"""
test_histogram_codec.py — regression locks for the histogram body codec.

The codec is verified byte-exact against BW's ASCII export across the
in-repo histogram fixture bundle.  Each test cross-checks decoded
binary fields against the corresponding .TXT row.

Run:
    python -m pytest tests/test_histogram_codec.py -q
"""

from __future__ import annotations

import os
import re
import sys
from pathlib import Path

import pytest

sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))

from minimateplus.blastware_file import _WAVEFORM_HEADER_SIZE
from minimateplus.histogram_codec import (
    _BLOCK_SIZE,
    decode_histogram_body,
    decode_histogram_body_full,
    geo_count_to_ins,
    half_period_to_hz,
    walk_body,
)
from minimateplus.waveform_codec import mic_count_to_db


_FIXTURE_DIR = Path(__file__).resolve().parent.parent / "example-events" / "histogram"


def _extract_body(path: Path) -> bytes:
    """Locate the body of a BW event file — bytes between the STRT
    record and the 26-byte footer."""
    raw = path.read_bytes()
    body_start = _WAVEFORM_HEADER_SIZE + 21
    pos = body_start
    footer_pos = -1
    while True:
        pos = raw.find(b"\x0e\x08", pos)
        if pos < 0 or pos + 26 > len(raw):
            break
        yr = (raw[pos + 4] << 8) | raw[pos + 5]
        if 2015 <= yr <= 2050:
            footer_pos = pos
            break
        pos += 1
    if footer_pos < 0:
        footer_pos = len(raw) - 26
    return raw[body_start:footer_pos]


def _parse_txt_rows(path: Path) -> list[tuple[str, list]]:
    """Parse a histogram .TXT into ``[(time_str, [10 col values]), …]``.

    Special tokens:
      - ``">100"`` (the BW-display sentinel for freq > 100 Hz) → ``None``
      - non-numeric → ``None``
    """
    text = path.read_text()
    lines = text.splitlines()
    hdr = None
    for i, line in enumerate(lines):
        if re.match(r"^Tran\s+", line.strip()):
            hdr = i + 3      # skip 2-row header + units row
            break
    if hdr is None:
        return []
    rows: list[tuple[str, list]] = []
    for line in lines[hdr:]:
        parts = line.split("\t")
        if len(parts) != 11:
            continue
        vals: list = []
        for p in parts[1:]:
            s = p.strip()
            if s.startswith(">"):
                vals.append(None)        # ">100 Hz" sentinel
                continue
            try:
                vals.append(float(s))
            except ValueError:
                vals.append(None)
        rows.append((parts[0].strip(), vals))
    return rows


# ── Block-walker plumbing ────────────────────────────────────────────────────


@pytest.mark.parametrize("fixture", [
    "N844L20G.630H",
    "N844L21H.2R0H",
    "N844L6Z8.ZR0H",
    "N844L6XE.BH0H",
    "N844L23B.ND0H",
])
def test_walk_body_returns_records(fixture: str):
    """Walker yields at least one valid block per fixture."""
    path = _FIXTURE_DIR / fixture
    if not path.exists():
        pytest.skip(f"fixture missing: {path}")
    records = walk_body(_extract_body(path))
    assert len(records) > 100, f"expected hundreds of blocks, got {len(records)}"


def test_walk_body_record_count_matches_txt_intervals():
    """Block count should match the .TXT interval count (off-by-one
    at the tail is acceptable — last interval may be truncated at
    recording stop)."""
    bin_path = _FIXTURE_DIR / "N844L20G.630H"
    txt_path = _FIXTURE_DIR / "N844L20G_630H_ASCII.TXT"
    if not bin_path.exists() or not txt_path.exists():
        pytest.skip("fixture missing")
    records = walk_body(_extract_body(bin_path))
    txt_rows = _parse_txt_rows(txt_path)
    # Allow off-by-one (final block may have been mid-write at stop)
    assert abs(len(records) - len(txt_rows)) <= 1, (
        f"binary {len(records)} blocks vs TXT {len(txt_rows)} intervals"
    )


def test_walk_body_segment_id_increments_every_256_blocks():
    """Segment ID advances 0→1→2→… after every 256 blocks within
    one event."""
    path = _FIXTURE_DIR / "N844L20G.630H"
    if not path.exists():
        pytest.skip("fixture missing")
    records = walk_body(_extract_body(path))
    # Group by segment_id and verify counts make sense
    from collections import Counter
    seg_counts = Counter(r["segment_id"] for r in records)
    # First 3 segments should each have exactly 256 blocks (N844L20G has
    # 791 blocks → 256+256+256+23 → segments 0/1/2/3)
    assert seg_counts[0] == 256
    assert seg_counts[1] == 256
    assert seg_counts[2] == 256
    assert seg_counts[3] == len(records) - 3 * 256


