# Copyright 2026 Umbra Tools (umbratools.com)
# SPDX-License-Identifier: Apache-2.0

"""The m4b must ship the same audio spec as the AR MP3 package.

Previously the m4b path had no sample-rate flag, no channel layout, and no
loudness handling at all, so it produced 24 kHz / ~96 kbps AAC while the MP3
masters were 44.1 kHz / 192 kbps CBR mono. Measured on a real build, the
delivered m4b peaked at -2.0 dB and failed the -3 dB ceiling that Author's
Republic and Spotify both require.
"""
from __future__ import annotations

import shutil
import subprocess
from typing import TYPE_CHECKING

import numpy as np
import pytest
import soundfile as sf

if TYPE_CHECKING:
    from pathlib import Path

from umbraaudio.assembly.ar_export import (
    PEAK_MAX_DB,
    RMS_HI_DB,
    RMS_LO_DB,
    TARGET_SAMPLE_RATE,
)
from umbraaudio.assembly.export import AudiobookExporter

SR = 24000
needs_ffmpeg = pytest.mark.skipif(
    shutil.which("ffmpeg") is None, reason="ffmpeg required"
)


def _chapter_wav(path: Path, seconds: float = 2.0, amp: float = 0.2) -> Path:
    sf.write(str(path), (amp * np.random.randn(int(SR * seconds))).astype(np.float32), SR)
    return path


def _built_m4b(tmp_path: Path, chapters: int = 2) -> Path:
    """Concatenate real chapter WAVs and run the real m4b encode path."""
    audio = tmp_path / "chapter_audio"
    audio.mkdir(parents=True, exist_ok=True)
    files = [_chapter_wav(audio / f"ch{i}_full.wav") for i in range(1, chapters + 1)]

    exporter = AudiobookExporter()
    concat = tmp_path / "concat.wav"
    exporter._concat_wavs_with_silence(files, concat, gap_ms=2000)
    out = tmp_path / "book.m4b"
    exporter._encode_aac_m4b(concat, out, work_dir=tmp_path)
    return out


@needs_ffmpeg
def test_m4b_is_44100_mono_not_the_tts_native_rate(tmp_path: Path) -> None:
    """The TTS renders at 24 kHz; the deliverable must not ship at that rate."""
    m4b = _built_m4b(tmp_path)
    proc = subprocess.run(
        ["ffprobe", "-v", "error", "-select_streams", "a:0",
         "-show_entries", "stream=sample_rate,channels", "-of", "csv=p=0", str(m4b)],
        capture_output=True, text=True, check=True,
    )
    rate, channels = proc.stdout.strip().split(",")[:2]
    assert int(rate) == TARGET_SAMPLE_RATE == 44100
    assert int(channels) == 1


@needs_ffmpeg
def test_m4b_meets_the_peak_ceiling(tmp_path: Path) -> None:
    """AAC overshoots the float ceiling, so the FILE is what gets enforced."""
    m4b = _built_m4b(tmp_path)
    report = AudiobookExporter().m4b_loudness_report(m4b)
    assert report["peak_db"] is not None
    assert report["peak_db"] <= PEAK_MAX_DB, report
    assert report["peak_ok"] is True, report


@needs_ffmpeg
def test_m4b_rms_sits_in_the_distributor_band(tmp_path: Path) -> None:
    m4b = _built_m4b(tmp_path)
    report = AudiobookExporter().m4b_loudness_report(m4b)
    assert report["rms_db"] is not None
    assert RMS_LO_DB <= report["rms_db"] <= RMS_HI_DB, report
    assert report["loudness_ok"] is True, report


@needs_ffmpeg
def test_aac_overshoot_margin_is_applied_so_trims_converge() -> None:
    """Trimming by the exact excess oscillates; the margin guarantees progress.

    Measured overshoot across successive passes was +0.8, +0.9, +1.6 dB, so an
    exact-excess loop ran out of passes still breaching.
    """
    from umbraaudio.assembly.export import AAC_ENFORCE_PASSES, AAC_OVERSHOOT_MARGIN_DB

    assert AAC_OVERSHOOT_MARGIN_DB > 0.0
    assert AAC_ENFORCE_PASSES >= 3


def test_stitcher_gap_matches_the_approved_path() -> None:
    """Spec 22 gap 1: the m4b stitched chapters with different silence.

    AudioStitcher's defaults (500 / 4000) are what ChapterBuilder - the
    reviewed path - uses. The m4b used 0 between chapters, so the packaged
    book differed from the audio a reviewer approved.
    """
    from umbraaudio.assembly import AudioStitcher

    defaults = AudioStitcher()
    assert defaults.silence_utt == 500
    assert defaults.silence_chap == 4000


@needs_ffmpeg
def test_concat_resamples_to_the_delivery_rate(tmp_path: Path) -> None:
    files = [_chapter_wav(tmp_path / "a.wav"), _chapter_wav(tmp_path / "b.wav")]
    exporter = AudiobookExporter()
    out = tmp_path / "concat.wav"
    exporter._concat_wavs_with_silence(files, out, gap_ms=100)
    info = sf.info(str(out))
    assert info.samplerate == TARGET_SAMPLE_RATE