial_matches_ground_truth(path, expected, n_required):
    """The Tran initial decoder produces values matching the BW ASCII export exactly."""
    if not os.path.exists(path):
        pytest.skip(f"fixture missing: {path}")
    with open(path, "rb") as f:
        raw = f.read()
    body = raw[43:-26]
    decoded = decode_tran_initial(body)
    assert decoded is not None
    # Check first len(expected) samples match exactly.
    for i in range(len(expected)):
        assert decoded[i] == expected[i], (
            f"sample {i}: decoded={decoded[i]} expected={expected[i]}"
        )
    # And we got at least n_required samples decoded.
    assert len(decoded) >= n_required, (
        f"decoded only {len(decoded)} samples, expected at least {n_required}"
    )


def test_decode_tran_initial_handles_empty():
    assert decode_tran_initial(b"") is None
    assert decode_tran_initial(b"not a body") is None


def test_decode_tran_initial_synthetic_body():
    """A synthetic body with preamble + one 10 04 block decodes correctly."""
    # Magic + T[0]=10 + T[1]=20 in 16-count units.
    # Then 10 04 block with 4 nibbles: (+1, -1, +2, -2)
    # Encoded high-nibble first: 0x1F = (1, -1), 0x2E = (2, -2)
    body = b"\x00\x02\x00\x00\x0a\x00\x14" + b"\x10\x04" + b"\x1f\x2e"
    decoded = decode_tran_initial(body)
    # T[0]=10, T[1]=20, then deltas (+1, -1, +2, -2) from T[1]=20
    assert decoded == [10, 20, 21, 20, 22, 20]


def test_decode_tran_initial_with_rle():
    """A synthetic body with 00 NN RLE block runs the current Tran value forward."""
    # T[0]=5, T[1]=5, then 00 08 RLE block = 8 zero deltas → T[2..9] = 5
    body = b"\x00\x02\x00\x00\x05\x00\x05" + b"\x00\x08"
    decoded = decode_tran_initial(body)
    assert decoded == [5, 5, 5, 5, 5, 5, 5, 5, 5, 5]


def test_decode_tran_initial_full_segment_silent_events():
    """For events with near-silent Tran, segment 0 (~482-510 samples) decodes fully."""
    for path, _, _ in TRAN_INITIAL_FIXTURES[3:]:  # JQ0 (Vert-heavy) and V70 (Mic-heavy)
        if not os.path.exists(path):
            pytest.skip(f"fixture missing: {path}")
        with open(path, "rb") as f:
            body = f.read()[43:-26]
        truth = _full_truth(path)
        decoded = decode_tran_initial(body)
        assert decoded is not None
        # The decoder should produce a clean run of samples; check ALL of them
        # match truth (segment 0 is fully solved for events where T is near zero).
        n = len(decoded)
        for i in range(n):
            assert decoded[i] == truth[i], (
                f"{os.path.basename(path)}: sample {i}: decoded={decoded[i]} truth={truth[i]}"
            )
        # And we should have decoded at least 400 samples (= segment 0 worth).
        assert n >= 400, f"only {n} samples decoded for {path}"