# ── Field-by-field decode verification against .TXT ground truth ─────────────


@pytest.mark.parametrize("fixture", [
    "N844L20G.630H",
    "N844L6Z8.ZR0H",
    "N844L6XE.BH0H",
    "N844L23B.ND0H",
])
def test_decoded_geo_peaks_match_txt(fixture: str):
    """For every block, decoded Tran/Vert/Long peak (count × 0.005)
    matches the corresponding .TXT cell."""
    bin_path = _FIXTURE_DIR / fixture
    txt_path = _FIXTURE_DIR / (fixture.replace(".", "_") + "_ASCII.TXT")
    if not bin_path.exists() or not txt_path.exists():
        pytest.skip("fixture missing")
    records  = walk_body(_extract_body(bin_path))
    txt_rows = _parse_txt_rows(txt_path)
    n = min(len(records), len(txt_rows))
    assert n > 0
    for i in range(n):
        rec = records[i]
        _ts, txt = txt_rows[i]
        # TXT cols 0/2/4 are T/V/L peak in in/s
        for slot, key in (("T", "t_peak"), ("V", "v_peak"), ("L", "l_peak")):
            col = {"T": 0, "V": 2, "L": 4}[slot]
            decoded_ips = geo_count_to_ins(rec[key])
            expected = txt[col]
            assert abs(decoded_ips - expected) < 0.0005, (
                f"{fixture} block {i} {slot}_peak: "
                f"decoded={decoded_ips:.4f} vs txt={expected:.4f}"
            )


@pytest.mark.parametrize("fixture", [
    "N844L6Z8.ZR0H",
    "N844L6XE.BH0H",
])
def test_decoded_geo_freqs_match_txt(fixture: str):
    """Decoded half-period → Hz matches the .TXT freq column for blocks
    where the freq is in-range (not the `>100 Hz` sentinel)."""
    bin_path = _FIXTURE_DIR / fixture
    txt_path = _FIXTURE_DIR / (fixture.replace(".", "_") + "_ASCII.TXT")
    if not bin_path.exists() or not txt_path.exists():
        pytest.skip("fixture missing")
    records  = walk_body(_extract_body(bin_path))
    txt_rows = _parse_txt_rows(txt_path)
    n = min(len(records), len(txt_rows))
    for i in range(n):
        rec = records[i]
        _ts, txt = txt_rows[i]
        for slot, key, col in (("T", "t_halfp", 1), ("V", "v_halfp", 3), ("L", "l_halfp", 5)):
            decoded_hz = half_period_to_hz(rec[key])
            expected = txt[col]
            if expected is None:
                # TXT shows `>100 Hz` — codec should also yield None
                assert decoded_hz is None or decoded_hz > 100, (
                    f"{fixture} block {i} {slot}_freq: codec says "
                    f"{decoded_hz} but TXT says >100"
                )
                continue
            # TXT rounds; allow ±1 Hz
            assert decoded_hz is not None
            assert abs(decoded_hz - expected) < 1.0, (
                f"{fixture} block {i} {slot}_freq: "
                f"decoded={decoded_hz:.2f} Hz vs txt={expected:.2f} Hz"
            )


@pytest.mark.parametrize("fixture", [
    "N844L6XE.BH0H",
    "N844L23B.ND0H",
    "N844L6Z8.ZR0H",
])
def test_decoded_mic_db_matches_txt(fixture: str):
    """Decoded MicL peak count → dB(L) via mic_count_to_db matches
    the .TXT dB(L) column."""
    bin_path = _FIXTURE_DIR / fixture
    txt_path = _FIXTURE_DIR / (fixture.replace(".", "_") + "_ASCII.TXT")
    if not bin_path.exists() or not txt_path.exists():
        pytest.skip("fixture missing")
    records  = walk_body(_extract_body(bin_path))
    txt_rows = _parse_txt_rows(txt_path)
    n = min(len(records), len(txt_rows))
    for i in range(n):
        rec = records[i]
        _ts, txt = txt_rows[i]
        # TXT col 8 = MicL dB(L)
        decoded_db = mic_count_to_db(rec["m_peak"])
        expected   = txt[8]
        if expected is None:
            continue
        # BW rounds to 1 decimal place for display.  Tolerance 0.1 dB
        # absorbs both rounding modes (truncate vs round-half-even).
        assert abs(decoded_db - expected) < 0.1, (
            f"{fixture} block {i} M_dB: "
            f"decoded={decoded_db:.2f} dB vs txt={expected:.2f} dB"
        )


@pytest.mark.parametrize("fixture", [
    "N844L20G.630H",
    "N844L6Z8.ZR0H",
])
def test_decoded_mic_freq_matches_txt(fixture: str):
    """Decoded MicL half-period → freq matches the .TXT col 9 freq."""
    bin_path = _FIXTURE_DIR / fixture
    txt_path = _FIXTURE_DIR / (fixture.replace(".", "_") + "_ASCII.TXT")
    if not bin_path.exists() or not txt_path.exists():
        pytest.skip("fixture missing")
    records  = walk_body(_extract_body(bin_path))
    txt_rows = _parse_txt_rows(txt_path)
    n = min(len(records), len(txt_rows))
    for i in range(n):
        rec = records[i]
        _ts, txt = txt_rows[i]
        decoded_hz = half_period_to_hz(rec["m_halfp"])
        expected   = txt[9]
        if expected is None:
            assert decoded_hz is None or decoded_hz > 100
            continue
        assert decoded_hz is not None
        assert abs(decoded_hz - expected) < 1.0, (
            f"{fixture} block {i} M_freq: "
            f"decoded={decoded_hz:.2f} Hz vs txt={expected:.2f} Hz"
        )


# ── Public API ───────────────────────────────────────────────────────────────


def test_decode_histogram_body_returns_four_channels():
    """The public API returns the standard 4-channel dict shape."""
    path = _FIXTURE_DIR / "N844L20G.630H"
    if not path.exists():
        pytest.skip("fixture missing")
    decoded = decode_histogram_body(_extract_body(path))
    assert decoded is not None
    assert set(decoded.keys()) == {"Tran", "Vert", "Long", "MicL"}
    # All channels same length (one value per histogram interval)
    n = len(decoded["Tran"])
    assert all(len(decoded[ch]) == n for ch in ("Vert", "Long", "MicL"))
    assert n > 100


def test_decode_histogram_body_returns_none_for_non_histogram():
    """A waveform-mode body (starts with 00 02 00) doesn't decode as
    a histogram body."""
    fake_waveform_body = b"\x00\x02\x00" + b"\x00" * 100
    assert decode_histogram_body(fake_waveform_body) is None


def test_decode_histogram_body_returns_none_for_garbage():
    """Bytes that don't form valid blocks return None."""
    assert decode_histogram_body(b"\xff" * 256) is None


def test_decode_histogram_body_full_preserves_frequency_data():
    """The structured-record API preserves the per-channel half-period
    fields that the flat-channel API drops."""
    path = _FIXTURE_DIR / "N844L20G.630H"
    if not path.exists():
        pytest.skip("fixture missing")
    records = decode_histogram_body_full(_extract_body(path))
    assert records is not None
    r0 = records[0]
    expected_fields = {
        "segment_id", "block_ctr",
        "t_peak", "t_halfp", "v_peak", "v_halfp",
        "l_peak", "l_halfp", "m_peak", "m_halfp",
        "meta_var",
    }
    assert set(r0.keys()) >= expected_fields


# ── Helpers ──────────────────────────────────────────────────────────────────


def test_half_period_to_hz_sentinel():
    """Half-period ≤ 5 returns None (the `>100 Hz` sentinel)."""
    assert half_period_to_hz(5) is None
    assert half_period_to_hz(1) is None
    # halfp=6 gives 512/6 = 85.3 Hz — below the >100 threshold
    assert half_period_to_hz(6) == pytest.approx(85.33, abs=0.01)


def test_geo_count_to_ins_scale():
    """1 count = 0.005 in/s at Normal range."""
    assert geo_count_to_ins(1)  == pytest.approx(0.005)
    assert geo_count_to_ins(10) == pytest.approx(0.050)
    assert geo_count_to_ins(0)  == 0.0